import { showMsg } from "@/utils/showMsg";
/**
 * 全环境通用文件保存工具
 * 支持：PC浏览器、手机浏览器、uniapp webview
 * 支持文件类型：图片、视频、纯文字
 */

// 文件类型枚举
export const FileType = {
    IMAGE: 'image',
    VIDEO: 'video',
    TEXT: 'text'
  }
  
  /**
   * 检测是否在uniapp webview环境中
   */
  const isUniAppWebview = () => {
    return typeof uni !== 'undefined' 
      && typeof uni.downloadFile === 'function' 
      && typeof uni.saveImageToPhotosAlbum === 'function'
  }
  
  /**
   * 检测是否是iOS设备
   */
  const isIOS = () => {
    return /iPhone|iPad|iPod/i.test(navigator.userAgent)
  }
  
  /**
   * 通用保存文件入口（所有环境通用）
   * @param {Object} options 保存选项
   * @param {string} options.type 文件类型：FileType.IMAGE / FileType.VIDEO / FileType.TEXT
   * @param {string} options.url 文件URL（图片/视频必填）
   * @param {string} options.content 文字内容（文字类型必填）
   * @param {string} options.fileName 保存的文件名（可选，自动生成）
   * @returns {Promise<void>}
   */
  export const saveFile = async (options) => {
    const { type, url, content, fileName } = options
  
    // 参数校验
    if (!type) {
      throw new Error('请指定文件类型')
    }
  
    if ((type === FileType.IMAGE || type === FileType.VIDEO) && !url) {
      throw new Error('请提供文件URL')
    }
  
    if (type === FileType.TEXT && !content) {
      throw new Error('请提供文字内容')
    }
  
    // 生成默认文件名
    const timestamp = Date.now()
    const defaultFileName = `file_${timestamp}`
    const finalFileName = fileName || defaultFileName
  
    // 自动选择保存方式
    if (isUniAppWebview()) {
      await saveInUniApp(type, url, content, finalFileName)
    } else {
      await saveInBrowser(type, url, content, finalFileName)
    }
  }
  
  /**
   * uniapp webview环境保存
   */
  const saveInUniApp = async (type, url, content, fileName) => {
    switch (type) {
      case FileType.IMAGE:
        await uniSaveImage(url)
        break
      case FileType.VIDEO:
        await uniSaveVideo(url)
        break
      case FileType.TEXT:
        // webview无法直接保存文件，降级为复制到剪贴板
        await uniCopyText(content)
        break
      default:
        throw new Error('不支持的文件类型')
    }
  }
  
  /**
   * 浏览器环境保存
   */
  const saveInBrowser = async (type, url, content, fileName) => {
    switch (type) {
      case FileType.IMAGE:
        await browserSaveImage(url, fileName)
        break
      case FileType.VIDEO:
        await browserSaveVideo(url, fileName)
        break
      case FileType.TEXT:
        browserSaveText(content, fileName)
        break
      default:
        throw new Error('不支持的文件类型')
    }
  }
  
  // ==================== uniapp保存方法 ====================
  const uniSaveImage = (url) => {
    return new Promise((resolve, reject) => {
      uni.showLoading({ title: '保存中...' })
      
      uni.downloadFile({
        url,
        success: (res) => {
          if (res.statusCode !== 200) {
            reject(new Error('图片下载失败'))
            return
          }
  
          uni.saveImageToPhotosAlbum({
            filePath: res.tempFilePath,
            success: () => resolve(),
            fail: (err) => {
              if (err.errMsg.includes('auth')) {
                reject(new Error('请在设置中开启相册权限后重试'))
              } else if (err.errMsg.includes('cancel')) {
                reject(new Error('已取消保存'))
              } else {
                reject(new Error('保存图片失败'))
              }
            }
          })
        },
        fail: () => reject(new Error('网络请求失败，请检查网络连接')),
        complete: () => uni.hideLoading()
      })
    })
  }
  
  const uniSaveVideo = (url) => {
    return new Promise((resolve, reject) => {
      uni.showLoading({ title: '保存中...' })
      
      uni.downloadFile({
        url,
        success: (res) => {
          if (res.statusCode !== 200) {
            reject(new Error('视频下载失败'))
            return
          }
  
          uni.saveVideoToPhotosAlbum({
            filePath: res.tempFilePath,
            success: () => resolve(),
            fail: (err) => {
              if (err.errMsg.includes('auth')) {
                reject(new Error('请在设置中开启相册权限后重试'))
              } else if (err.errMsg.includes('cancel')) {
                reject(new Error('已取消保存'))
              } else {
                reject(new Error('保存视频失败'))
              }
            }
          })
        },
        fail: () => reject(new Error('网络请求失败，请检查网络连接')),
        complete: () => uni.hideLoading()
      })
    })
  }
  
  const uniCopyText = (text) => {
    return new Promise((resolve, reject) => {
      uni.setClipboardData({
        data: text,
        success: () => {
          uni.showToast({ title: '文案已复制到剪贴板', icon: 'success' })
          resolve()
        },
        fail: () => reject(new Error('复制失败'))
      })
    })
  }
  
  // ==================== 浏览器保存方法 ====================
  const browserSaveImage = (url, fileName) => {
    return new Promise((resolve, reject) => {
      const img = new Image()
      img.crossOrigin = 'anonymous'
      
      img.onload = () => {
        try {
          const canvas = document.createElement('canvas')
          canvas.width = img.naturalWidth
          canvas.height = img.naturalHeight
          const ctx = canvas.getContext('2d')
  
          if (!ctx) {
            // Canvas不支持，降级为打开新标签页
            openInNewTab(url)
            resolve()
            return
          }
  
          ctx.drawImage(img, 0, 0)
          canvas.toBlob((blob) => {
            if (!blob) {
              openInNewTab(url)
              resolve()
              return
            }
            downloadBlob(blob, `${fileName}.png`)
            resolve()
          }, 'image/png')
        } catch (e) {
          // 发生错误，降级为打开新标签页
          openInNewTab(url)
          resolve()
        }
      }
  
      img.onerror = () => {
        openInNewTab(url)
        resolve()
      }
  
      img.src = url
    })
  }
  
  const browserSaveVideo = async (url, fileName) => {
    try {
      // iOS Safari不支持Blob下载视频，直接打开新标签页
      if (isIOS()) {
        openInNewTab(url)
        return
      }
  
      const response = await fetch(url)
      if (!response.ok) {
        throw new Error(`视频加载失败：${response.status}`)
      }
      const blob = await response.blob()
      downloadBlob(blob, `${fileName}.mp4`)
    } catch (error) {
      // 发生错误，降级为打开新标签页
      openInNewTab(url)
    }
  }
  
  const browserSaveText = (text, fileName) => {
    const blob = new Blob([text], { type: 'text/plain;charset=utf-8' })
    downloadBlob(blob, `${fileName}.txt`)
  }
  
  // ==================== 通用工具方法 ====================
  const downloadBlob = (blob, fileName) => {
    const url = URL.createObjectURL(blob)
    const a = document.createElement('a')
    a.href = url
    a.download = fileName
    a.style.display = 'none'
    document.body.appendChild(a)
    a.click()
    document.body.removeChild(a)
    URL.revokeObjectURL(url)
    showMsg("保存成功");
  }
  
  const openInNewTab = (url) => {
    const a = document.createElement('a')
    a.href = url
    a.target = '_blank'
    a.rel = 'noopener noreferrer'
    a.style.display = 'none'
    document.body.appendChild(a)
    a.click()
    document.body.removeChild(a)
  }
  
  // 导出默认对象，方便使用
  export default {
    saveFile,
    FileType
  }