class Engine {
    constructor(url) {
        this.socket = new WebSocket(url);
        this.socketQueueId = 0;
        this.socketQueue = {};

        this.income_handler = null;

        this.socket.onmessage = (event) => {
            let response = {};
            try {
                response = JSON.parse(event.data);
            } catch(e) {
                // string received
                console.log('Engine:', event.data);
            }

            // RPC responses
            if (typeof(response['cmd_id']) != 'undefined' && typeof(this.socketQueue['i_'+response['cmd_id']]) == 'function') {
                // action response
                let execFunc = this.socketQueue['i_'+response['cmd_id']];
                execFunc(response);
                delete this.socketQueue['i_'+response['cmd_id']];
            }
            else {
                // non RPC responses
                if (response != 'undefined' && Object.keys(response).length != 0) {

                    switch (response.entity == '--SERVICE--') {
                        case true:
                            // engine internal responses
                            if (response.action == 'init') {
                                console.log('Engine v', response.data.version);
                            }
                            break;
                        case false:
                            switch (response.action != null && response.entity != null) {
                                case true:
                                    this.income_handler(response);
                                    break;
                                case false:
                                    // errors and other
                                    console.log('Engine:', response.msg, response.data);
                            }
                            break;
                    }
                }
                else {
                    console.log(response);
                }
            }
        };
        this.socket.onopen = (event) => {
            console.log('Socket open.');
        };
        this.socket.onclose = () => {
            console.log('Socket close.');
        }
    }

    send(message, callback) {
        this.waitForConnection(() => {

            if (typeof callback !== 'undefined') {
                this.socketQueueId++;
                this.socketQueue['i_'+this.socketQueueId] = callback;
                message.cmd_id = this.socketQueueId;
                this.socket.send(JSON.stringify(message));
            }

        }, 1000);
    };

    waitForConnection(send_func, interval) {
        if (this.socket.readyState === 1) {
            send_func();
        } else {
            let that = this;
            setTimeout(function () {
                that.waitForConnection(send_func, interval);
            }, interval);
        }
    };

    action(message) {
        let inst = this;
        return new Promise((resolve, reject) => {
            inst.send(message, (response) => {resolve(response)});
        });
    }

    set_income_handler(handler) {
        this.income_handler = handler;
    }
}