EAGLESIX-2651: initial port of Avg Accumulator from v2.6.5

lib/pipeline/accumulators/AvgAccumulator.js

@@ -8,57 +8,53 @@
  * @constructor
  **/
 var AvgAccumulator = module.exports = function AvgAccumulator(){
-	this.subTotalName = "subTotal";
-	this.countName = "count";
-	this.totalIsANumber = true;
-	this.total = 0;
-	this.count = 0;
+	this.reset();
 	base.call(this);
 }, klass = AvgAccumulator, Accumulator = require("./Accumulator"), base = Accumulator, proto = klass.prototype = Object.create(base.prototype, {constructor:{value:klass}});
 
-// NOTE: Skipping the create function, using the constructor instead
-
-// DEPENDENCIES
 var Value = require("../Value");
 
-// MEMBER FUNCTIONS
+var SUB_TOTAL_NAME = "subTotal";
+var COUNT_NAME = "count";
+
 proto.processInternal = function processInternal(input, merging) {
 	if (!merging) {
-		if (typeof input !== "number") {
-			return;
-		}
-		this.total += input;
-		this.count += 1;
+		// non numeric types have no impact on average
+		if (typeof input != "number") return;
+
+		this._total += input;
+		this._count += 1;
 	} else {
-		Value.verifyDocument(input);
-		this.total += input[this.subTotalName];
-		this.count += input[this.countName];
+		// We expect an object that contains both a subtotal and a count.
+		// This is what getValue(true) produced below.
+		if (!(input instanceof Object)) throw new Error("Assertion error");
+		this._total += input[SUB_TOTAL_NAME];
+		this._count += input[COUNT_NAME];
 	}
 };
 
-proto.getValue = function getValue(toBeMerged){
+klass.create = function create() {
+	return new AvgAccumulator();
+};
+
+proto.getValue = function getValue(toBeMerged) {
 	if (!toBeMerged) {
-		if (this.totalIsANumber && this.count > 0) {
-			return this.total / this.count;
-		} else if (this.count === 0) {
-			return 0;
-		} else {
-			throw new Error("$sum resulted in a non-numeric type");
-		}
+		if (this._count === 0)
+			return 0.0;
+		return this._total / this._count;
 	} else {
-		var ret = {};
-		ret[this.subTotalName] = this.total;
-		ret[this.countName] = this.count;
-
-		return ret;
+		var doc = {};
+		doc[SUB_TOTAL_NAME] = this._total;
+		doc[COUNT_NAME] = this._count;
+		return doc;
 	}
 };
 
 proto.reset = function reset() {
-	this.total = 0;
-	this.count = 0;
+	this._total = 0;
+	this._count = 0;
 };
 
-proto.getOpName = function getOpName(){
+proto.getOpName = function getOpName() {
 	return "$avg";
 };