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

"use strict";

/**
 * Get the DayOfYear from a date.
 * @class DayOfYearExpression
 * @namespace mungedb-aggregate.pipeline.expressions
 * @module mungedb-aggregate
 * @constructor
 **/
var DayOfYearExpression = module.exports = function DayOfYearExpression(){
	base.call(this);
}, klass = DayOfYearExpression, base = require("./FixedArityExpressionT")(klass, 1), proto = klass.prototype = Object.create(base.prototype, {constructor:{value:klass}});

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

// STATIC MEMBERS
klass.extract = function extract(date) {
	return klass.getDateDayOfYear(date);
};

klass.opName = "$dayOfYear";

klass.getDateDayOfYear = function getDateDayOfYear(d){
    var y11 = new Date(d.getUTCFullYear(), 0, 1),       // same year, first month, first day; time omitted
	ymd = new Date(d.getUTCFullYear(), d.getUTCMonth(), d.getUTCDate()+1);  // same y,m,d; time omitted, add 1 because days start at 1
    return Math.ceil((ymd - y11) / 86400000);   //NOTE: 86400000 ms is 1 day
};

// PROTOTYPE MEMBERS
proto.getOpName = function getOpName(){
    return klass.opName;
};

/**
 * Takes a date and returns the day of the year as a number between 1 and 366.
 * @method evaluate
 **/
proto.evaluateInternal = function evaluateInternal(vars){
	//NOTE: the below silliness is to deal with the leap year scenario when we should be returning 366
    var date = this.operands[0].evaluateInternal(vars);
    return klass.extract(date);
};

/** Register Expression */
Expression.registerExpression(klass.opName, base.parse);