import { computed, ref, watch } from 'vue'

/**
 * ISO 날짜를 datetime-local 입력값으로 변환한다.
 * @param {string} value - ISO 날짜 문자열
 * @returns {string} datetime-local 입력값
 */
export const toAdminPostDateTimeLocalValue = (value) => {
  if (!value) {
    return ''
  }

  const date = new Date(value)

  if (Number.isNaN(date.getTime())) {
    return ''
  }

  const offsetDate = new Date(date.getTime() - date.getTimezoneOffset() * 60000)

  return offsetDate.toISOString().slice(0, 16)
}

/**
 * datetime-local 입력값을 ISO 문자열로 변환한다.
 * @param {string} value - datetime-local 입력값
 * @returns {string | null} ISO 날짜 문자열
 */
const toIsoDateTime = (value) => {
  if (!value) {
    return null
  }

  const date = new Date(value)

  if (Number.isNaN(date.getTime())) {
    return null
  }

  return date.toISOString()
}

/**
 * datetime-local 값을 날짜·시간 필드로 분리한다.
 * @param {string} value - datetime-local 문자열
 * @returns {{ date: string, time: string }}
 */
const splitDateTimeLocal = (value) => {
  if (!value || !value.includes('T')) {
    return { date: '', time: '' }
  }
  const [date, time] = value.split('T')
  return { date: date || '', time: (time || '').slice(0, 5) }
}

/**
 * 날짜·시간 필드를 datetime-local 문자열로 합친다.
 * @param {string} date - YYYY-MM-DD
 * @param {string} time - HH:mm
 * @returns {string}
 */
const joinDateTimeLocal = (date, time) => {
  if (!date) {
    return ''
  }
  return `${date}T${time || '00:00'}`
}

/**
 * 서버에 반영된 게시 형태를 계산한다.
 * @param {Object} post - 게시물
 * @returns {'draft' | 'publishedLive' | 'scheduled' | 'members' | 'private'} 게시 형태
 */
const getPersistedPublishKind = (post) => {
  if (!post?.id) {
    return 'draft'
  }
  const st = post.status || 'draft'
  if (st === 'members' || st === 'private') {
    return st
  }
  if (st !== 'published') {
    return 'draft'
  }
  const pa = post.publishedAt
  if (pa && new Date(pa) > new Date()) {
    return 'scheduled'
  }
  return 'publishedLive'
}

/**
 * 관리자 게시물 폼의 발행·예약·발행 취소 상태를 만든다.
 * @param {Object} options - 발행 상태 옵션
 * @param {Object} options.form - 게시물 폼 reactive 객체
 * @param {import('vue').ComputedRef<Object>} options.initialPost - 서버 게시물 입력값
 * @returns {Object} 발행 상태와 이벤트 처리기
 */
export const useAdminPostPublishState = ({
  form,
  initialPost
}) => {
  const getInitialPost = () => initialPost.value || {}
  const persistedPublishKind = ref(getPersistedPublishKind(getInitialPost()))
  const persistedPublishedAtIso = ref(getInitialPost().publishedAt || null)
  const isPublishModalOpen = ref(false)
  const isUnpublishModalOpen = ref(false)
  const publishStatus = ref('draft')
  const publishTiming = ref('now')
  const scheduledPublishAt = ref('')
  const publishModalExpandedSection = ref(null)

  watch(
    initialPost,
    (post) => {
      persistedPublishKind.value = getPersistedPublishKind(post)
      if (post?.publishedAt) {
        persistedPublishedAtIso.value = post.publishedAt
      }
    },
    { deep: true }
  )

  /**
   * 예약 발행 여부를 확인한다.
   * @returns {boolean} 예약 발행 여부
   */
  const isScheduledPost = () => {
    const publishedAt = toIsoDateTime(form.publishedAt)

    return form.status === 'published' && Boolean(publishedAt) && new Date(publishedAt) > new Date()
  }

  const isDraftLike = computed(() => form.status === 'draft' && !isScheduledPost())
  const isPublishedLive = computed(() => form.status === 'published' && !isScheduledPost())
  const displayPublishedLive = computed(() =>
    persistedPublishKind.value === 'publishedLive'
    || (persistedPublishKind.value === 'draft' && isPublishedLive.value))
  const displayScheduled = computed(() =>
    persistedPublishKind.value === 'scheduled'
    || (persistedPublishKind.value === 'draft' && isScheduledPost()))
  const displayMembersOnly = computed(() =>
    persistedPublishKind.value === 'members'
    || (persistedPublishKind.value === 'draft' && form.status === 'members'))
  const displayPrivatePost = computed(() =>
    persistedPublishKind.value === 'private'
    || (persistedPublishKind.value === 'draft' && form.status === 'private'))

  const publishStatusSummaryLabel = computed(() => {
    if (publishStatus.value === 'published') {
      return '발행'
    }

    return '초안'
  })

  const publishTimingSummaryLabel = computed(() => {
    if (publishTiming.value === 'now') {
      return '지금 바로'
    }

    const raw = scheduledPublishAt.value

    if (!raw) {
      return '예약'
    }

    const date = new Date(raw)

    if (Number.isNaN(date.getTime())) {
      return '예약'
    }

    return new Intl.DateTimeFormat('ko-KR', {
      dateStyle: 'medium',
      timeStyle: 'short'
    }).format(date)
  })

  /**
   * 저장 요청용 발행 시각을 결정한다.
   * @param {{ allowNewPublishTimestamp?: boolean }} [options] - 신규 발행 시각 허용 여부
   * @returns {string|null} ISO 발행 시각 또는 null
   */
  const resolvePayloadPublishedAt = (options = {}) => {
    if (form.status !== 'published') {
      return null
    }

    const fromForm = toIsoDateTime(form.publishedAt)

    if (fromForm) {
      return fromForm
    }

    if (persistedPublishedAtIso.value) {
      return persistedPublishedAtIso.value
    }

    if (getInitialPost().publishedAt) {
      return getInitialPost().publishedAt
    }

    if (options.allowNewPublishTimestamp) {
      return new Date().toISOString()
    }

    return null
  }

  const scheduledStatusTooltip = computed(() => {
    const iso = toIsoDateTime(form.publishedAt)
    if (!iso) {
      return ''
    }
    const d = new Date(iso)
    if (Number.isNaN(d.getTime())) {
      return ''
    }
    const line = d.toLocaleString('en-GB', {
      dateStyle: 'long',
      timeStyle: 'short'
    })
    return `Scheduled to be published on ${line}`
  })

  /**
   * 발행 모달을 현재 폼 상태로 초기화한다.
   * @returns {void}
   */
  const syncPublishModalStateFromForm = () => {
    if (persistedPublishKind.value === 'draft') {
      publishStatus.value = 'published'
      publishTiming.value = 'now'
      scheduledPublishAt.value = toAdminPostDateTimeLocalValue(new Date().toISOString())
      return
    }

    publishStatus.value = form.status === 'published' ? 'published' : 'draft'
    scheduledPublishAt.value = form.publishedAt || toAdminPostDateTimeLocalValue(new Date(Date.now() + 3600000).toISOString())
    publishTiming.value = isScheduledPost() ? 'schedule' : 'now'
  }

  /**
   * 발행 모달을 연다.
   * @returns {void}
   */
  const openPublishModal = () => {
    syncPublishModalStateFromForm()
    publishModalExpandedSection.value = null
    isPublishModalOpen.value = true
  }

  /**
   * 발행 모달을 닫는다.
   * @returns {void}
   */
  const closePublishModal = () => {
    isPublishModalOpen.value = false
  }

  /**
   * 발행 취소·예약 취소 확인 화면을 연다.
   * @returns {void}
   */
  const openUnpublishModal = () => {
    isUnpublishModalOpen.value = true
  }

  /**
   * 발행 취소·예약 취소 확인 화면을 닫는다.
   * @returns {void}
   */
  const closeUnpublishModal = () => {
    isUnpublishModalOpen.value = false
  }

  /**
   * 발행 모달에서 선택한 값을 폼에 반영한다.
   * @returns {void}
   */
  const applyPublishSelectionToForm = () => {
    form.status = publishStatus.value

    if (publishStatus.value !== 'published') {
      form.publishedAt = ''
      return
    }

    if (publishTiming.value === 'schedule') {
      form.publishedAt = scheduledPublishAt.value || toAdminPostDateTimeLocalValue(new Date(Date.now() + 3600000).toISOString())
      return
    }

    form.publishedAt = toAdminPostDateTimeLocalValue(new Date().toISOString())
  }

  /**
   * 발행 모달에서 설정 행 펼침을 토글한다.
   * @param {'status' | 'timing'} section - 펼칠 행
   * @returns {void}
   */
  const togglePublishModalSection = (section) => {
    publishModalExpandedSection.value =
      publishModalExpandedSection.value === section ? null : section
  }

  /**
   * 발행 모달에서 게시 상태를 선택한다.
   * @param {'published' | 'draft'} status - 선택 상태
   * @returns {void}
   */
  const selectPublishStatus = (status) => {
    publishStatus.value = status
    publishModalExpandedSection.value = null

    if (status !== 'published') {
      publishTiming.value = 'now'
    }
  }

  /**
   * 발행 모달에서 발행 시점을 선택한다.
   * @param {'now' | 'schedule'} timing - 즉시 또는 예약
   * @returns {void}
   */
  const selectPublishTiming = (timing) => {
    publishTiming.value = timing

    if (timing === 'now') {
      publishModalExpandedSection.value = null
    } else if (!scheduledPublishAt.value) {
      scheduledPublishAt.value = toAdminPostDateTimeLocalValue(new Date(Date.now() + 3600000).toISOString())
    }
  }

  const settingsPublishDate = computed({
    get: () => splitDateTimeLocal(form.publishedAt).date,
    set: (date) => {
      const { time } = splitDateTimeLocal(form.publishedAt)
      form.publishedAt = joinDateTimeLocal(date, time || '12:00')
    }
  })

  const settingsPublishTime = computed({
    get: () => splitDateTimeLocal(form.publishedAt).time,
    set: (time) => {
      const { date } = splitDateTimeLocal(form.publishedAt)
      const baseDate = date || new Date().toISOString().slice(0, 10)
      form.publishedAt = joinDateTimeLocal(baseDate, time || '12:00')
    }
  })

  const modalScheduleDate = computed({
    get: () => splitDateTimeLocal(scheduledPublishAt.value).date,
    set: (date) => {
      const { time } = splitDateTimeLocal(scheduledPublishAt.value)
      scheduledPublishAt.value = joinDateTimeLocal(date, time || '12:00')
    }
  })

  const modalScheduleTime = computed({
    get: () => splitDateTimeLocal(scheduledPublishAt.value).time,
    set: (time) => {
      const { date } = splitDateTimeLocal(scheduledPublishAt.value)
      const baseDate = date || new Date().toISOString().slice(0, 10)
      scheduledPublishAt.value = joinDateTimeLocal(baseDate, time || '12:00')
    }
  })

  const unpublishPersistedPublishedLabel = computed(() => {
    const iso = getInitialPost().publishedAt
    if (!iso) {
      return ''
    }
    const d = new Date(iso)
    if (Number.isNaN(d.getTime())) {
      return ''
    }
    return new Intl.DateTimeFormat('ko-KR', {
      dateStyle: 'long',
      timeStyle: 'short'
    }).format(d)
  })

  const unpublishModalKind = computed(() => (
    persistedPublishKind.value === 'scheduled' ? 'scheduled' : 'published'
  ))

  /**
   * 저장 성공 후 발행 기준 시각을 갱신한다.
   * @param {string|null} publishedAt - 저장된 발행 시각
   * @returns {void}
   */
  const markPublishStateSaved = (publishedAt) => {
    if (publishedAt) {
      persistedPublishedAtIso.value = publishedAt
    }
  }

  watch(publishStatus, (next) => {
    if (next !== 'published') {
      publishTiming.value = 'now'

      if (publishModalExpandedSection.value === 'timing') {
        publishModalExpandedSection.value = null
      }
    }
  })

  watch(() => form.status, (next) => {
    if (next === 'published' && !toIsoDateTime(form.publishedAt)) {
      form.publishedAt = toAdminPostDateTimeLocalValue(new Date().toISOString())
    }
  })

  return {
    applyPublishSelectionToForm,
    closePublishModal,
    closeUnpublishModal,
    displayMembersOnly,
    displayPrivatePost,
    displayPublishedLive,
    displayScheduled,
    isDraftLike,
    isPublishModalOpen,
    isScheduledPost,
    isUnpublishModalOpen,
    markPublishStateSaved,
    modalScheduleDate,
    modalScheduleTime,
    openPublishModal,
    openUnpublishModal,
    persistedPublishKind,
    publishModalExpandedSection,
    publishStatus,
    publishStatusSummaryLabel,
    publishTiming,
    publishTimingSummaryLabel,
    resolvePayloadPublishedAt,
    scheduledStatusTooltip,
    selectPublishStatus,
    selectPublishTiming,
    settingsPublishDate,
    settingsPublishTime,
    togglePublishModalSection,
    unpublishModalKind,
    unpublishPersistedPublishedLabel
  }
}