import { useCallback, useEffect, useRef, useState } from "react";
import { Button, Modal, Table } from "react-bootstrap";
import { FontAwesomeIcon } from "@fortawesome/react-fontawesome";
import { faCaretDown, faCaretLeft, faCaretRight, faCaretUp } from "@fortawesome/free-solid-svg-icons";
import { socket } from "../context/socket";
import { useAuth } from "../context/auth";
import { getToken } from "../Utils";
import { useGameIcon } from "../games/themeIcons";
import { useTouchDevice } from "../hooks/useTouchDevice";
import TouchButton from "./TouchButton";
import "./SnakeGame.scss";

// Typy musí odpovídat server/src/snakeGame.ts (stav chodí přes websocket, ne přes OpenAPI)
type Cell = [number, number];
type Direction = 'up' | 'down' | 'left' | 'right';
type SnakePhase = 'idle' | 'lobby' | 'countdown' | 'playing' | 'finished';
type SnakePlayer = { login: string, color: number, body: Cell[], alive: boolean, score: number, place?: number };
type SnakeState = {
    phase: SnakePhase,
    host?: string,
    players: SnakePlayer[],
    food: Cell[],
    tick: number,
    maxTicks: number,
    countdown?: number,
    width: number,
    height: number,
    minPlayers: number,
};

const OPEN_EVENT = 'luncher:open-snake';

/** Otevře okno hada. */
export const openSnakeGame = () => window.dispatchEvent(new Event(OPEN_EVENT));

const COLORS = ['#4ade80', '#60a5fa', '#f472b6', '#facc15', '#a78bfa', '#fb923c', '#2dd4bf', '#f87171'];
const MEDALS = ['🥇', '🥈', '🥉'];
const TICK_MS = 120;

const KEY_DIRECTIONS: Record<string, Direction> = {
    ArrowUp: 'up', ArrowDown: 'down', ArrowLeft: 'left', ArrowRight: 'right',
    KeyW: 'up', KeyS: 'down', KeyA: 'left', KeyD: 'right',
};

/** Délka tahu prstem po ploše (px), od které se bere jako zatočení. */
const SWIPE_PX = 24;

/** Vykreslí hrací plochu do canvasu. */
function draw(canvas: HTMLCanvasElement, state: SnakeState, me?: string) {
    const ctx = canvas.getContext('2d');
    if (!ctx) return;
    const cell = canvas.width / state.width;
    ctx.fillStyle = '#111827';
    ctx.fillRect(0, 0, canvas.width, canvas.height);
    ctx.fillStyle = '#1f2937';
    for (let x = 0; x < state.width; x++) {
        for (let y = 0; y < state.height; y++) {
            if ((x + y) % 2 === 0) ctx.fillRect(x * cell, y * cell, cell, cell);
        }
    }
    for (const [x, y] of state.food) {
        ctx.fillStyle = '#ef4444';
        ctx.beginPath();
        ctx.arc((x + 0.5) * cell, (y + 0.5) * cell, cell * 0.35, 0, Math.PI * 2);
        ctx.fill();
    }
    for (const p of state.players) {
        const color = COLORS[p.color % COLORS.length];
        // Tělo tlumeně, hlava se kreslí zvlášť až nakonec
        ctx.fillStyle = color;
        ctx.globalAlpha = 0.65;
        p.body.slice(1).forEach(([x, y]) => ctx.fillRect(x * cell + 2, y * cell + 2, cell - 4, cell - 4));
        ctx.globalAlpha = 1;
        if (p.body[0]) drawHead(ctx, p.body, cell, color, p.login === me);
    }
}

/** Hlava: plná barva, zaoblená, přes okraj políčka a s očima ve směru pohybu. */
function drawHead(ctx: CanvasRenderingContext2D, body: Cell[], cell: number, color: string, mine: boolean) {
    const [x, y] = body[0];
    const neck = body[1];
    const dx = neck ? Math.sign(x - neck[0]) : 1;
    const dy = neck ? Math.sign(y - neck[1]) : 0;
    const cx = (x + 0.5) * cell;
    const cy = (y + 0.5) * cell;
    const size = cell * 1.1;

    ctx.fillStyle = color;
    ctx.beginPath();
    ctx.roundRect(cx - size / 2, cy - size / 2, size, size, cell * 0.35);
    ctx.fill();
    // Vlastní had má bílý obrys hlavy, ostatní tmavý — hlava se tak odliší od těla i pozadí
    ctx.strokeStyle = mine ? '#fff' : '#0b0f19';
    ctx.lineWidth = 2;
    ctx.stroke();

    // Oči: posunuté ve směru pohybu, rozložené kolmo na něj
    const forward = cell * 0.18;
    const side = cell * 0.22;
    for (const s of [-1, 1]) {
        const ex = cx + dx * forward + -dy * side * s;
        const ey = cy + dy * forward + dx * side * s;
        ctx.fillStyle = '#fff';
        ctx.beginPath();
        ctx.arc(ex, ey, cell * 0.14, 0, Math.PI * 2);
        ctx.fill();
        ctx.fillStyle = '#000';
        ctx.beginPath();
        ctx.arc(ex + dx * cell * 0.05, ey + dy * cell * 0.05, cell * 0.07, 0, Math.PI * 2);
        ctx.fill();
    }
}

/** Multiplayerový had — lobby, hrací plocha a výsledky; simulaci drží server. */
export default function SnakeGame() {
    const auth = useAuth();
    const login = auth?.login;
    const [state, setState] = useState<SnakeState | null>(null);
    const [open, setOpen] = useState(false);
    const [error, setError] = useState<string | null>(null);
    const canvasRef = useRef<HTMLCanvasElement>(null);
    const prevPhase = useRef<SnakePhase>('idle');
    const icon = useGameIcon('snake');
    const touch = useTouchDevice();
    /** Rozpracovaný tah prstem — bod, od kterého se měří další zatočení, a poslední směr v tomto tahu. */
    const swipe = useRef<{ pointerId: number, x: number, y: number, last?: Direction } | null>(null);

    const send = useCallback((event: string, extra?: object) => {
        setError(null);
        socket.emit(event, { token: getToken(), ...extra });
    }, []);

    useEffect(() => {
        const onState = (s: SnakeState) => setState(s);
        const onError = (msg: string) => setError(msg);
        const onOpen = () => setOpen(true);
        const sync = () => socket.emit('snake:sync');
        socket.on('snake:state', onState);
        socket.on('snake:error', onError);
        socket.on('connect', sync);
        window.addEventListener(OPEN_EVENT, onOpen);
        sync();
        return () => {
            socket.off('snake:state', onState);
            socket.off('snake:error', onError);
            socket.off('connect', sync);
            window.removeEventListener(OPEN_EVENT, onOpen);
        };
    }, []);

    // Průběžné snímky hry dostávají jen klienti s otevřeným oknem
    useEffect(() => {
        if (!open) return;
        const watch = () => socket.emit('snake:watch');
        watch();
        socket.on('connect', watch);
        return () => {
            socket.off('connect', watch);
            socket.emit('snake:unwatch');
        };
    }, [open]);

    const isPlayer = !!login && !!state?.players.some(p => p.login === login);
    const phase = state?.phase ?? 'idle';
    const inGame = phase === 'countdown' || phase === 'playing';
    const controllable = open && inGame && isPlayer;

    const turn = useCallback((dir: Direction) => {
        if (controllable) send('snake:turn', { dir });
    }, [controllable, send]);

    // Hráčům se okno otevře samo, jakmile hra začne
    useEffect(() => {
        if (prevPhase.current === 'lobby' && phase === 'countdown' && isPlayer) {
            setOpen(true);
        }
        prevPhase.current = phase;
    }, [phase, isPlayer]);

    // Ovládání šipkami a WSAD
    useEffect(() => {
        if (!controllable) return;
        const onKey = (e: KeyboardEvent) => {
            const dir = KEY_DIRECTIONS[e.code];
            if (!dir) return;
            e.preventDefault();
            if (!e.repeat) turn(dir);
        };
        window.addEventListener('keydown', onKey);
        return () => window.removeEventListener('keydown', onKey);
    }, [controllable, turn]);

    // Ovládání tahem prstu po ploše; v jednom tahu jde zatočit i víckrát (cik-cak)
    const onBoardPointerDown = (e: React.PointerEvent<HTMLCanvasElement>) => {
        if (e.pointerType === 'mouse' || !controllable) return;
        e.preventDefault();
        e.currentTarget.setPointerCapture(e.pointerId);
        swipe.current = { pointerId: e.pointerId, x: e.clientX, y: e.clientY };
    };

    const onBoardPointerMove = (e: React.PointerEvent<HTMLCanvasElement>) => {
        const s = swipe.current;
        if (!s || s.pointerId !== e.pointerId) return;
        const dx = e.clientX - s.x;
        const dy = e.clientY - s.y;
        if (Math.max(Math.abs(dx), Math.abs(dy)) < SWIPE_PX) return;
        const dir: Direction = Math.abs(dx) > Math.abs(dy) ? (dx > 0 ? 'right' : 'left') : (dy > 0 ? 'down' : 'up');
        if (dir !== s.last) turn(dir);
        swipe.current = { ...s, x: e.clientX, y: e.clientY, last: dir };
    };

    const onBoardPointerEnd = () => {
        swipe.current = null;
    };

    useEffect(() => {
        if (canvasRef.current && state && (inGame || phase === 'finished')) {
            draw(canvasRef.current, state, login);
        }
    }, [state, inGame, phase, login]);

    if (!login) return null;

    const showInvite = !open && phase === 'lobby' && !isPlayer;
    const showReturn = !open && isPlayer && inGame;
    const ranked = [...(state?.players ?? [])].sort((a, b) => (a.place ?? 99) - (b.place ?? 99) || b.score - a.score);
    const secondsLeft = state ? Math.max(0, Math.ceil((state.maxTicks - state.tick) * TICK_MS / 1000)) : 0;

    const renderBoard = () => state && (
        <div className="snake-board-wrap">
            <canvas ref={canvasRef} className="snake-board" width={state.width * 24} height={state.height * 24}
                onPointerDown={onBoardPointerDown} onPointerMove={onBoardPointerMove}
                onPointerUp={onBoardPointerEnd} onPointerCancel={onBoardPointerEnd} />
            {phase === 'countdown' && <div className="snake-overlay">{state.countdown}</div>}
        </div>
    );

    const renderScores = () => (
        <Table size="sm" className="snake-scores">
            <thead>
                <tr><th>#</th><th>Hráč</th><th>Jídla</th><th>Délka</th></tr>
            </thead>
            <tbody>
                {ranked.map((p, i) => (
                    <tr key={p.login} className={p.alive || phase !== 'playing' ? undefined : 'snake-dead'}>
                        <td>{phase === 'finished' && i < 3 ? MEDALS[i] : (phase === 'finished' ? i + 1 : '')}</td>
                        <td>
                            <span className="snake-dot" style={{ background: COLORS[p.color % COLORS.length] }} />
                            {p.login}{p.login === login && ' (vy)'}{!p.alive && inGame && ' 💀'}
                        </td>
                        <td>{p.score}</td>
                        <td>{p.body.length || '—'}</td>
                    </tr>
                ))}
            </tbody>
        </Table>
    );

    const renderBody = () => {
        switch (phase) {
            case 'idle':
                return (
                    <p>
                        Klasický had pro více hráčů. Ovládání šipkami nebo WSAD, na dotykovém displeji tahem prstu
                        po ploše nebo tlačítky. Jezte jídlo a vyhněte se zdem,
                        sobě i ostatním — čelní srážka zabije oba. Vyhrává ten, kdo přežije nejdéle;
                        hra trvá nejvýš 3 minuty. Hrát se dá i sólo.
                    </p>
                );
            case 'lobby':
                return (
                    <>
                        <p>Lobby založil(a) <strong>{state?.host}</strong>. Hráči ({state?.players.length}):</p>
                        <ul className="snake-players">
                            {state?.players.map(p => (
                                <li key={p.login}>
                                    <span className="snake-dot" style={{ background: COLORS[p.color % COLORS.length] }} />
                                    {p.login}{p.login === state.host && ' 👑'}
                                </li>
                            ))}
                        </ul>
                    </>
                );
            case 'countdown':
            case 'playing':
                return (
                    <>
                        {renderBoard()}
                        <div className="snake-status">
                            {isPlayer ? (touch ? 'Táhněte prstem po ploše' : 'Šipky / WSAD') : 'Sledujete hru'} · zbývá {secondsLeft} s
                        </div>
                        {touch && isPlayer && (
                            <div className="snake-touch-pad">
                                <TouchButton label="Nahoru" className="up" onPress={() => turn('up')}><FontAwesomeIcon icon={faCaretUp} /></TouchButton>
                                <TouchButton label="Doleva" className="left" onPress={() => turn('left')}><FontAwesomeIcon icon={faCaretLeft} /></TouchButton>
                                <TouchButton label="Doprava" className="right" onPress={() => turn('right')}><FontAwesomeIcon icon={faCaretRight} /></TouchButton>
                                <TouchButton label="Dolů" className="down" onPress={() => turn('down')}><FontAwesomeIcon icon={faCaretDown} /></TouchButton>
                            </div>
                        )}
                        {renderScores()}
                    </>
                );
            case 'finished':
                return (
                    <>
                        {renderBoard()}
                        {renderScores()}
                    </>
                );
        }
    };

    const renderFooter = () => {
        const buttons = [];
        if (phase === 'idle' || phase === 'finished') {
            buttons.push(<Button key="new" onClick={() => send('snake:join')}>{phase === 'idle' ? 'Založit lobby' : 'Nová hra'}</Button>);
        }
        if (phase === 'lobby') {
            if (!isPlayer) {
                buttons.push(<Button key="join" onClick={() => send('snake:join')}>Připojit se</Button>);
            } else {
                buttons.push(<Button key="leave" variant="outline-secondary" onClick={() => send('snake:leave')}>
                    {login === state?.host ? 'Zrušit lobby' : 'Odejít'}
                </Button>);
                if (login === state?.host) {
                    buttons.push(<Button key="start" onClick={() => send('snake:start')}
                        disabled={(state?.players.length ?? 0) < (state?.minPlayers ?? 1)}>Spustit hru</Button>);
                }
            }
        }
        buttons.push(<Button key="close" variant="secondary" onClick={() => setOpen(false)}>Zavřít</Button>);
        return buttons;
    };

    return (
        <>
            {showInvite && (
                <button className="duel-invite snake-invite" onClick={() => setOpen(true)}>
                    {icon} <strong>{state?.host}</strong> zve na hada — připojit se
                </button>
            )}
            {showReturn && (
                <button className="duel-invite snake-invite" onClick={() => setOpen(true)}>
                    {icon} Had běží — zpět do hry
                </button>
            )}
            <Modal show={open} onHide={() => setOpen(false)} size="xl" fullscreen="sm-down" className="snake-game-modal">
                <Modal.Header closeButton>
                    <Modal.Title><h2>{icon} Had</h2></Modal.Title>
                </Modal.Header>
                <Modal.Body>
                    {renderBody()}
                    {error && <div className="text-danger mt-2">{error}</div>}
                </Modal.Body>
                <Modal.Footer>{renderFooter()}</Modal.Footer>
            </Modal>
        </>
    );
}