/**
 * ASCIIBarChart - A dynamic ASCII-based vertical bar chart renderer
 * 
 * Creates real-time animated bar charts using monospaced characters (X)
 * with automatic scaling, labels, and responsive font sizing.
 */
class ASCIIBarChart {
    /**
     * Create a new ASCII bar chart
     * @param {string} containerId - The ID of the HTML element to render the chart in
     * @param {Object} options - Configuration options
     * @param {number} [options.maxHeight=20] - Maximum height of the chart in rows
     * @param {number} [options.maxDataPoints=30] - Maximum number of data columns before scrolling
     * @param {string} [options.title=''] - Chart title (displayed centered at top)
     * @param {string} [options.xAxisLabel=''] - X-axis label (displayed centered at bottom)
     * @param {string} [options.yAxisLabel=''] - Y-axis label (displayed vertically on left)
     * @param {boolean} [options.autoFitWidth=true] - Automatically adjust font size to fit container width
     */
    constructor(containerId, options = {}) {
        this.container = document.getElementById(containerId);
        this.data = [];
        this.maxHeight = options.maxHeight || 20;
        this.maxDataPoints = options.maxDataPoints || 30;
        this.totalDataPoints = 0; // Track total number of data points added
        this.title = options.title || '';
        this.xAxisLabel = options.xAxisLabel || '';
        this.yAxisLabel = options.yAxisLabel || '';
        this.autoFitWidth = options.autoFitWidth !== false; // Default to true
        
        // Set up resize observer if auto-fit is enabled
        if (this.autoFitWidth) {
            this.resizeObserver = new ResizeObserver(() => {
                this.adjustFontSize();
            });
            this.resizeObserver.observe(this.container);
        }
    }
    
    /**
     * Add a new data point to the chart
     * @param {number} value - The numeric value to add
     */
    addValue(value) {
        this.data.push(value);
        this.totalDataPoints++;
        
        // Keep only the most recent data points
        if (this.data.length > this.maxDataPoints) {
            this.data.shift();
        }
        
        this.render();
        this.updateInfo();
    }
    
    /**
     * Clear all data from the chart
     */
    clear() {
        this.data = [];
        this.totalDataPoints = 0;
        this.render();
        this.updateInfo();
    }
    
    /**
     * Calculate the width of the chart in characters
     * @returns {number} The chart width in characters
     * @private
     */
    getChartWidth() {
        if (this.data.length === 0) return 50; // Default width for empty chart
        
        const yAxisPadding = this.yAxisLabel ? 2 : 0;
        const yAxisNumbers = 3; // Width of Y-axis numbers
        const separator = 1; // The '|' character
        const dataWidth = this.data.length * 2; // Each column is 2 characters wide
        const padding = 1; // Extra padding
        
        return yAxisPadding + yAxisNumbers + separator + dataWidth + padding;
    }
    
    /**
     * Adjust font size to fit container width
     * @private
     */
    adjustFontSize() {
        if (!this.autoFitWidth) return;
        
        const containerWidth = this.container.clientWidth;
        const chartWidth = this.getChartWidth();
        
        if (chartWidth === 0) return;
        
        // Calculate optimal font size
        // For monospace fonts, character width is approximately 0.6 * font size
        const charWidthRatio = 0.6;
        const padding = 40; // Account for container padding
        const availableWidth = containerWidth - padding;
        const optimalFontSize = Math.floor((availableWidth / chartWidth) / charWidthRatio);
        
        // Set reasonable bounds (min 4px, max 20px)
        const fontSize = Math.max(4, Math.min(20, optimalFontSize));
        
        this.container.style.fontSize = fontSize + 'px';
        this.container.style.lineHeight = '1.0';
    }
    
    /**
     * Render the chart to the container
     * @private
     */
    render() {
        if (this.data.length === 0) {
            this.container.textContent = 'No data yet. Click Start to begin.';
            return;
        }
        
        let output = '';
        const maxValue = Math.max(...this.data);
        const minValue = Math.min(...this.data);
        const valueRange = maxValue - minValue;
        const scale = this.maxHeight;
        
        // Calculate Y-axis label width (for vertical text)
        const yLabelWidth = this.yAxisLabel ? 2 : 0;
        const yAxisPadding = this.yAxisLabel ? '  ' : '';
        
        // Add title if provided (centered)
        if (this.title) {
            const chartWidth = 4 + this.data.length * 2; // Y-axis numbers + data columns
            const titlePadding = Math.floor((chartWidth - this.title.length) / 2);
            output += yAxisPadding + ' '.repeat(Math.max(0, titlePadding)) + this.title + '\n\n';
        }
        
        // Draw from top to bottom
        for (let row = scale; row > 0; row--) {
            let line = '';
            
            // Add vertical Y-axis label character
            if (this.yAxisLabel) {
                const L = this.yAxisLabel.length;
                const startRow = Math.floor((scale - L) / 2) + 1;
                const relativeRow = scale - row + 1; // 1 at top, scale at bottom
                if (relativeRow >= startRow && relativeRow < startRow + L) {
                    const labelIndex = relativeRow - startRow;
                    line += this.yAxisLabel[labelIndex] + ' ';
                } else {
                    line += '  ';
                }
            }
            
            // Calculate the actual value this row represents
            const rowValue = minValue + (valueRange * (row - 1) / (scale - 1));
            
            // Add Y-axis label (show actual values)
            line += String(Math.round(rowValue)).padStart(3, ' ') + ' |';
            
            // Draw each column
            for (let i = 0; i < this.data.length; i++) {
                const value = this.data[i];
                
                // Scale the value to fit between 1 and scale
                let scaledValue;
                if (valueRange === 0) {
                    // All values are the same
                    scaledValue = 1;
                } else {
                    scaledValue = 1 + Math.round(((value - minValue) / valueRange) * (scale - 1));
                }
                
                if (scaledValue >= row) {
                    line += ' X';
                } else {
                    line += '  ';
                }
            }
            
            output += line + '\n';
        }
        
        // Draw X-axis
        output += yAxisPadding + '    +' + '-'.repeat(this.data.length * 2) + '\n';
        
        // Draw X-axis labels (column numbers that move with the data)
        let xAxisLabels = yAxisPadding + '     ';
        const startIndex = this.totalDataPoints - this.data.length + 1;
        for (let i = 0; i < this.data.length; i++) {
            const dataPointNumber = startIndex + i;
            if (i % 5 === 0) {
                xAxisLabels += String(dataPointNumber).padStart(2, ' ');
            } else {
                xAxisLabels += '  ';
            }
        }
        output += xAxisLabels + '\n';
        
        // Add X-axis label if provided
        if (this.xAxisLabel) {
            const labelPadding = Math.floor((this.data.length * 2 - this.xAxisLabel.length) / 2);
            output += '\n' + yAxisPadding + '     ' + ' '.repeat(Math.max(0, labelPadding)) + this.xAxisLabel + '\n';
        }
        
        this.container.textContent = output;
        
        // Adjust font size to fit width
        if (this.autoFitWidth) {
            this.adjustFontSize();
        }
        
        // Update the external info display
        document.getElementById('values').textContent = `[${this.data.join(', ')}]`;
        document.getElementById('max-value').textContent = maxValue;
        document.getElementById('scale').textContent = `Min: ${minValue}, Max: ${maxValue}, Height: ${scale}`;
    }
    
    /**
     * Update the info display
     * @private
     */
    updateInfo() {
        document.getElementById('count').textContent = this.data.length;
    }
}