shanxia2.0/web-admin/src/utils/download-attachment.ts

import { ElMessage } from 'element-plus'
import { fetchAttachmentDownloadUrl, fetchAttachmentPreviewUrl } from '@/api/admin'

export type AttachmentDownloadItem = {
  fileUrl?: string
  fileName?: string
}

export type AttachmentPreviewKind = 'image' | 'pdf' | 'other'

/** 将 JSON 数组或逗号分隔的附件 URL 统一为逗号分隔字符串 */
export function normalizeAttachmentUrls(raw?: string | null): string {
  if (!raw) return ''
  const trimmed = String(raw).trim()
  if (!trimmed) return ''
  if (trimmed.startsWith('[')) {
    try {
      const parsed = JSON.parse(trimmed)
      if (Array.isArray(parsed)) {
        return parsed.map((url) => String(url).trim()).filter(Boolean).join(',')
      }
    } catch {
      /* ignore */
    }
  }
  return trimmed
}

function triggerAnchorDownload(href: string, fileName: string) {
  const a = document.createElement('a')
  a.href = href
  a.download = fileName
  a.rel = 'noopener'
  document.body.appendChild(a)
  a.click()
  document.body.removeChild(a)
}

function escapeHtmlAttr(value: string) {
  return String(value || '')
    .replace(/&/g, '&')
    .replace(/"/g, '"')
    .replace(/</g, '&lt;')
    .replace(/>/g, '&gt;')
}

/** 根据文件名/URL 推断预览类型 */
export function detectAttachmentPreviewKind(file: AttachmentDownloadItem): AttachmentPreviewKind {
  const name = String(file.fileName || '').toLowerCase()
  const url = String(file.fileUrl || '')
    .split('?')[0]
    .toLowerCase()
  if (/\.(jpg|jpeg|png|gif|bmp|webp|svg)$/i.test(name) || /\.(jpg|jpeg|png|gif|bmp|webp|svg)$/i.test(url)) {
    return 'image'
  }
  if (/\.pdf$/i.test(name) || /\.pdf$/i.test(url)) {
    return 'pdf'
  }
  return 'other'
}

/** 图片用 HTML 内嵌展示，避免 Content-Type 为 octet-stream 时顶级导航触发下载 */
function openImagePreviewDocument(previewWindow: Window | null, href: string, title: string) {
  const safeSrc = escapeHtmlAttr(href)
  const safeTitle = escapeHtmlAttr(title || '图片预览')
  const html = `<!DOCTYPE html><html><head><meta charset="utf-8"><meta name="viewport" content="width=device-width,initial-scale=1"><title>${safeTitle}</title><style>html,body{margin:0;height:100%;background:#0f172a}body{display:flex;align-items:center;justify-content:center}img{max-width:100%;max-height:100vh;object-fit:contain}</style></head><body><img src="${safeSrc}" alt="${safeTitle}"/></body></html>`
  if (previewWindow) {
    previewWindow.document.open()
    previewWindow.document.write(html)
    previewWindow.document.close()
    return
  }
  const blobUrl = URL.createObjectURL(new Blob([html], { type: 'text/html;charset=utf-8' }))
  window.open(blobUrl, '_blank', 'noopener,noreferrer')
}

/** 附件预览：优先走后端预签名 inline URL，供 PDF iframe 等内联展示。 */
export async function resolveAttachmentPreviewUrl(
  file: AttachmentDownloadItem,
  options?: { fullFileUrl?: (url: string) => string }
): Promise<string> {
  const fileUrl = String(file.fileUrl || '').trim()
  if (!fileUrl) return ''
  const resolveUrl = options?.fullFileUrl || ((url: string) => url)

  try {
    const res = await fetchAttachmentPreviewUrl({ fileUrl, fileName: file.fileName })
    if (res?.previewUrl) return res.previewUrl
  } catch {
    // 预签名失败时回退直连
  }

  return resolveUrl(fileUrl)
}

/**
 * 在浏览器新标签页打开附件预览（图片 HTML 内嵌 / PDF 直开）。
 * 不支持在线预览的类型会提示并返回 false。
 */
export async function openAttachmentPreviewInNewTab(
  file: AttachmentDownloadItem,
  options?: {
    fullFileUrl?: (url: string) => string
    kind?: AttachmentPreviewKind
  }
): Promise<boolean> {
  const fileUrl = String(file.fileUrl || '').trim()
  if (!fileUrl) {
    ElMessage.error('无法获取文件预览地址')
    return false
  }

  const kind = options?.kind || detectAttachmentPreviewKind(file)
  if (kind === 'other') {
    ElMessage.warning('该文件类型暂不支持在线预览，请使用下载查看')
    return false
  }

  const previewWindow = window.open('about:blank', '_blank')
  try {
    const previewUrl = await resolveAttachmentPreviewUrl(file, {
      fullFileUrl: options?.fullFileUrl
    })
    const href =
      previewUrl || (options?.fullFileUrl ? options.fullFileUrl(fileUrl) : fileUrl)
    if (!href) {
      previewWindow?.close()
      ElMessage.error('无法获取文件预览地址')
      return false
    }
    if (kind === 'image') {
      openImagePreviewDocument(previewWindow, href, file.fileName || '图片预览')
      return true
    }
    if (previewWindow) {
      previewWindow.location.href = href
    } else {
      window.open(href, '_blank', 'noopener,noreferrer')
    }
    return true
  } catch (error) {
    console.error('打开附件预览失败:', error)
    const fallback = options?.fullFileUrl ? options.fullFileUrl(fileUrl) : fileUrl
    if (fallback && kind === 'image') {
      openImagePreviewDocument(previewWindow, fallback, file.fileName || '图片预览')
      return true
    }
    if (fallback && previewWindow) {
      previewWindow.location.href = fallback
      return true
    }
    previewWindow?.close()
    ElMessage.error('打开预览失败，请稍后重试或使用下载')
    return false
  }
}

/** 附件下载：优先走后端预签名 URL，保证跨域场景下保留原始文件名与后缀。 */
export async function downloadAttachmentFile(
  file: AttachmentDownloadItem,
  options?: { fullFileUrl?: (url: string) => string }
) {
  const fileUrl = String(file.fileUrl || '').trim()
  if (!fileUrl) return
  const fileName = String(file.fileName || '').trim() || fileUrl.split('/').pop() || 'download'

  try {
    const res = await fetchAttachmentDownloadUrl({ fileUrl, fileName })
    if (res?.downloadUrl) {
      triggerAnchorDownload(res.downloadUrl, fileName)
      return
    }
  } catch {
    // 预签名失败时回退直连
  }

  const resolveUrl = options?.fullFileUrl || ((url: string) => url)
  const href = resolveUrl(fileUrl)
  if (!href) {
    ElMessage.error('无法下载附件')
    return
  }
  triggerAnchorDownload(href, fileName)
}