Source: src/main/javascript/oracle/oj/ojdvt-base/AttributeGroupHandler.js

/**
 * Creates an attribute group handler that will generate stylistic attribute values such as colors or shapes based on data set categories.
 * @param {Object} [matchRules] A map of key value pairs for categories and the matching attribute value e.g. {"soda" : "square", "water" : "circle", "iced tea" : "triangleUp"}.
 *                            Attribute values listed in the matchRules object will be reserved only for the matching categories when getAttributeValue is called.
 * @export
 * @constructor
 */
oj.AttributeGroupHandler = function(matchRules) {
  this.Init(matchRules);
};

oj.Object.createSubclass(oj.AttributeGroupHandler, oj.Object, "oj.AttributeGroupHandler");

oj.AttributeGroupHandler.prototype.Init = function(matchRules) {
  oj.AttributeGroupHandler.superclass.Init.call(this);
  this._matchRules = matchRules ? matchRules : {};
  this._assignments = {};
  this._valueIndex = 0;
  this.Values = this.getValueRamp();
  for (var key in this._matchRules) {
    // remove match rule value from attribute group values
    var idx = this.Values.indexOf(this._matchRules[key]);
    if (idx !== -1)
      this.Values.splice(idx, 1);
  }
}

/**
 * Returns the array of possible attribute values for this attribute group handler.
 * This array can be modified so subclasses should return a copy of its internal value ramp.
 * @returns {Array} The array of attribute values
 * @export
 */
oj.AttributeGroupHandler.prototype.getValueRamp = function() {
  return [];
}

/**
 * Assigns the given category an attribute value.  Will consistently return the same attribute value for equal categories.
 * @param {Object} category The category to assign
 * @returns {Object} The attribute value for the category
 * @export
 */
oj.AttributeGroupHandler.prototype.getValue = function(category) {
  if (this._matchRules[category])
    return this._matchRules[category];
  else if (this._assignments[category])
    return this._assignments[category];
  else {
    this._assignments[category] = this.Values[this._valueIndex];
    if (this._valueIndex == this.Values.length - 1)
      this._valueIndex = 0;
    else
      this._valueIndex++;
    return this._assignments[category];
  } 
}

/**
 * Returns the current map of key value pairs for categories and the assigned attribute values
 * @return {Array} The current list of category and value pairing
 * @export
 */
oj.AttributeGroupHandler.prototype.getCategoryAssignments  = function() {
  var assignments = [];
  for (var i in this._assignments)
    assignments.push({"category": i, "value": this._assignments[i]});
  return assignments;
}

/**
 * Reserves an attribute value for the given category
 * @param {String} category Used for checking inputs to getAttributeValue against when assigning an attribute value
 * @param {String} attributeValue The attribute value to assign for inputs matching the given category e.g. "square" or "circle"
 * @export
 */
oj.AttributeGroupHandler.prototype.addMatchRule = function(category, attributeValue) {
  this._matchRules[category] = attributeValue;
}