mungedb-aggregate/lib/pipeline/expressions/ModExpression.js

"use strict";

/** 
 * An $mod pipeline expression.
 * @see evaluate
 * @class ModExpression
 * @namespace mungedb-aggregate.pipeline.expressions
 * @module mungedb-aggregate
 * @constructor
 **/
var ModExpression = module.exports = function ModExpression() {
		this.fixedArity(2);
		if (arguments.length !== 0) throw new Error("zero args expected");
		base.call(this);
}, klass = ModExpression,
		base = require("./NaryExpression"),
		proto = klass.prototype = Object.create(base.prototype, {
				constructor: {
						value: klass
				}
		});

// DEPENDENCIES
var Value = require("../Value"),
		Expression = require("./Expression");

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

/** 
 * Takes an array that contains a pair of numbers and returns the remainder of the first number divided by the second number.
 * @method evaluate
 **/
proto.evaluateInternal = function evaluateInternal(doc) {
		this.checkArgCount(2);
		var left = this.operands[0].evaluateInternal(doc),
				right = this.operands[1].evaluateInternal(doc);
		if (left instanceof Date || right instanceof Date) throw new Error("$mod does not support dates; code 16374");

		// pass along jstNULLs and Undefineds
		if (left === undefined || left === null) return left;
		if (right === undefined || right === null) return right;

		// ensure we aren't modding by 0
		right = Value.coerceToDouble(right);
		if (right === 0) return undefined;

		left = Value.coerceToDouble(left);
		return left % right;
};

/** Register Expression */
Expression.registerExpression("$mod", ModExpression.parse);