//https://github.com/bgrins/colorwheel-1k/tree/gh-pages
(function() {

  // Declare constants and variables to help with minification
  // Some of these are inlined (with comments to the side with the actual equation)
  var doc = document;
  doc.c = doc.createElement;
  b.a = b.appendChild;

  var width = c.width = c.height = 400,
    label = b.a(doc.c("p")),
    input = b.a(doc.c("input")),
    imageData = a.createImageData(width, width),
    pixels = imageData.data,
    oneHundred = input.value = input.max = 100,
    circleOffset = 10,
    diameter = 380,                  //width-circleOffset*2,
    radius = 190,                    //diameter / 2,
    radiusPlusOffset = 200,          //radius + circleOffset
    radiusSquared = radius * radius,
    two55 = 255,
    currentY = oneHundred,
    currentX = -currentY,
    wheelPixel = 16040;              // circleOffset*4*width+circleOffset*4;

  // Math helpers
  var math = Math,
    PI = math.PI,
    PI2 = PI * 2,
    sqrt = math.sqrt,
    atan2 = math.atan2;

  // Setup DOM properties
  b.style.textAlign="center";
  label.style.font = "2em courier";
  input.type = "range";

  // Load color wheel data into memory.
  for (y = input.min = 0; y < width; y++) {
    for (x = 0; x < width; x++) {
      var rx = x - radius,
        ry = y - radius,
        d = rx * rx + ry * ry,
        rgb = hsvToRgb(
          (atan2(ry, rx) + PI) / PI2,     // Hue
          sqrt(d) / radius,               // Saturation
          1                               // Value
        );

      // Print current color, but hide if outside the area of the circle
      pixels[wheelPixel++] = rgb[0];
      pixels[wheelPixel++] = rgb[1];
      pixels[wheelPixel++] = rgb[2];
      pixels[wheelPixel++] = d > radiusSquared ? 0 : two55;
    }
  }

  // Bind Event Handlers
  input.onchange = redraw;
  c.onmousedown = doc.onmouseup = function(e) {
    // Unbind mousemove if this is a mouseup event, or bind mousemove if this a mousedown event
    doc.onmousemove = /p/.test(e.type) ? 0 : (redraw(e), redraw);
  }

  // Handle manual calls + mousemove event handler + input change event handler all in one place.
  function redraw(e) {

    // Only process an actual change if it is triggered by the mousemove or mousedown event.
    // Otherwise e.pageX will be undefined, which will cause the result to be NaN, so it will fallback to the current value
    currentX = e.pageX - c.offsetLeft - radiusPlusOffset || currentX;
    currentY = e.pageY - c.offsetTop - radiusPlusOffset  || currentY;

    // Scope these locally so the compiler will minify the names.  Will manually remove the 'var' keyword in the minified version.
    var theta = atan2(currentY, currentX),
      d = currentX * currentX + currentY * currentY;

    // If the x/y is not in the circle, find angle between center and mouse point:
    //   Draw a line at that angle from center with the distance of radius
    //   Use that point on the circumference as the draggable location
    if (d > radiusSquared) {
      currentX = radius * math.cos(theta);
      currentY = radius * math.sin(theta);
      theta = atan2(currentY, currentX);
      d = currentX * currentX + currentY * currentY;
    }

    label.textContent = b.style.background = hsvToRgb(
      (theta + PI) / PI2,         // Current hue (how many degrees along the circle)
      sqrt(d) / radius,           // Current saturation (how close to the middle)
      input.value / oneHundred    // Current value (input type="range" slider value)
    )[3];

    // Reset to color wheel and draw a spot on the current location.
    a.putImageData(imageData, 0, 0);

    // Draw the current spot.
    // I have tried a rectangle, circle, and heart shape.
    /*
     // Rectangle:
     a.fillStyle = '#000';
     a.fillRect(currentX+radiusPlusOffset,currentY+radiusPlusOffset, 6, 6);
     */
    /*
     // Circle:
     a.beginPath();
     a.strokeStyle = '#000';
     a.arc(~~currentX+radiusPlusOffset,~~currentY+radiusPlusOffset, 4, 0, PI2);
     a.stroke();
     */

    // Heart:
    a.font = "1em arial";
    a.fillText("♥", currentX+radiusPlusOffset-4,currentY+radiusPlusOffset+4);

  }

  // Created a shorter version of the HSV to RGB conversion function in TinyColor
  // https://github.com/bgrins/TinyColor/blob/master/tinycolor.js
  function hsvToRgb(h, s, v) {
    h*=6;
    var i = ~~h,
      f = h - i,
      p = v * (1 - s),
      q = v * (1 - f * s),
      t = v * (1 - (1 - f) * s),
      mod = i % 6,
      r = [v, q, p, p, t, v][mod] * two55,
      g = [t, v, v, q, p, p][mod] * two55,
      b = [p, p, t, v, v, q][mod] * two55;

    return [r, g, b, "rgb("+ ~~r + "," + ~~g + "," + ~~b + ")"];
  }

  // Kick everything off
  redraw(0);

  /*
   // Just an idea I had to kick everything off with some changing colors…
   // Probably no way to squeeze this into 1k, but it could probably be a lot smaller than this:
   currentX = currentY = 1;
   var interval = setInterval(function() {
   currentX--;
   currentY*=1.05;
   redraw(0)
   }, 7);

   setTimeout(function() {
   clearInterval(interval)
   }, 700)
   */

})();