import { useEffect, useRef, useState } from 'react'
import { Link, useParams } from 'react-router-dom'
import { loadLiveRoom, subscribeLiveRoom } from '../lib/api'
import type { LiveRoomDetail } from '../types'

type RoomSpectatorPageProps = {
  onConfirmFinished: () => void
}

const ROOM_POLL_MS = 1500

type RoomClosedDialog = {
  message: string
  title: string
} | null

export function RoomSpectatorPage({ onConfirmFinished }: RoomSpectatorPageProps) {
  const { roomId = '' } = useParams()
  const [error, setError] = useState('')
  const [loading, setLoading] = useState(true)
  const [room, setRoom] = useState<LiveRoomDetail | null>(null)
  const [showFinishedDialog, setShowFinishedDialog] = useState(false)
  const [roomClosedDialog, setRoomClosedDialog] = useState<RoomClosedDialog>(null)
  const previousStatusRef = useRef<string | null>(null)
  const hasRoomRef = useRef(false)

  useEffect(() => {
    if (!roomId) {
      return
    }

    let active = true
    hasRoomRef.current = false
    previousStatusRef.current = null

    const applyRoomUpdate = (nextRoom: LiveRoomDetail) => {
      if (!active) {
        return
      }

      if (nextRoom.status === 'finished' && previousStatusRef.current !== 'finished') {
        setShowFinishedDialog(true)
      }

      previousStatusRef.current = nextRoom.status
      hasRoomRef.current = true
      setRoom(nextRoom)
      setError('')
      setLoading(false)
    }

    const load = async (showLoadError = true) => {
      try {
        const nextRoom = await loadLiveRoom(roomId)
        applyRoomUpdate(nextRoom)
      } catch (loadError) {
        if (!active) {
          return
        }

        if (showLoadError || !hasRoomRef.current) {
          setError(loadError instanceof Error ? loadError.message : '載入觀戰房間失敗。')
          setLoading(false)
        }
      }
    }

    void load()
    const unsubscribe = subscribeLiveRoom(
      roomId,
      (nextRoom) => {
        applyRoomUpdate(nextRoom)
      },
      () => {
        if (!active) {
          return
        }

        if (!hasRoomRef.current) {
          setError('觀戰連線中斷，請稍後重試。')
          setLoading(false)
        }
      },
      (payload) => {
        if (!active) {
          return
        }

        if (payload.status === 'released') {
          setRoomClosedDialog({
            title: '房間已關閉',
            message: '房主已重整頁面、離開記分板或重新選隊伍，本房間已結束觀戰。',
          })
          setLoading(false)
        }
      },
    )

    const timer = window.setInterval(() => {
      void load(false)
    }, ROOM_POLL_MS)

    return () => {
      active = false
      window.clearInterval(timer)
      unsubscribe()
    }
  }, [roomId])

  if (loading) {
    return (
      <section className="page-grid">
        <article className="panel full-span">
          <p>正在載入觀戰房間...</p>
        </article>
      </section>
    )
  }

  if (!room && error) {
    return (
      <section className="page-grid">
        <article className="panel panel-hero full-span">
          <p className="panel-kicker">Spectator</p>
          <h2>無法進入房間</h2>
          <p className="panel-copy">{error}</p>
          <Link className="primary-button inline-link" to="/rooms">
            返回房間列表
          </Link>
        </article>
      </section>
    )
  }

  return (
    <>
      <section className="page-grid">
        <article className="panel panel-hero full-span">
          <p className="panel-kicker">Spectator</p>
          <h2>房號 {room?.roomId ?? roomId}</h2>
          <p className="panel-copy">這是觀戰模式，只會即時同步比分，不提供任何操作。</p>
        </article>

        {room ? (
          <article className="panel full-span room-watch-panel">
            <div className="room-watch-scoreboard">
              <div className="room-watch-team">
                <small>{room.leftTeamName}</small>
                <strong>{room.scoreState.scoreLeft}</strong>
              </div>
              <div className="room-watch-divider">:</div>
              <div className="room-watch-team">
                <small>{room.rightTeamName}</small>
                <strong>{room.scoreState.scoreRight}</strong>
              </div>
            </div>

            <div className="room-watch-meta">
              <span>目標分數 {room.scoreState.targetScore}</span>
              <span>房間狀態 {room.status === 'finished' ? '已結束' : '進行中'}</span>
              <span>
                最後更新 {new Date(room.updatedAt).toLocaleTimeString('zh-TW', { hour12: false })}
              </span>
            </div>
          </article>
        ) : (
          <article className="panel full-span">
            <p className="history-empty">房間已不存在，請返回房間列表。</p>
          </article>
        )}
      </section>

      {showFinishedDialog && room ? (
        <div className="finish-dialog-overlay" role="presentation">
          <div aria-modal="true" className="finish-dialog" role="dialog">
            <p className="panel-kicker">比賽結束</p>
            <h3>{room.winnerTeamName ?? '已有獲勝隊伍'}</h3>
            <p className="finish-dialog-copy">
              {room.winnerTeamName
                ? `${room.winnerTeamName} 已獲勝，按下確定後返回房間列表。`
                : '比賽已結束，按下確定後返回房間列表。'}
            </p>
            <div className="finish-dialog-actions">
              <button
                className="team-picker-confirm"
                type="button"
                onClick={() => {
                  setShowFinishedDialog(false)
                  onConfirmFinished()
                }}
              >
                確定
              </button>
            </div>
          </div>
        </div>
      ) : null}

      {roomClosedDialog ? (
        <div className="finish-dialog-overlay" role="presentation">
          <div aria-modal="true" className="finish-dialog" role="dialog">
            <p className="panel-kicker">觀戰提醒</p>
            <h3>{roomClosedDialog.title}</h3>
            <p className="finish-dialog-copy">{roomClosedDialog.message}</p>
            <div className="finish-dialog-actions">
              <button
                className="team-picker-confirm"
                type="button"
                onClick={() => {
                  setRoomClosedDialog(null)
                  onConfirmFinished()
                }}
              >
                確定
              </button>
            </div>
          </div>
        </div>
      ) : null}
    </>
  )
}