import { ref, reactive } from 'vue'

export const usePdfPreview = () => {
  const state = reactive({
    visible: false,
    url: '',
    name: '',
    blobUrl: '',
    images: [] as string[]
  })
  const frameRef = ref<HTMLIFrameElement | null>(null)

  // 动态加载 pdf.js（优先本地依赖，失败回退 CDN）
  const loadPdfJs = async (): Promise<any> => {
    // 统一使用 CDN，避免本地依赖缺失导致打包时报错
    const ensure = (src: string) =>
      new Promise<void>((resolve, reject) => {
        const s = document.createElement('script')
        s.src = src
        s.onload = () => resolve()
        s.onerror = () => reject(new Error('load script failed'))
        document.head.appendChild(s)
      })
    await ensure('https://cdnjs.cloudflare.com/ajax/libs/pdf.js/3.11.174/pdf.min.js')
    await ensure('https://cdnjs.cloudflare.com/ajax/libs/pdf.js/3.11.174/pdf.worker.min.js')
    return (window as any).pdfjsLib
  }

  const open = (url: string, name = '') => {
    if (!url) return
    state.url = url
    state.name = name
    state.visible = true
    state.images = []
  }

  const openWithResponse = (res: any) => {
    const url = res?.data?.file_url_full || res?.file_url_full
    const name = res?.data?.file_url || res?.file_url || ''
    open(url, name)
  }

  const inferFilenameFromUrl = (url: string): string => {
    try {
      const u = new URL(url)
      const parts = u.pathname.split('/')
      return parts[parts.length - 1] || 'document.pdf'
    } catch (e) {
      const parts = (url || '').split('?')[0].split('/')
      return parts[parts.length - 1] || 'document.pdf'
    }
  }

  const download = async () => {
    if (!state.url) return
    const filename = state.name || inferFilenameFromUrl(state.url)
    try {
      const resp = await fetch(state.url, { credentials: 'omit' })
      const blob = await resp.blob()
      const url = window.URL.createObjectURL(blob)
      const link = document.createElement('a')
      link.href = url
      link.download = filename
      document.body.appendChild(link)
      link.click()
      document.body.removeChild(link)
      window.URL.revokeObjectURL(url)
    } catch {
      window.open(state.url, '_blank')
    }
  }

  // 预览时也用 blob，提升兼容性
  const preparePreview = async () => {
    if (!state.url) return
    try {
      const resp = await fetch(state.url, { credentials: 'omit' })
      const blob = await resp.blob()
      state.blobUrl && window.URL.revokeObjectURL(state.blobUrl)
      state.blobUrl = window.URL.createObjectURL(blob)
    } catch {
      state.blobUrl = ''
    }
  }

  // 生成图片以便无需浏览器 PDF 插件即可展示
  const prepareImages = async () => {
    if (!state.url) return
    state.images = []
    try {
      const resp = await fetch(state.url, { credentials: 'omit' })
      const arrayBuffer = await resp.arrayBuffer()
      const pdfjsLib = await loadPdfJs()
      const pdf = await pdfjsLib.getDocument({ data: arrayBuffer }).promise
      const images: string[] = []
      for (let p = 1; p <= pdf.numPages; p++) {
        const page = await pdf.getPage(p)
        const viewport = page.getViewport({ scale: 1.5 })
        const canvas = document.createElement('canvas')
        const context = canvas.getContext('2d')
        if (!context) continue
        canvas.width = viewport.width
        canvas.height = viewport.height
        await page.render({ canvasContext: context, viewport }).promise
        images.push(canvas.toDataURL('image/png'))
      }
      state.images = images
    } catch {
      state.images = []
    }
  }

  const print = () => {
    const frame = frameRef.value
    if (frame && frame.contentWindow) {
      frame.contentWindow.focus()
      frame.contentWindow.print()
      return
    }
    if (state.url) {
      const win = window.open(state.url, '_blank')
      if (win) {
        win.addEventListener('load', () => win.print())
      }
    }
  }

  return {
    pdf: state,
    frameRef,
    open,
    openWithResponse,
    download,
    print,
    preparePreview,
    prepareImages
  }
}