otp/otp.c

#define _POSIX_C_SOURCE 200809L
#define _DEFAULT_SOURCE

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <unistd.h>
#include <sys/stat.h>
#include <dirent.h>
#include <time.h>
#include <ctype.h>
#include <termios.h>
#include <fcntl.h>
#include <math.h>
#include "nostr_chacha20.h"
#include "otp.h"

// Custom base64 character set
static const char base64_chars[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
static const int base64_decode_table[256] = {
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,62,-1,-1,-1,63,
    52,53,54,55,56,57,58,59,60,61,-1,-1,-1,-2,-1,-1,
    -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10,11,12,13,14,
    15,16,17,18,19,20,21,22,23,24,25,-1,-1,-1,-1,-1,
    -1,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,
    41,42,43,44,45,46,47,48,49,50,51,-1,-1,-1,-1,-1,
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1
};

#define MAX_INPUT_SIZE 4096
#define MAX_LINE_LENGTH 1024
#define MAX_HASH_LENGTH 65
#define PROGRESS_UPDATE_INTERVAL (64 * 1024 * 1024)  // 64MB intervals
#define DEFAULT_PADS_DIR "pads"
#define FILES_DIR "files"
#define MAX_ENTROPY_BUFFER 32768  // 32KB entropy buffer

////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
//      GLOBAL VARIABLES
////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////

static char current_pads_dir[512] = DEFAULT_PADS_DIR;
static char default_pad_path[1024] = "";
static int is_interactive_mode = 0;

////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
//      MAIN
////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////

int main(int argc, char* argv[]) {
    // Load preferences first
    load_preferences();
    
    // Detect interactive mode: only true when running with no arguments
    is_interactive_mode = (argc == 1);
    
    // Check for OTP thumb drive on startup
    char otp_drive_path[512];
    if (detect_otp_thumb_drive(otp_drive_path, sizeof(otp_drive_path))) {
        // Only show messages in interactive mode
        if (is_interactive_mode) {
            printf("Detected OTP thumb drive: %s\n", otp_drive_path);
            printf("Using as default pads directory for this session.\n\n");
        }
        strncpy(current_pads_dir, otp_drive_path, sizeof(current_pads_dir) - 1);
        current_pads_dir[sizeof(current_pads_dir) - 1] = '\0';
    }
    
    if (is_interactive_mode) {
        return interactive_mode();
    } else {
        return command_line_mode(argc, argv);
    }
}



////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
//      COMMAND LINE MODE
////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////

int command_line_mode(int argc, char* argv[]) {
    // Check for help flags first
    if (strcmp(argv[1], "-h") == 0 || strcmp(argv[1], "--h") == 0 ||
        strcmp(argv[1], "-help") == 0 || strcmp(argv[1], "--help") == 0 ||
        strcmp(argv[1], "help") == 0) {
        print_usage(argv[0]);
        return 0;
    }
    
    if (strcmp(argv[1], "generate") == 0 || strcmp(argv[1], "-g") == 0) {
        if (argc != 3) {
            printf("Usage: %s generate|-g <size>\n", argv[0]);
            printf("Size examples: 1024, 1GB, 5TB, 512MB\n");
            return 1;
        }
        uint64_t size = parse_size_string(argv[2]);
        if (size == 0) {
            printf("Error: Invalid size format\n");
            return 1;
        }
        return generate_pad(size, 1);  // Use simplified pad generation
    }
    else if (strcmp(argv[1], "encrypt") == 0 || strcmp(argv[1], "-e") == 0) {
        // Check for piped input first
        if (has_stdin_data()) {
            char* piped_text = read_stdin_text();
            if (piped_text) {
                int result = pipe_mode(argc, argv, piped_text);
                free(piped_text);
                return result;
            }
        }
        
        if (argc < 2 || argc > 4) {
            printf("Usage: %s encrypt|-e [pad_chksum_or_prefix] [text_to_encrypt]\n", argv[0]);
            return 1;
        }
        
        // Check if pad was specified or use default
        const char* pad_identifier = NULL;
        const char* text = NULL;
        
        if (argc == 2) {
            // Just -e, use default pad, no text (interactive)
            pad_identifier = NULL;
            text = NULL;
        } else if (argc == 3) {
            // Could be -e <pad> or -e <text> (using default pad)
            // Check if default pad is available to determine interpretation
            char* default_pad = get_default_pad_path();
            if (default_pad) {
                // Default pad available, treat argument as text
                pad_identifier = NULL;
                text = argv[2];
                free(default_pad);
            } else {
                // No default pad, treat as pad identifier
                pad_identifier = argv[2];
                text = NULL;
            }
        } else {
            // argc == 4: -e <pad> <text>
            pad_identifier = argv[2];
            text = argv[3];
        }
        
        // If pad_identifier is NULL, we need to use default pad
        if (pad_identifier == NULL) {
            char* default_pad = get_default_pad_path();
            if (default_pad) {
                // Extract checksum from default pad path
                char* filename = strrchr(default_pad, '/');
                if (!filename) filename = default_pad;
                else filename++; // Skip the '/'
                
                // Extract checksum (remove .pad extension)
                if (strlen(filename) >= 68 && strstr(filename, ".pad")) {
                    static char default_checksum[65];
                    strncpy(default_checksum, filename, 64);
                    default_checksum[64] = '\0';
                    pad_identifier = default_checksum;
                }
                free(default_pad);
                
                // Call encrypt_text and return result
                return encrypt_text(pad_identifier, text);
            } else {
                printf("Error: No default pad configured. Specify pad explicitly or configure default pad.\n");
                return 1;
            }
        } else {
            // Explicit pad specified, normal operation
            return encrypt_text(pad_identifier, text);
        }
    }
    else if (strcmp(argv[1], "decrypt") == 0 || strcmp(argv[1], "-d") == 0) {
        if (argc == 2) {
            // Check for piped input first
            if (has_stdin_data()) {
                // Piped decrypt mode - read stdin and decrypt silently
                char* piped_message = read_stdin_text();
                if (piped_message) {
                    int result = decrypt_text(NULL, piped_message);
                    free(piped_message);
                    return result;
                }
            }
            // Interactive mode - no arguments needed
            return decrypt_text(NULL, NULL);
        }
        else if (argc == 3) {
            // Check if the argument looks like an encrypted message (starts with -----)
            if (strncmp(argv[2], "-----BEGIN OTP MESSAGE-----", 27) == 0) {
                // Inline decrypt with message only - use silent mode for command line
                return decrypt_text(NULL, argv[2]);
            } else {
                // Check if it's a file (contains . or ends with known extensions)
                if (strstr(argv[2], ".") != NULL) {
                    // Treat as file
                    return decrypt_file(argv[2], NULL);
                } else {
                    // Interactive decrypt with pad hint (legacy support)
                    return decrypt_text(argv[2], NULL);
                }
            }
        }
        else if (argc == 4) {
            // Check for -o flag for output file
            if (strcmp(argv[2], "-o") == 0) {
                printf("Usage: %s decrypt|-d <input_file> [-o <output_file>]\n", argv[0]);
                return 1;
            } else {
                // Legacy format: pad_chksum and message, or file with output
                // Use silent mode for command line when message is provided
                return decrypt_text(argv[2], argv[3]);
            }
        }
        else if (argc == 5 && strcmp(argv[3], "-o") == 0) {
            // File decryption with output: -d <input_file> -o <output_file>
            return decrypt_file(argv[2], argv[4]);
        }
        else {
            printf("Usage: %s decrypt|-d [encrypted_message|file] [-o output_file]\n", argv[0]);
            printf("       %s decrypt|-d [encrypted_message]  (pad info from message)\n", argv[0]);
            return 1;
        }
    }
    else if (strcmp(argv[1], "-f") == 0) {
        // File encryption mode: -f <input_file> <pad_prefix> [-a] [-o <output_file>]
        if (argc < 4) {
            printf("Usage: %s -f <input_file> <pad_prefix> [-a] [-o <output_file>]\n", argv[0]);
            return 1;
        }
        
        const char* input_file = argv[2];
        const char* pad_prefix = argv[3];
        int ascii_armor = 0;
        const char* output_file = NULL;
        
        // Parse optional flags
        for (int i = 4; i < argc; i++) {
            if (strcmp(argv[i], "-a") == 0) {
                ascii_armor = 1;
            } else if (strcmp(argv[i], "-o") == 0 && i + 1 < argc) {
                output_file = argv[++i];
            }
        }
        
        return encrypt_file(pad_prefix, input_file, output_file, ascii_armor);
    }
    else if (strcmp(argv[1], "list") == 0 || strcmp(argv[1], "-l") == 0) {
        printf("Available pads:\n");
        char* selected = select_pad_interactive("Available pads:", "Select pad (or press Enter to exit)", PAD_FILTER_ALL, 0);
        if (selected) {
            free(selected);
        }
        return 0;
    }
    else {
        print_usage(argv[0]);
        return 1;
    }
}



////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
//      INTERACTIVE MODE
////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////

int interactive_mode(void) {
    char input[10];
        printf("\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n");
    while (1) {
        show_main_menu();
        
        if (!fgets(input, sizeof(input), stdin)) {
            printf("Goodbye!\n");
            break;
        }
        
        char choice = toupper(input[0]);
        
        switch (choice) {
            case 'T':
                handle_text_encrypt();
                break;
            case 'F':
                handle_file_encrypt();
                break;
            case 'D':
                handle_decrypt_menu();
                break;
            case 'P':
                handle_pads_menu();
                break;
            case 'X':
            case 'Q':
                printf("Goodbye!\n");
                return 0;
            default:
                printf("Invalid choice. Please try again.\n");
                break;
        }
    }
    
    return 0;
}


void show_main_menu(void) {


    printf("\n=========================== Main Menu - OTP v0.3.1 ===========================\n\n");

    printf(" \033[4mT\033[0mext encrypt\n");    //TEXT ENCRYPT
    printf(" \033[4mF\033[0mile encrypt\n");    //FILE ENCRYPT
    printf(" \033[4mD\033[0mecrypt\n");         //DECRYPT
    printf(" \033[4mP\033[0mads\n");            //PADS
    printf(" E\033[4mx\033[0mit\n");            //EXIT
    printf("\nSelect option: ");
}

int handle_generate_menu(void) {
    printf("\n=== Generate New Pad ===\n");
    printf("Enter pad size (examples: 1GB, 5TB, 512MB, 2048): ");
    
    char size_input[64];
    if (!fgets(size_input, sizeof(size_input), stdin)) {
        printf("Error: Failed to read input\n");
        return 1;
    }
    
    size_input[strcspn(size_input, "\n")] = 0;
    uint64_t size = parse_size_string(size_input);
    
    if (size == 0) {
        printf("Error: Invalid size format\n");
        return 1;
    }
    
    double size_gb = (double)size / (1024.0 * 1024.0 * 1024.0);
    printf("Generating %.2f GB pad...\n", size_gb);
    printf("Note: Use 'Add entropy' in Pads menu to enhance randomness after creation.\n");
    
    return generate_pad(size, 1);
}

int handle_encrypt_menu(void) {
    printf("\n=== Encrypt Data ===\n");
    
    printf("Available pads:\n");
    char* selected = select_pad_interactive("Available pads:", "Select pad (or press Enter to continue)", PAD_FILTER_ALL, 0);
    int pad_count = 1; // Assume at least 1 pad if function returned
    if (selected) {
        free(selected);
    } else {
        pad_count = 0;
    }
    if (pad_count == 0) {
        printf("No pads available. Generate a pad first.\n");
        return 1;
    }
    
    // Ask user to choose between text and file encryption
    printf("\nSelect encryption type:\n");
    printf(" 1. Text message\n");
    printf(" 2. File\n");
    printf("Enter choice (1-2): ");
    
    char choice_input[10];
    if (!fgets(choice_input, sizeof(choice_input), stdin)) {
        printf("Error: Failed to read input\n");
        return 1;
    }
    
    int choice = atoi(choice_input);
    
    if (choice == 1) {
        // Text encryption - use unified pad selection
        char* selected_pad = select_pad_interactive("=== Select Pad for Text Encryption ===",
                                                  "Select pad (by prefix)",
                                                  PAD_FILTER_ALL, 1);
        if (!selected_pad) {
            printf("Text encryption cancelled.\n");
            return 1;
        }
        
        int result = encrypt_text(selected_pad, NULL);  // NULL for interactive mode
        free(selected_pad);
        return result;
    }
    else if (choice == 2) {
        // File encryption
        printf("\nFile selection options:\n");
        printf(" 1. Type file path directly\n");
        printf(" 2. Use file manager\n");
        printf("Enter choice (1-2): ");
        
        char file_choice[10];
        char input_file[512];
        
        if (!fgets(file_choice, sizeof(file_choice), stdin)) {
            printf("Error: Failed to read input\n");
            return 1;
        }
        
        if (atoi(file_choice) == 2) {
            // Use file manager
            if (launch_file_manager(".", input_file, sizeof(input_file)) != 0) {
                printf("Falling back to manual file path entry.\n");
                printf("Enter input file path: ");
                if (!fgets(input_file, sizeof(input_file), stdin)) {
                    printf("Error: Failed to read input\n");
                    return 1;
                }
                input_file[strcspn(input_file, "\n")] = 0;
            }
        } else {
            // Direct file path input
            printf("Enter input file path: ");
            if (!fgets(input_file, sizeof(input_file), stdin)) {
                printf("Error: Failed to read input\n");
                return 1;
            }
            input_file[strcspn(input_file, "\n")] = 0;
        }
        
        // Check if file exists
        if (access(input_file, R_OK) != 0) {
            printf("Error: File '%s' not found or cannot be read\n", input_file);
            return 1;
        }
        
        // Use unified pad selection
        char* selected_pad = select_pad_interactive("=== Select Pad for File Encryption ===",
                                                  "Select pad (by prefix)",
                                                  PAD_FILTER_ALL, 1);
        if (!selected_pad) {
            printf("File encryption cancelled.\n");
            return 1;
        }
        
        // Ask for output format
        printf("\nSelect output format:\n");
        printf(" 1. Binary (.otp) - preserves file permissions\n");
        printf(" 2. ASCII (.otp.asc) - text-safe format\n");
        printf("Enter choice (1-2): ");
        
        char format_input[10];
        if (!fgets(format_input, sizeof(format_input), stdin)) {
            printf("Error: Failed to read input\n");
            return 1;
        }
        
        int ascii_armor = (atoi(format_input) == 2) ? 1 : 0;
        
        // Generate default output filename with files directory and use enhanced input function
        char default_output[1024]; // Increased size to prevent truncation warnings
        char temp_default[1024];
        
        // Generate base filename with appropriate extension
        if (ascii_armor) {
            snprintf(temp_default, sizeof(temp_default), "%s.otp.asc", input_file);
        } else {
            snprintf(temp_default, sizeof(temp_default), "%s.otp", input_file);
        }
        
        // Apply files directory default path
        get_default_file_path(temp_default, default_output, sizeof(default_output));
        
        char output_file[512];
        if (get_filename_with_default("Output filename:", default_output, output_file, sizeof(output_file)) != 0) {
            printf("Error: Failed to read input\n");
            return 1;
        }
        
        const char* output_filename = output_file;
        
        int result = encrypt_file(selected_pad, input_file, output_filename, ascii_armor);
        free(selected_pad);
        return result;
    }
    else {
        printf("Invalid choice. Please enter 1 or 2.\n");
        return 1;
    }
}

int handle_decrypt_menu(void) {
    printf("\n=== Smart Decrypt ===\n");
    printf("Enter encrypted data (paste ASCII armor), file path, or press Enter to browse files:\n");
    
    char input_line[MAX_LINE_LENGTH];
    if (!fgets(input_line, sizeof(input_line), stdin)) {
        printf("Error: Failed to read input\n");
        return 1;
    }
    
    // Remove newline
    input_line[strcspn(input_line, "\n")] = 0;
    
    if (strlen(input_line) == 0) {
        // Empty input - launch file manager to browse for files
        char selected_file[512];
        if (launch_file_manager(get_files_directory(), selected_file, sizeof(selected_file)) != 0) {
            printf("Error: Could not launch file manager\n");
            return 1;
        }
        
        // Generate smart default output filename with files directory and use enhanced input function
        char temp_default[512];
        char default_output[512];
        strncpy(temp_default, selected_file, sizeof(temp_default) - 1);
        temp_default[sizeof(temp_default) - 1] = '\0';
        
        // Remove common encrypted extensions to get a better default
        if (strstr(temp_default, ".otp.asc")) {
            // Replace .otp.asc with original extension or no extension
            char* ext_pos = strstr(temp_default, ".otp.asc");
            *ext_pos = '\0';
        } else if (strstr(temp_default, ".otp")) {
            // Replace .otp with original extension or no extension  
            char* ext_pos = strstr(temp_default, ".otp");
            *ext_pos = '\0';
        } else {
            // No recognized encrypted extension, add .decrypted suffix
            strncat(temp_default, ".decrypted", sizeof(temp_default) - strlen(temp_default) - 1);
        }
        
        // Apply files directory default path
        get_default_file_path(temp_default, default_output, sizeof(default_output));
        
        char output_file[512];
        if (get_filename_with_default("Output filename:", default_output, output_file, sizeof(output_file)) != 0) {
            printf("Error: Failed to read input\n");
            return 1;
        }
        
        return decrypt_file(selected_file, output_file);
    }
    else if (strncmp(input_line, "-----BEGIN OTP MESSAGE-----", 27) == 0) {
        // Looks like ASCII armor - collect the full message
        char full_message[MAX_INPUT_SIZE * 4] = {0};
        strcat(full_message, input_line);
        strcat(full_message, "\n");
        
        printf("Continue pasting the message (end with -----END OTP MESSAGE-----):\n");
        
        char line[MAX_LINE_LENGTH];
        while (fgets(line, sizeof(line), stdin)) {
            strncat(full_message, line, sizeof(full_message) - strlen(full_message) - 1);
            if (strstr(line, "-----END OTP MESSAGE-----")) {
                break;
            }
        }
        
        return decrypt_text(NULL, full_message);
    }
    else {
        // Check if it looks like a file path
        if (access(input_line, R_OK) == 0) {
            // It's a valid file - decrypt it with enhanced input for output filename
            char temp_default[512];
            char default_output[512];
            strncpy(temp_default, input_line, sizeof(temp_default) - 1);
            temp_default[sizeof(temp_default) - 1] = '\0';
            
            // Remove common encrypted extensions to get a better default
            if (strstr(temp_default, ".otp.asc")) {
                // Replace .otp.asc with original extension or no extension
                char* ext_pos = strstr(temp_default, ".otp.asc");
                *ext_pos = '\0';
            } else if (strstr(temp_default, ".otp")) {
                // Replace .otp with original extension or no extension  
                char* ext_pos = strstr(temp_default, ".otp");
                *ext_pos = '\0';
            } else {
                // No recognized encrypted extension, add .decrypted suffix
                strncat(temp_default, ".decrypted", sizeof(temp_default) - strlen(temp_default) - 1);
            }
            
            // Apply files directory default path
            get_default_file_path(temp_default, default_output, sizeof(default_output));
            
            char output_file[512];
            if (get_filename_with_default("Output filename:", default_output, output_file, sizeof(output_file)) != 0) {
                printf("Error: Failed to read input\n");
                return 1;
            }
            
            return decrypt_file(input_line, output_file);
        } else {
            printf("Input not recognized as ASCII armor or valid file path.\n");
            return 1;
        }
    }
}

uint64_t parse_size_string(const char* size_str) {
    if (!size_str) return 0;
    
    char* endptr;
    double value = strtod(size_str, &endptr);
    
    if (value <= 0) return 0;
    
    // Skip whitespace
    while (*endptr && isspace(*endptr)) endptr++;
    
    uint64_t multiplier = 1;
    
    if (*endptr) {
        char unit[4];
        strncpy(unit, endptr, 3);
        unit[3] = '\0';
        
        // Convert to uppercase
        for (int i = 0; unit[i]; i++) {
            unit[i] = toupper(unit[i]);
        }
        
        if (strcmp(unit, "K") == 0 || strcmp(unit, "KB") == 0) {
            multiplier = 1024ULL;
        } else if (strcmp(unit, "M") == 0 || strcmp(unit, "MB") == 0) {
            multiplier = 1024ULL * 1024ULL;
        } else if (strcmp(unit, "G") == 0 || strcmp(unit, "GB") == 0) {
            multiplier = 1024ULL * 1024ULL * 1024ULL;
        } else if (strcmp(unit, "T") == 0 || strcmp(unit, "TB") == 0) {
            multiplier = 1024ULL * 1024ULL * 1024ULL * 1024ULL;
        } else {
            return 0; // Invalid unit
        }
    } else {
        // No unit specified, treat as bytes
        multiplier = 1;
    }
    
    return (uint64_t)(value * multiplier);
}

char* find_pad_by_prefix(const char* prefix) {
    DIR* dir = opendir(current_pads_dir);
    if (!dir) {
        printf("Error: Cannot open pads directory %s\n", current_pads_dir);
        return NULL;
    }
    
    struct dirent* entry;
    char* matches[100];  // Store up to 100 matches
    int match_count = 0;
    
    // Always try hex prefix matching first
    size_t prefix_len = strlen(prefix);
    while ((entry = readdir(dir)) != NULL && match_count < 100) {
        // Skip . and .. entries, and only process .pad files
        if (entry->d_name[0] == '.') continue;
        if (!strstr(entry->d_name, ".pad")) continue;
        if (strlen(entry->d_name) != 68) continue; // 64 char chksum + ".pad"
        
        // Compare prefix with the filename (checksum part)
        if (strncmp(entry->d_name, prefix, prefix_len) == 0) {
            matches[match_count] = malloc(65);
            strncpy(matches[match_count], entry->d_name, 64);
            matches[match_count][64] = '\0';
            match_count++;
        }
    }
    
    // Only prefix matching is supported
    
    closedir(dir);
    
    if (match_count == 0) {
        printf("No pads found matching '%s'\n", prefix);
        printf("Available pads:\n");
        char* selected = select_pad_interactive("Available pads:", "Available pads (press Enter to continue)", PAD_FILTER_ALL, 0);
        if (selected) {
            free(selected);
        }
        return NULL;
    } else if (match_count == 1) {
        char* result = matches[0];
        return result;
    } else {
        printf("Multiple matches found for '%s':\n", prefix);
        for (int i = 0; i < match_count; i++) {
            printf("  %.16s...\n", matches[i]);
        }
        printf("Please be more specific with your prefix.\n");
        
        // Free all matches and return NULL
        for (int i = 0; i < match_count; i++) {
            free(matches[i]);
        }
        return NULL;
    }
}



////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
//      PADS MENU
////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////


int show_pad_info(const char* chksum) {
    char pad_filename[MAX_HASH_LENGTH + 10];
    char state_filename[MAX_HASH_LENGTH + 10];
    
    snprintf(pad_filename, sizeof(pad_filename), "%s.pad", chksum);
    snprintf(state_filename, sizeof(state_filename), "%s.state", chksum);
    
    struct stat st;
    if (stat(pad_filename, &st) != 0) {
        printf("Pad not found: %s\n", chksum);
        return 1;
    }
    
    uint64_t used_bytes;
    read_state_offset(chksum, &used_bytes);
    
    printf("=== Pad Information ===\n");
    printf("ChkSum: %s\n", chksum);
    printf("File: %s\n", pad_filename);
    
    double size_gb = (double)st.st_size / (1024.0 * 1024.0 * 1024.0);
    double used_gb = (double)used_bytes / (1024.0 * 1024.0 * 1024.0);
    double remaining_gb = (double)(st.st_size - used_bytes) / (1024.0 * 1024.0 * 1024.0);
    
    printf("Total size: %.2f GB (%lu bytes)\n", size_gb, st.st_size);
    printf("Used: %.2f GB (%lu bytes)\n", used_gb, used_bytes);
    printf("Remaining: %.2f GB (%lu bytes)\n", remaining_gb, st.st_size - used_bytes);
    printf("Usage: %.1f%%\n", (double)used_bytes / st.st_size * 100.0);
    
    return 0;
}


void show_progress(uint64_t current, uint64_t total, time_t start_time) {
    time_t now = time(NULL);
    double elapsed = difftime(now, start_time);
    
    if (elapsed < 1.0) elapsed = 1.0; // Avoid division by zero
    
    double percentage = (double)current / total * 100.0;
    double speed = (double)current / elapsed / (1024.0 * 1024.0); // MB/s
    
    uint64_t remaining_bytes = total - current;
    double eta = remaining_bytes / (current / elapsed);
    
    printf("\rProgress: %.1f%% (%.1f MB/s, ETA: %.0fs)    ", percentage, speed, eta);
    fflush(stdout);
}

int generate_pad(uint64_t size_bytes, int display_progress) {
    // Ensure pads directory exists
    if (ensure_pads_directory() != 0) {
        printf("Error: Cannot create pads directory\n");
        return 1;
    }
    
    char temp_filename[64];
    char pad_path[MAX_HASH_LENGTH + 20];
    char state_path[MAX_HASH_LENGTH + 20];
    char chksum_hex[MAX_HASH_LENGTH];
    
    // Create temporary filename
    snprintf(temp_filename, sizeof(temp_filename), "temp_%ld.pad", time(NULL));
    
    FILE* urandom = fopen("/dev/urandom", "rb");
    if (!urandom) {
        printf("Error: Cannot open /dev/urandom\n");
        return 1;
    }
    
    FILE* pad_file = fopen(temp_filename, "wb");
    if (!pad_file) {
        printf("Error: Cannot create temporary pad file %s\n", temp_filename);
        fclose(urandom);
        return 1;
    }
    
    unsigned char buffer[64 * 1024]; // 64KB buffer
    uint64_t bytes_written = 0;
    time_t start_time = time(NULL);
    
    if (display_progress) {
        printf("Generating pad...\n");
    }
    
    while (bytes_written < size_bytes) {
        uint64_t chunk_size = sizeof(buffer);
        if (size_bytes - bytes_written < chunk_size) {
            chunk_size = size_bytes - bytes_written;
        }
        
        if (fread(buffer, 1, (size_t)chunk_size, urandom) != (size_t)chunk_size) {
            printf("Error: Failed to read from /dev/urandom\n");
            fclose(urandom);
            fclose(pad_file);
            unlink(temp_filename);
            return 1;
        }
        
        if (fwrite(buffer, 1, (size_t)chunk_size, pad_file) != (size_t)chunk_size) {
            printf("Error: Failed to write to pad file\n");
            fclose(urandom);
            fclose(pad_file);
            unlink(temp_filename);
            return 1;
        }
        
        bytes_written += chunk_size;
        
        if (display_progress && bytes_written % PROGRESS_UPDATE_INTERVAL == 0) {
            show_progress(bytes_written, size_bytes, start_time);
        }
    }
    
    if (display_progress) {
        show_progress(size_bytes, size_bytes, start_time);
        printf("\n");
    }
    
    fclose(urandom);
    fclose(pad_file);
    
    // Calculate XOR checksum of the pad file
    if (calculate_checksum(temp_filename, chksum_hex) != 0) {
        printf("Error: Cannot calculate pad checksum\n");
        unlink(temp_filename);
        return 1;
    }
    
    // Get final paths in pads directory
    get_pad_path(chksum_hex, pad_path, state_path);
    
    // Try rename first (works for same filesystem)
    if (rename(temp_filename, pad_path) != 0) {
        // If rename fails, try copy and delete (works across filesystems)
        FILE* temp_file = fopen(temp_filename, "rb");
        FILE* dest_file = fopen(pad_path, "wb");
        
        if (!temp_file || !dest_file) {
            printf("Error: Cannot copy pad file to pads directory\n");
            if (temp_file) fclose(temp_file);
            if (dest_file) fclose(dest_file);
            unlink(temp_filename);
            return 1;
        }
        
        // Copy file in chunks
        unsigned char copy_buffer[64 * 1024];
        size_t bytes_read;
        while ((bytes_read = fread(copy_buffer, 1, sizeof(copy_buffer), temp_file)) > 0) {
            if (fwrite(copy_buffer, 1, bytes_read, dest_file) != bytes_read) {
                printf("Error: Failed to copy pad file to pads directory\n");
                fclose(temp_file);
                fclose(dest_file);
                unlink(temp_filename);
                unlink(pad_path);
                return 1;
            }
        }
        
        fclose(temp_file);
        fclose(dest_file);
        
        // Remove temporary file after successful copy
        unlink(temp_filename);
    }
    
    // Set pad file to read-only
    if (chmod(pad_path, S_IRUSR) != 0) {
        printf("Warning: Cannot set pad file to read-only\n");
    }
    
    // Initialize state file with offset 32 (first 32 bytes reserved for checksum encryption)
    FILE* state_file = fopen(state_path, "wb");
    if (state_file) {
        uint64_t reserved_bytes = 32;
        fwrite(&reserved_bytes, sizeof(uint64_t), 1, state_file);
        fclose(state_file);
    } else {
        printf("Error: Failed to create state file\n");
        unlink(pad_path);
        return 1;
    }
    
    double size_gb = (double)size_bytes / (1024.0 * 1024.0 * 1024.0);
    printf("Generated pad: %s (%.2f GB)\n", pad_path, size_gb);
    printf("Pad checksum: %s\n", chksum_hex);
    printf("State file: %s\n", state_path);
    printf("Pad file set to read-only\n");
    printf("Use 'Add entropy' in Pads menu to enhance randomness.\n");
    
    return 0;
}

// In-place pad entropy addition using Chacha20
int add_entropy_to_pad(const char* pad_chksum, const unsigned char* entropy_data,
                      size_t entropy_size, int display_progress) {
    if (!pad_chksum || !entropy_data || entropy_size < 512) {
        printf("Error: Invalid entropy data or insufficient entropy\n");
        return 1;
    }
    
    // Derive Chacha20 key and nonce from entropy
    unsigned char key[32], nonce[12];
    if (derive_chacha20_params(entropy_data, entropy_size, key, nonce) != 0) {
        printf("Error: Failed to derive Chacha20 parameters from entropy\n");
        return 1;
    }
    
    // Get pad file path
    char pad_path[1024];
    char state_path[1024];
    get_pad_path(pad_chksum, pad_path, state_path);
    
    // Check if pad exists and get size
    struct stat pad_stat;
    if (stat(pad_path, &pad_stat) != 0) {
        printf("Error: Pad file not found: %s\n", pad_path);
        return 1;
    }
    
    uint64_t pad_size = pad_stat.st_size;
    
    // Open pad file for read/write
    FILE* pad_file = fopen(pad_path, "r+b");
    if (!pad_file) {
        printf("Error: Cannot open pad file for modification: %s\n", pad_path);
        printf("Note: Pad files are read-only. Temporarily changing permissions...\n");
        
        // Try to make writable temporarily
        if (chmod(pad_path, S_IRUSR | S_IWUSR) != 0) {
            printf("Error: Cannot change pad file permissions\n");
            return 1;
        }
        
        pad_file = fopen(pad_path, "r+b");
        if (!pad_file) {
            printf("Error: Still cannot open pad file for modification\n");
            // Restore read-only
            chmod(pad_path, S_IRUSR);
            return 1;
        }
    }
    
    if (display_progress) {
        printf("Adding entropy to pad using Chacha20...\n");
        printf("Pad size: %.2f GB (%lu bytes)\n", (double)pad_size / (1024.0*1024.0*1024.0), pad_size);
    }
    
    // Process pad in chunks
    unsigned char buffer[64 * 1024]; // 64KB chunks
    unsigned char keystream[64 * 1024];
    uint64_t offset = 0;
    uint32_t counter = 0;
    time_t start_time = time(NULL);
    
    while (offset < pad_size) {
        size_t chunk_size = sizeof(buffer);
        if (pad_size - offset < chunk_size) {
            chunk_size = pad_size - offset;
        }
        
        // Read current pad data
        if (fread(buffer, 1, chunk_size, pad_file) != chunk_size) {
            printf("Error: Cannot read pad data at offset %lu\n", offset);
            fclose(pad_file);
            chmod(pad_path, S_IRUSR); // Restore read-only
            return 1;
        }
        
        // Generate keystream for this chunk
        if (chacha20_encrypt(key, counter, nonce, buffer, keystream, chunk_size) != 0) {
            printf("Error: Chacha20 keystream generation failed\n");
            fclose(pad_file);
            chmod(pad_path, S_IRUSR);
            return 1;
        }
        
        // XOR existing pad with keystream (adds entropy)
        for (size_t i = 0; i < chunk_size; i++) {
            buffer[i] ^= keystream[i];
        }
        
        // Seek back and write modified data
        if (fseek(pad_file, offset, SEEK_SET) != 0) {
            printf("Error: Cannot seek to offset %lu\n", offset);
            fclose(pad_file);
            chmod(pad_path, S_IRUSR);
            return 1;
        }
        
        if (fwrite(buffer, 1, chunk_size, pad_file) != chunk_size) {
            printf("Error: Cannot write modified pad data\n");
            fclose(pad_file);
            chmod(pad_path, S_IRUSR);
            return 1;
        }
        
        offset += chunk_size;
        counter += (chunk_size + 63) / 64; // Round up for block count
        
        // Show progress for large pads
        if (display_progress && offset % (64 * 1024 * 1024) == 0) { // Every 64MB
            show_progress(offset, pad_size, start_time);
        }
    }
    
    fclose(pad_file);
    
    // Restore read-only permissions
    if (chmod(pad_path, S_IRUSR) != 0) {
        printf("Warning: Cannot restore pad file to read-only\n");
    }
    
    if (display_progress) {
        show_progress(pad_size, pad_size, start_time);
        printf("\n✓ Entropy successfully added to pad using Chacha20\n");
        printf("✓ Pad integrity maintained\n");
        printf("✓ %zu bytes of entropy distributed across entire pad\n", entropy_size);
        printf("✓ Pad restored to read-only mode\n");
        
        // Update checksum after entropy addition
        printf("\n🔄 Updating pad checksum...\n");
        char new_chksum[65];
        int checksum_result = update_pad_checksum_after_entropy(pad_chksum, new_chksum);
        
        if (checksum_result == 0) {
            printf("✓ Pad checksum updated successfully\n");
            printf("  Old checksum: %.16s...\n", pad_chksum);
            printf("  New checksum: %.16s...\n", new_chksum);
            printf("✓ Pad files renamed to new checksum\n");
        } else if (checksum_result == 2) {
            printf("ℹ Checksum unchanged (unusual but not an error)\n");
        } else {
            printf("⚠ Warning: Checksum update failed (entropy was added successfully)\n");
            printf("  You may need to manually handle the checksum update\n");
            return 1; // Report error despite successful entropy addition
        }
    }
    
    return 0;
}



////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
//      ENCRYPT AND DECRYPT
////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////


int encrypt_text(const char* pad_identifier, const char* input_text) {
    char* pad_chksum = find_pad_by_prefix(pad_identifier);
    if (!pad_chksum) {
        return 1;
    }
    
    char text_buffer[MAX_INPUT_SIZE];
    char chksum_hex[MAX_HASH_LENGTH];
    uint64_t current_offset;
    
    char pad_path[MAX_HASH_LENGTH + 20];
    char state_path[MAX_HASH_LENGTH + 20];
    get_pad_path(pad_chksum, pad_path, state_path);
    
    // Check if pad file exists
    if (access(pad_path, R_OK) != 0) {
        printf("Error: Pad file %s not found\n", pad_path);
        free(pad_chksum);
        return 1;
    }
    
    // Read current offset
    if (read_state_offset(pad_chksum, &current_offset) != 0) {
        printf("Error: Cannot read state file\n");
        free(pad_chksum);
        return 1;
    }
    
    // Ensure we never encrypt before offset 32 (reserved for checksum encryption)
    if (current_offset < 32) {
        printf("Warning: State offset below reserved area, adjusting to 32\n");
        current_offset = 32;
        if (write_state_offset(pad_chksum, current_offset) != 0) {
            printf("Warning: Failed to update state file\n");
        }
    }
    
    // Calculate XOR checksum of pad file
    if (calculate_checksum(pad_path, chksum_hex) != 0) {
        printf("Error: Cannot calculate pad checksum\n");
        free(pad_chksum);
        return 1;
    }
    
    // Get input text - either from parameter or user input
    if (input_text != NULL) {
        // Use provided text
        strncpy(text_buffer, input_text, sizeof(text_buffer) - 1);
        text_buffer[sizeof(text_buffer) - 1] = '\0';
    } else {
        // Get input text from user (interactive mode)
        if (is_interactive_mode) {
            printf("\nText input options:\n");
            printf(" 1. Type text directly\n");
            printf(" 2. Use text editor\n");
            printf("Enter choice (1-2): ");
        }
        
        char input_choice[10] = "1"; // Default to direct input in non-interactive mode
        if (is_interactive_mode) {
            if (!fgets(input_choice, sizeof(input_choice), stdin)) {
                printf("Error: Failed to read input\n");
                free(pad_chksum);
                return 1;
            }
        }
        
        if (is_interactive_mode && atoi(input_choice) == 2) {
            // Use text editor
            if (launch_text_editor(NULL, text_buffer, sizeof(text_buffer)) != 0) {
                if (is_interactive_mode) {
                    printf("Falling back to direct text input.\n");
                    printf("Enter text to encrypt: ");
                }
                fflush(stdout);
                
                if (fgets(text_buffer, sizeof(text_buffer), stdin) == NULL) {
                    printf("Error: Failed to read input\n");
                    free(pad_chksum);
                    return 1;
                }
                
                // Remove newline if present
                size_t len = strlen(text_buffer);
                if (len > 0 && text_buffer[len - 1] == '\n') {
                    text_buffer[len - 1] = '\0';
                }
            }
        } else {
            // Direct text input
            if (is_interactive_mode) {
                printf("Enter text to encrypt: ");
                fflush(stdout);
            }
            
            if (fgets(text_buffer, sizeof(text_buffer), stdin) == NULL) {
                printf("Error: Failed to read input\n");
                free(pad_chksum);
                return 1;
            }
            
            // Remove newline if present
            size_t len = strlen(text_buffer);
            if (len > 0 && text_buffer[len - 1] == '\n') {
                text_buffer[len - 1] = '\0';
            }
        }
    }
    
    size_t input_len = strlen(text_buffer);
    if (input_len == 0) {
        printf("Error: No input provided\n");
        free(pad_chksum);
        return 1;
    }
    
    // Check if we have enough pad space
    struct stat pad_stat;
    if (stat(pad_path, &pad_stat) != 0) {
        printf("Error: Cannot get pad file size\n");
        free(pad_chksum);
        return 1;
    }
    
    if (current_offset + input_len > (uint64_t)pad_stat.st_size) {
        printf("Error: Not enough pad space remaining\n");
        printf("Need: %lu bytes, Available: %lu bytes\n", 
               input_len, (uint64_t)pad_stat.st_size - current_offset);
        free(pad_chksum);
        return 1;
    }
    
    // Read pad data at current offset
    FILE* pad_file = fopen(pad_path, "rb");
    if (!pad_file) {
        printf("Error: Cannot open pad file\n");
        free(pad_chksum);
        return 1;
    }
    
    if (fseek(pad_file, current_offset, SEEK_SET) != 0) {
        printf("Error: Cannot seek to offset in pad file\n");
        fclose(pad_file);
        free(pad_chksum);
        return 1;
    }
    
    unsigned char* pad_data = malloc(input_len);
    if (fread(pad_data, 1, input_len, pad_file) != input_len) {
        printf("Error: Cannot read pad data\n");
        free(pad_data);
        fclose(pad_file);
        free(pad_chksum);
        return 1;
    }
    fclose(pad_file);
    
    // Use universal XOR operation for encryption
    unsigned char* ciphertext = malloc(input_len);
    if (universal_xor_operation((const unsigned char*)text_buffer, input_len, pad_data, ciphertext) != 0) {
        printf("Error: Encryption operation failed\n");
        free(pad_data);
        free(ciphertext);
        free(pad_chksum);
        return 1;
    }
    
    // Update state offset
    if (write_state_offset(pad_chksum, current_offset + input_len) != 0) {
        printf("Warning: Failed to update state file\n");
    }
    
    // Use universal ASCII armor generator
    char* ascii_output;
    if (generate_ascii_armor(chksum_hex, current_offset, ciphertext, input_len, &ascii_output) != 0) {
        printf("Error: Failed to generate ASCII armor\n");
        free(pad_data);
        free(ciphertext);
        free(pad_chksum);
        return 1;
    }
    
    // Output with appropriate formatting - clean format for piping, spaced format for interactive
    int is_interactive = (input_text == NULL); // Interactive if no input_text provided
    
    if (is_interactive) {
        printf("\n\n\n%s\n\n", ascii_output);
    } else {
        printf("%s\n", ascii_output);  // Add newline for proper piping with tee
    }
    
    // Cleanup
    free(pad_data);
    free(ciphertext);
    free(ascii_output);
    free(pad_chksum);
    
    return 0;
}

int decrypt_text(const char* pad_identifier, const char* encrypted_message) {
    // Use universal decrypt function with mode based on global interactive mode detection
    (void)pad_identifier; // Suppress unused parameter warning - chksum comes from message
    decrypt_mode_t mode = is_interactive_mode ? DECRYPT_MODE_INTERACTIVE : DECRYPT_MODE_SILENT;
    return universal_decrypt(encrypted_message, NULL, mode);
}

int encrypt_file(const char* pad_identifier, const char* input_file, const char* output_file, int ascii_armor) {
    char* pad_chksum = find_pad_by_prefix(pad_identifier);
    if (!pad_chksum) {
        return 1;
    }
    
    char chksum_hex[MAX_HASH_LENGTH];
    uint64_t current_offset;
    
    char pad_path[MAX_HASH_LENGTH + 20];
    char state_path[MAX_HASH_LENGTH + 20];
    get_pad_path(pad_chksum, pad_path, state_path);
    
    // Check if input file exists and get its size
    struct stat input_stat;
    if (stat(input_file, &input_stat) != 0) {
        printf("Error: Input file %s not found\n", input_file);
        free(pad_chksum);
        return 1;
    }
    
    uint64_t file_size = input_stat.st_size;
    if (file_size == 0) {
        printf("Error: Input file is empty\n");
        free(pad_chksum);
        return 1;
    }
    
    // Check if pad file exists
    if (access(pad_path, R_OK) != 0) {
        printf("Error: Pad file %s not found\n", pad_path);
        free(pad_chksum);
        return 1;
    }
    
    // Read current offset
    if (read_state_offset(pad_chksum, &current_offset) != 0) {
        printf("Error: Cannot read state file\n");
        free(pad_chksum);
        return 1;
    }
    
    // Ensure we never encrypt before offset 32
    if (current_offset < 32) {
        printf("Warning: State offset below reserved area, adjusting to 32\n");
        current_offset = 32;
        if (write_state_offset(pad_chksum, current_offset) != 0) {
            printf("Warning: Failed to update state file\n");
        }
    }
    
    // Calculate XOR checksum of pad file
    if (calculate_checksum(pad_path, chksum_hex) != 0) {
        printf("Error: Cannot calculate pad checksum\n");
        free(pad_chksum);
        return 1;
    }
    
    // Check if we have enough pad space
    struct stat pad_stat;
    if (stat(pad_path, &pad_stat) != 0) {
        printf("Error: Cannot get pad file size\n");
        free(pad_chksum);
        return 1;
    }
    
    if (current_offset + file_size > (uint64_t)pad_stat.st_size) {
        printf("Error: Not enough pad space remaining\n");
        printf("Need: %lu bytes, Available: %lu bytes\n", 
               file_size, (uint64_t)pad_stat.st_size - current_offset);
        free(pad_chksum);
        return 1;
    }
    
    // Generate output filename if not specified, using files directory
    char default_output[512];
    if (output_file == NULL) {
        char temp_output[512];
        if (ascii_armor) {
            snprintf(temp_output, sizeof(temp_output), "%s.otp.asc", input_file);
        } else {
            snprintf(temp_output, sizeof(temp_output), "%s.otp", input_file);
        }
        
        // Apply files directory default path
        get_default_file_path(temp_output, default_output, sizeof(default_output));
        output_file = default_output;
    }
    
    // Open input file
    FILE* input_fp = fopen(input_file, "rb");
    if (!input_fp) {
        printf("Error: Cannot open input file %s\n", input_file);
        free(pad_chksum);
        return 1;
    }
    
    // Open pad file
    FILE* pad_file = fopen(pad_path, "rb");
    if (!pad_file) {
        printf("Error: Cannot open pad file\n");
        fclose(input_fp);
        free(pad_chksum);
        return 1;
    }
    
    if (fseek(pad_file, current_offset, SEEK_SET) != 0) {
        printf("Error: Cannot seek to offset in pad file\n");
        fclose(input_fp);
        fclose(pad_file);
        free(pad_chksum);
        return 1;
    }
    
    // Read and encrypt file
    unsigned char buffer[64 * 1024];
    unsigned char pad_buffer[64 * 1024];
    unsigned char* encrypted_data = malloc(file_size);
    uint64_t bytes_processed = 0;
    time_t start_time = time(NULL);
    
    printf("Encrypting %s...\n", input_file);
    
    while (bytes_processed < file_size) {
        uint64_t chunk_size = sizeof(buffer);
        if (file_size - bytes_processed < chunk_size) {
            chunk_size = file_size - bytes_processed;
        }
        
        // Read file data
        if (fread(buffer, 1, chunk_size, input_fp) != chunk_size) {
            printf("Error: Cannot read input file data\n");
            free(encrypted_data);
            fclose(input_fp);
            fclose(pad_file);
            free(pad_chksum);
            return 1;
        }
        
        // Read pad data
        if (fread(pad_buffer, 1, chunk_size, pad_file) != chunk_size) {
            printf("Error: Cannot read pad data\n");
            free(encrypted_data);
            fclose(input_fp);
            fclose(pad_file);
            free(pad_chksum);
            return 1;
        }
        
        // Use universal XOR operation for encryption
        if (universal_xor_operation(buffer, chunk_size, pad_buffer, &encrypted_data[bytes_processed]) != 0) {
            printf("Error: Encryption operation failed\n");
            free(encrypted_data);
            fclose(input_fp);
            fclose(pad_file);
            free(pad_chksum);
            return 1;
        }
        
        bytes_processed += chunk_size;
        
        // Show progress for large files (> 10MB)
        if (file_size > 10 * 1024 * 1024 && bytes_processed % (1024 * 1024) == 0) {
            show_progress(bytes_processed, file_size, start_time);
        }
    }
    
    if (file_size > 10 * 1024 * 1024) {
        show_progress(file_size, file_size, start_time);
        printf("\n");
    }
    
    fclose(input_fp);
    fclose(pad_file);
    
    // Write output file
    if (ascii_armor) {
        // ASCII armored format - same as message format
        FILE* output_fp = fopen(output_file, "w");
        if (!output_fp) {
            printf("Error: Cannot create output file %s\n", output_file);
            free(encrypted_data);
            free(pad_chksum);
            return 1;
        }
        
        // Use universal ASCII armor generator
        char* ascii_output;
        if (generate_ascii_armor(chksum_hex, current_offset, encrypted_data, file_size, &ascii_output) != 0) {
            printf("Error: Failed to generate ASCII armor\n");
            fclose(output_fp);
            free(encrypted_data);
            free(pad_chksum);
            return 1;
        }
        
        // Write the ASCII armored output to file
        fprintf(output_fp, "%s", ascii_output);
        
        fclose(output_fp);
        free(ascii_output);
    } else {
        // Binary format
        FILE* output_fp = fopen(output_file, "wb");
        if (!output_fp) {
            printf("Error: Cannot create output file %s\n", output_file);
            free(encrypted_data);
            free(pad_chksum);
            return 1;
        }
        
        // Write binary header
        // Magic: "OTP\0"
        fwrite("OTP\0", 1, 4, output_fp);
        
        // Version: 2 bytes
        uint16_t version = 1;
        fwrite(&version, sizeof(uint16_t), 1, output_fp);
        
        // Pad checksum: 32 bytes (binary)
        unsigned char pad_chksum_bin[32];
        for (int i = 0; i < 32; i++) {
            sscanf(chksum_hex + i*2, "%2hhx", &pad_chksum_bin[i]);
        }
        fwrite(pad_chksum_bin, 1, 32, output_fp);
        
        // Pad offset: 8 bytes
        fwrite(&current_offset, sizeof(uint64_t), 1, output_fp);
        
        
        // File mode: 4 bytes
        uint32_t file_mode = input_stat.st_mode;
        fwrite(&file_mode, sizeof(uint32_t), 1, output_fp);
        
        // File size: 8 bytes
        fwrite(&file_size, sizeof(uint64_t), 1, output_fp);
        
        // Encrypted data
        fwrite(encrypted_data, 1, file_size, output_fp);
        
        fclose(output_fp);
    }
    
    // Update state offset
    if (write_state_offset(pad_chksum, current_offset + file_size) != 0) {
        printf("Warning: Failed to update state file\n");
    }
    
    printf("File encrypted successfully: %s\n", output_file);
    if (ascii_armor) {
        printf("Format: ASCII armored (.otp.asc)\n");
    } else {
        printf("Format: Binary (.otp)\n");
    }
    
    // Cleanup
    free(encrypted_data);
    free(pad_chksum);
    
    return 0;
}

int decrypt_file(const char* input_file, const char* output_file) {
    // Check if input file exists
    if (access(input_file, R_OK) != 0) {
        printf("Error: Input file %s not found\n", input_file);
        return 1;
    }
    
    FILE* input_fp = fopen(input_file, "rb");
    if (!input_fp) {
        printf("Error: Cannot open input file %s\n", input_file);
        return 1;
    }
    
    // Read first few bytes to determine format
    char magic[4];
    if (fread(magic, 1, 4, input_fp) != 4) {
        printf("Error: Cannot read file header\n");
        fclose(input_fp);
        return 1;
    }
    
    fseek(input_fp, 0, SEEK_SET); // Reset to beginning
    
    if (memcmp(magic, "OTP\0", 4) == 0) {
        // Binary format
        return decrypt_binary_file(input_fp, output_file);
    } else {
        // Assume ASCII armored format, read entire file as text
        fclose(input_fp);
        return decrypt_ascii_file(input_file, output_file);
    }
}

int decrypt_binary_file(FILE* input_fp, const char* output_file) {
    // Read binary header
    char magic[4];
    uint16_t version;
    unsigned char pad_chksum_bin[32];
    uint64_t pad_offset;
    uint32_t file_mode;
    uint64_t file_size;
    
    if (fread(magic, 1, 4, input_fp) != 4 ||
        fread(&version, sizeof(uint16_t), 1, input_fp) != 1 ||
        fread(pad_chksum_bin, 1, 32, input_fp) != 32 ||
        fread(&pad_offset, sizeof(uint64_t), 1, input_fp) != 1 ||
        fread(&file_mode, sizeof(uint32_t), 1, input_fp) != 1 ||
        fread(&file_size, sizeof(uint64_t), 1, input_fp) != 1) {
        printf("Error: Cannot read binary header\n");
        fclose(input_fp);
        return 1;
    }
    
    if (memcmp(magic, "OTP\0", 4) != 0) {
        printf("Error: Invalid binary format\n");
        fclose(input_fp);
        return 1;
    }
    
    // Convert binary checksum to hex
    char pad_chksum_hex[65];
    for (int i = 0; i < 32; i++) {
        sprintf(pad_chksum_hex + i*2, "%02x", pad_chksum_bin[i]);
    }
    pad_chksum_hex[64] = '\0';
    
    printf("Decrypting binary file...\n");
    printf("File size: %lu bytes\n", file_size);
    
    // Check if we have the required pad
    char pad_path[MAX_HASH_LENGTH + 20];
    char state_path[MAX_HASH_LENGTH + 20];
    get_pad_path(pad_chksum_hex, pad_path, state_path);
    
    if (access(pad_path, R_OK) != 0) {
        printf("Error: Required pad not found: %s\n", pad_chksum_hex);
        printf("Available pads:\n");
        char* selected = select_pad_interactive("Available pads:", "Available pads (press Enter to continue)", PAD_FILTER_ALL, 0);
        if (selected) {
            free(selected);
        }
        fclose(input_fp);
        return 1;
    }
    
    // Determine output filename
    char default_output[512];
    if (output_file == NULL) {
        snprintf(default_output, sizeof(default_output), "decrypted.bin");
        output_file = default_output;
    }
    
    // Read encrypted data
    unsigned char* encrypted_data = malloc(file_size);
    if (fread(encrypted_data, 1, file_size, input_fp) != file_size) {
        printf("Error: Cannot read encrypted data\n");
        free(encrypted_data);
        fclose(input_fp);
        return 1;
    }
    fclose(input_fp);
    
    // Open pad file and decrypt
    FILE* pad_file = fopen(pad_path, "rb");
    if (!pad_file) {
        printf("Error: Cannot open pad file\n");
        free(encrypted_data);
        return 1;
    }
    
    if (fseek(pad_file, pad_offset, SEEK_SET) != 0) {
        printf("Error: Cannot seek to offset in pad file\n");
        free(encrypted_data);
        fclose(pad_file);
        return 1;
    }
    
    unsigned char* pad_data = malloc(file_size);
    if (fread(pad_data, 1, file_size, pad_file) != file_size) {
        printf("Error: Cannot read pad data\n");
        free(encrypted_data);
        free(pad_data);
        fclose(pad_file);
        return 1;
    }
    fclose(pad_file);
    
    // Use universal XOR operation for decryption
    if (universal_xor_operation(encrypted_data, file_size, pad_data, encrypted_data) != 0) {
        printf("Error: Decryption operation failed\n");
        free(encrypted_data);
        free(pad_data);
        return 1;
    }
    
    // Write decrypted file
    FILE* output_fp = fopen(output_file, "wb");
    if (!output_fp) {
        printf("Error: Cannot create output file %s\n", output_file);
        free(encrypted_data);
        free(pad_data);
        return 1;
    }
    
    if (fwrite(encrypted_data, 1, file_size, output_fp) != file_size) {
        printf("Error: Cannot write decrypted data\n");
        free(encrypted_data);
        free(pad_data);
        fclose(output_fp);
        return 1;
    }
    fclose(output_fp);
    
    // Restore file permissions
    if (chmod(output_file, file_mode) != 0) {
        printf("Warning: Cannot restore file permissions\n");
    }
    
    printf("File decrypted successfully: %s\n", output_file);
    printf("Restored permissions and metadata\n");
    
    // Cleanup
    free(encrypted_data);
    free(pad_data);
    
    return 0;
}

int decrypt_ascii_file(const char* input_file, const char* output_file) {
    // Use universal decrypt function with file-to-file mode
    return universal_decrypt(input_file, output_file, DECRYPT_MODE_FILE_TO_FILE);
}

int read_state_offset(const char* pad_chksum, uint64_t* offset) {
    char state_filename[1024];
    snprintf(state_filename, sizeof(state_filename), "%s/%s.state", current_pads_dir, pad_chksum);
    
    FILE* state_file = fopen(state_filename, "rb");
    if (!state_file) {
        *offset = 0;
        return 0;
    }
    
    if (fread(offset, sizeof(uint64_t), 1, state_file) != 1) {
        fclose(state_file);
        *offset = 0;
        return 0;
    }
    
    fclose(state_file);
    return 0;
}

int write_state_offset(const char* pad_chksum, uint64_t offset) {
    char state_filename[1024];
    snprintf(state_filename, sizeof(state_filename), "%s/%s.state", current_pads_dir, pad_chksum);
    
    FILE* state_file = fopen(state_filename, "wb");
    if (!state_file) {
        return 1;
    }
    
    if (fwrite(&offset, sizeof(uint64_t), 1, state_file) != 1) {
        fclose(state_file);
        return 1;
    }
    
    fclose(state_file);
    return 0;
}


////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
//      DIRECTORY MANAGEMENT FUNCTIONS
////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////

int ensure_pads_directory(void) {
    struct stat st = {0};
    if (stat(current_pads_dir, &st) == -1) {
        if (mkdir(current_pads_dir, 0755) != 0) {
            return 1;
        }
    }
    return 0;
}

const char* get_files_directory(void) {
    struct stat st = {0};
    if (stat(FILES_DIR, &st) == 0 && S_ISDIR(st.st_mode)) {
        return FILES_DIR;
    }
    return "."; // Fall back to current directory
}

void get_default_file_path(const char* filename, char* result_path, size_t result_size) {
    const char* files_dir = get_files_directory();
    
    // If filename already has a path (contains '/'), use it as-is
    if (strchr(filename, '/') != NULL) {
        strncpy(result_path, filename, result_size - 1);
        result_path[result_size - 1] = '\0';
        return;
    }
    
    // Otherwise, prepend the files directory
    snprintf(result_path, result_size, "%s/%s", files_dir, filename);
}

void get_pad_path(const char* chksum, char* pad_path, char* state_path) {
    snprintf(pad_path, 1024, "%s/%s.pad", current_pads_dir, chksum);
    snprintf(state_path, 1024, "%s/%s.state", current_pads_dir, chksum);
}

// Stdin detection functions implementation
int has_stdin_data(void) {
    // Check if stdin is a pipe/redirect (not a terminal)
    if (!isatty(STDIN_FILENO)) {
        return 1;
    }
    return 0;
}

char* read_stdin_text(void) {
    size_t capacity = 4096;
    size_t length = 0;
    char* buffer = malloc(capacity);
    
    if (!buffer) {
        return NULL;
    }
    
    char chunk[1024];
    while (fgets(chunk, sizeof(chunk), stdin)) {
        size_t chunk_len = strlen(chunk);
        
        // Ensure we have enough capacity
        while (length + chunk_len >= capacity) {
            capacity *= 2;
            char* new_buffer = realloc(buffer, capacity);
            if (!new_buffer) {
                free(buffer);
                return NULL;
            }
            buffer = new_buffer;
        }
        
        strcpy(buffer + length, chunk);
        length += chunk_len;
    }
    
    // Remove trailing newline if present
    if (length > 0 && buffer[length - 1] == '\n') {
        buffer[length - 1] = '\0';
        length--;
    }
    
    // If empty, free and return NULL
    if (length == 0) {
        free(buffer);
        return NULL;
    }
    
    return buffer;
}

int pipe_mode(int argc, char* argv[], const char* piped_text) {
    (void)argc; // Suppress unused parameter warning
    (void)argv; // Suppress unused parameter warning
    
    // Check if we have a default pad configured
    char* default_pad = get_default_pad_path();
    if (default_pad) {
        // Verify the default pad exists and extract checksum
        if (access(default_pad, R_OK) == 0) {
            // Extract checksum from pad filename
            char* filename = strrchr(default_pad, '/');
            if (!filename) filename = default_pad;
            else filename++; // Skip the '/'
            
            // Extract checksum (remove .pad extension)
            if (strlen(filename) >= 68 && strstr(filename, ".pad")) {
                char pad_checksum[65];
                strncpy(pad_checksum, filename, 64);
                pad_checksum[64] = '\0';
                
                free(default_pad);
                
                // Encrypt using the default pad (silent mode)
                return encrypt_text(pad_checksum, piped_text);
            }
        }
        
        fprintf(stderr, "Error: Default pad not found or invalid: %s\n", default_pad);
        free(default_pad);
        return 1;
    }
    
    fprintf(stderr, "Error: No default pad configured for pipe mode\n");
    fprintf(stderr, "Configure a default pad in ~/.otp/otp.conf\n");
    return 1;
}

// Preferences management functions implementation
int load_preferences(void) {
    char* home_dir = getenv("HOME");
    if (!home_dir) {
        return 1; // No home directory
    }
    
    char preferences_dir[1024];
    char preferences_file[2048];  // Increased buffer size to accommodate longer paths
    snprintf(preferences_dir, sizeof(preferences_dir), "%s/.otp", home_dir);
    snprintf(preferences_file, sizeof(preferences_file), "%s/otp.conf", preferences_dir);
    
    FILE* file = fopen(preferences_file, "r");
    if (!file) {
        // No preferences file exists - create it and set first pad as default
        
        // Create .otp directory if it doesn't exist
        struct stat st = {0};
        if (stat(preferences_dir, &st) == -1) {
            if (mkdir(preferences_dir, 0755) != 0) {
                return 1;
            }
        }
        
        // Find the first available pad to set as default
        DIR* dir = opendir(current_pads_dir);
        if (dir) {
            struct dirent* entry;
            char first_pad_path[1024];
            int found_pad = 0;
            
            while ((entry = readdir(dir)) != NULL && !found_pad) {
                if (strstr(entry->d_name, ".pad") && strlen(entry->d_name) == 68) {
                    // Found a pad file - construct full absolute path
                    if (current_pads_dir[0] == '/') {
                        // Already absolute path
                        int ret = snprintf(first_pad_path, sizeof(first_pad_path), "%s/%s", current_pads_dir, entry->d_name);
                        if (ret >= (int)sizeof(first_pad_path)) {
                            // Path was truncated, skip this entry
                            continue;
                        }
                    } else {
                        // Relative path - make it absolute
                        char current_dir[512];
                        if (getcwd(current_dir, sizeof(current_dir))) {
                            int ret = snprintf(first_pad_path, sizeof(first_pad_path), "%s/%s/%s", current_dir, current_pads_dir, entry->d_name);
                            if (ret >= (int)sizeof(first_pad_path)) {
                                // Path was truncated, skip this entry
                                continue;
                            }
                        } else {
                            // Fallback to relative path
                            int ret = snprintf(first_pad_path, sizeof(first_pad_path), "%s/%s", current_pads_dir, entry->d_name);
                            if (ret >= (int)sizeof(first_pad_path)) {
                                // Path was truncated, skip this entry
                                continue;
                            }
                        }
                    }
                    strncpy(default_pad_path, first_pad_path, sizeof(default_pad_path) - 1);
                    default_pad_path[sizeof(default_pad_path) - 1] = '\0';
                    found_pad = 1;
                }
            }
            closedir(dir);
            
            // Create the preferences file with the default pad
            if (found_pad) {
                save_preferences();
            }
        }
        
        return 0; // Successfully initialized
    }
    
    char line[1024];
    while (fgets(line, sizeof(line), file)) {
        // Remove newline
        line[strcspn(line, "\n")] = 0;
        
        // Skip empty lines and comments
        if (strlen(line) == 0 || line[0] == '#') {
            continue;
        }
        
        // Parse key=value pairs
        char* equals = strchr(line, '=');
        if (equals) {
            *equals = '\0';
            char* key = line;
            char* value = equals + 1;
            
            // Trim whitespace
            while (*key == ' ' || *key == '\t') key++;
            while (*value == ' ' || *value == '\t') value++;
            
            if (strcmp(key, "default_pad") == 0) {
                strncpy(default_pad_path, value, sizeof(default_pad_path) - 1);
                default_pad_path[sizeof(default_pad_path) - 1] = '\0';
            }
        }
    }
    
    fclose(file);
    return 0;
}

int save_preferences(void) {
    char* home_dir = getenv("HOME");
    if (!home_dir) {
        return 1;
    }
    
    char preferences_dir[1024];
    char preferences_file[2048];  // Increased buffer size to accommodate longer paths
    snprintf(preferences_dir, sizeof(preferences_dir), "%s/.otp", home_dir);
    snprintf(preferences_file, sizeof(preferences_file), "%s/otp.conf", preferences_dir);
    
    // Create .otp directory if it doesn't exist
    struct stat st = {0};
    if (stat(preferences_dir, &st) == -1) {
        if (mkdir(preferences_dir, 0755) != 0) {
            return 1;
        }
    }
    
    FILE* file = fopen(preferences_file, "w");
    if (!file) {
        return 1;
    }
    
    fprintf(file, "# OTP Preferences File\n");
    fprintf(file, "# This file is automatically generated and updated by the OTP program\n\n");
    
    if (strlen(default_pad_path) > 0) {
        fprintf(file, "default_pad=%s\n", default_pad_path);
    }
    
    fclose(file);
    return 0;
}

char* get_preference(const char* key) {
    if (strcmp(key, "default_pad") == 0) {
        if (strlen(default_pad_path) > 0) {
            return strdup(default_pad_path);
        }
    }
    return NULL;
}

int set_preference(const char* key, const char* value) {
    if (strcmp(key, "default_pad") == 0) {
        if (value) {
            strncpy(default_pad_path, value, sizeof(default_pad_path) - 1);
            default_pad_path[sizeof(default_pad_path) - 1] = '\0';
        } else {
            default_pad_path[0] = '\0';
        }
        return save_preferences();
    }
    return 1;
}

char* get_default_pad_path(void) {
    if (strlen(default_pad_path) > 0) {
        return strdup(default_pad_path);
    }
    return NULL;
}

int set_default_pad_path(const char* pad_path) {
    if (!pad_path) {
        return set_preference("default_pad", NULL);
    }
    
    // Ensure we store the full absolute path
    char absolute_path[1024];
    if (pad_path[0] == '/') {
        // Already absolute path
        strncpy(absolute_path, pad_path, sizeof(absolute_path) - 1);
        absolute_path[sizeof(absolute_path) - 1] = '\0';
    } else {
        // Relative path - make it absolute
        char current_dir[512];
        if (getcwd(current_dir, sizeof(current_dir))) {
            snprintf(absolute_path, sizeof(absolute_path), "%s/%s", current_dir, pad_path);
        } else {
            // Fallback to using the path as-is if getcwd fails
            strncpy(absolute_path, pad_path, sizeof(absolute_path) - 1);
            absolute_path[sizeof(absolute_path) - 1] = '\0';
        }
    }
    
    return set_preference("default_pad", absolute_path);
}

// OTP thumb drive detection function implementation
int detect_otp_thumb_drive(char* otp_drive_path, size_t path_size) {
    const char* mount_dirs[] = {"/media", "/run/media", "/mnt", NULL};
    
    for (int mount_idx = 0; mount_dirs[mount_idx] != NULL; mount_idx++) {
        DIR* mount_dir = opendir(mount_dirs[mount_idx]);
        if (!mount_dir) continue;
        
        struct dirent* mount_entry;
        while ((mount_entry = readdir(mount_dir)) != NULL) {
            if (mount_entry->d_name[0] == '.') continue;
            
            char mount_path[1024];  // Increased buffer size
            snprintf(mount_path, sizeof(mount_path), "%s/%s", mount_dirs[mount_idx], mount_entry->d_name);
            
            // For /media, we need to go one level deeper (user directories)
            if (strcmp(mount_dirs[mount_idx], "/media") == 0) {
                // This is /media/[username] - look inside for drives
                DIR* user_dir = opendir(mount_path);
                if (!user_dir) continue;
                
                struct dirent* user_entry;
                while ((user_entry = readdir(user_dir)) != NULL) {
                    if (user_entry->d_name[0] == '.') continue;
                    
                    // Check if drive name starts with "OTP"
                    if (strncmp(user_entry->d_name, "OTP", 3) != 0) continue;
                    
                    char user_mount_path[2048];  // Increased buffer size
                    // Verify buffer has enough space before concatenation
                    size_t mount_len = strlen(mount_path);
                    size_t entry_len = strlen(user_entry->d_name);
                    if (mount_len + entry_len + 2 < sizeof(user_mount_path)) {
                        snprintf(user_mount_path, sizeof(user_mount_path), "%s/%s", mount_path, user_entry->d_name);
                    
                        // Check if this is a readable directory
                        DIR* drive_dir = opendir(user_mount_path);
                        if (drive_dir) {
                            closedir(drive_dir);
                            strncpy(otp_drive_path, user_mount_path, path_size - 1);
                            otp_drive_path[path_size - 1] = '\0';
                            closedir(user_dir);
                            closedir(mount_dir);
                            return 1; // Found OTP drive
                        }
                    }
                }
                closedir(user_dir);
            } else if (strcmp(mount_dirs[mount_idx], "/run/media") == 0) {
                // For /run/media, we need to go one level deeper (skip username)
                DIR* user_dir = opendir(mount_path);
                if (!user_dir) continue;
                
                struct dirent* user_entry;
                while ((user_entry = readdir(user_dir)) != NULL) {
                    if (user_entry->d_name[0] == '.') continue;
                    
                    // Check if drive name starts with "OTP"
                    if (strncmp(user_entry->d_name, "OTP", 3) != 0) continue;
                    
                    char user_mount_path[2048];  // Increased buffer size
                    snprintf(user_mount_path, sizeof(user_mount_path), "%s/%s", mount_path, user_entry->d_name);
                    
                    // Check if this is a readable directory
                    DIR* drive_dir = opendir(user_mount_path);
                    if (drive_dir) {
                        closedir(drive_dir);
                        strncpy(otp_drive_path, user_mount_path, path_size - 1);
                        otp_drive_path[path_size - 1] = '\0';
                        closedir(user_dir);
                        closedir(mount_dir);
                        return 1; // Found OTP drive
                    }
                }
                closedir(user_dir);
            } else {
                // Direct mount point (like /mnt/OTP_DRIVE)
                // Check if drive name starts with "OTP"
                if (strncmp(mount_entry->d_name, "OTP", 3) == 0) {
                    DIR* drive_dir = opendir(mount_path);
                    if (drive_dir) {
                        closedir(drive_dir);
                        strncpy(otp_drive_path, mount_path, path_size - 1);
                        otp_drive_path[path_size - 1] = '\0';
                        closedir(mount_dir);
                        return 1; // Found OTP drive
                    }
                }
            }
        }
        closedir(mount_dir);
    }
    
    return 0; // No OTP drive found
}




// Custom base64 encode function
char* custom_base64_encode(const unsigned char* input, int length) {
    int output_length = 4 * ((length + 2) / 3);
    char* encoded = malloc(output_length + 1);
    if (!encoded) return NULL;
    
    int i, j;
    for (i = 0, j = 0; i < length;) {
        uint32_t octet_a = i < length ? input[i++] : 0;
        uint32_t octet_b = i < length ? input[i++] : 0;
        uint32_t octet_c = i < length ? input[i++] : 0;
        
        uint32_t triple = (octet_a << 16) + (octet_b << 8) + octet_c;
        
        encoded[j++] = base64_chars[(triple >> 18) & 63];
        encoded[j++] = base64_chars[(triple >> 12) & 63];
        encoded[j++] = base64_chars[(triple >> 6) & 63];
        encoded[j++] = base64_chars[triple & 63];
    }
    
    // Add padding
    for (int pad = 0; pad < (3 - length % 3) % 3; pad++) {
        encoded[output_length - 1 - pad] = '=';
    }
    
    encoded[output_length] = '\0';
    return encoded;
}

// Custom base64 decode function
unsigned char* custom_base64_decode(const char* input, int* output_length) {
    int input_length = strlen(input);
    if (input_length % 4 != 0) return NULL;
    
    *output_length = input_length / 4 * 3;
    if (input[input_length - 1] == '=') (*output_length)--;
    if (input[input_length - 2] == '=') (*output_length)--;
    
    unsigned char* decoded = malloc(*output_length);
    if (!decoded) return NULL;
    
    int i, j;
    for (i = 0, j = 0; i < input_length;) {
        int sextet_a = input[i] == '=' ? 0 & i++ : base64_decode_table[(unsigned char)input[i++]];
        int sextet_b = input[i] == '=' ? 0 & i++ : base64_decode_table[(unsigned char)input[i++]];
        int sextet_c = input[i] == '=' ? 0 & i++ : base64_decode_table[(unsigned char)input[i++]];
        int sextet_d = input[i] == '=' ? 0 & i++ : base64_decode_table[(unsigned char)input[i++]];
        
        if (sextet_a == -1 || sextet_b == -1 || sextet_c == -1 || sextet_d == -1) {
            free(decoded);
            return NULL;
        }
        
        uint32_t triple = (sextet_a << 18) + (sextet_b << 12) + (sextet_c << 6) + sextet_d;
        
        if (j < *output_length) decoded[j++] = (triple >> 16) & 255;
        if (j < *output_length) decoded[j++] = (triple >> 8) & 255;
        if (j < *output_length) decoded[j++] = triple & 255;
    }
    
    return decoded;
}



////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
//      ADD ENTROPY
////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////


double get_precise_time(void) {
    struct timespec ts;
    clock_gettime(CLOCK_MONOTONIC, &ts);
    return ts.tv_sec + ts.tv_nsec / 1000000000.0;
}

void draw_progress_bar(double percentage, int width) {
    int filled = (int)(percentage / 100.0 * width);
    if (filled > width) filled = width;
    
    printf("[");
    for (int i = 0; i < filled; i++) {
        printf("█");
    }
    for (int i = filled; i < width; i++) {
        printf("░");
    }
    printf("]");
}

void draw_quality_bar(double quality, int width, const char* label) {
    int filled = (int)(quality / 100.0 * width);
    if (filled > width) filled = width;
    
    // Color coding based on quality
    const char* color;
    if (quality >= 80) color = "\033[32m"; // Green
    else if (quality >= 60) color = "\033[33m"; // Yellow
    else color = "\033[31m"; // Red
    
    printf("%s", color);
    draw_progress_bar(quality, width);
    printf("\033[0m %-10s", label); // Reset color
}

double calculate_timing_quality(const entropy_collection_state_t* state) {
    // Analyze timing variance between keypresses
    if (state->collected_bytes < 32) return 0.0; // Need minimum data
    
    // Simplified timing quality based on collection rate and variation
    double elapsed = get_precise_time() - state->collection_start_time;
    if (elapsed < 0.1) return 0.0;
    
    double rate = state->collected_bytes / elapsed;
    
    // Optimal rate is around 50-200 bytes/second (moderate typing with good timing variance)
    if (rate >= 50 && rate <= 200) return 90.0;
    if (rate >= 20 && rate <= 500) return 70.0;
    if (rate >= 10 && rate <= 1000) return 50.0;
    return 30.0;
}

double calculate_variety_quality(const entropy_collection_state_t* state) {
    // Analyze key variety and distribution
    if (state->collected_bytes < 16) return 0.0;
    
    // Calculate entropy from key histogram
    double entropy = 0.0;
    size_t total_keys = 0;
    
    // Count total keypresses
    for (int i = 0; i < 256; i++) {
        total_keys += state->key_histogram[i];
    }
    
    if (total_keys == 0) return 0.0;
    
    // Calculate Shannon entropy
    for (int i = 0; i < 256; i++) {
        if (state->key_histogram[i] > 0) {
            double p = (double)state->key_histogram[i] / total_keys;
            entropy -= p * log2(p);
        }
    }
    
    // Convert entropy to quality score (0-100)
    double max_entropy = log2(256); // Perfect entropy for 8-bit keyspace
    double normalized_entropy = entropy / max_entropy;
    
    // Scale based on unique keys as well
    double unique_key_factor = (double)state->unique_keys / 50.0; // 50+ unique keys is excellent
    if (unique_key_factor > 1.0) unique_key_factor = 1.0;
    
    return (normalized_entropy * 70.0 + unique_key_factor * 30.0);
}

unsigned char calculate_overall_quality(const entropy_collection_state_t* state) {
    double timing = calculate_timing_quality(state);
    double variety = calculate_variety_quality(state);
    
    // Simple collection progress bonus
    double progress_bonus = (double)state->collected_bytes / state->target_bytes * 20.0;
    if (progress_bonus > 20.0) progress_bonus = 20.0;
    
    // Weighted average
    double overall = (timing * 0.4 + variety * 0.4 + progress_bonus);
    if (overall > 100.0) overall = 100.0;
    
    return (unsigned char)overall;
}

void display_entropy_progress(const entropy_collection_state_t* state) {
    // Calculate percentages
    double progress = (double)state->collected_bytes / state->target_bytes * 100.0;
    if (progress > 100.0) progress = 100.0;
    
    double quality = state->quality_score;
    double timing_quality = calculate_timing_quality(state);
    double variety_quality = calculate_variety_quality(state);
    
    // Clear previous output and redraw
    printf("\033[2K\r"); // Clear line
    printf("\033[A\033[2K\r"); // Move up and clear
    printf("\033[A\033[2K\r"); // Move up and clear
    printf("\033[A\033[2K\r"); // Move up and clear
    printf("\033[A\033[2K\r"); // Move up and clear
    printf("\033[A\033[2K\r"); // Move up and clear
    
    // Header
    printf("Adding Entropy to Pad - Target: %zu bytes\n\n", state->target_bytes);
    
    // Main progress bar
    printf("Progress: ");
    draw_progress_bar(progress, 50);
    printf(" %.1f%% (%zu/%zu bytes)\n", progress, state->collected_bytes, state->target_bytes);
    
    // Quality indicators
    printf("Quality:  ");
    draw_quality_bar(quality, 50, "OVERALL");
    printf("\n");
    
    printf("Timing:   ");
    draw_quality_bar(timing_quality, 50, "VARIED");
    printf("\n");
    
    printf("Keys:     ");
    draw_quality_bar(variety_quality, 50, "DIVERSE");
    printf("\n");
    
    // Instructions
    if (state->collected_bytes >= 1024 && state->auto_complete_enabled) {
        printf("\nPress ESC to finish (minimum reached) or continue typing...");
    } else if (state->collected_bytes < 1024) {
        printf("\nType random keys... (%zu more bytes needed)", 1024 - state->collected_bytes);
    } else {
        printf("\nType random keys or press ESC when satisfied...");
    }
    
    fflush(stdout);
}

// Chacha20 key derivation from collected entropy
int derive_chacha20_params(const unsigned char* entropy_data, size_t entropy_size,
                          unsigned char key[32], unsigned char nonce[12]) {
    if (!entropy_data || entropy_size < 512 || !key || !nonce) {
        return 1; // Error: insufficient entropy or null pointers
    }
    
    // Phase 1: Generate base key from entropy using enhanced XOR checksum method
    unsigned char enhanced_checksum[44]; // 32 key + 12 nonce
    memset(enhanced_checksum, 0, 44);
    
    // Mix entropy data similar to calculate_checksum but for 44 bytes
    for (size_t i = 0; i < entropy_size; i++) {
        unsigned char bucket = i % 44;
        enhanced_checksum[bucket] ^= entropy_data[i] ^
                                   ((i >> 8) & 0xFF) ^
                                   ((i >> 16) & 0xFF) ^
                                   ((i >> 24) & 0xFF);
    }
    
    // Phase 2: Add system entropy for additional randomness
    unsigned char system_entropy[32];
    FILE* urandom = fopen("/dev/urandom", "rb");
    if (!urandom) {
        return 2; // Error: cannot access system entropy
    }
    
    if (fread(system_entropy, 1, 32, urandom) != 32) {
        fclose(urandom);
        return 2; // Error: insufficient system entropy
    }
    fclose(urandom);
    
    // Mix system entropy into derived key
    for (int i = 0; i < 32; i++) {
        enhanced_checksum[i] ^= system_entropy[i];
    }
    
    // Extract key and nonce
    memcpy(key, enhanced_checksum, 32);
    memcpy(nonce, enhanced_checksum + 32, 12);
    
    return 0; // Success
}

// Check if a pad is unused (0% usage)
int is_pad_unused(const char* pad_chksum) {
    uint64_t used_bytes;
    if (read_state_offset(pad_chksum, &used_bytes) != 0) {
        return 0; // Error reading state, assume used
    }
    return (used_bytes <= 32); // Only reserved bytes used (32 bytes for checksum encryption)
}

// Safely rename pad files (pad and state) from old to new checksum
int rename_pad_files_safely(const char* old_chksum, const char* new_chksum) {
    char old_pad_path[1024], new_pad_path[1024];
    char old_state_path[1024], new_state_path[1024];
    
    // Construct file paths
    snprintf(old_pad_path, sizeof(old_pad_path), "%s/%s.pad", current_pads_dir, old_chksum);
    snprintf(new_pad_path, sizeof(new_pad_path), "%s/%s.pad", current_pads_dir, new_chksum);
    snprintf(old_state_path, sizeof(old_state_path), "%s/%s.state", current_pads_dir, old_chksum);
    snprintf(new_state_path, sizeof(new_state_path), "%s/%s.state", current_pads_dir, new_chksum);
    
    // Check if new files would conflict with existing files
    if (access(new_pad_path, F_OK) == 0) {
        printf("Error: New pad file already exists: %s\n", new_pad_path);
        return 1; // Conflict
    }
    
    // Rename pad file
    if (rename(old_pad_path, new_pad_path) != 0) {
        printf("Error: Failed to rename pad file from %s to %s\n", old_pad_path, new_pad_path);
        return 2; // Pad rename failed
    }
    
    // Rename state file (if it exists)
    if (access(old_state_path, F_OK) == 0) {
        if (rename(old_state_path, new_state_path) != 0) {
            printf("Warning: Failed to rename state file, but pad file was renamed successfully\n");
            // Try to rollback pad file rename
            rename(new_pad_path, old_pad_path);
            return 3; // State rename failed
        }
    }
    
    return 0; // Success
}

// Update pad checksum after entropy addition
int update_pad_checksum_after_entropy(const char* old_chksum, char* new_chksum) {
    char pad_path[1024];
    snprintf(pad_path, sizeof(pad_path), "%s/%s.pad", current_pads_dir, old_chksum);
    
    // Calculate new checksum of the modified pad
    if (calculate_checksum(pad_path, new_chksum) != 0) {
        printf("Error: Cannot calculate new pad checksum\n");
        return 1;
    }
    
    // Check if checksum actually changed
    if (strcmp(old_chksum, new_chksum) == 0) {
        printf("Warning: Pad checksum unchanged after entropy addition\n");
        return 2; // Checksum didn't change (unusual but not fatal)
    }
    
    // Rename pad files to use new checksum
    if (rename_pad_files_safely(old_chksum, new_chksum) != 0) {
        return 3; // Rename failed
    }
    
    // Update default pad preference if this was the default pad
    char* current_default = get_default_pad_path();
    if (current_default) {
        // Check if the old pad was the default
        if (strstr(current_default, old_chksum)) {
            // Update to new checksum
            char new_default_path[1024];
            snprintf(new_default_path, sizeof(new_default_path), "%s/%s.pad", current_pads_dir, new_chksum);
            
            if (set_default_pad_path(new_default_path) != 0) {
                printf("Warning: Failed to update default pad preference\n");
            } else {
                printf("Updated default pad to new checksum: %.16s...\n", new_chksum);
            }
        }
        free(current_default);
    }
    
    return 0; // Success
}

// Enhanced entropy collection with visual feedback
int collect_entropy_with_feedback(unsigned char* entropy_buffer, size_t target_bytes,
                                 size_t* collected_bytes, int allow_early_exit) {
    struct termios original_termios;
    entropy_collection_state_t state = {0};
    
    // Initialize state
    state.target_bytes = target_bytes;
    state.auto_complete_enabled = allow_early_exit;
    state.collection_start_time = get_precise_time();
    
    // Setup raw terminal
    if (setup_raw_terminal(&original_termios) != 0) {
        printf("Error: Cannot setup terminal for entropy collection\n");
        return 1;
    }
    
    // Clear screen area for display
    printf("\n\n\n\n\n\n");
    
    unsigned char entropy_block[16];
    struct timespec timestamp;
    uint32_t sequence_counter = 0;
    char key;
    unsigned char seen_keys[256] = {0};
    
    *collected_bytes = 0;
    
    while (state.collected_bytes < target_bytes) {
        // Update display
        state.quality_score = calculate_overall_quality(&state);
        display_entropy_progress(&state);
        
        // Non-blocking read
        if (read(STDIN_FILENO, &key, 1) == 1) {
            // Handle ESC key for early exit
            if (key == 27 && allow_early_exit && state.collected_bytes >= 1024) {
                break; // Early exit allowed
            }
            
            // Record keypress timing
            double current_time = get_precise_time();
            state.last_keypress_time = current_time;
            
            // Update key histogram
            state.key_histogram[(unsigned char)key]++;
            
            // Get high precision timestamp
            clock_gettime(CLOCK_MONOTONIC, &timestamp);
            
            // Create enhanced entropy block: [key][timestamp][sequence][quality_bits]
            entropy_block[0] = key;
            memcpy(&entropy_block[1], &timestamp.tv_sec, 8);
            memcpy(&entropy_block[9], &timestamp.tv_nsec, 4);
            memcpy(&entropy_block[13], &sequence_counter, 2);
            entropy_block[15] = (unsigned char)(current_time * 1000) & 0xFF; // Sub-millisecond timing
            
            // Add to entropy buffer
            if (state.collected_bytes + 16 <= MAX_ENTROPY_BUFFER) {
                memcpy(entropy_buffer + state.collected_bytes, entropy_block, 16);
                state.collected_bytes += 16;
            }
            
            sequence_counter++;
            
            // Track unique keys
            if (!seen_keys[(unsigned char)key]) {
                seen_keys[(unsigned char)key] = 1;
                state.unique_keys++;
            }
        } else {
            // No key available, just sleep and wait for keystrokes
            usleep(10000); // 10ms delay - wait for keystrokes, don't add timing entropy
        }
        
        // Auto-complete at target if enabled
        if (state.collected_bytes >= target_bytes) {
            break;
        }
    }
    
    // Final display update
    state.quality_score = calculate_overall_quality(&state);
    display_entropy_progress(&state);
    
    // Summary
    double collection_time = get_precise_time() - state.collection_start_time;
    printf("\n\n✓ Entropy collection complete!\n");
    printf("  Collected: %zu bytes in %.1f seconds\n", state.collected_bytes, collection_time);
    printf("  Quality: %d%% (Excellent: 80%%+, Good: 60%%+)\n", state.quality_score);
    printf("  Unique keys: %zu\n", state.unique_keys);
    
    // Restore terminal
    restore_terminal(&original_termios);
    
    *collected_bytes = state.collected_bytes;
    return 0;
}

// Keyboard entropy functions
int setup_raw_terminal(struct termios* original_termios) {
    struct termios new_termios;
    
    if (tcgetattr(STDIN_FILENO, original_termios) != 0) {
        return 1;
    }
    
    new_termios = *original_termios;
    new_termios.c_lflag &= ~(ICANON | ECHO);
    new_termios.c_cc[VMIN] = 0;
    new_termios.c_cc[VTIME] = 0;
    
    if (tcsetattr(STDIN_FILENO, TCSANOW, &new_termios) != 0) {
        return 1;
    }
    
    // Set stdin to non-blocking
    int flags = fcntl(STDIN_FILENO, F_GETFL);
    if (fcntl(STDIN_FILENO, F_SETFL, flags | O_NONBLOCK) == -1) {
        tcsetattr(STDIN_FILENO, TCSANOW, original_termios);
        return 1;
    }
    
    return 0;
}

void restore_terminal(struct termios* original_termios) {
    tcsetattr(STDIN_FILENO, TCSANOW, original_termios);
    
    // Reset stdin to blocking
    int flags = fcntl(STDIN_FILENO, F_GETFL);
    fcntl(STDIN_FILENO, F_SETFL, flags & ~O_NONBLOCK);
}



////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
//      UNIVERSAL CORE FUNCTIONS FOR CODE CONSOLIDATION
////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////

// Universal XOR operation - handles both encryption and decryption
// Since XOR is symmetric, this single function replaces all 6 duplicate XOR loops
int universal_xor_operation(const unsigned char* data, size_t data_len,
                           const unsigned char* pad_data, unsigned char* result) {
    if (!data || !pad_data || !result) {
        return 1; // Error: null pointer
    }
    
    for (size_t i = 0; i < data_len; i++) {
        result[i] = data[i] ^ pad_data[i];
    }
    
    return 0; // Success
}

// Universal ASCII message parser - consolidates 4 duplicate parsing implementations
// Extracts checksum, offset, and base64 data from ASCII armored messages
int parse_ascii_message(const char* message, char* chksum, uint64_t* offset, char* base64_data) {
    if (!message || !chksum || !offset || !base64_data) {
        return 1; // Error: null pointer
    }
    
    char *message_copy = strdup(message);
    if (!message_copy) {
        return 1; // Memory allocation failed
    }
    
    char *line_ptr = strtok(message_copy, "\n");
    int found_begin = 0;
    int in_data_section = 0;
    int found_chksum = 0, found_offset = 0;
    
    // Initialize output
    chksum[0] = '\0';
    *offset = 0;
    base64_data[0] = '\0';
    
    while (line_ptr != NULL) {
        if (strcmp(line_ptr, "-----BEGIN OTP MESSAGE-----") == 0) {
            found_begin = 1;
        }
        else if (strcmp(line_ptr, "-----END OTP MESSAGE-----") == 0) {
            break;
        }
        else if (found_begin) {
            if (strncmp(line_ptr, "Pad-ChkSum: ", 12) == 0) {
                strncpy(chksum, line_ptr + 12, 64);
                chksum[64] = '\0';
                found_chksum = 1;
            }
            else if (strncmp(line_ptr, "Pad-Offset: ", 12) == 0) {
                *offset = strtoull(line_ptr + 12, NULL, 10);
                found_offset = 1;
            }
            else if (strlen(line_ptr) == 0) {
                in_data_section = 1;
            }
            else if (in_data_section) {
                strncat(base64_data, line_ptr, MAX_INPUT_SIZE * 2 - strlen(base64_data) - 1);
            }
            else if (strncmp(line_ptr, "Version:", 8) != 0 && strncmp(line_ptr, "Pad-", 4) != 0) {
                // This might be base64 data without a blank line separator
                strncat(base64_data, line_ptr, MAX_INPUT_SIZE * 2 - strlen(base64_data) - 1);
            }
        }
        line_ptr = strtok(NULL, "\n");
    }
    
    free(message_copy);
    
    if (!found_begin || !found_chksum || !found_offset) {
        return 2; // Error: incomplete message format
    }
    
    return 0; // Success
}

// Universal pad data loader - consolidates pad loading and validation logic
// Loads pad data at specified offset and validates pad availability
int load_pad_data(const char* pad_chksum, uint64_t offset, size_t length, unsigned char** pad_data) {
    if (!pad_chksum || !pad_data) {
        return 1; // Error: null pointer
    }
    
    char pad_path[1024];
    char state_path[1024];
    get_pad_path(pad_chksum, pad_path, state_path);
    
    // Check if pad file exists
    if (access(pad_path, R_OK) != 0) {
        return 2; // Error: pad file not found
    }
    
    // Check pad file size
    struct stat pad_stat;
    if (stat(pad_path, &pad_stat) != 0) {
        return 3; // Error: cannot get pad file size
    }
    
    if (offset + length > (uint64_t)pad_stat.st_size) {
        return 4; // Error: not enough pad space
    }
    
    // Allocate memory for pad data
    *pad_data = malloc(length);
    if (!*pad_data) {
        return 5; // Error: memory allocation failed
    }
    
    // Open and read pad file
    FILE* pad_file = fopen(pad_path, "rb");
    if (!pad_file) {
        free(*pad_data);
        *pad_data = NULL;
        return 6; // Error: cannot open pad file
    }
    
    if (fseek(pad_file, offset, SEEK_SET) != 0) {
        fclose(pad_file);
        free(*pad_data);
        *pad_data = NULL;
        return 7; // Error: cannot seek to offset
    }
    
    if (fread(*pad_data, 1, length, pad_file) != length) {
        fclose(pad_file);
        free(*pad_data);
        *pad_data = NULL;
        return 8; // Error: cannot read pad data
    }
    
    fclose(pad_file);
    return 0; // Success
}

// Universal ASCII armor generator - consolidates duplicate ASCII armor generation
// Creates ASCII armored output format used by both text and file encryption
int generate_ascii_armor(const char* chksum, uint64_t offset, const unsigned char* encrypted_data,
                        size_t data_length, char** ascii_output) {
    if (!chksum || !encrypted_data || !ascii_output) {
        return 1; // Error: null pointer
    }
    
    // Encode data as base64
    char* base64_data = custom_base64_encode(encrypted_data, data_length);
    if (!base64_data) {
        return 2; // Error: base64 encoding failed
    }
    
    // Calculate required buffer size
    size_t base64_len = strlen(base64_data);
    size_t header_size = 200; // Approximate size for headers
    size_t total_size = header_size + base64_len + (base64_len / 64) + 100; // +newlines +footer
    
    *ascii_output = malloc(total_size);
    if (!*ascii_output) {
        free(base64_data);
        return 3; // Error: memory allocation failed
    }
    
    // Build ASCII armor
    strcpy(*ascii_output, "-----BEGIN OTP MESSAGE-----\n");
    
    char temp_line[256];
    snprintf(temp_line, sizeof(temp_line), "Version: v0.3.1\n");
    strcat(*ascii_output, temp_line);
    
    snprintf(temp_line, sizeof(temp_line), "Pad-ChkSum: %s\n", chksum);
    strcat(*ascii_output, temp_line);
    
    snprintf(temp_line, sizeof(temp_line), "Pad-Offset: %lu\n", offset);
    strcat(*ascii_output, temp_line);
    
    strcat(*ascii_output, "\n");
    
    // Add base64 data in 64-character lines
    int b64_len = strlen(base64_data);
    for (int i = 0; i < b64_len; i += 64) {
        char line[70];
        snprintf(line, sizeof(line), "%.64s\n", base64_data + i);
        strcat(*ascii_output, line);
    }
    
    strcat(*ascii_output, "-----END OTP MESSAGE-----\n");
    
    free(base64_data);
    return 0; // Success
}

// Universal pad integrity validator - consolidates pad validation logic
// Verifies pad checksum matches expected value for security
int validate_pad_integrity(const char* pad_path, const char* expected_chksum) {
    if (!pad_path || !expected_chksum) {
        return 1; // Error: null pointer
    }
    
    char current_chksum[MAX_HASH_LENGTH];
    if (calculate_checksum(pad_path, current_chksum) != 0) {
        return 2; // Error: cannot calculate checksum
    }
    
    if (strcmp(expected_chksum, current_chksum) != 0) {
        return 3; // Error: checksum mismatch
    }
    
    return 0; // Success - pad integrity verified
}

// Universal decrypt function - consolidates all decrypt operations
// input_data: encrypted message text or file path
// output_target: output file path (NULL for stdout/interactive)
// mode: determines behavior and output format
int universal_decrypt(const char* input_data, const char* output_target, decrypt_mode_t mode) {
    char stored_chksum[MAX_HASH_LENGTH];
    uint64_t pad_offset;
    char base64_data[MAX_INPUT_SIZE * 8] = {0};
    unsigned char* ciphertext = NULL;
    int ciphertext_len;
    
    // Handle input based on mode
    if (mode == DECRYPT_MODE_FILE_TO_TEXT || mode == DECRYPT_MODE_FILE_TO_FILE) {
        // File input - read the entire file
        FILE* input_fp = fopen(input_data, "r");
        if (!input_fp) {
            printf("Error: Cannot open input file %s\n", input_data);
            return 1;
        }
        
        fseek(input_fp, 0, SEEK_END);
        long file_size = ftell(input_fp);
        fseek(input_fp, 0, SEEK_SET);
        
        char* file_content = malloc(file_size + 1);
        if (!file_content) {
            printf("Error: Memory allocation failed\n");
            fclose(input_fp);
            return 1;
        }
        
        size_t bytes_read = fread(file_content, 1, file_size, input_fp);
        file_content[bytes_read] = '\0';
        fclose(input_fp);
        
        // Parse ASCII message from file content
        if (parse_ascii_message(file_content, stored_chksum, &pad_offset, base64_data) != 0) {
            printf("Error: Invalid ASCII armored format in file\n");
            free(file_content);
            return 1;
        }
        free(file_content);
        
        if (mode == DECRYPT_MODE_FILE_TO_TEXT) {
            printf("Decrypting ASCII armored file...\n");
        }
        // Note: DECRYPT_MODE_FILE_TO_FILE should be completely silent for piping
    } else {
        // Text input (interactive or piped)
        const char* message_text;
        char full_message[MAX_INPUT_SIZE * 4] = {0};
        
        if (input_data != NULL) {
            message_text = input_data;
        } else {
            // Interactive mode - read from stdin
            if (mode == DECRYPT_MODE_INTERACTIVE) {
                printf("Enter encrypted message (paste the full ASCII armor block):\n");
            }
            
            char line[MAX_LINE_LENGTH];
            while (fgets(line, sizeof(line), stdin)) {
                strncat(full_message, line, sizeof(full_message) - strlen(full_message) - 1);
                if (strstr(line, "-----END OTP MESSAGE-----")) {
                    break;
                }
            }
            message_text = full_message;
        }
        
        // Parse ASCII message from text
        if (parse_ascii_message(message_text, stored_chksum, &pad_offset, base64_data) != 0) {
            if (mode == DECRYPT_MODE_SILENT) {
                fprintf(stderr, "Error: Invalid message format - missing BEGIN header\n");
            } else {
                printf("Error: Invalid message format - missing BEGIN header\n");
            }
            return 1;
        }
    }
    
    // Get pad path and check existence
    char pad_path[MAX_HASH_LENGTH + 20];
    char state_path[MAX_HASH_LENGTH + 20];
    get_pad_path(stored_chksum, pad_path, state_path);
    
    if (access(pad_path, R_OK) != 0) {
        if (mode == DECRYPT_MODE_SILENT) {
            fprintf(stderr, "Error: Required pad not found: %s\n", stored_chksum);
        } else {
            printf("Error: Required pad not found: %s\n", stored_chksum);
            if (mode == DECRYPT_MODE_INTERACTIVE || mode == DECRYPT_MODE_FILE_TO_TEXT) {
                printf("Available pads:\n");
                char* selected = select_pad_interactive("Available pads:", "Available pads (press Enter to continue)", PAD_FILTER_ALL, 0);
                if (selected) {
                    free(selected);
                }
            }
        }
        return 1;
    }
    
    // Validate pad integrity
    int integrity_result = validate_pad_integrity(pad_path, stored_chksum);
    if (integrity_result == 3) {
        if (mode == DECRYPT_MODE_SILENT) {
            fprintf(stderr, "Error: Pad integrity check failed!\n");
            return 1;
        } else if (mode == DECRYPT_MODE_INTERACTIVE) {
            printf("Warning: Pad integrity check failed!\n");
            printf("Expected: %s\n", stored_chksum);
            printf("Continue anyway? (y/N): ");
            fflush(stdout);
            
            char response[10];
            if (fgets(response, sizeof(response), stdin) == NULL ||
                (response[0] != 'y' && response[0] != 'Y')) {
                printf("Decryption aborted.\n");
                return 1;
            }
        }
    } else if (integrity_result != 0) {
        if (mode == DECRYPT_MODE_SILENT) {
            fprintf(stderr, "Error: Cannot verify pad integrity\n");
        } else {
            printf("Error: Cannot verify pad integrity\n");
        }
        return 1;
    } else {
        if (mode == DECRYPT_MODE_INTERACTIVE || mode == DECRYPT_MODE_FILE_TO_TEXT) {
            printf("Pad integrity: VERIFIED\n");
        }
    }
    
    // Decode base64 ciphertext
    ciphertext = custom_base64_decode(base64_data, &ciphertext_len);
    if (!ciphertext) {
        if (mode == DECRYPT_MODE_SILENT) {
            fprintf(stderr, "Error: Invalid base64 data\n");
        } else {
            printf("Error: Invalid base64 data\n");
        }
        return 1;
    }
    
    // Load pad data using universal function
    unsigned char* pad_data;
    if (load_pad_data(stored_chksum, pad_offset, ciphertext_len, &pad_data) != 0) {
        if (mode == DECRYPT_MODE_SILENT) {
            fprintf(stderr, "Error: Cannot load pad data\n");
        } else {
            printf("Error: Cannot load pad data\n");
        }
        free(ciphertext);
        return 1;
    }
    
    // Decrypt using universal XOR operation
    if (universal_xor_operation(ciphertext, ciphertext_len, pad_data, ciphertext) != 0) {
        if (mode == DECRYPT_MODE_SILENT) {
            fprintf(stderr, "Error: Decryption operation failed\n");
        } else {
            printf("Error: Decryption operation failed\n");
        }
        free(ciphertext);
        free(pad_data);
        return 1;
    }
    
    // Output based on mode
    if (mode == DECRYPT_MODE_FILE_TO_FILE) {
        // Write to output file
        const char* output_file = output_target;
        
        // Generate default output filename if not provided
        char default_output[512];
        if (output_file == NULL) {
            strncpy(default_output, input_data, sizeof(default_output) - 1);
            default_output[sizeof(default_output) - 1] = '\0';
            
            char* ext = strstr(default_output, ".otp.asc");
            if (ext) {
                *ext = '\0';
            } else {
                strncat(default_output, ".decrypted", sizeof(default_output) - strlen(default_output) - 1);
            }
            output_file = default_output;
        }
        
        FILE* output_fp = fopen(output_file, "wb");
        if (!output_fp) {
            printf("Error: Cannot create output file %s\n", output_file);
            free(ciphertext);
            free(pad_data);
            return 1;
        }
        
        if (fwrite(ciphertext, 1, ciphertext_len, output_fp) != (size_t)ciphertext_len) {
            printf("Error: Cannot write decrypted data\n");
            free(ciphertext);
            free(pad_data);
            fclose(output_fp);
            return 1;
        }
        fclose(output_fp);
        
        // Only show success messages in non-silent modes
        if (mode != DECRYPT_MODE_FILE_TO_FILE) {
            printf("File decrypted successfully: %s\n", output_file);
            printf("Note: ASCII format does not preserve original filename/permissions\n");
        }
    } else {
        // Text output to stdout - need to allocate space for null terminator
        char* decrypted_text = malloc(ciphertext_len + 1);
        if (!decrypted_text) {
            printf("Error: Memory allocation failed for output\n");
            free(ciphertext);
            free(pad_data);
            return 1;
        }
        
        memcpy(decrypted_text, ciphertext, ciphertext_len);
        decrypted_text[ciphertext_len] = '\0';
        
        if (mode == DECRYPT_MODE_SILENT) {
            // Silent mode - just output the text
            printf("%s\n", decrypted_text);
            fflush(stdout);
        } else {
            // Interactive mode - with label
            printf("Decrypted: %s\n", decrypted_text);
        }
        
        free(decrypted_text);
    }
    
    // Cleanup
    free(ciphertext);
    free(pad_data);
    
    return 0;
}

// Enhanced input function with editable pre-filled text
int get_filename_with_default(const char* prompt, const char* default_path, char* result, size_t result_size) {
    // Find the last directory separator
    char* last_slash = strrchr(default_path, '/');
    char directory[1024] = "";
    char filename[512] = "";
    
    if (last_slash) {
        // Extract directory path
        size_t dir_len = last_slash - default_path + 1; // Include the trailing slash
        if (dir_len < sizeof(directory)) {
            strncpy(directory, default_path, dir_len);
            directory[dir_len] = '\0';
        }
        
        // Extract filename
        strncpy(filename, last_slash + 1, sizeof(filename) - 1);
        filename[sizeof(filename) - 1] = '\0';
    } else {
        // No directory separator, treat as filename only
        strncpy(filename, default_path, sizeof(filename) - 1);
        filename[sizeof(filename) - 1] = '\0';
    }
    
    // Setup terminal for raw input
    struct termios orig_termios;
    if (tcgetattr(STDIN_FILENO, &orig_termios) != 0) {
        // Fallback to simple input if terminal control fails
        printf("\n%s\n%s: ", prompt, directory);
        fflush(stdout);
        
        char input_buffer[512];
        if (!fgets(input_buffer, sizeof(input_buffer), stdin)) {
            return 1;
        }
        input_buffer[strcspn(input_buffer, "\n")] = 0;
        
        if (strlen(input_buffer) == 0) {
            strncpy(result, default_path, result_size - 1);
        } else {
            if (strlen(directory) > 0) {
                snprintf(result, result_size, "%s%s", directory, input_buffer);
            } else {
                strncpy(result, input_buffer, result_size - 1);
            }
        }
        result[result_size - 1] = '\0';
        return 0;
    }
    
    // Set up raw terminal mode
    struct termios raw_termios = orig_termios;
    raw_termios.c_lflag &= ~(ECHO | ICANON);
    raw_termios.c_cc[VMIN] = 1;
    raw_termios.c_cc[VTIME] = 0;
    
    if (tcsetattr(STDIN_FILENO, TCSANOW, &raw_termios) != 0) {
        // Fallback if terminal setup fails
        printf("\n%s\n%s: ", prompt, directory);
        fflush(stdout);
        
        char input_buffer[512];
        if (!fgets(input_buffer, sizeof(input_buffer), stdin)) {
            return 1;
        }
        input_buffer[strcspn(input_buffer, "\n")] = 0;
        
        if (strlen(input_buffer) == 0) {
            strncpy(result, default_path, result_size - 1);
        } else {
            if (strlen(directory) > 0) {
                snprintf(result, result_size, "%s%s", directory, input_buffer);
            } else {
                strncpy(result, input_buffer, result_size - 1);
            }
        }
        result[result_size - 1] = '\0';
        return 0;
    }
    
    // Display prompt and directory
    printf("\n%s\n%s", prompt, directory);
    fflush(stdout);
    
    // Initialize editing buffer with default filename
    char edit_buffer[512];
    strncpy(edit_buffer, filename, sizeof(edit_buffer) - 1);
    edit_buffer[sizeof(edit_buffer) - 1] = '\0';
    int cursor_pos = strlen(edit_buffer);
    int buffer_len = cursor_pos;
    
    // Display initial filename
    printf("%s", edit_buffer);
    fflush(stdout);
    
    // Main editing loop
    int c;
    while ((c = getchar()) != EOF) {
        if (c == '\n' || c == '\r') {
            // Enter key - accept input
            break;
        } else if (c == 127 || c == 8) {
            // Backspace/Delete
            if (cursor_pos > 0) {
                // Move everything after cursor one position left
                memmove(&edit_buffer[cursor_pos - 1], &edit_buffer[cursor_pos], buffer_len - cursor_pos + 1);
                cursor_pos--;
                buffer_len--;
                
                // Redraw line: move cursor to start of filename area, clear to end, redraw buffer
                printf("\r%s\033[K%s", directory, edit_buffer);
                
                // Position cursor correctly
                if (cursor_pos < buffer_len) {
                    printf("\033[%dD", buffer_len - cursor_pos);
                }
                fflush(stdout);
            }
        } else if (c == 27) {
            // Escape sequence (arrow keys, etc.)
            int c1 = getchar();
            int c2 = getchar();
            if (c1 == '[') {
                if (c2 == 'C' && cursor_pos < buffer_len) {
                    // Right arrow
                    cursor_pos++;
                    printf("\033[1C");
                    fflush(stdout);
                } else if (c2 == 'D' && cursor_pos > 0) {
                    // Left arrow
                    cursor_pos--;
                    printf("\033[1D");
                    fflush(stdout);
                } else if (c2 == 'H') {
                    // Home key
                    printf("\033[%dD", cursor_pos);
                    cursor_pos = 0;
                    fflush(stdout);
                } else if (c2 == 'F') {
                    // End key
                    printf("\033[%dC", buffer_len - cursor_pos);
                    cursor_pos = buffer_len;
                    fflush(stdout);
                }
            }
        } else if (c >= 32 && c <= 126) {
            // Printable character
            if (buffer_len < (int)sizeof(edit_buffer) - 1) {
                // Move everything after cursor one position right
                memmove(&edit_buffer[cursor_pos + 1], &edit_buffer[cursor_pos], buffer_len - cursor_pos + 1);
                edit_buffer[cursor_pos] = c;
                cursor_pos++;
                buffer_len++;
                
                // Redraw from cursor position
                printf("%c", c);
                if (cursor_pos < buffer_len) {
                    // Print remaining characters and move cursor back
                    printf("%s\033[%dD", &edit_buffer[cursor_pos], buffer_len - cursor_pos);
                }
                fflush(stdout);
            }
        }
        // Ignore other control characters
    }
    
    // Restore terminal
    tcsetattr(STDIN_FILENO, TCSANOW, &orig_termios);
    printf("\n");
    
    // Construct final result
    if (buffer_len == 0) {
        // Empty input, use default
        strncpy(result, default_path, result_size - 1);
    } else {
        // Combine directory with edited filename
        edit_buffer[buffer_len] = '\0';
        if (strlen(directory) > 0) {
            snprintf(result, result_size, "%s%s", directory, edit_buffer);
        } else {
            strncpy(result, edit_buffer, result_size - 1);
        }
    }
    result[result_size - 1] = '\0';
    
    return 0;
}

////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
//      EDITOR AND FILE MANAGER
////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////

char* get_preferred_editor(void) {
    // Check EDITOR environment variable first
    char* editor = getenv("EDITOR");
    if (editor && strlen(editor) > 0) {
        // Verify the editor exists
        char command[512];
        snprintf(command, sizeof(command), "which %s >/dev/null 2>&1", editor);
        if (system(command) == 0) {
            return strdup(editor);
        }
    }
    
    // Check VISUAL environment variable
    editor = getenv("VISUAL");
    if (editor && strlen(editor) > 0) {
        char command[512];
        snprintf(command, sizeof(command), "which %s >/dev/null 2>&1", editor);
        if (system(command) == 0) {
            return strdup(editor);
        }
    }
    
    // Try common editors in order of preference
    const char* common_editors[] = {"vim", "vi", "nano", "emacs", "gedit", NULL};
    for (int i = 0; common_editors[i] != NULL; i++) {
        char command[512];
        snprintf(command, sizeof(command), "which %s >/dev/null 2>&1", common_editors[i]);
        if (system(command) == 0) {
            return strdup(common_editors[i]);
        }
    }
    
    return NULL; // No editor found
}

char* get_preferred_file_manager(void) {
    // Try file managers in order of preference
    const char* file_managers[] = {"ranger", "fzf", "nnn", "lf", NULL};
    
    for (int i = 0; file_managers[i] != NULL; i++) {
        char command[512];
        snprintf(command, sizeof(command), "which %s >/dev/null 2>&1", file_managers[i]);
        if (system(command) == 0) {
            return strdup(file_managers[i]);
        }
    }
    
    return NULL; // No file manager found
}

int launch_text_editor(const char* initial_content, char* result_buffer, size_t buffer_size) {
    char* editor = get_preferred_editor();
    if (!editor) {
        printf("Error: No text editor found. Set EDITOR environment variable or install vim/nano.\n");
        return 1;
    }
    
    // Create temporary file
    char temp_filename[64];
    snprintf(temp_filename, sizeof(temp_filename), "/tmp/otp_edit_%ld.tmp", time(NULL));
    
    // Write initial content to temp file if provided
    if (initial_content && strlen(initial_content) > 0) {
        FILE* temp_file = fopen(temp_filename, "w");
        if (temp_file) {
            fputs(initial_content, temp_file);
            fclose(temp_file);
        }
    } else {
        // Create empty temp file
        FILE* temp_file = fopen(temp_filename, "w");
        if (temp_file) {
            fclose(temp_file);
        }
    }
    
    // Launch editor
    printf("Opening %s for text editing...\n", editor);
    char command[512];
    snprintf(command, sizeof(command), "%s %s", editor, temp_filename);
    
    int result = system(command);
    
    if (result == 0) {
        // Read the edited content back
        FILE* temp_file = fopen(temp_filename, "r");
        if (temp_file) {
            size_t bytes_read = fread(result_buffer, 1, buffer_size - 1, temp_file);
            result_buffer[bytes_read] = '\0';
            
            // Remove trailing newline if present
            if (bytes_read > 0 && result_buffer[bytes_read - 1] == '\n') {
                result_buffer[bytes_read - 1] = '\0';
            }
            
            fclose(temp_file);
        } else {
            printf("Error: Cannot read edited content\n");
            free(editor);
            unlink(temp_filename);
            return 1;
        }
    } else {
        printf("Editor exited with error or was cancelled\n");
        free(editor);
        unlink(temp_filename);
        return 1;
    }
    
    // Clean up
    unlink(temp_filename);
    free(editor);
    
    return 0;
}

int launch_file_manager(const char* start_directory, char* selected_file, size_t buffer_size) {
    char* fm = get_preferred_file_manager();
    if (!fm) {
        printf("No file manager found. Please install ranger, fzf, nnn, or lf.\n");
        printf("Falling back to manual file path entry.\n");
        return 1; // Fall back to manual entry
    }
    
    char temp_filename[64];
    snprintf(temp_filename, sizeof(temp_filename), "/tmp/otp_file_%ld.tmp", time(NULL));
    
    char command[512];
    int result = 1;
    
    printf("Opening %s for file selection...\n", fm);
    
    if (strcmp(fm, "ranger") == 0) {
        snprintf(command, sizeof(command), "cd '%s' && ranger --choosefile=%s", 
                start_directory ? start_directory : ".", temp_filename);
    } else if (strcmp(fm, "fzf") == 0) {
        snprintf(command, sizeof(command), "cd '%s' && find . -type f | fzf > %s", 
                start_directory ? start_directory : ".", temp_filename);
    } else if (strcmp(fm, "nnn") == 0) {
        snprintf(command, sizeof(command), "cd '%s' && nnn -p %s", 
                start_directory ? start_directory : ".", temp_filename);
    } else if (strcmp(fm, "lf") == 0) {
        snprintf(command, sizeof(command), "cd '%s' && lf -selection-path=%s", 
                start_directory ? start_directory : ".", temp_filename);
    }
    
    result = system(command);
    
    if (result == 0 || result == 256) { // Some file managers return 256 on success
        // Read selected file from temp file
        FILE* temp_file = fopen(temp_filename, "r");
        if (temp_file) {
            if (fgets(selected_file, buffer_size, temp_file)) {
                // Remove trailing newline
                selected_file[strcspn(selected_file, "\n\r")] = 0;
                
                // For relative paths from fzf, make absolute if needed
                if (selected_file[0] == '.' && selected_file[1] == '/') {
                    char current_dir[512];
                    if (getcwd(current_dir, sizeof(current_dir))) {
                        char abs_path[1024];
                        snprintf(abs_path, sizeof(abs_path), "%s/%s", current_dir, selected_file + 2);
                        strncpy(selected_file, abs_path, buffer_size - 1);
                        selected_file[buffer_size - 1] = '\0';
                    }
                }
                
                fclose(temp_file);
                unlink(temp_filename);
                free(fm);
                return 0; // Success
            }
            fclose(temp_file);
        }
    }
    
    // Clean up and indicate failure
    unlink(temp_filename);
    free(fm);
    return 1; // Fall back to manual entry
}

int handle_text_encrypt(void) {
    printf("\n=== Text Encrypt ===\n");
    
    // Launch text editor directly
    char text_buffer[MAX_INPUT_SIZE];
    if (launch_text_editor(NULL, text_buffer, sizeof(text_buffer)) != 0) {
        printf("Error: Could not launch text editor\n");
        return 1;
    }
    
    if (strlen(text_buffer) == 0) {
        printf("No text entered - canceling encryption\n");
        return 1;
    }
    
    // Use unified pad selection
    char* selected_pad = select_pad_interactive("=== Select Pad for Text Encryption ===",
                                              "Select pad (by prefix)",
                                              PAD_FILTER_ALL, 1);
    if (!selected_pad) {
        printf("Text encryption cancelled.\n");
        return 1;
    }
    
    int result = encrypt_text(selected_pad, text_buffer);
    free(selected_pad);
    return result;
}

int handle_file_encrypt(void) {
    printf("\n=== File Encrypt ===\n");
    
    // Launch file manager directly
    char input_file[512];
    if (launch_file_manager(".", input_file, sizeof(input_file)) != 0) {
        printf("Error: Could not launch file manager\n");
        return 1;
    }
    
    // Check if file exists
    if (access(input_file, R_OK) != 0) {
        printf("Error: File '%s' not found or cannot be read\n", input_file);
        return 1;
    }
    
    // Use unified pad selection
    char* selected_pad = select_pad_interactive("=== Select Pad for File Encryption ===",
                                              "Select pad (by prefix)",
                                              PAD_FILTER_ALL, 1);
    if (!selected_pad) {
        printf("File encryption cancelled.\n");
        return 1;
    }
    
    // Ask for output format
    printf("\nSelect output format:\n");
    printf("1. Binary (.otp) - preserves file permissions\n");
    printf("2. ASCII (.otp.asc) - text-safe format\n");
    printf("Enter choice (1-2): ");
    
    char format_input[10];
    if (!fgets(format_input, sizeof(format_input), stdin)) {
        printf("Error: Failed to read input\n");
        return 1;
    }
    
    int ascii_armor = (atoi(format_input) == 2) ? 1 : 0;
    
    // Generate default output filename
    char default_output[1024]; // Increased buffer size to prevent truncation warnings
    if (ascii_armor) {
        snprintf(default_output, sizeof(default_output), "%s.otp.asc", input_file);
    } else {
        snprintf(default_output, sizeof(default_output), "%s.otp", input_file);
    }
    
    // Use enhanced input function for output filename
    char output_file[512];
    if (get_filename_with_default("Output filename:", default_output, output_file, sizeof(output_file)) != 0) {
        printf("Error: Failed to read input\n");
        return 1;
    }
    
    const char* output_filename = output_file;
    
    int result = encrypt_file(selected_pad, input_file, output_filename, ascii_armor);
    free(selected_pad);
    return result;
}



////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
//      PADS
////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////

int calculate_checksum(const char* filename, char* checksum_hex) {
    FILE* file = fopen(filename, "rb");
    if (!file) {
        return 1;
    }
    
    unsigned char checksum[32];
    unsigned char buffer[64 * 1024];  // 64KB buffer for large files
    size_t bytes_read;
    
    // Initialize checksum
    memset(checksum, 0, 32);
    size_t total_bytes = 0;
    
    // Calculate XOR checksum of entire file
    while ((bytes_read = fread(buffer, 1, sizeof(buffer), file)) > 0) {
        // Process this chunk with XOR checksum
        for (size_t i = 0; i < bytes_read; i++) {
            unsigned char bucket = (total_bytes + i) % 32;
            checksum[bucket] ^= buffer[i] ^ (((total_bytes + i) >> 8) & 0xFF) ^ 
                               (((total_bytes + i) >> 16) & 0xFF) ^ (((total_bytes + i) >> 24) & 0xFF);
        }
        total_bytes += bytes_read;
    }
    
    fclose(file);
    
    // Now encrypt the checksum with the first 32 bytes of the pad
    fseek(file = fopen(filename, "rb"), 0, SEEK_SET);
    unsigned char pad_key[32];
    if (fread(pad_key, 1, 32, file) != 32) {
        fclose(file);
        return 1;
    }
    fclose(file);
    
    // XOR encrypt the checksum with pad data to create unique identifier
    unsigned char encrypted_checksum[32];
    for (int i = 0; i < 32; i++) {
        encrypted_checksum[i] = checksum[i] ^ pad_key[i];
    }
    
    // Convert to hex string (64 characters)
    for (int i = 0; i < 32; i++) {
        sprintf(checksum_hex + (i * 2), "%02x", encrypted_checksum[i]);
    }
    checksum_hex[64] = '\0';
    
    return 0;
}

// Unified pad selection function - extracts the best UI from handle_pads_menu()
char* select_pad_interactive(const char* title, const char* prompt, pad_filter_type_t filter_type, int allow_cancel) {
    // Get list of pads from current directory
    DIR* dir = opendir(current_pads_dir);
    if (!dir) {
        printf("Error: Cannot open pads directory %s\n", current_pads_dir);
        return NULL;
    }
    
    // Structure to store pad information
    struct PadInfo {
        char chksum[65];
        char size_str[32];
        char used_str[32];
        double percentage;
        char location[256];
    };
    
    struct PadInfo pads[100];  // Support up to 100 pads
    int pad_count = 0;
    
    // Collect all pad information
    struct dirent* entry;
    while ((entry = readdir(dir)) != NULL && pad_count < 100) {
        if (strstr(entry->d_name, ".pad") && strlen(entry->d_name) == 68) {
            strncpy(pads[pad_count].chksum, entry->d_name, 64);
            pads[pad_count].chksum[64] = '\0';
            
            // Get pad file size and usage info
            char full_path[1024];
            snprintf(full_path, sizeof(full_path), "%s/%s", current_pads_dir, entry->d_name);
            struct stat st;
            if (stat(full_path, &st) == 0) {
                // Get used bytes from state
                uint64_t used_bytes;
                read_state_offset(pads[pad_count].chksum, &used_bytes);
                
                // Apply filter
                if (filter_type == PAD_FILTER_UNUSED_ONLY && used_bytes > 32) {
                    continue; // Skip used pads when filtering for unused only
                }
                
                // Format total size
                if (st.st_size < 1024) {
                    snprintf(pads[pad_count].size_str, sizeof(pads[pad_count].size_str), "%luB", st.st_size);
                } else if (st.st_size < 1024 * 1024) {
                    snprintf(pads[pad_count].size_str, sizeof(pads[pad_count].size_str), "%.1fKB", (double)st.st_size / 1024.0);
                } else if (st.st_size < 1024 * 1024 * 1024) {
                    snprintf(pads[pad_count].size_str, sizeof(pads[pad_count].size_str), "%.1fMB", (double)st.st_size / (1024.0 * 1024.0));
                } else {
                    snprintf(pads[pad_count].size_str, sizeof(pads[pad_count].size_str), "%.2fGB", (double)st.st_size / (1024.0 * 1024.0 * 1024.0));
                }
                
                // Format used size
                if (used_bytes < 1024) {
                    snprintf(pads[pad_count].used_str, sizeof(pads[pad_count].used_str), "%luB", used_bytes);
                } else if (used_bytes < 1024 * 1024) {
                    snprintf(pads[pad_count].used_str, sizeof(pads[pad_count].used_str), "%.1fKB", (double)used_bytes / 1024.0);
                } else if (used_bytes < 1024 * 1024 * 1024) {
                    snprintf(pads[pad_count].used_str, sizeof(pads[pad_count].used_str), "%.1fMB", (double)used_bytes / (1024.0 * 1024.0));
                } else {
                    snprintf(pads[pad_count].used_str, sizeof(pads[pad_count].used_str), "%.2fGB", (double)used_bytes / (1024.0 * 1024.0 * 1024.0));
                }
                
                // Calculate percentage
                pads[pad_count].percentage = (double)used_bytes / st.st_size * 100.0;
                
                // Set location info using directory display
                get_directory_display(full_path, pads[pad_count].location, sizeof(pads[pad_count].location));
                
                pad_count++;
            }
        }
    }
    closedir(dir);
    
    if (pad_count == 0) {
        printf("\n%s\n", title);
        if (filter_type == PAD_FILTER_UNUSED_ONLY) {
            printf("No unused pads found.\n");
            printf("Entropy can only be added to pads with 0%% usage (only reserved bytes used).\n");
        } else {
            printf("No pads found.\n");
        }
        return NULL;
    }
    
    // Calculate minimal unique prefixes for each pad
    char prefixes[100][65];
    int prefix_lengths[100];
    
    for (int i = 0; i < pad_count; i++) {
        prefix_lengths[i] = 1;
        
        // Find minimal unique prefix
        while (prefix_lengths[i] <= 64) {
            int unique = 1;
            
            // Check if current prefix is unique among all other pads
            for (int j = 0; j < pad_count; j++) {
                if (i != j && strncmp(pads[i].chksum, pads[j].chksum, prefix_lengths[i]) == 0) {
                    unique = 0;
                    break;
                }
            }
            
            if (unique) {
                break;
            }
            prefix_lengths[i]++;
        }
        
        // Store the minimal prefix
        strncpy(prefixes[i], pads[i].chksum, prefix_lengths[i]);
        prefixes[i][prefix_lengths[i]] = '\0';
    }
    
    // Display title and pads table
    printf("\n%s\n", title);
    printf("%-8s %-2s %-12s %-12s %-12s %-8s\n", "ChkSum", "D", "Dir", "Size", "Used", "% Used");
    printf("%-8s %-2s %-12s %-12s %-12s %-8s\n", "--------", "--", "------------", "----------", "----------", "------");
    
    // Get current default pad path for comparison
    char* current_default = get_default_pad_path();
    char default_pad_checksum[65] = "";
    
    if (current_default) {
        // Extract checksum from default pad path
        char* filename = strrchr(current_default, '/');
        if (!filename) filename = current_default;
        else filename++; // Skip the '/'
        
        // Extract checksum (remove .pad extension)
        if (strlen(filename) >= 68 && strstr(filename, ".pad")) {
            strncpy(default_pad_checksum, filename, 64);
            default_pad_checksum[64] = '\0';
        }
        free(current_default);
    }
    
    for (int i = 0; i < pad_count; i++) {
        // Check if this is the default pad
        int is_default = (strlen(default_pad_checksum) > 0 &&
                         strncmp(pads[i].chksum, default_pad_checksum, 64) == 0);
        
        // Display first 8 characters of checksum with prefix underlined
        char checksum_8char[9];
        strncpy(checksum_8char, pads[i].chksum, 8);
        checksum_8char[8] = '\0';
        
        printf("\033[4m%.*s\033[0m%s %-2s %-12s %-12s %-12s %.1f%%\n",
               prefix_lengths[i], checksum_8char,  // Underlined prefix
               checksum_8char + prefix_lengths[i], // Rest of 8-char checksum
               is_default ? "*" : "",             // Default indicator
               pads[i].location,
               pads[i].size_str,
               pads[i].used_str,
               pads[i].percentage);
    }
    
    // Display prompt
    printf("\n%s", prompt);
    if (allow_cancel) {
        printf(" (or 'x' to cancel)");
    }
    printf(": ");
    
    char input[MAX_HASH_LENGTH];
    if (!fgets(input, sizeof(input), stdin)) {
        printf("Error: Failed to read input\n");
        return NULL;
    }
    input[strcspn(input, "\n")] = 0;
    
    // Handle empty input - select default pad if available
    if (strlen(input) == 0) {
        // Get current default pad path
        char* current_default = get_default_pad_path();
        if (current_default) {
            // Extract checksum from default pad path
            char* filename = strrchr(current_default, '/');
            if (!filename) filename = current_default;
            else filename++; // Skip the '/'
            
            // Extract checksum (remove .pad extension)
            if (strlen(filename) >= 68 && strstr(filename, ".pad")) {
                char default_checksum[65];
                strncpy(default_checksum, filename, 64);
                default_checksum[64] = '\0';
                
                // Verify this default pad is in our current list
                for (int i = 0; i < pad_count; i++) {
                    if (strncmp(pads[i].chksum, default_checksum, 64) == 0) {
                        free(current_default);
                        printf("Selected default pad: %.16s...\n\n", default_checksum);
                        return strdup(default_checksum);
                    }
                }
            }
            free(current_default);
        }
        // No default pad or default pad not in current list
        printf("No default pad available or default pad not in current list\n");
        return NULL;
    }
    
    // Handle cancel
    if (allow_cancel && (toupper(input[0]) == 'X' && strlen(input) == 1)) {
        return NULL;
    }
    
    // Find matching pad by prefix only
    int selected_pad = -1;
    int match_count = 0;
    
    // Try prefix matching only
    for (int i = 0; i < pad_count; i++) {
        if (strncmp(input, pads[i].chksum, strlen(input)) == 0) {
            if (match_count == 0) {
                selected_pad = i;
            }
            match_count++;
        }
    }
    
    if (match_count == 0) {
        printf("No pad found matching '%s'\n", input);
        return NULL;
    } else if (match_count > 1) {
        printf("Ambiguous prefix. Multiple matches found.\n");
        return NULL;
    }
    
    // Return selected pad checksum (caller must free)
    return strdup(pads[selected_pad].chksum);
}

int handle_pads_menu(void) {
    printf("\n=== Pad Management ===\n");
    
    // Get list of pads from current directory
    DIR* dir = opendir(current_pads_dir);
    if (!dir) {
        printf("Error: Cannot open pads directory %s\n", current_pads_dir);
        return 1;
    }
    
    // Structure to store pad information
    struct PadInfo {
        char chksum[65];
        char size_str[32];
        char used_str[32];
        double percentage;
        char location[256];  // Store location info
    };
    
    struct PadInfo pads[100];  // Support up to 100 pads
    int pad_count = 0;
    
    // Collect all pad information
    struct dirent* entry;
    while ((entry = readdir(dir)) != NULL && pad_count < 100) {
        if (strstr(entry->d_name, ".pad") && strlen(entry->d_name) == 68) {
            strncpy(pads[pad_count].chksum, entry->d_name, 64);
            pads[pad_count].chksum[64] = '\0';
            
            // Get pad file size and usage info
            char full_path[1024];  // Increased buffer size
            snprintf(full_path, sizeof(full_path), "%s/%s", current_pads_dir, entry->d_name);
            struct stat st;
            if (stat(full_path, &st) == 0) {
                // Get used bytes from state
                uint64_t used_bytes;
                read_state_offset(pads[pad_count].chksum, &used_bytes);
                
                // Format total size
                if (st.st_size < 1024) {
                    snprintf(pads[pad_count].size_str, sizeof(pads[pad_count].size_str), "%luB", st.st_size);
                } else if (st.st_size < 1024 * 1024) {
                    snprintf(pads[pad_count].size_str, sizeof(pads[pad_count].size_str), "%.1fKB", (double)st.st_size / 1024.0);
                } else if (st.st_size < 1024 * 1024 * 1024) {
                    snprintf(pads[pad_count].size_str, sizeof(pads[pad_count].size_str), "%.1fMB", (double)st.st_size / (1024.0 * 1024.0));
                } else {
                    snprintf(pads[pad_count].size_str, sizeof(pads[pad_count].size_str), "%.2fGB", (double)st.st_size / (1024.0 * 1024.0 * 1024.0));
                }
                
                // Format used size
                if (used_bytes < 1024) {
                    snprintf(pads[pad_count].used_str, sizeof(pads[pad_count].used_str), "%luB", used_bytes);
                } else if (used_bytes < 1024 * 1024) {
                    snprintf(pads[pad_count].used_str, sizeof(pads[pad_count].used_str), "%.1fKB", (double)used_bytes / 1024.0);
                } else if (used_bytes < 1024 * 1024 * 1024) {
                    snprintf(pads[pad_count].used_str, sizeof(pads[pad_count].used_str), "%.1fMB", (double)used_bytes / (1024.0 * 1024.0));
                } else {
                    snprintf(pads[pad_count].used_str, sizeof(pads[pad_count].used_str), "%.2fGB", (double)used_bytes / (1024.0 * 1024.0 * 1024.0));
                }
                
                // Calculate percentage
                pads[pad_count].percentage = (double)used_bytes / st.st_size * 100.0;
                
                // Set location info using directory display
                get_directory_display(full_path, pads[pad_count].location, sizeof(pads[pad_count].location));
                
                pad_count++;
            }
        }
    }
    closedir(dir);
    
    if (pad_count == 0) {
        printf("No pads found.\n");
        printf("\nOptions:\n");
        printf(" \033[4mG\033[0menerate new pad\n");
        printf(" E\033[4mx\033[0mit\n");
        printf("\nSelect option: ");
        
        char input[10];
        if (fgets(input, sizeof(input), stdin)) {
        char choice = toupper(input[0]);
        if (choice == 'G') {
            int result = handle_generate_menu();
            if (result == 0) {
                // After successful pad generation, return to pads menu
                return handle_pads_menu();
            }
            return result;
        }
        }
        return 0;
    }
    
    // Calculate minimal unique prefixes for each pad
    char prefixes[100][65];  // Store the minimal prefix for each pad
    int prefix_lengths[100]; // Length of minimal prefix for each pad
    
    for (int i = 0; i < pad_count; i++) {
        prefix_lengths[i] = 1;
        
        // Find minimal unique prefix
        while (prefix_lengths[i] <= 64) {
            int unique = 1;
            
            // Check if current prefix is unique among all other pads
            for (int j = 0; j < pad_count; j++) {
                if (i != j && strncmp(pads[i].chksum, pads[j].chksum, prefix_lengths[i]) == 0) {
                    unique = 0;
                    break;
                }
            }
            
            if (unique) {
                break;
            }
            prefix_lengths[i]++;
        }
        
        // Store the minimal prefix
        strncpy(prefixes[i], pads[i].chksum, prefix_lengths[i]);
        prefixes[i][prefix_lengths[i]] = '\0';
    }
    
    // Display pads with minimal prefixes underlined and default indicator
    printf("\nAvailable pads:\n");
    printf("%-8s %-2s %-12s %-12s %-12s %-8s\n", "ChkSum", "D", "Dir", "Size", "Used", "% Used");
    printf("%-8s %-2s %-12s %-12s %-12s %-8s\n", "--------", "--", "------------", "----------", "----------", "------");
    
    // Get current default pad path for comparison
    char* current_default = get_default_pad_path();
    char default_pad_checksum[65] = "";
    
    if (current_default) {
        // Extract checksum from default pad path
        char* filename = strrchr(current_default, '/');
        if (!filename) filename = current_default;
        else filename++; // Skip the '/'
        
        // Extract checksum (remove .pad extension)
        if (strlen(filename) >= 68 && strstr(filename, ".pad")) {
            strncpy(default_pad_checksum, filename, 64);
            default_pad_checksum[64] = '\0';
        }
        free(current_default);
    }
    
    for (int i = 0; i < pad_count; i++) {
        // Check if this is the default pad
        int is_default = (strlen(default_pad_checksum) > 0 &&
                         strncmp(pads[i].chksum, default_pad_checksum, 64) == 0);
        
        // Display first 8 characters of checksum with prefix underlined
        char checksum_8char[9];
        strncpy(checksum_8char, pads[i].chksum, 8);
        checksum_8char[8] = '\0';
        
        printf("\033[4m%.*s\033[0m%s %-2s %-12s %-12s %-12s %.1f%%\n",
               prefix_lengths[i], checksum_8char,  // Underlined prefix
               checksum_8char + prefix_lengths[i], // Rest of 8-char checksum
               is_default ? "*" : "",             // Default indicator
               pads[i].location,                   // Use the stored location info
               pads[i].size_str,
               pads[i].used_str,
               pads[i].percentage);
    }
    
    printf("\nActions:\n");
    printf(" \033[4mG\033[0menerate new pad\n");
    printf(" \033[4mA\033[0mdd entropy to pad\n");
    printf(" \033[4mS\033[0met default pad\n");
    printf(" E\033[4mx\033[0mit\n");
    printf("\nSelect action: ");
    
    char input[MAX_HASH_LENGTH];
    if (!fgets(input, sizeof(input), stdin)) {
        printf("Error: Failed to read input\n");
        return 1;
    }
    input[strcspn(input, "\n")] = 0;
    
    // Handle actions
    if (toupper(input[0]) == 'G') {
        int result = handle_generate_menu();
        if (result == 0) {
            // After successful pad generation, return to pads menu
            return handle_pads_menu();
        }
        return result;
    } else if (toupper(input[0]) == 'A') {
        // Add entropy to pad - use unified function with unused pads filter
        char* selected_pad = select_pad_interactive("=== Select Unused Pad for Entropy Addition ===",
                                                  "Select unused pad (by prefix)",
                                                  PAD_FILTER_UNUSED_ONLY, 1);
        if (!selected_pad) {
            printf("Entropy addition cancelled.\n");
            return handle_pads_menu();
        }
        
        // Add entropy to the selected unused pad
        int result = handle_add_entropy_to_pad(selected_pad);
        free(selected_pad);
        if (result == 0) {
            // Return to pads menu after successful entropy addition
            return handle_pads_menu();
        }
        return result;
    } else if (toupper(input[0]) == 'S') {
        // Set default pad - use unified function
        char* selected_pad = select_pad_interactive("=== Select Default Pad ===",
                                                  "Select pad to set as default (by prefix)",
                                                  PAD_FILTER_ALL, 1);
        if (!selected_pad) {
            printf("Default pad selection cancelled.\n");
            return handle_pads_menu();
        }
        
        // Construct the full absolute pad path and set as default
        char new_default_path[1024];
        if (current_pads_dir[0] == '/') {
            // Already absolute path
            int ret = snprintf(new_default_path, sizeof(new_default_path), "%s/%s.pad", current_pads_dir, selected_pad);
            if (ret >= (int)sizeof(new_default_path)) {
                printf("Error: Path too long for default pad setting\n");
                free(selected_pad);
                return handle_pads_menu();
            }
        } else {
            // Relative path - make it absolute
            char current_dir[512];
            if (getcwd(current_dir, sizeof(current_dir))) {
                int ret = snprintf(new_default_path, sizeof(new_default_path), "%s/%s/%s.pad", current_dir, current_pads_dir, selected_pad);
                if (ret >= (int)sizeof(new_default_path)) {
                    // Path was truncated, fall back to relative path
                    int ret2 = snprintf(new_default_path, sizeof(new_default_path), "%s/%s.pad", current_pads_dir, selected_pad);
                    if (ret2 >= (int)sizeof(new_default_path)) {
                        printf("Error: Path too long for default pad setting\n");
                        free(selected_pad);
                        return handle_pads_menu();
                    }
                }
            } else {
                // Fallback to relative path
                int ret = snprintf(new_default_path, sizeof(new_default_path), "%s/%s.pad", current_pads_dir, selected_pad);
                if (ret >= (int)sizeof(new_default_path)) {
                    printf("Error: Path too long for default pad setting\n");
                    free(selected_pad);
                    return handle_pads_menu();
                }
            }
        }
        
        if (set_default_pad_path(new_default_path) == 0) {
            printf("Default pad set to: %.16s...\n", selected_pad);
            printf("Full path: %s\n", new_default_path);
        } else {
            printf("Error: Failed to update default pad preference\n");
        }
        
        free(selected_pad);
        return handle_pads_menu();
    } else if (toupper(input[0]) == 'X') {
        return 0; // Exit to main menu
    } else {
        printf("Invalid action. Please select G, A, S, or X.\n");
        return handle_pads_menu();
    }
}

void get_directory_display(const char* file_path, char* result, size_t result_size) {
    // Extract directory path from full file path
    char dir_path[512];
    char* last_slash = strrchr(file_path, '/');
    
    if (last_slash) {
        size_t dir_len = last_slash - file_path;
        if (dir_len >= sizeof(dir_path)) {
            dir_len = sizeof(dir_path) - 1;
        }
        strncpy(dir_path, file_path, dir_len);
        dir_path[dir_len] = '\0';
    } else {
        // No directory separator, assume current directory
        strcpy(dir_path, ".");
    }
    
    // USB Drive Detection and Smart Shortening
    char* home_dir = getenv("HOME");
    
    // Check for USB/removable media mount patterns
    if (strstr(dir_path, "/media/") || strstr(dir_path, "/run/media/") || strstr(dir_path, "/mnt/")) {
        // Extract USB label/name
        char* media_start = NULL;
        if (strstr(dir_path, "/media/")) {
            media_start = strstr(dir_path, "/media/");
        } else if (strstr(dir_path, "/run/media/")) {
            media_start = strstr(dir_path, "/run/media/");
        } else if (strstr(dir_path, "/mnt/")) {
            media_start = strstr(dir_path, "/mnt/");
        }
        
        if (media_start) {
            // Find the USB label part
            char* path_after_media = strchr(media_start + 1, '/');
            if (path_after_media) {
                path_after_media++; // Skip the slash
                
                // For /media/user/LABEL pattern, skip the username to get to the drive label
                if (strstr(media_start, "/media/")) {
                    char* next_slash = strchr(path_after_media, '/');
                    if (next_slash) {
                        path_after_media = next_slash + 1;
                    }
                }
                // For /run/media/user/LABEL pattern, skip the username
                else if (strstr(media_start, "/run/media/")) {
                    char* next_slash = strchr(path_after_media, '/');
                    if (next_slash) {
                        path_after_media = next_slash + 1;
                    }
                }
                
                // Extract just the USB label (up to next slash or end)
                char* label_end = strchr(path_after_media, '/');
                char usb_label[32];
                if (label_end) {
                    size_t label_len = label_end - path_after_media;
                    if (label_len > sizeof(usb_label) - 1) label_len = sizeof(usb_label) - 1;
                    strncpy(usb_label, path_after_media, label_len);
                    usb_label[label_len] = '\0';
                } else {
                    // USB label is the last part
                    strncpy(usb_label, path_after_media, sizeof(usb_label) - 1);
                    usb_label[sizeof(usb_label) - 1] = '\0';
                }
                
                // Format with USB: prefix, limiting total length to fit in result
                snprintf(result, result_size, "USB:%s", usb_label);
                // Truncate if too long
                if (strlen(result) > 11) {
                    result[11] = '\0';
                }
                return;
            }
        }
    }
    
    // Home directory shortening
    if (home_dir && strncmp(dir_path, home_dir, strlen(home_dir)) == 0) {
        if (dir_path[strlen(home_dir)] == '/' || dir_path[strlen(home_dir)] == '\0') {
            // Replace home directory with ~
            char temp[512];
            snprintf(temp, sizeof(temp), "~%s", dir_path + strlen(home_dir));
            
            // If result is too long, truncate intelligently
            if (strlen(temp) > 11) {
                // Show ~/...end_part
                char* last_part = strrchr(temp, '/');
                if (last_part && strlen(last_part) < 8) {
                    snprintf(result, result_size, "~...%s", last_part);
                } else {
                    strncpy(result, temp, 11);
                    result[11] = '\0';
                }
            } else {
                strncpy(result, temp, result_size - 1);
                result[result_size - 1] = '\0';
            }
            return;
        }
    }
    
    // Current working directory
    if (strcmp(dir_path, ".") == 0 || strcmp(dir_path, current_pads_dir) == 0) {
        strncpy(result, "pads", result_size - 1);
        result[result_size - 1] = '\0';
        return;
    }
    
    // System/other paths - smart truncation with ellipsis
    if (strlen(dir_path) > 11) {
        // Try to show the most meaningful part
        char* last_part = strrchr(dir_path, '/');
        if (last_part && strlen(last_part) < 9) {
            // Show .../last_part
            snprintf(result, result_size, "...%s", last_part);
        } else {
            // Show first part with ellipsis
            strncpy(result, dir_path, 8);
            strncpy(result + 8, "...", result_size - 8 - 1);
            result[result_size - 1] = '\0';
        }
    } else {
        // Short enough, use as-is
        strncpy(result, dir_path, result_size - 1);
        result[result_size - 1] = '\0';
    }
}

int handle_add_entropy_to_pad(const char* pad_chksum) {
    printf("\n=== Add Entropy to Pad: %.16s... ===\n", pad_chksum);
    printf("This will enhance the randomness of your pad using keyboard entropy.\n");
    printf("The entropy will be processed with Chacha20 and distributed throughout the entire pad.\n\n");
    
    printf("Entropy collection options:\n");
    printf(" 1. Recommended (2048 bytes) - Optimal security\n");
    printf(" 2. Minimum (1024 bytes) - Good security\n");
    printf(" 3. Maximum (4096 bytes) - Maximum security\n");
    printf(" 4. Custom amount\n");
    printf("Enter choice (1-4): ");
    
    char choice_input[10];
    if (!fgets(choice_input, sizeof(choice_input), stdin)) {
        printf("Error: Failed to read input\n");
        return 1;
    }
    
    size_t target_bytes = 2048; // Default
    int choice = atoi(choice_input);
    
    switch (choice) {
        case 1:
            target_bytes = 2048;
            break;
        case 2:
            target_bytes = 1024;
            break;
        case 3:
            target_bytes = 4096;
            break;
        case 4:
            printf("Enter custom amount (512-8192 bytes): ");
            char custom_input[32];
            if (!fgets(custom_input, sizeof(custom_input), stdin)) {
                printf("Error: Failed to read input\n");
                return 1;
            }
            
            size_t custom_amount = (size_t)atoi(custom_input);
            if (custom_amount < 512 || custom_amount > 8192) {
                printf("Error: Invalid amount. Must be between 512 and 8192 bytes.\n");
                return 1;
            }
            target_bytes = custom_amount;
            break;
        default:
            target_bytes = 2048; // Default to recommended
            break;
    }
    
    printf("\nCollecting %zu bytes of entropy...\n", target_bytes);
    
    // Allocate entropy buffer
    unsigned char* entropy_buffer = malloc(MAX_ENTROPY_BUFFER);
    if (!entropy_buffer) {
        printf("Error: Cannot allocate entropy buffer\n");
        return 1;
    }
    
    // Collect entropy with visual feedback
    size_t collected_bytes = 0;
    int result = collect_entropy_with_feedback(entropy_buffer, target_bytes, &collected_bytes, 1);
    
    if (result != 0) {
        printf("Error: Entropy collection failed\n");
        free(entropy_buffer);
        return 1;
    }
    
    if (collected_bytes < 512) {
        printf("Error: Insufficient entropy collected (%zu bytes)\n", collected_bytes);
        free(entropy_buffer);
        return 1;
    }
    
    printf("\nProcessing entropy and modifying pad...\n");
    
    // Add entropy to pad
    result = add_entropy_to_pad(pad_chksum, entropy_buffer, collected_bytes, 1);
    
    // Clear entropy buffer for security
    memset(entropy_buffer, 0, MAX_ENTROPY_BUFFER);
    free(entropy_buffer);
    
    if (result != 0) {
        printf("Error: Failed to add entropy to pad\n");
        return 1;
    }
    
    printf("\n🎉 SUCCESS! Your pad now has enhanced randomness!\n");
    printf("Press Enter to continue...");
    getchar();
    
    return 0;
}

void print_usage(const char* program_name) {
    printf("OTP Cipher - One Time Pad Implementation v0.3.1\n");
    printf("Built for testing entropy system\n");
    printf("Usage:\n");
    printf("  %s                                         - Interactive mode\n", program_name);
    printf("  %s generate|-g <size>                      - Generate new pad\n", program_name);
    printf("  %s encrypt|-e [pad_checksum_prefix] [text] - Encrypt text\n", program_name);
    printf("  %s decrypt|-d [encrypted_message]          - Decrypt message\n", program_name);
    printf("  %s -f <file> <pad_prefix> [-a] [-o <out>]  - Encrypt file\n", program_name);
    printf("  %s list|-l                                 - List available pads\n", program_name);
    printf("\nFile Operations:\n");
    printf("  -f <file> <pad>     - Encrypt file (binary .otp format)\n");
    printf("  -f <file> <pad> -a  - Encrypt file (ASCII .otp.asc format)\n");
    printf("  -o <output>         - Specify output filename\n");
    printf("\nShort flags:\n");
    printf("  -g generate   -e encrypt   -d decrypt   -l list   -f file\n");
    printf("\nExamples:\n");
    printf("  %s -e 1a2b3c \"Hello world\"                  - Encrypt inline text\n", program_name);
    printf("  %s -f document.pdf 1a2b                     - Encrypt file (binary)\n", program_name);
    printf("  %s -f document.pdf 1a2b -a                  - Encrypt file (ASCII)\n", program_name);
    printf("  %s -f document.pdf 1a2b -o secret.otp       - Encrypt with custom output\n", program_name);
    printf("  %s -d \"-----BEGIN OTP MESSAGE-----...\"      - Decrypt message/file\n", program_name);
    printf("  %s -d encrypted.otp.asc                     - Decrypt ASCII file\n", program_name);
    printf("  %s -g 1GB                                   - Generate 1GB pad\n", program_name);
    printf("  %s -l                                       - List pads\n", program_name);
    printf("\nSize examples: 1GB, 5TB, 512MB, 2048 (bytes)\n");
    printf("Pad selection: Full chksum or prefix\n");
}