"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() {
	if (arguments.length !== 0) throw new Error(klass.name + ": no args expected");
	base.call(this);
}, klass = DayOfYearExpression, base = require("./FixedArityExpressionT")(DayOfYearExpression, 1), proto = klass.prototype = Object.create(base.prototype, {constructor:{value:klass}});

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

proto.evaluateInternal = function evaluateInternal(vars) {
	var pDate = this.operands[0].evaluateInternal(vars),
		date = Value.coerceToDate(pDate),
		//NOTE: DEVIATION FROM MONGO: our calculations are a little different but are equivalent
		y11 = new Date(date.getUTCFullYear(), 0, 1), // same year, first month, first day; time omitted
		ymd = new Date(date.getUTCFullYear(), date.getUTCMonth(), date.getUTCDate() + 1), // same y,m,d; time omitted, add 1 because days start at 1
		yday = Math.ceil((ymd - y11) / 86400000); // count days
	return yday;
};

proto.getOpName = function getOpName() {
	return "$dayOfYear";
};

Expression.registerExpression("$dayOfYear", base.parse);