const Gpio = require('onoff').Gpio;
const i2c = require('i2c-bus');

const MAX9744_I2CADDR = 0x4b;
const MAX_VOLUME = 63;
const MIN_VOLUME = 0;
const VOLUME_STEPS = 1;

let currentVolume = MIN_VOLUME;
let i2c1;

async function readVolume() {
    const rBuf = Buffer.alloc(1);
    const data = await i2c1.i2cRead(MAX9744_I2CADDR, rBuf.length, rBuf);
    return data.buffer.readUInt8();
}

async function writeVolume(volume) {
    const wBuf = Buffer.from([volume]);
    await i2c1.i2cWrite(MAX9744_I2CADDR, wBuf.length, wBuf);
    console.log("Volume set: ", volume);
}

async function increaseVolume() {
    console.log("Increasing volume");
    currentVolume = currentVolume < MAX_VOLUME - VOLUME_STEPS ? currentVolume + VOLUME_STEPS : MAX_VOLUME;
    await writeVolume(currentVolume);
}

async function decreaseVolume() {
    console.log("Decreasing volume");
    currentVolume = currentVolume > MIN_VOLUME + VOLUME_STEPS ? currentVolume - VOLUME_STEPS : MIN_VOLUME;
    await writeVolume(currentVolume);

}

async function handleButtonTick(button) {
    console.log("Handling button tick");
    if(button.active) {
        await button.action();
        button.cycles++;
        let timeout = 1400 - (button.cycles * 200);
        if(timeout < 200) {
            timeout = 200;
        }
        button.watcher = setTimeout(async () => {
            await handleButtonTick(button);
        }, timeout);
    } else if(button.watcher) {
        clearTimeout(button.watcher);
        button.cycles = 0;
    }
}

const buttons = {
    volumeUp: {pin: 17, gpio: null, active: false, watcher: null, action: increaseVolume, cycles: 0},
    volumeDown: {pin: 27, gpio: null, active: false, watcher: null, action: decreaseVolume, cycles: 0}
};
function watchButton(button) {
    button.gpio.watch(async (err, value) => {
        if(err) {
            button.active = false;
            if(button.watcher) {
                clearInterval(button.watcher);
                button.cycles = 0;
            }
            console.error(err);
        } else {
            if (value === 1) {
                button.active = true;
                await handleButtonTick(button);
            } else {
                button.active = false;
                if(button.watcher) {
                    clearInterval(button.watcher);
                }
            }
        }
    });
}

function initButton(button) {
    button.gpio = new Gpio(button.pin, 'in', 'both', { activeLow: true});
    watchButton(button);
}

async function main() {
    try {
        i2c1 = await i2c.openPromisified(1);
        currentVolume = await readVolume();

        initButton(buttons.volumeUp);
        initButton(buttons.volumeDown);
    } catch (err) {
        console.error(err);
    }
}
main();