export async function ensureLocal(url) {
  return new Promise((resolve) => {
    try {
      const cache = uni.getStorageSync('asset_cache_v1') || {}
      const hit = cache[url]
      if (hit && typeof hit === 'string' && hit) { resolve(hit); return }
      uni.downloadFile({
        url,
        success: (res) => {
          const tmp = res.tempFilePath || ''
          if (!tmp) { resolve(url); return }
          uni.saveFile({
            tempFilePath: tmp,
            success: (s) => {
              const saved = s.savedFilePath || tmp
              cache[url] = saved
              uni.setStorageSync('asset_cache_v1', cache)
              resolve(saved)
            },
            fail: () => { resolve(tmp) }
          })
        },
        fail: () => { resolve(url) }
      })
    } catch (_) { resolve(url) }
  })
}

export async function preloadAssets(urls) {
  const tasks = urls.map(u => ensureLocal(u))
  const results = await Promise.allSettled(tasks)
  const map = {}
  results.forEach((r, i) => { map[urls[i]] = r.status === 'fulfilled' ? r.value : urls[i] })
  return map
}