console.log("loading input system");

const inputStates = Object.freeze({
    DEFAULT: 0,
});

const inputSystem = (engine) => {
    engine("registerEvent", "moveDown");
    engine("registerEvent", "moveUp");
    engine("registerEvent", "moveLeft");
    engine("registerEvent", "moveRight");

    let state = inputStates.DEFAULT;
    let currentPresses = new Set();

    const stateEvents = {};
    stateEvents[inputStates.DEFAULT] = {
        ArrowDown: () => engine("queueEvent", "moveDown"),
        ArrowUp: () => engine("queueEvent", "moveUp"),
        ArrowLeft: () => engine("queueEvent", "moveLeft",),
        ArrowRight: () => engine("queueEvent", "moveRight")
    };

    const process = () => {
        currentPresses.forEach(press => {
            // nop function for unmapped keypresses
            (stateEvents[state][press] || (() => null))();
        });
    };

    document.addEventListener('keydown', (event) => {
        currentPresses.add(event.key);
        process();
    });

    document.addEventListener('keyup', (event) => {
        currentPresses.delete(event.key);
        process();
    });

    return (message, ...messageArgs) => {
        switch (message) {
        case "inputState": {
            return state;
        }
        case "setInputState": {
            let stateKey = messageArgs[0];
            state = inputStates[stateKey];
            break;
        }
        };
    };
};