import { useEffect, useRef, useState, useCallback } from 'react'
import {
  createGameConnection,
  STATE_PLACING_SHIPS,
  STATE_OPPONENT_READY,
  STATE_WAIT_OPPONENT_READY,
  STATE_YOUR_TURN,
  STATE_WAIT_OPPONENT_TURN,
} from '../game'
import ShipPlacementScreen from './ShipPlacementScreen'

export default function GameScreen({ session, onLeave }) {
  const [status, setStatus] = useState('connecting') // 'connecting' | 'placing' | 'game' | 'error'
  const [gameState, setGameState] = useState(STATE_PLACING_SHIPS)
  const [isSubmitting, setIsSubmitting] = useState(false)
  const [opponentReady, setOpponentReady] = useState(false)
  const [error, setError] = useState(null)

  const connectionRef = useRef(null)
  const attemptRef = useRef(0)

  useEffect(() => {
    const attempt = ++attemptRef.current
    let cancelled = false
    const connInstance = createGameConnection(session)

    connInstance.promise
      .then((conn) => {
        if (cancelled || attempt !== attemptRef.current) return
        connectionRef.current = conn

        conn.onState = (newState) => {
          if (cancelled || attempt !== attemptRef.current) return

          if (newState === STATE_OPPONENT_READY) {
            setOpponentReady(true)
          } else if (
            newState === STATE_WAIT_OPPONENT_READY ||
            newState === STATE_YOUR_TURN ||
            newState === STATE_WAIT_OPPONENT_TURN
          ) {
            setIsSubmitting(false)
            setGameState(newState)
            setStatus('game')
          }
        }

        conn.onEnd = (_code, reason) => {
          if (cancelled || attempt !== attemptRef.current) return
          setIsSubmitting(false)
          setError(reason || 'Партия завершена')
          setStatus('error')
        }

        conn.onClose = () => {
          if (cancelled || attempt !== attemptRef.current) return
          setIsSubmitting(false)
          setStatus((prev) => {
            if (prev !== 'error') {
              setError('Соединение с сервером прервано')
              return 'error'
            }
            return prev
          })
        }

        setStatus('placing')
      })
      .catch((err) => {
        if (cancelled || attempt !== attemptRef.current) return
        setError(err.message || 'Не удалось подключиться к игре')
        setStatus('error')
      })

    return () => {
      cancelled = true
      connInstance.cancel()
    }
  }, [session])

  const handleReady = useCallback((ships) => {
    if (!connectionRef.current) return
    setIsSubmitting(true)
    connectionRef.current.placeShips(ships)
  }, [])

  // Текст заглушки в зависимости от состояния игры
  const getGameStubText = () => {
    switch (gameState) {
      case STATE_WAIT_OPPONENT_READY:
        return 'Соперник расставляет корабли...'
      case STATE_YOUR_TURN:
        return 'Ваш ход'
      case STATE_WAIT_OPPONENT_TURN:
        return 'Соперник ходит'
      default:
        return ''
    }
  }

  return (
    <div className="page game-page">
      {status === 'connecting' && (
        <main className="search-screen">
          <div className="search-label">Подключение к игре...</div>
          <div className="bouncing-dots" aria-hidden="true">
            <span />
            <span />
            <span />
          </div>
        </main>
      )}

      {status === 'placing' && (
        <main className="game-screen-main">
          <ShipPlacementScreen
            onReady={handleReady}
            isSubmitting={isSubmitting}
            opponentReady={opponentReady}
          />
        </main>
      )}

      {status === 'game' && (
        <main className="search-screen">
          <div className="search-label">{getGameStubText()}</div>
          {(gameState === STATE_WAIT_OPPONENT_READY ||
            gameState === STATE_WAIT_OPPONENT_TURN) && (
            <div className="bouncing-dots" aria-hidden="true">
              <span />
              <span />
              <span />
            </div>
          )}
        </main>
      )}

      {status === 'error' && (
        <main className="search-screen">
          <div className="search-error">{error}</div>
          <button className="btn btn-big btn-secondary" onClick={onLeave}>
            Назад в меню
          </button>
        </main>
      )}

      {/* Модальный pop-up с надписью "Загрузка...", пока сервер не ответит сменой состояния */}
      {isSubmitting && (
        <div className="modal-overlay">
          <div className="modal loading-modal">
            <h2 className="modal-title">Загрузка...</h2>
            <div className="bouncing-dots" style={{ justifyContent: 'center', marginTop: 16 }}>
              <span />
              <span />
              <span />
            </div>
          </div>
        </div>
      )}
    </div>
  )
}