var AddToSetAccumulator = module.exports = (function(){

	// DEPENDENCIES
	var Value = require("../Value");
	require("es6-shim");

	// CONSTRUCTOR
	/** 
	 * Create an expression that finds the sum of n operands.
	 *
	 * @class AddSoSetAccumulator
	 * @namespace munge.pipeline.accumulators
	 * @module munge
	 * @constructor
	**/
	var klass = module.exports = function AddToSetAccumulator(/* pCtx */){
		if(arguments.length !== 0) throw new Error("zero args expected");
		this.set = new Map();
		//this.itr = undefined; /* Shoudln't need an iterator for the set */
		//this.pCtx = undefined; /* Not using the context object currently as it is related to sharding */
		base.call(this);
	}, Accumulator = require("./Accumulator"), base = Accumulator, proto = klass.prototype = Object.create(base.prototype, {constructor:{value:klass}});

	// PROTOTYPE MEMBERS
	proto.getOpName = function getOpName(){
		return "$addToSet";
	};

	proto.getFactory = function getFactory(){
		return klass;	// using the ctor rather than a separate .create() method
	};

	proto.evaluate = function evaluate(doc) {
		if(arguments.length !== 1) throw new Error("One and only one arg expected");
		var rhs = this.operands[0].evaluate(doc);
		if ('undefined' != typeof rhs) {
			this.set.set(rhs, rhs); //Sorry about variable names here... just following the rules!
		}
		return undefined;
	};

	proto.getValue = function getValue() {
		return this.set.values();
	};

	return klass;
})();