/**
 * Voice prompt utility for the timer.
 *
 * 4 fixed, polished prompts live in `cloudfunctions/tts`. We call that
 * cloud function with a key, get back an audio URL (cached in cloud
 * storage after first synthesis), and play it via createInnerAudioContext.
 *
 * The in-memory `_urlCache` avoids hitting the cloud function more than
 * once per prompt per session. The audio context is a singleton so
 * overlapping prompts interrupt each other cleanly.
 *
 * If the cloud function is unconfigured (no TTS credentials) and returns
 * `success: false`, we fall back to a silent no-op — better than spamming
 * the user with toast errors mid-plank.
 */

const PROMPTS = {
  halfway: '已完成一半啦,坚持就是胜利!',
  last30: '最后30秒,保持呼吸,稳住姿势!',
  last10: '最后10秒,再加把劲!',
  complete: '太棒了!今天的目标已完成,继续加油!'
}

let _ctx = null
const _urlCache = {}     // { promptKey: audioUrl }

const _getCtx = () => {
  if (!_ctx) {
    _ctx = wx.createInnerAudioContext()
    // Play even when the device is in silent mode — we want the user to
    // actually hear training cues during a session.
    _ctx.obeyMuteSwitch = false
  }
  return _ctx
}

const _fetchUrl = async (promptKey) => {
  if (_urlCache[promptKey]) return _urlCache[promptKey]
  try {
    const res = await wx.cloud.callFunction({
      name: 'tts',
      data: { promptKey },
      // Default WeChat cloud timeout is 3s, which is exactly the TTS
      // first-call budget (synth + upload + tempURL). Bump to 30s for
      // cold starts; cached calls return in <500ms.
      config: { timeout: 30000 }
    })
    if (res && res.result && res.result.success && res.result.audioUrl) {
      _urlCache[promptKey] = res.result.audioUrl
      return res.result.audioUrl
    }
  } catch (e) {
    // cloud function not deployed or other error — silent fallback
  }
  return null
}

/**
 * Play a prompt. Returns a Promise that resolves when playback starts
 * (or immediately if there's no audio available).
 */
const play = async (promptKey) => {
  if (!PROMPTS[promptKey]) return
  const url = await _fetchUrl(promptKey)
  if (!url) return
  const ctx = _getCtx()
  try {
    ctx.stop()
    ctx.src = url
    ctx.play()
  } catch (e) { /* ignore playback errors */ }
}

/**
 * Stop any currently-playing voice prompt. Call this when the user
 * pauses/stops/finishes training to avoid stray audio.
 */
const stop = () => {
  if (_ctx) {
    try { _ctx.stop() } catch (e) { /* ignore */ }
  }
}

/**
 * Tear down the audio context. Call on page unload.
 */
const destroy = () => {
  if (_ctx) {
    try { _ctx.destroy() } catch (e) { /* ignore */ }
    _ctx = null
  }
}

module.exports = { play, stop, destroy, PROMPTS }