Procedural color creation for nodes

* color hue is based on the first 2 letters of node rank
* color lightness is based on the first 2 letters of node label

client/app/scripts/charts/node.js

@@ -23,7 +23,7 @@ const Node = React.createClass({
     let labelOffsetY = 18;
     let subLabelOffsetY = 35;
     const isPseudo = !!this.props.pseudo;
-    const color = isPseudo ? '' : this.getNodeColor(this.props.rank);
+    const color = isPseudo ? '' : this.getNodeColor(this.props.rank, this.props.label);
     const onMouseEnter = this.handleMouseEnter;
     const onMouseLeave = this.handleMouseLeave;
     const onMouseClick = this.handleMouseClick;

client/app/scripts/components/node-details.js

@@ -61,7 +61,7 @@ const NodeDetails = React.createClass({
       return this.renderLoading();
     }
 
-    const nodeColor = this.getNodeColorDark(details.rank);
+    const nodeColor = this.getNodeColorDark(details.rank, details.label_major);
     const styles = {
       controls: {
         'backgroundColor': this.brightenColor(nodeColor)

client/app/scripts/mixins/node-color-mixin.js

@@ -1,25 +1,48 @@
 const d3 = require('d3');
 
-const colors = d3.scale.category20();
 const PSEUDO_COLOR = '#b1b1cb';
-let colorIndex = 0;
+const hueScale = d3.scale.linear().range([0, 359]);
+const lightnessScale = d3.scale.linear().domain([0, 359]).range([0.3, 0.7]);
+const startLetterRange = 'A'.charCodeAt();
+const endLetterRange = 'Z'.charCodeAt();
+const letterRange = endLetterRange - startLetterRange;
+
+/**
+ * Converts a text to a 360 degree value
+ */
+function text2degree(text) {
+  const input = text.substr(0, 2).toUpperCase();
+  let num = 0;
+  let charCode;
+  for (let i = 0; i < input.length; i++) {
+    charCode = Math.max(Math.min(input[i].charCodeAt(), endLetterRange), startLetterRange);
+    num += Math.pow(letterRange, input.length - i - 1) * (charCode - startLetterRange);
+  }
+  hueScale.domain([0, Math.pow(letterRange, input.length)]);
+  return hueScale(num);
+}
+
+function colors(text, secondText) {
+  const hue = text2degree(text);
+  const saturation = 0.8;
+  let lightness = 0.5;
+  if (secondText) {
+    // reuse text2degree and feed degree to lightness scale
+    lightness = lightnessScale(text2degree(secondText));
+  }
+  const color = d3.hsl(hue, saturation, lightness);
+  return color;
+}
 
 const NodeColorMixin = {
-  getNodeColor: function(text) {
-    colorIndex++;
-    // skip green and red (index 5-8 in d3.scale.category20)
-    if (colorIndex > 4 && colorIndex < 9) {
-      colors('_' + colorIndex);
-      return this.getNodeColor(text);
-    }
-
-    return colors(text);
+  getNodeColor: function(text, secondText) {
+    return colors(text, secondText);
   },
-  getNodeColorDark: function(text) {
+  getNodeColorDark: function(text, secondText) {
     if (text === undefined) {
       return PSEUDO_COLOR;
     }
-    const color = d3.rgb(colors(text));
+    const color = d3.rgb(colors(text, secondText));
     let hsl = color.hsl();
 
     // ensure darkness