const STORAGE_KEY = 'wedding_music_pick_v1'
const DAY_MS = 24 * 60 * 60 * 1000

function readCache() {
  try {
    const raw = localStorage.getItem(STORAGE_KEY)
    if (!raw) return null
    const parsed = JSON.parse(raw)
    if (!parsed?.url || !parsed?.ts) return null
    return parsed
  } catch {
    return null
  }
}

export function rememberMusicPick(url) {
  if (!url) return
  try {
    localStorage.setItem(STORAGE_KEY, JSON.stringify({ url, ts: Date.now() }))
  } catch { /* ignore quota */ }
}

/**
 * Resolve which track to play.
 * When random is enabled, reuse local cache within 24h if still in list; otherwise pick randomly.
 */
export function pickMusicUrl(musicList, activeMusicUrl, musicRandomEnabled) {
  const list = Array.isArray(musicList) ? musicList.filter((t) => t && t.url) : []
  if (!list.length) return ''

  if (!musicRandomEnabled) {
    if (activeMusicUrl && list.some((t) => t.url === activeMusicUrl)) return activeMusicUrl
    return list[0].url
  }

  const cache = readCache()
  if (cache && Date.now() - cache.ts < DAY_MS && list.some((t) => t.url === cache.url)) {
    return cache.url
  }

  const picked = list[Math.floor(Math.random() * list.length)].url
  rememberMusicPick(picked)
  return picked
}