import { useCallback, useState } from 'react'
import * as MediaLibrary from 'expo-media-library'

export type MediaType = 'image' | 'video'

export interface DownloadResult {
  success: boolean
  error?: string
}

// 使用 fetch 下载文件并转换为 base64
const downloadToCache = async (url: string, fileName: string): Promise<string> => {
  const response = await fetch(url)
  if (!response.ok) {
    throw new Error('Download failed')
  }

  const blob = await response.blob()

  return new Promise((resolve, reject) => {
    const reader = new FileReader()
    reader.onloadend = () => {
      const base64data = reader.result as string
      resolve(base64data)
    }
    reader.onerror = reject
    reader.readAsDataURL(blob)
  })
}

export const useDownloadMedia = () => {
  const [loading, setLoading] = useState(false)
  const [error, setError] = useState<string | null>(null)
  const [progress, setProgress] = useState(0)

  const download = useCallback(async (url: string, type: MediaType): Promise<DownloadResult> => {
    setLoading(true)
    setError(null)
    setProgress(0)

    try {
      // 1. 请求媒体库权限
      const { status } = await MediaLibrary.requestPermissionsAsync()
      if (status !== 'granted') {
        setError('Permission denied')
        setLoading(false)
        return { success: false, error: 'Permission denied' }
      }

      setProgress(0.3)

      // 2. 使用 MediaLibrary.saveToLibraryAsync 直接从 URL 保存
      // 这个方法可以直接接受远程 URL
      await MediaLibrary.saveToLibraryAsync(url)

      setProgress(1)
      setLoading(false)
      setProgress(0)
      return { success: true }
    } catch (e) {
      const errorMessage = e instanceof Error ? e.message : 'Download failed'
      setError(errorMessage)
      setLoading(false)
      setProgress(0)

      return { success: false, error: errorMessage }
    }
  }, [])

  return { download, loading, error, progress }
}