import {computed, onBeforeUnmount, ref, watch} from 'vue'
import {onBeforeRouteLeave, onBeforeRouteUpdate, useRoute} from 'vue-router'
import {ElMessage, ElMessageBox} from 'element-plus'
import {http} from '@/utils/axios'
import lang from '../../i18n/i18n'

export function useDraft({router, groupStore, ruleForm, valueHtml, fileList, editorRef, showCcBcc, isSending, pendingFiles}) {
  const route = useRoute()
  const draftID = ref(0)
  const draftVersion = ref('')
  const isSaving = ref(false)
  const isLoading = ref(true)
  const loadFailed = ref(false)
  const replyTo = ref([])
  const isBusy = computed(() => isSaving.value || isSending.value || isLoading.value || loadFailed.value || pendingFiles.value > 0)
  let savedSnapshot = ''
  let sent = false
  let loadSequence = 0
  let disposed = false

  const buildMessage = () => ({
    draft_id: draftID.value,
    draft_version: draftVersion.value,
    from: {name: ruleForm.nickName, email: `${ruleForm.sender}@${ruleForm.pickedDomain}`},
    to: ruleForm.receivers.map(email => ({name: '', email})),
    cc: ruleForm.cc.map(email => ({name: '', email})),
    bcc: ruleForm.bcc.map(email => ({name: '', email})),
    reply_to: replyTo.value,
    subject: ruleForm.subject,
    text: editorRef.value?.getText() || '',
    html: valueHtml.value,
    attrs: fileList.map(item => ({name: item.name, data: item.data}))
  })

  const snapshot = () => JSON.stringify({
    from: [ruleForm.nickName, ruleForm.sender, ruleForm.pickedDomain],
    to: ruleForm.receivers, cc: ruleForm.cc, bcc: ruleForm.bcc,
    subject: ruleForm.subject, html: valueHtml.value, attrs: fileList
  })
  const isDirty = () => !sent && savedSnapshot !== '' && snapshot() !== savedSnapshot

  const loadDraft = async () => {
    const sequence = ++loadSequence
    isLoading.value = true
    loadFailed.value = false
    const rawID = route.query.draft
    if (rawID === undefined) {
      draftID.value = 0
      draftVersion.value = ''
      replyTo.value = []
      ruleForm.receivers = []
      ruleForm.cc = []
      ruleForm.bcc = []
      ruleForm.subject = ''
      valueHtml.value = '<p><br></p>'
      fileList.splice(0)
      showCcBcc.value = false
      sent = false
      savedSnapshot = snapshot()
      isLoading.value = false
      return
    }
    try {
      const id = Number(rawID)
      if (!Number.isSafeInteger(id) || id <= 0) throw new Error(lang.draft_load_failed)
      const result = await http.post('/api/v1/email/draft/detail', {id})
      if (disposed || sequence !== loadSequence) return
      if (result.errorNo !== 0) throw new Error(result.errorMsg || lang.draft_load_failed)
      const data = result.data
      const message = data?.message
      if (data?.id !== id || !data.version || !message?.from?.email) throw new Error(lang.draft_load_failed)
      const split = message.from.email.lastIndexOf('@')
      if (split <= 0) throw new Error(lang.draft_load_failed)
      draftID.value = data.id
      draftVersion.value = data.version
      ruleForm.sender = message.from.email.slice(0, split)
      ruleForm.pickedDomain = message.from.email.slice(split + 1)
      ruleForm.nickName = message.from.name || ''
      ruleForm.receivers = (message.to || []).map(item => item.email)
      ruleForm.cc = (message.cc || []).map(item => item.email)
      ruleForm.bcc = (message.bcc || []).map(item => item.email)
      replyTo.value = message.reply_to || []
      ruleForm.subject = message.subject || ''
      valueHtml.value = message.html || '<p><br></p>'
      fileList.splice(0, fileList.length, ...(message.attrs || []))
      showCcBcc.value = ruleForm.cc.length > 0 || ruleForm.bcc.length > 0
      sent = false
      savedSnapshot = snapshot()
    } catch (error) {
      if (disposed || sequence !== loadSequence) return
      loadFailed.value = true
      ElMessage.error(error.message || lang.draft_load_failed)
    } finally {
      if (!disposed && sequence === loadSequence) isLoading.value = false
    }
  }

  const saveDraft = async () => {
    if (isBusy.value || !editorRef.value) return
    isSaving.value = true
    const submittedSnapshot = snapshot()
    try {
      const result = await http.post('/api/v1/email/draft/save', buildMessage())
      if (result.errorNo !== 0) throw new Error(result.errorMsg || lang.fail)
      if (!Number.isSafeInteger(result.data?.id) || result.data.id <= 0 || !result.data.version) throw new Error(lang.fail)
      draftID.value = result.data.id
      draftVersion.value = result.data.version
      savedSnapshot = submittedSnapshot
      groupStore.invalidate()
      // 将已保存草稿写入地址，刷新后仍可恢复；先释放保存锁再更新路由。
      isSaving.value = false
      await router.replace({name: 'editer', query: {draft: String(draftID.value)}})
      ElMessage.success(lang.draft_saved)
    } catch (error) {
      ElMessage.error(error.message || lang.fail)
    } finally {
      isSaving.value = false
    }
  }

  const confirmLeave = async () => {
    if (sent) return true
    if (isSaving.value || isSending.value || pendingFiles.value > 0) return false
    if (!isDirty()) return true
    try {
      await ElMessageBox.confirm(lang.draft_leave_warning, lang.draft_title, {
        confirmButtonText: lang.draft_leave, cancelButtonText: lang.draft_stay, type: 'warning'
      })
      return true
    } catch {
      return false
    }
  }
  onBeforeRouteLeave(confirmLeave)
  onBeforeRouteUpdate((to, from) => to.query.draft === from.query.draft ? true : confirmLeave())
  watch(() => route.query.draft, value => {
    if (String(value || '') !== String(draftID.value || '')) loadDraft()
  })
  watch([editorRef, isBusy], ([editor, busy]) => {
    if (!editor || editor.isDestroyed) return
    if (busy) editor.disable()
    else editor.enable()
  })
  const beforeUnload = event => {
    if (isDirty() || isSaving.value || isSending.value || pendingFiles.value > 0) {
      event.preventDefault()
      event.returnValue = ''
    }
  }
  window.addEventListener('beforeunload', beforeUnload)
  onBeforeUnmount(() => {
    disposed = true
    loadSequence += 1
    window.removeEventListener('beforeunload', beforeUnload)
  })
  const markSent = () => {
    sent = true
    groupStore.invalidate()
  }
  return {draftID, draftVersion, isSaving, isLoading, isBusy, loadFailed, loadDraft, saveDraft, buildMessage, markSent}
}