const WS = {
    _ws: null,
    _url: '',
    _reconnectTimer: null,
    _reconnectDelay: 2000,
    _handlers: {},
    _connected: false,
    _lastPong: 0,

    init() {
        const protocol = location.protocol === 'https:' ? 'wss:' : 'ws:';
        this._url = `${protocol}//${location.host}/ws`;
        this._connect();

        document.addEventListener('visibilitychange', () => {
            if (!document.hidden && !this._connected) {
                this._reconnectDelay = 500;
                this._connect();
            }
            if (!document.hidden && this._connected) {
                this.send({type: 'ping'});
            }
        });
    },

    _connect() {
        if (this._ws && (this._ws.readyState === WebSocket.OPEN || this._ws.readyState === WebSocket.CONNECTING)) return;

        try {
            this._ws = new WebSocket(this._url);
        } catch (e) {
            this._scheduleReconnect();
            return;
        }

        this._ws.onopen = () => {
            this._connected = true;
            this._lastPong = Date.now();
            this._reconnectDelay = 2000;
            this._emit('connection', true);
            this._emit('status', 'connected');
        };

        this._ws.onmessage = (event) => {
            try {
                const msg = JSON.parse(event.data);
                if (msg.type === 'pong') { this._lastPong = Date.now(); return; }
                this._emit(msg.type || 'message', msg.data || msg);
                if (msg.type === 'telemetry') {
                    this._emit('telemetry', msg.data);
                }
            } catch (e) { console.error(e); }
        };

        this._ws.onclose = () => {
            this._connected = false;
            this._emit('connection', false);
            this._emit('status', 'disconnected');
            this._scheduleReconnect();
        };

        this._ws.onerror = () => {
            this._emit('status', 'disconnected');
            this._connected = false;
        };
    },

    _scheduleReconnect() {
        if (this._reconnectTimer) return;
        this._reconnectTimer = setTimeout(() => {
            this._reconnectTimer = null;
            this._reconnectDelay = Math.min(this._reconnectDelay * 1.5, 10000);
            this._connect();
        }, this._reconnectDelay);
    },

    on(event, handler) {
        if (!this._handlers[event]) this._handlers[event] = [];
        this._handlers[event].push(handler);
    },

    off(event, handler) {
        if (!this._handlers[event]) return;
        this._handlers[event] = this._handlers[event].filter(h => h !== handler);
    },

    _emit(event, data) {
        if (!this._handlers[event]) return;
        this._handlers[event].forEach(h => h(data));
    },

    send(data) {
        if (this._ws && this._ws.readyState === WebSocket.OPEN) {
            this._ws.send(JSON.stringify(data));
        }
    },

    get connected() { return this._connected; }
};

window.WS = WS;