export class Utilities {

  /**
   * Converts an RGB color value to HSL. Conversion formula
   * adapted from http://en.wikipedia.org/wiki/HSL_color_space.
   * Assumes r, g, and b are contained in the set [0, 255] and
   * returns h, s, and l in the set [0, 1].
   *
   * @param   Number  r       The red color value
   * @param   Number  g       The green color value
   * @param   Number  b       The blue color value
   * @return  Array           The HSL representation
   */
  rgb2hsl(r, g, b){
    r /= 255, g /= 255, b /= 255;
    var max = Math.max(r, g, b), min = Math.min(r, g, b);
    var h, s, l = (max + min) / 2;

    if (max == min){
      h = s = 0; // achromatic
    } else {
      var d = max - min;
      s = l > 0.5 ? d / (2 - max - min) : d / (max + min);
      switch(max){
        case r: h = (g - b) / d + (g < b ? 6 : 0); break;
        case g: h = (b - r) / d + 2; break;
        case b: h = (r - g) / d + 4; break;
      }
      h /= 6;
    }

    return [h, s, l];
  }

  /**
   * Converts an HSL color value to RGB. Conversion formula
   * adapted from http://en.wikipedia.org/wiki/HSL_color_space.
   * Assumes h, s, and l are contained in the set [0, 1] and
   * returns r, g, and b in the set [0, 255].
   *
   * @param   Number  h       The hue
   * @param   Number  s       The saturation
   * @param   Number  l       The lightness
   * @return  Array           The RGB representation
   */
  hsl2rgb(h, s, l){
    var r, g, b;

    if (s == 0){
      r = g = b = l; // achromatic
    } else {
      function hue2rgb(p, q, t) {
        if(t < 0) t += 1;
        if(t > 1) t -= 1;
        if(t < 1/6) return p + (q - p) * 6 * t;
        if(t < 1/2) return q;
        if(t < 2/3) return p + (q - p) * (2/3 - t) * 6;
        return p;
      }

      var q = l < 0.5 ? l * (1 + s) : l + s - l * s;
      var p = 2 * l - q;
      r = hue2rgb(p, q, h + 1/3);
      g = hue2rgb(p, q, h);
      b = hue2rgb(p, q, h - 1/3);
    }

    return [r * 255, g * 255, b * 255];
  }

  /*
   * Converts an RGB color value to HSV. Conversion formula
   * adapted from http://en.wikipedia.org/wiki/HSV_color_space.
   * Assumes r, g, and b are contained in the set [0, 255] and
   * returns h, s, and v in the set [0, 1].
   *
   * @param   Number  r       The red color value
   * @param   Number  g       The green color value
   * @param   Number  b       The blue color value
   * @return  Array           The HSV representation
   */

  rgb2hsv(r, g, b){
    r = r/255, g = g/255, b = b/255;
    var max = Math.max(r, g, b), min = Math.min(r, g, b);
    var h, s, v = max;

    var d = max - min;
    s = max == 0 ? 0 : d / max;

    if(max == min){
      h = 0; // achromatic
    }else{
      switch(max){
        case r: h = (g - b) / d + (g < b ? 6 : 0); break;
        case g: h = (b - r) / d + 2; break;
        case b: h = (r - g) / d + 4; break;
      }
      h /= 6;
    }

    return [h, s, v];
  }

  /**
   * Converts an HSV color value to RGB. Conversion formula
   * adapted from http://en.wikipedia.org/wiki/HSV_color_space.
   * Assumes h, s, and v are contained in the set [0, 1] and
   * returns r, g, and b in the set [0, 255].
   *
   * @param   Number  h       The hue
   * @param   Number  s       The saturation
   * @param   Number  v       The value
   * @return  Array           The RGB representation
   */
  hsv2rgb(h, s, v){
    var r, g, b;

    var i = Math.floor(h * 6);
    var f = h * 6 - i;
    var p = v * (1 - s);
    var q = v * (1 - f * s);
    var t = v * (1 - (1 - f) * s);

    switch(i % 6){
      case 0: r = v, g = t, b = p; break;
      case 1: r = q, g = v, b = p; break;
      case 2: r = p, g = v, b = t; break;
      case 3: r = p, g = q, b = v; break;
      case 4: r = t, g = p, b = v; break;
      case 5: r = v, g = p, b = q; break;
    }

    return [r * 255, g * 255, b * 255];
  }

  rgb2hex(r, g, b) {
    return "#" + Math.round((1 << 24) + (r << 16) + (g << 8) + b).toString(16).slice(1);
  }

  hex2rgb(hex) {
    // Expand shorthand form (e.g. "03F") to full form (e.g. "0033FF")
    var shorthandRegex = /^#?([a-f\d])([a-f\d])([a-f\d])$/i;
    hex = hex.replace(shorthandRegex, function(m, r, g, b) {
      return r + r + g + g + b + b;
    });

    var result = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(hex);
    return result ? [
      parseInt(result[1], 16),
      parseInt(result[2], 16),
      parseInt(result[3], 16)
    ] : null;
  }

}