import { onBeforeUnmount, ref } from 'vue'
import { versionDownloadPath, wordOpenUrl, type VersionFormat } from '../utils/versionDownload'

/** Shared by history and generate success. Links stay available even if the focus heuristic fires. */
export function useVersionOpen() {
  const { apiJson } = useApi()
  const openingVersionId = ref<string | null>(null)
  const downloadError = ref<string | null>(null)
  const fallbackUrl = ref<string | null>(null)
  const openNotice = ref<string | null>(null)
  let cleanup = () => {}
  let generation = 0
  let pendingTab: Window | null = null

  function resetOpen() {
    generation++
    pendingTab?.close()
    pendingTab = null
    cleanup()
    openingVersionId.value = null
    downloadError.value = null
    fallbackUrl.value = null
    openNotice.value = null
  }

  async function openVersion(documentId: string, versionId: string, format: VersionFormat = 'docx') {
    if (openingVersionId.value) return
    resetOpen()
    const current = generation
    openingVersionId.value = versionId
    // Reserve a tab during the user gesture, before the authenticated request loses activation.
    let tab: Window | null = null
    try {
      tab = format === 'pdf' ? window.open('about:blank', '_blank') : null
      if (tab) tab.opener = null
      pendingTab = tab
      const link = await apiJson<{ url: string; expiresAt: string }>(versionDownloadPath(documentId, versionId, format))
      if (current !== generation) { tab?.close(); return }
      if (!link) throw new Error('ขอลิงก์เปิดไฟล์ไม่สำเร็จ')
      fallbackUrl.value = link.url
      if (format === 'pdf') {
        if (tab && !tab.closed) {
          tab.location.replace(link.url)
          pendingTab = null
        }
        else openNotice.value = 'เบราว์เซอร์บล็อกแท็บใหม่ กรุณากดลิงก์เปิดไฟล์ด้านล่าง'
      } else {
        let switched = false
        const onBlur = () => { switched = true }
        const onVisibility = () => { if (document.hidden) switched = true }
        window.addEventListener('blur', onBlur)
        document.addEventListener('visibilitychange', onVisibility)
        const timer = window.setTimeout(() => {
          if (!switched) openNotice.value = 'หาก Word ไม่เปิด กรุณาดาวน์โหลดไฟล์แล้วเปิดใน Word'
          cleanup()
        }, 1500)
        cleanup = () => {
          window.clearTimeout(timer)
          window.removeEventListener('blur', onBlur)
          document.removeEventListener('visibilitychange', onVisibility)
        }
        window.location.assign(wordOpenUrl(link.url))
      }
    } catch (err) {
      tab?.close()
      if (pendingTab === tab) pendingTab = null
      if (current === generation) downloadError.value = err instanceof Error ? err.message : 'เปิดไฟล์ไม่สำเร็จ'
    } finally {
      if (current === generation) openingVersionId.value = null
    }
  }

  onBeforeUnmount(resetOpen)
  return { openingVersionId, downloadError, fallbackUrl, openNotice, openVersion, resetOpen }
}