import { computed, ref, watch } from 'vue'
import { RealtimeClient, createApiClient } from '@/shared'
import type {
  AthleteStanding,
  Change,
  DisplayCommand,
  EventResultGroup,
  RealtimeStatus,
  SnapshotMessage,
  StandingRow,
} from '@/shared'
import {
  parseSettings,
  parseSnapshot,
  parseStandingRow,
  parseStandingRows,
  parseTeamBreakdown,
} from './guards'
import type { DisplaySettings } from './guards'
import { DEFAULT_ANNOUNCE_SECONDS, createAnnouncement, resolveAnnounceText } from './announce'
import { applyDisplayFonts } from './fonts'
import { createMockAthletes, createMockSnapshot } from './mock'
import { readCachedSnapshot, writeCachedSnapshot } from './storage'
import { DISPLAY_PAGES, normalizePage } from './types'
import type {
  DetailOverlayState,
  DisplayPageKey,
  DisplaySource,
  DisplayUrlOptions,
} from './types'
import { prefersReducedMotion } from './useReducedMotion'

/** 整页轮播间隔（06 第 4 节：后台可切换为整页轮播，每页 20s）。 */
const PAGE_ROTATE_MS = 20_000
/** 名次升降箭头保留时长（06 第 7 节：2s 后淡出）。 */
const RANK_DELTA_MS = 2_000

const api = createApiClient()
const reducedMotion = prefersReducedMotion()

const source = ref<DisplaySource>('live')
const status = ref<RealtimeStatus>('idle')
const version = ref<number | null>(null)
const settings = ref<DisplaySettings | null>(null)
const standings = ref<StandingRow[]>([])
const athletes = ref<AthleteStanding[]>([])
const latestResults = ref<EventResultGroup[]>([])
const rankDelta = ref<Record<number, number>>({})
const page = ref<DisplayPageKey>('standings')
const locked = ref(true)
const authRequired = ref(false)
const options = ref<DisplayUrlOptions>({
  page: null,
  locked: true,
  screen: null,
  instance: null,
  resultsCount: 3,
})
const detail = ref<DetailOverlayState | null>(null)
const booted = ref(false)

/** 公告状态机：全屏退场后正文继续留着，底栏读的就是它。 */
const announcementStore = createAnnouncement({
  page,
  onFullscreenEnter: () => {
    page.value = 'announcement'
    // 公告不在轮播页清单里，20s 整页轮播会把它切走；公告期间必须停轮播。
    stopPageRotation()
  },
  onFullscreenExit: (returnPage) => {
    // 全屏期间可能被 goto 抢走页面，这时不能再把页拉回公告前那一页。
    if (page.value === 'announcement') page.value = returnPage
    if (!locked.value) startPageRotation()
  },
})
const announcement = announcementStore.current
/** 底栏与公告页的公告正文：推送中的实时值优先，其次是服务端持久化的当前公告。 */
const announceText = computed(() =>
  resolveAnnounceText(announcement.value, settings.value?.display?.announce),
)

let client: RealtimeClient | null = null
let rankTimer: ReturnType<typeof setTimeout> | null = null
let detailTimer: ReturnType<typeof setTimeout> | null = null
let pageTimer: ReturnType<typeof setInterval> | null = null
let athletesLoading = false
/** 上一次见过的「服务端持久化公告」，用来判断设置里的值是真的变了。 */
let seenSettingsAnnounce = ''

const showAthleteBoard = computed(() => settings.value?.standings.showIndividualBoard ?? true)

/** 参与整页轮播的页；公告是手动触发的页，个人榜按配置可隐藏。 */
const rotationPages = computed<DisplayPageKey[]>(() =>
  DISPLAY_PAGES.map((item) => item.key).filter(
    (key) => key !== 'announcement' && (key !== 'athlete-standings' || showAthleteBoard.value),
  ),
)

function compareStanding(a: StandingRow, b: StandingRow): number {
  return a.rank - b.rank || b.totalPoints - a.totalPoints
}

function clearTimer(timer: ReturnType<typeof setTimeout> | null): null {
  if (timer !== null) clearTimeout(timer)
  return null
}

// 翻页（含整页轮播）后把当前页同步给服务端，管理端实例看板才不会一直显示旧页。
// 模块级单例与页面同生命周期，不需要随组件卸载停表。
watch(page, (next) => {
  client?.setPage(next)
})

// ---------------------------------------------------------------------------
// 数据落地
// ---------------------------------------------------------------------------

/**
 * 用新的积分榜替换本地榜单，并算出相对上一次的名次变化。
 *
 * 服务端给的 rankChange 优先；没有基准（首屏 / 刚换页）时用本地前后对比兜底，
 * 这样断线重连后即使服务端没带 rankChange，箭头也不会凭空消失。
 */
function applyStandings(rows: StandingRow[]): void {
  const previous = new Map(standings.value.map((row) => [row.teamId, row.rank]))
  const deltas: Record<number, number> = {}
  const next = rows.map((row) => {
    const before = previous.get(row.teamId)
    const local = before === undefined ? null : before - row.rank
    const delta = row.rankChange ?? local
    if (delta !== null && delta !== 0) deltas[row.teamId] = delta
    return { ...row, rankChange: delta }
  })

  standings.value = next.sort(compareStanding)

  if (Object.keys(deltas).length === 0) return
  rankDelta.value = deltas
  rankTimer = clearTimer(rankTimer)
  rankTimer = setTimeout(() => {
    rankDelta.value = {}
    rankTimer = null
  }, RANK_DELTA_MS)
}

function applySnapshot(snapshot: SnapshotMessage, kind: DisplaySource): void {
  settings.value = snapshot.settings
  latestResults.value = snapshot.latestResults
  version.value = snapshot.version
  applyStandings(snapshot.standings)
  source.value = kind
}

function mergeStanding(row: StandingRow): void {
  applyStandings([...standings.value.filter((item) => item.teamId !== row.teamId), row])
}

/**
 * 应用增量变更。
 *
 * 只有总积分榜能在客户端可靠合并；其余实体（逐条成绩、分项成绩等）的合并规则在服务端，
 * 这里直接 resync 拉全量——宁可多拉一次，也不允许大屏上出现算错的分数。
 * 个人榜不在快照 / 增量里，总榜一变就单独重拉一次，否则它会停在开屏那一刻。
 */
function applyChanges(changes: Change[]): void {
  let resyncNeeded = false
  let standingsTouched = false

  for (const change of changes) {
    if (change.entity !== 'standings') {
      resyncNeeded = true
      continue
    }
    if (change.action === 'replace' && Array.isArray(change.data)) {
      applyStandings(parseStandingRows(change.data))
      standingsTouched = true
    } else if (change.action === 'upsert') {
      mergeStanding(parseStandingRow(change.data))
      standingsTouched = true
    } else {
      // replace 载荷不是榜单数组时不能当空数组用（会把大屏清空），回退全量。
      resyncNeeded = true
    }
  }

  if (standingsTouched) void refreshAthletes()
  if (resyncNeeded) client?.requestResync()
}

/**
 * 个人榜单独走 REST：服务端快照不含 athletes，增量也不写这个 entity。
 * 拉取失败时保留上一份，不能因为附属榜单把实时主数据挡住。
 */
async function refreshAthletes(): Promise<void> {
  if (athletesLoading) return
  athletesLoading = true
  try {
    athletes.value = await api.standings.athletes()
  } catch {
    // 静默保留旧数据，下一次榜单变更会再试。
  } finally {
    athletesLoading = false
  }
}

// ---------------------------------------------------------------------------
// 断线兜底与启动
// ---------------------------------------------------------------------------

function hydrateFromCache(): void {
  const cached = readCachedSnapshot()
  if (cached === null) return
  applySnapshot(cached.snapshot, 'cache')
}

/**
 * REST 兜底。
 *
 * 大屏不请求 /api/settings（admin-only，guest 必然 403），配置只认 WS 快照与本地缓存；
 * 快照比 REST 权威（REST 没有 version），且请求飞行途中可能已有快照到达，
 * 所以是否套用 REST 必须在 await 之后重新判断，不能沿用发请求前的结论。
 */
async function loadRest(): Promise<boolean> {
  const [standingsResult, athletesResult] = await Promise.allSettled([
    api.standings.teams(),
    api.standings.athletes(),
  ])
  const hasSnapshot = version.value !== null

  let ok = false
  if (standingsResult.status === 'fulfilled' && !hasSnapshot) {
    applyStandings(standingsResult.value)
    ok = true
  }
  if (athletesResult.status === 'fulfilled') {
    athletes.value = athletesResult.value
    ok = true
  }
  return ok
}

function activateMock(): void {
  const snapshot = createMockSnapshot()
  settings.value = parseSettings(snapshot.settings)
  latestResults.value = snapshot.latestResults
  athletes.value = createMockAthletes()
  standings.value = snapshot.standings
  source.value = 'mock'

  // 示例数据也把升降箭头演示出来，方便验收动效。
  const deltas: Record<number, number> = {}
  for (const row of snapshot.standings) {
    if (row.rankChange !== null && row.rankChange !== 0) deltas[row.teamId] = row.rankChange
  }
  rankDelta.value = deltas
  rankTimer = clearTimer(rankTimer)
  rankTimer = setTimeout(() => {
    rankDelta.value = {}
    rankTimer = null
  }, RANK_DELTA_MS)
}

function readUrlOptions(): DisplayUrlOptions {
  const params = new URLSearchParams(window.location.search)
  const lockParam = params.get('lock')
  return {
    page: normalizePage(params.get('page')),
    // 主区域默认锁定总积分榜，只有显式 lock=0 才开整页轮播。
    locked: lockParam !== '0' && lockParam !== 'false',
    screen: params.get('screen'),
    instance: params.get('instance'),
    // 分项成绩每组最小宽度约 450px，5 组起就超出 1920 舞台，上限压到 4。
    resultsCount: clampInt(params.get('n'), 1, 4, 3),
  }
}

function clampInt(value: string | null, min: number, max: number, fallback: number): number {
  if (value === null) return fallback
  const parsed = Number.parseInt(value, 10)
  if (!Number.isFinite(parsed)) return fallback
  return Math.min(max, Math.max(min, parsed))
}

// ---------------------------------------------------------------------------
// 轮播
// ---------------------------------------------------------------------------

function stopPageRotation(): void {
  if (pageTimer !== null) {
    clearInterval(pageTimer)
    pageTimer = null
  }
}

function startPageRotation(): void {
  stopPageRotation()
  // 公告不在轮播页清单里，轮播会把公告切走；公告期间一律不启动。
  if (locked.value || reducedMotion.value || page.value === 'announcement') return
  const order = rotationPages.value
  if (order.length < 2) return

  pageTimer = setInterval(() => {
    const current = order.indexOf(page.value)
    const next = order[(current + 1) % order.length]
    if (next !== undefined) page.value = next
  }, PAGE_ROTATE_MS)
}

function setLocked(value: boolean): void {
  locked.value = value
  if (value) stopPageRotation()
  else startPageRotation()
}

// ---------------------------------------------------------------------------
// 覆盖层与公告
// ---------------------------------------------------------------------------

function clearDetailTimer(): void {
  detailTimer = clearTimer(detailTimer)
}

function closeDetail(): void {
  clearDetailTimer()
  detail.value = null
  if (!locked.value) startPageRotation()
}

async function openDetail(command: DisplayCommand): Promise<void> {
  const payload = command.payload
  const provided = payload.detail === undefined ? null : parseTeamBreakdown(payload.detail)
  const teamId = typeof payload.teamId === 'number' ? payload.teamId : null
  const openedAt = Date.now()

  detail.value = {
    title: payload.title ?? provided?.teamName ?? '积分明细',
    detail: provided,
    autoCloseSeconds: payload.autoCloseSeconds ?? 60,
    openedAt,
    loading: provided === null && teamId !== null,
  }
  // 明细覆盖期间暂停轮播（06 第 5 节）。
  stopPageRotation()
  clearDetailTimer()
  if (detail.value.autoCloseSeconds > 0) {
    detailTimer = setTimeout(closeDetail, detail.value.autoCloseSeconds * 1000)
  }

  if (!detail.value.loading || teamId === null) return
  try {
    const breakdown = parseTeamBreakdown(await api.standings.breakdown(teamId))
    // 请求期间可能已被 hide-detail 或自动关闭，用 openedAt 判断这份响应还属于当前覆盖层。
    if (detail.value !== null && detail.value.openedAt === openedAt) {
      detail.value.detail = breakdown
      detail.value.loading = false
    }
  } catch {
    if (detail.value !== null && detail.value.openedAt === openedAt) detail.value.loading = false
  }
}

function handleCommand(command: DisplayCommand): void {
  switch (command.action) {
    case 'goto': {
      const target = normalizePage(command.payload.page)
      if (target !== null) {
        closeDetail()
        page.value = target
        // 公告期间轮播是停着的，goto 抢回控制权后按锁定状态恢复。
        if (!locked.value) startPageRotation()
      }
      break
    }
    case 'lock':
      setLocked(true)
      break
    case 'unlock':
      setLocked(false)
      break
    case 'reload':
      window.location.reload()
      break
    case 'announce':
      // 全屏 seconds 秒后正文留在底栏，只有新公告或 announce_clear 才替换它。
      announcementStore.push(command.payload.text ?? '', command.payload.seconds ?? 0)
      break
    case 'announce_clear':
      announcementStore.clear()
      break
    case 'show-detail':
      void openDetail(command)
      break
    case 'hide-detail':
      closeDetail()
      break
  }
}

// 大屏字体随设置变化：快照、缓存、示例数据任何一条路径改动 settings 都要重新挂字体。
watch(
  settings,
  (next) => {
    void applyDisplayFonts(next)
  },
  { immediate: true },
)

/**
 * 服务端把当前公告持久化在设置里（display.announce），快照与设置接口都带它。
 *
 * 指令可能因为断线、重开窗口而错过，所以设置里的值也当作一条公告来源：
 * 变成本机没有的新内容就广播一次全屏，服务端清空后本地跟着清掉。
 */
watch(
  () => settings.value?.display?.announce ?? null,
  (next) => {
    const text = next?.trim() ?? ''
    if (text === seenSettingsAnnounce) return
    seenSettingsAnnounce = text
    if (text === '') {
      announcementStore.clear()
      return
    }
    // 指令刚推过同一条（持久化会跟着回推一次设置），不重复全屏。
    if (announcement.value?.text === text) return
    announcementStore.push(text, DEFAULT_ANNOUNCE_SECONDS)
  },
)

// ---------------------------------------------------------------------------
// 生命周期
// ---------------------------------------------------------------------------

function connect(): void {
  if (client !== null) return
  client = new RealtimeClient({
    role: 'display',
    displayKey: options.value.instance ?? options.value.screen ?? undefined,
    instanceId: options.value.instance ?? undefined,
    page: page.value,
    initialVersion: version.value,
    onSnapshot: (message) => {
      // 快照载荷一律过解析层逐字段兜底，解析失败则整包丢弃（心跳/重连会再给一次）。
      const snapshot = parseSnapshot(message)
      if (snapshot === null) return
      applySnapshot(snapshot, 'live')
      writeCachedSnapshot(snapshot)
      // 个人榜不在快照里，每次拿到快照（含 resync 结果）都单独补拉一次。
      void refreshAthletes()
    },
    onCatchup: (message) => {
      applyChanges(message.changes)
    },
    onChange: (message) => {
      applyChanges(message.changes)
    },
    onCommand: handleCommand,
    onStatusChange: (next) => {
      status.value = next
      if (next === 'online') authRequired.value = false
    },
    onVersionChange: (next) => {
      version.value = next
    },
    onAuthRequired: () => {
      authRequired.value = true
    },
    onError: (error) => {
      // 心跳超时 / 非 JSON / 握手失败都只在这里可见，现场排障要靠它。
      console.warn('[大屏实时]', error.message)
    },
  })
  client.connect()
}

async function bootstrap(): Promise<void> {
  if (booted.value) return
  booted.value = true

  const parsed = readUrlOptions()
  options.value = parsed
  if (parsed.page !== null) page.value = parsed.page
  locked.value = parsed.locked

  hydrateFromCache()
  connect()

  const restOk = await loadRest()
  if (!restOk && version.value === null) activateMock()

  if (!locked.value) startPageRotation()
}

function dispose(): void {
  stopPageRotation()
  clearDetailTimer()
  rankTimer = clearTimer(rankTimer)
  announcementStore.dispose()
  client?.close()
  client = null
  booted.value = false
}

function rankDeltaFor(teamId: number): number | null {
  return rankDelta.value[teamId] ?? null
}

/**
 * 大屏只有这一份状态：多块屏各自是独立窗口/标签页，不需要跨实例共享，
 * 所以用模块级单例而不是 Pinia，少一层依赖。
 */
export function useScoreboard() {
  return {
    source,
    status,
    version,
    settings,
    standings,
    athletes,
    latestResults,
    page,
    authRequired,
    options,
    detail,
    announcement,
    announceText,
    booted,
    bootstrap,
    dispose,
    rankDeltaFor,
  }
}