var colors = {};

colors.hslToRgb = function(hsl) {
    var h = hsl[0];
    var s = hsl[1];
    var l = hsl[2];
    var m1,
        m2;

    /* Some simple corrections for h, s and l. */
    h = isNaN(h) ? 0 : (h %= 360) < 0 ? h + 360 : h;
    s = isNaN(s) ? 0 : s < 0 ? 0 : s > 1 ? 1 : s;
    l = l < 0 ? 0 : l > 1 ? 1 : l;

    /* From FvD 13.37, CSS Color Module Level 3 */
    m2 = l <= .5 ? l * (1 + s) : l + s - l * s;
    m1 = 2 * l - m2;

    function v(h) {
        if (h > 360) h -= 360;
        else if (h < 0) h += 360;
        if (h < 60) return m1 + (m2 - m1) * h / 60;
        if (h < 180) return m2;
        if (h < 240) return m1 + (m2 - m1) * (240 - h) / 60;
        return m1;
    }

    function vv(h) {
        return Math.round(v(h) * 255);
    }

    return [vv(h + 120), vv(h), vv(h - 120)];
};

colors.rgbToHsl = function(rgb) {
    var r = rgb[0],
        g = rgb[1],
        b = rgb[2];

    var min = Math.min(r /= 255, g /= 255, b /= 255),
        max = Math.max(r, g, b),
        d = max - min,
        h,
        s,
        l = (max + min) / 2;
    if (d) {
        s = l < .5 ? d / (max + min) : d / (2 - max - min);
        if (r == max) h = (g - b) / d + (g < b ? 6 : 0);
        else if (g == max) h = (b - r) / d + 2;
        else h = (r - g) / d + 4;
        h *= 60;
    } else {
        h = NaN;
        s = l > 0 && l < 1 ? 0 : h;
    }
    return [h, s, l]
};

colors.hexToRgb = function(format) {
    var r, g, b, color;

    if (format != null && format.charAt(0) === "#" && !isNaN(color = parseInt(format.slice(1), 16))) {
        if (format.length === 4) {
            r = (color & 0xf00) >> 4; r = (r >> 4) | r;
            g = (color & 0xf0); g = (g >> 4) | g;
            b = (color & 0xf); b = (b << 4) | b;
        } else if (format.length === 7) {
            r = (color & 0xff0000) >> 16;
            g = (color & 0xff00) >> 8;
            b = (color & 0xff);
        }
    }

    return [r, g, b];
};

colors.darkerRgb = function(rgb, k) {
    k = Math.pow(0.7, k);
    return [Math.round(k * rgb[0]), Math.round(k * rgb[1]), Math.round(k * rgb[2])];
};

colors.rgbToHex = function(rgb) {
    return "#" + _rgb_hex(rgb[0]) + _rgb_hex(rgb[1]) + _rgb_hex(rgb[2]);
};

function _rgb_hex(v) {
    return v < 0x10
        ? "0" + Math.max(0, v).toString(16)
        : Math.min(255, v).toString(16);
}

module.exports = colors;