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

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

/** 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)
}

/** 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)
}