Display driver

// display.js
function Display(x, y) {
    this.ws281x = require('rpi-ws281x-native');
    this.x = x;
    this.y = y;
    this.ledsAmount = x * y;
    this.dmaNum = 10;
    this.pixelData = new Uint32Array(this.ledsAmount);
    this.ledDirection = 'top-bottom-right-up';
    this.animationHandler = null;
}

Display.prototype.init = function () {
    this.ws281x.init(this.ledsAmount, {dmaNum: this.dmaNum});

    var self = this;
    if (this.animationHandler) {
        clearInterval(this.animationHandler);
    }
    this.animationHandler = setInterval(function(){
        self.ws281x.render(self.pixelData);
    }, 5);
}

Display.prototype.setDMA = function (number) {
    this.dmaNum = number;
}

Display.prototype.setLedDirection = function (direction) {
    this.ledDirection = direction;
}

Display.prototype.setPixel = function(x, y, color) {
    if (x > this.x - 1) {
        throw 'X dimension exceeded ' + this.x + ': ' + x;
    }
    if (y > this.y - 1) {
        throw 'Y dimension exceeded ' + this.y + ': ' + y;
    }

    var targetColor = [0, 0, 0];
    if (Array.isArray(color)) {
        targetColor = color;
    }
    else if (typeof color == 'string') {
        targetColor = _parseColorString(color);
    }

    function _parseColorString(color) {
        if (color.substr(0, 1) == '#') {
            color = color.substr(1);
        }
        var color = color.match(/.{1,2}/g);
        color = color.map(function(e){
            return parseInt(e, 16);
        });
        return color;
    }

    var finalCoord = this.calculatePosition(x, y);
    this.pixelData[finalCoord] = this.rgb2int(targetColor[0], targetColor[1], targetColor[2]);
}

Display.prototype.calculatePosition = function(x, y) {
    var position = 0;
    switch(this.ledDirection) {
        default:
        case 'top-bottom-right-up':
            position = this.y * x + (x % 2 ? (this.y - y - 1) : y );
            break;
    }
    return position;
}

Display.prototype.rainbow = function() {
    var offset = 0;
    var self = this;

    if (this.animationHandler) {
        clearInterval(this.animationHandler);
    }

    this.animationHandler = setInterval(function () {
        for (var i = 0; i < self.ledsAmount; i++) {
            self.pixelData[i] = colorwheel((offset + i) % 256);
        }
        offset = (offset + 1) % 256;
    }, 5);

    function colorwheel(pos) {
        pos = 255 - pos;
        if (pos < 85) { return self.rgb2int(255 - pos * 3, 0, pos * 3); }
        else if (pos < 170) { pos -= 85; return self.rgb2int(0, pos * 3, 255 - pos * 3); }
        else { pos -= 170; return self.rgb2int(pos * 3, 255 - pos * 3, 0); }
    }
}
Display.prototype.rgb2int = function(r, g, b) {
    return ((r & 0xff) << 16) | ((g & 0xff) << 8) | (b & 0xff);
}

Display.prototype.reset = function () {
    this.ws281x.reset();
}

Display.prototype.ws281x = function () {
    return this.ws281x;
}

module.exports = Display;
// end display.js

// index.js:
var DisplayModule = require('./display.js');
var display = new DisplayModule(32, 8);
display.init();

process.on('SIGINT', function () {
    display.reset();
    process.nextTick(function () {
        process.exit(0);
    });
});

display.setPixel(5, 0, '#0F0F0F');
console.log('Press <ctrl>+C to exit.');