class Comms {
    constructor() {

        // Callback collections that will receive various updates.
        this.candleUpdateCallbacks = [];
        this.candleCloseCallbacks = [];
        this.indicatorUpdateCallbacks = [];

        // Flags
        this.connectionOpen = false;
    }

    /**
     * Register a callback function to receive updates for a specific target.
     * @param {string} target - The target for the callback ('candle_update', 'candle_close', or 'indicator_update').
     * @param {function} callbackFunc - The callback function to register.
     */
    registerCallback(target, callbackFunc) {
        const callbackMap = {
            'candle_update': this.candleUpdateCallbacks,
            'candle_close': this.candleCloseCallbacks,
            'indicator_update': this.indicatorUpdateCallbacks
        };

        const callbackList = callbackMap[target];
        if (callbackList) {
            callbackList.push(callbackFunc);
        } else {
            console.log('Comms: Invalid target for callback');
        }
    }

    /* Callback declarations */

    candleUpdate(newCandle) {
        for (const callback of this.candleUpdateCallbacks) {
            callback(newCandle);
        }
    }

   candleClose(newCandle) {
        this.sendToApp('candle_data', newCandle);

        for (const callback of this.candleCloseCallbacks) {
            callback(newCandle);
        }
    }

    indicatorUpdate(data) {
        for (const callback of this.indicatorUpdateCallbacks) {
            callback(data);
        }
    }

    /**
     * Fetches the price history data for a user.
     * @param {string} userName - The name of the user.
     * @returns {Promise<Object|null>} - A promise that resolves
     * to the fetched price history data, or null if an error occurs.
     */
     async getPriceHistory(userName) {
        try {
            const response = await fetch('http://localhost:5000/api/history', {
                credentials: 'include',
                mode: 'cors',
                method: 'POST',
                headers: { 'Content-Type': 'application/json' },
                body: JSON.stringify({ "user_name": userName })
            });

            const data = await response.json();
            console.log('Communication[56]: Received candles from the server:');
            console.log(data);
            return data;
        } catch (error) {
            console.error('Error fetching price history:', error);
            return null;
        }
    }
    /**
     * Fetches the Indicator data for a specific user.
     * @param {string} userName - The name of the user.
     * @returns {Promise<Object|null>} - A promise that resolves
     * to the fetched Indicator data, or null if an error occurs.
     */
    async getIndicatorData(userName) {
        try {
            const response = await fetch('http://localhost:5000/api/indicator_init', {
                credentials: 'same-origin',
                mode: 'cors',
                method: 'POST',
                headers: { 'Content-Type': 'application/json' },
                body: JSON.stringify({ "user_name": userName })
            });

            const data = await response.json();
            return data;
        } catch (error) {
            console.error('Error fetching indicator data:', error);
            return null;
        }
    }

    /**
     * Sends a message to the application server.
     * @param {string} messageType - The type of the message.
     * @param {Object} data - The data to be sent with the message.
     */
    sendToApp(messageType, data) {
        console.log('window.UI.data.comms.sendToApp(): Sending->');
        console.log(JSON.stringify({ message_type: messageType, data: data }));

        if (this.connectionOpen) {
            this.appCon.send(JSON.stringify({ message_type: messageType, data: data }));
        } else {
            setTimeout(() => {
                window.UI.data.comms.appCon.send(JSON.stringify({ message_type: messageType, data: data }));
            }, 1000);
        }
    }

    /**
     * Sets up the WebSocket connection to the application server.
     */
    setAppCon() {
        this.appCon = new WebSocket('ws://localhost:5000/ws');
        this.appCon.onopen = () => {
            this.appCon.send("Connection OK");
            this.connectionOpen = true;
        };

        this.appCon.addEventListener('message', (event) => {
            if (event.data) {
                const message = JSON.parse(event.data);

                if (message && message.request !== undefined) {
                    console.log('Received a request from the server');
                    console.log(message.request);
                }

                if (message && message.reply !== undefined) {
                    if (message.reply === 'updates') {
                        const { i_updates, s_updates, stg_updts, trade_updts } = message.data;

                        if (i_updates) {
                            this.indicatorUpdate(i_updates);
                            window.UI.signals.i_update(i_updates);
                        }
                        if (s_updates) {
                            const updates = s_updates;
                            window.UI.signals.update_signal_states(updates);
                            window.UI.alerts.publish_alerts('signal_changes', updates);
                        }
                        if (stg_updts) {
                            const stg_updts = stg_updts;
                            window.UI.strats.update_received(stg_updts);
                        }
                        if (trade_updts) {
                            const trade_updts = trade_updts;
                            window.UI.trade.update_received(trade_updts);
                        }
                    } else if (message.reply === 'signals') {
                        window.UI.signals.set_data(message.data);
                    } else if (message.reply === 'strategies') {
                        window.UI.strats.set_data(message.data);
                    } else if (message.reply === 'trades') {
                        window.UI.trade.set_data(message.data);
                    } else if (message.reply === 'signal_created') {
                        const list_of_one = [message.data];
                        window.UI.signals.set_data(list_of_one);
                    } else if (message.reply === 'trade_created') {
                        const list_of_one = [message.data];
                        window.UI.trade.set_data(list_of_one);
                    } else {
                        console.log(message.reply);
                        console.log(message.data);
                    }
                }
            }
        });
    }

    /**
     * Sets up a WebSocket connection to the exchange for receiving candlestick data.
     * @param {string} interval - The interval of the candlestick data.
     * @param {string} tradingPair - The trading pair to subscribe to.
     */
    setExchangeCon(interval, tradingPair) {
        tradingPair = tradingPair.toLowerCase();
        const ws = `wss://stream.binance.com:9443/ws/${tradingPair}@kline_${interval}`;
        this.exchangeCon = new WebSocket(ws);

        this.exchangeCon.onmessage = (event) => {
            let message = JSON.parse(event.data);
            let candlestick = message.k;
            let newCandle = {
                time: candlestick.t / 1000,
                open: candlestick.o,
                high: candlestick.h,
                low: candlestick.l,
                close: candlestick.c,
                vol: candlestick.v
            };
            this.candleUpdate(newCandle);

            if (candlestick.x === true) {
                this.candleClose(newCandle);
            }
        };
    }
}