Add NIP-30 module for custom emojis

nip30.ts

@@ -0,0 +1,54 @@
+/** Regex for a single emoji shortcode. */
+export const EMOJI_SHORTCODE_REGEX = /:(\w+):/
+
+/** Regex to find emoji shortcodes in content. */
+export const regex = () => new RegExp(`\\B${EMOJI_SHORTCODE_REGEX.source}\\B`, 'g')
+
+/** Represents a Nostr custom emoji. */
+export interface CustomEmoji {
+  /** The matched emoji name with colons. */
+  shortcode: `:${string}:`
+  /** The matched emoji name without colons. */
+  name: string
+}
+
+/** Match result for a custom emoji in text content. */
+export interface CustomEmojiMatch extends CustomEmoji {
+  /** Index where the emoji begins in the text content. */
+  start: number
+  /** Index where the emoji ends in the text content. */
+  end: number
+}
+
+/** Find all custom emoji shortcodes. */
+export function * matchAll(content: string): Iterable<CustomEmojiMatch> {
+  const matches = content.matchAll(regex())
+
+  for (const match of matches) {
+    try {
+      const [shortcode, name] = match
+
+      yield {
+        shortcode: shortcode as `:${string}:`,
+        name,
+        start: match.index!,
+        end: match.index! + shortcode.length
+      }
+    } catch (_e) {
+      // do nothing
+    }
+  }
+}
+
+/** Replace all emoji shortcodes in the content. */
+export function replaceAll(
+  content: string,
+  replacer: (match: CustomEmoji) => string
+): string {
+  return content.replaceAll(regex(), (shortcode, name) => {
+    return replacer({
+      shortcode: shortcode as `:${string}:`,
+      name,
+    })
+  })
+}