console.log("loading engine");

const initEvent = () => {
    let subscribers = {};

    return (message, ...messageArgs) => {
        switch (message) {
        case "addSubscriber":
            let subscriberName = messageArgs[0];
            let subscriberFunc = messageArgs[1];
            subscribers[subscriberName] = subscriberFunc;
            break;
        case "raise":
            let delta = messageArgs[0];
            let eventData = messageArgs[1];
            Object.entries(subscribers).forEach(([id, subscriber]) => {
                subscriber(delta, eventData);
            });
            break;
        }
    };
};

const engine = (() => {
    let queue = [];
    let timer;
    let time = Date.now();
    let entities = {};
    let events = {};

    const engineTick = 1000 / 60;
    const tick = () => {
        let now = Date.now();
        let delta = now - time;
        time = now;
        while (queue.length > 0) {
            let eventName = queue.shift();
            events[eventName]("raise", delta);
        }
        timer = setTimeout(tick, engineTick);
    };
    const halt = () => {
        console.log("halted");
        clearTimeout(timer);
    };
    return (message, ...messageArgs) => {
        switch (message) {
        case "queueEvent":
            queue.push(messageArgs[0]);
            break;
        case "events":
            return events;
            break;
        case "registerEntity":
            break;
        case "removeEntity":
            break;
        case "registerEvent":
            {let eventName = messageArgs[0];
            let newEvent = initEvent();
             events[eventName] = newEvent;}
            break;
        case "subscribeToEvent":
            {let eventName = messageArgs[0];
             let subscriberName = messageArgs[1];
             let newSubscriber = messageArgs[2];
             events[eventName]("addSubscriber", subscriberName, newSubscriber);}
            break;
        case 'start':
            tick();
            break;
        case 'halt':
            halt();
            break;
        };
    };
})();

inputSystem(engine);
playerSystem(engine);

engine("start");