/** 东八区日历日 YYYY-MM-DD（与后端活动状态一致，勿对 ISO 直接 slice(0,10)） */
export function ymdInShanghai(iso?: string | null): string {
  if (!iso) return ''
  const d = new Date(String(iso))
  if (Number.isNaN(d.getTime())) return String(iso).slice(0, 10)
  return new Intl.DateTimeFormat('en-CA', {
    timeZone: 'Asia/Shanghai',
    year: 'numeric',
    month: '2-digit',
    day: '2-digit',
  }).format(d)
}

function todayYmdShanghai(): string {
  return new Intl.DateTimeFormat('en-CA', {
    timeZone: 'Asia/Shanghai',
    year: 'numeric',
    month: '2-digit',
    day: '2-digit',
  }).format(new Date())
}

function compareYmd(a: string, b: string): number {
  if (!a || !b) return 0
  if (a < b) return -1
  if (a > b) return 1
  return 0
}

/** 与后台活动列表一致：未开始 / 进行中 / 已结束 */
export type ActivityScheduleStatus = 'not_started' | 'ongoing' | 'ended'

export function computeActivityScheduleStatus(
  startAt?: string | null,
  endAt?: string | null,
): ActivityScheduleStatus {
  const today = todayYmdShanghai()
  const startD = ymdInShanghai(startAt)
  const endD = ymdInShanghai(endAt)
  if (!startD && !endD) return 'ongoing'
  if (startD && !endD) {
    return compareYmd(today, startD) < 0 ? 'not_started' : 'ongoing'
  }
  if (!startD && endD) {
    return compareYmd(today, endD) > 0 ? 'ended' : 'ongoing'
  }
  if (compareYmd(today, startD) < 0) return 'not_started'
  if (compareYmd(today, endD) > 0) return 'ended'
  return 'ongoing'
}

export function activityScheduleStatusLabel(s: ActivityScheduleStatus): string {
  if (s === 'not_started') return '未开始'
  if (s === 'ended') return '已结束'
  return '进行中'
}

/** 活动是否已按「日历日」结束：结束日期早于今天则视为不可报名 */
export function isActivityEndedByCalendar(endAt?: string | null): boolean {
  if (!endAt) return false
  const endDay = ymdInShanghai(endAt)
  if (!endDay) return false
  const todayStr = todayYmdShanghai()
  return endDay < todayStr
}

/** 活动日期：同年为「2026年4月1日至5月3日」，跨年则两年份都写 */
export function formatActivityCnRange(startAt?: string | null, endAt?: string | null) {
  const parse = (raw?: string | null) => {
    if (!raw) return null
    const s = String(raw).trim()
    if (/^\d{4}-\d{2}-\d{2}$/.test(s)) {
      const p = s.split('-').map(Number)
      if (p.length !== 3) return null
      const [y, m, d] = p
      if (!Number.isFinite(y) || !Number.isFinite(m) || !Number.isFinite(d)) return null
      return { y, m, d }
    }
    const ymd = ymdInShanghai(s)
    if (!ymd) return null
    const p = ymd.split('-').map(Number)
    if (p.length !== 3) return null
    const [y, m, d] = p
    if (!Number.isFinite(y) || !Number.isFinite(m) || !Number.isFinite(d)) return null
    return { y, m, d }
  }
  const s = parse(startAt)
  const e = parse(endAt)
  if (!s && !e) return '日期待定'
  if (s && !e) return `${s.y}年${s.m}月${s.d}日`
  if (!s && e) return `${e.y}年${e.m}月${e.d}日`
  if (s && e) {
    if (s.y === e.y && s.m === e.m && s.d === e.d) {
      return `${s.y}年${s.m}月${s.d}日`
    }
    if (s.y === e.y) {
      return `${s.y}年${s.m}月${s.d}日至${e.m}月${e.d}日`
    }
    return `${s.y}年${s.m}月${s.d}日至${e.y}年${e.m}月${e.d}日`
  }
  return '日期待定'
}

const RESERVATION_ONLINE = 'online'

/** 与后端一致：需在平台在线报名（需要预约） */
export function activityIsPlatformOnlineBooking(row: { reservation_type?: string | null }): boolean {
  const t = String(row?.reservation_type ?? RESERVATION_ONLINE).trim()
  return t === '' || t === RESERVATION_ONLINE
}

function listRowScheduleStatus(row: {
  schedule_status?: string
  start_at?: string | null
  end_at?: string | null
}): ActivityScheduleStatus {
  const s = row?.schedule_status
  if (s === 'not_started' || s === 'ongoing' || s === 'ended') return s
  return computeActivityScheduleStatus(row?.start_at, row?.end_at)
}

export type ActivityCoverCornerKind = 'brand' | 'muted' | 'accent'

/**
 * 活动列表/首页封面右下角标签（抢票由页面单独处理）。
 * - 平台预约：可预约 / 已报名x人（满员仍显示已报名x人）
 * - 非平台预约：无需预约 / 科普研学（收费）
 */
export function activityListCoverCorner(row: {
  list_kind?: string
  reservation_type?: string | null
  offline_reservation_method?: string | null
  schedule_status?: string
  start_at?: string | null
  end_at?: string | null
  registered_count?: number
  is_bookable?: boolean
}): { text: string; kind: ActivityCoverCornerKind } | null {
  if (row?.list_kind === 'ticket_grab') return null

  const sched = listRowScheduleStatus(row)
  const reg = Math.max(0, Number(row?.registered_count) || 0)

  if (activityIsPlatformOnlineBooking(row)) {
    if (sched === 'ended') {
      return reg > 0 ? { text: `已报名${reg}人`, kind: 'brand' } : null
    }
    if (row?.is_bookable === true) {
      return { text: reg > 0 ? `已报名${reg}人` : '可预约', kind: 'brand' }
    }
    if (reg > 0) {
      return { text: `已报名${reg}人`, kind: 'brand' }
    }
    return null
  }

  const paid = String(row?.offline_reservation_method ?? '').trim() === 'paid'
  return {
    text: paid ? '科普研学' : '无需预约',
    kind: paid ? 'accent' : 'muted',
  }
}

/** 列表行「立即预约 / 预约已满 / 截止预约(不可点) / 立即抢票」 */
export function activityListReserveButton(row: {
  list_kind?: string
  reservation_type?: string | null
  start_at?: string | null
  end_at?: string | null
  schedule_status?: string
  is_bookable?: boolean
  registered_count?: number
  /** 后端：各场次 day_quota 均已无余量（与是否在预约窗口内无关） */
  all_slots_full?: boolean
  /** 后端：预约时间已过但仍有未约满名额 */
  booking_closed_not_full?: boolean
}): { show: boolean; text: string; muted?: boolean } {
  if (row?.list_kind === 'ticket_grab') {
    if (isActivityEndedByCalendar(row?.end_at)) return { show: false, text: '' }
    if (row?.is_bookable === true) return { show: true, text: '立即抢票' }
    return { show: false, text: '' }
  }
  if (!activityIsPlatformOnlineBooking(row)) {
    return { show: false, text: '' }
  }
  const sched = listRowScheduleStatus(row)
  if (sched === 'ended' || isActivityEndedByCalendar(row?.end_at)) {
    return { show: false, text: '' }
  }
  if (row?.is_bookable === true) {
    return { show: true, text: '立即预约' }
  }
  if (row?.all_slots_full === true) {
    return { show: true, text: '预约已满', muted: true }
  }
  if (row?.booking_closed_not_full === true) {
    return { show: true, text: '截止预约', muted: true }
  }
  return { show: false, text: '' }
}