export type MediaCacheIndex =UTSJSONObject

type DownloadFileResult = {
  statusCode?: number
  tempFilePath?: string
  tempFilePathArray?: string[]
  apFilePath?: string
  // UTS不支持索引签名，已移除
}
export class MediaCacheService {
  static STORAGE_KEY: string = 'media-cache-index'
  static index: MediaCacheIndex | null = null

  static async init(): Promise<void> {
    if (this.index != null) return
    try {
      const res = await new Promise<UTSJSONObject | null>((resolve) => {
          uni.getStorage({
            key: this.STORAGE_KEY,
              success: (result) => {
                const json = result.data as UTSJSONObject
                const data = json['data'] as UTSJSONObject | null
                resolve(data)
            },
            fail: () => resolve(null)
          })
      })
      if (res != null) {
        this.index = res
      } else {
        this.index = {}
      }
    } catch (_) {
      this.index = {}
    }
  }

  static async persist(): Promise<void> {
    try {
      // @ts-ignore
      await uni.setStorage({ key: this.STORAGE_KEY, data: this.index ?? {} })
    } catch (_) {}
  }

  static async getCachedPath(url: string): Promise<string> {
    await this.init()
      if (this.index == null) return url
      const index = this.index!
      const existing = index[url] as string | null
      if (existing != null && await this.fileExists(existing)) {
        return existing
      }
      const saved = await this.downloadAndSave(url)
        if (saved != null) {
        this.index[url] = saved
      await this.persist()
      return saved
    }
    // fallback to remote url if save failed
    return url
  }

  static async clear(url?: string): Promise<void> {
    await this.init()
      if (this.index == null) return
          if (url != null && url != '') {
        this.index[url] = null
    } else {
      this.index = {}
    }
    await this.persist()
  }

  private static async fileExists(filePath: string): Promise<boolean> {
    return await new Promise<boolean>((resolve) => {
      try {
        const fs = uni.getFileSystemManager()
        let settled = false
        const finish = (value: boolean) => {
          if (settled) {
            return
          }
          settled = true
          resolve(value)
        }
        fs.access({
          path: filePath,
          success: () => finish(true),
          fail: () => finish(false)
        })
      } catch (_) {
        resolve(false)
      }
    })
  }
  
  private static async downloadAndSave(url: string): Promise<string | null> {
    const dlRes = await new Promise<DownloadFileResult | null>((resolve) => {
      try {
        uni.downloadFile({
          url,
          success: (res) => {
            const result: DownloadFileResult = {
              statusCode: res.statusCode,
              tempFilePath: res['tempFilePath'] as string | null,
              tempFilePathArray: res['tempFilePathArray'] as string[] | null,
              apFilePath: res['apFilePath'] as string | null
            }
            resolve(result)
          },
          fail: () => resolve(null)
        })
      } catch (_) {
        resolve(null)
      }
    })
    const statusCode = dlRes?.statusCode
    if (dlRes == null || statusCode == null || statusCode < 200 || statusCode >= 400) {
      return null
    }
    const tempFilePath = dlRes.tempFilePath ?? (dlRes.tempFilePathArray != null ? dlRes.tempFilePathArray[0] : null) ?? dlRes.apFilePath ?? null
    if (tempFilePath == null) return null
    const savedPath = await new Promise<string | null>((resolve) => {
      try {
        const fs = uni.getFileSystemManager()
        let settled = false
        const finish = (value: string | null) => {
          if (settled) {
            return
          }
          settled = true
          resolve(value)
        }
        const options: SaveFileOptions = {
          tempFilePath: tempFilePath,
          success: (res) => {
            const savedPath = res.savedFilePath
            if (savedPath != null && savedPath.length > 0) {
              finish(savedPath)
              return
            }
            finish(null)
          },
          fail: () => finish(null)
        }
          fs.saveFile(options as SaveFileOptions)
      } catch (_) {
        resolve(null)
      }
    })
    if (savedPath != null && savedPath.length > 0) {
      return savedPath
    }
    return null
  }
}

export default MediaCacheService