/**
 * Audio file utilities: voice IDs, filename conventions, and file listing.
 */

import { join } from '@std/path'
import { Locale } from '$/enums.ts'

/** Azure Neural TTS voice ID used per locale. */
export const VOICE_IDS: Record<Locale, string> = {
  [Locale.zh_CN]: 'zh-CN-XiaoxiaoNeural',
  [Locale.zh_HK]: 'zh-HK-WanLungNeural',
  [Locale.zh_TW]: 'zh-TW-YunJheNeural',
  [Locale.ja]: 'ja-JP-NanamiNeural',
}

/**
 * Returns the audio filename for a given subject id and locale.
 * When col and reading are both provided, appends `_{col}_{reading}` to disambiguate
 * subjects with multiple readings (e.g. polyphonic characters).
 */
export function getFilename(id: string, locale: Locale, col?: string, reading?: string): string {
  const base = `${id}_${locale.replace('_', '-')}_${VOICE_IDS[locale]}`
  if (col && reading) return `${base}_${col}_${reading}.mp3`
  return `${base}.mp3`
}

/**
 * Parses an audio filename into its components.
 * Handles both formats:
 *   {id}_{locale}_{voiceId}.mp3
 *   {id}_{locale}_{voiceId}_{col}_{reading}.mp3
 * Returns null if the filename doesn't match.
 */
export function parseAudioFilename(
  filename: string,
): { id: string; locale: string; voiceId: string; col?: string; reading?: string } | null {
  const parts = filename.replace('.mp3', '').split('_')
  if (parts.length < 3) return null
  const [id, localeHyphen, voiceId, col, reading] = parts
  const locale = localeHyphen.replace('-', '_')
  return { id, locale, voiceId, col, reading }
}

/**
 * Returns all existing audio filenames (not full paths) for the given locales.
 * Skips locales whose audio directories don't exist yet (e.g. before first audio run).
 */
export function listAudioFiles(locales: string[] = ['zh_CN', 'zh_HK', 'zh_TW', 'ja']): string[] {
  return locales
    .filter((locale) => locale !== 'tmp')
    .flatMap((locale) => {
      try {
        return Array.from(Deno.readDirSync(join('www/static/gen/audio', locale)))
      } catch {
        return []
      }
    })
    .filter(({ name }) => /.*\.mp3$/.test(name))
    .map((file) => file.name)
}