/**
 * XDate v0.8
 * Docs & Licensing: http://arshaw.com/xdate/
 */

/*
 * Internal Architecture
 * ---------------------
 * An XDate wraps a native Date. The native Date is stored in the '0' property of the object.
 * UTC-mode is determined by whether the internal native Date's toString method is set to
 * Date.prototype.toUTCString (see getUTCMode).
 *
 */

var XDate = (function(Date, Math, Array, undefined) {


/** @const */ var FULLYEAR     = 0;
/** @const */ var MONTH        = 1;
/** @const */ var DATE         = 2;
/** @const */ var HOURS        = 3;
/** @const */ var MINUTES      = 4;
/** @const */ var SECONDS      = 5;
/** @const */ var MILLISECONDS = 6;
/** @const */ var DAY          = 7;
/** @const */ var YEAR         = 8;
/** @const */ var WEEK         = 9;
/** @const */ var DAY_MS = 86400000;
var ISO_FORMAT_STRING = "yyyy-MM-dd'T'HH:mm:ss(.fff)";
var ISO_FORMAT_STRING_TZ = ISO_FORMAT_STRING + "zzz";


var methodSubjects = [
	'FullYear',     // 0
	'Month',        // 1
	'Date',         // 2
	'Hours',        // 3
	'Minutes',      // 4
	'Seconds',      // 5
	'Milliseconds', // 6
	'Day',          // 7
	'Year'          // 8
];
var subjectPlurals = [
	'Years',        // 0
	'Months',       // 1
	'Days'          // 2
];
var unitsWithin = [
	12,   // months in year
	31,   // days in month (sort of)
	24,   // hours in day
	60,   // minutes in hour
	60,   // seconds in minute
	1000, // milliseconds in second
	1     //
];
var formatStringRE = new RegExp(
	"(([a-zA-Z])\\2*)|" + // 1, 2
	"(\\(" + "(('.*?'|\\(.*?\\)|.)*?)" + "\\))|" + // 3, 4, 5 (allows for 1 level of inner quotes or parens)
	"('(.*?)')" // 6, 7
);
var UTC = Date.UTC;
var toUTCString = Date.prototype.toUTCString;
var proto = XDate.prototype;



// This makes an XDate look pretty in Firebug and Web Inspector.
// It makes an XDate seem array-like, and displays [ <internal-date>.toString() ]
proto.length = 1;
proto.splice = Array.prototype.splice;




/* Constructor
---------------------------------------------------------------------------------*/

// TODO: in future, I'd change signature for the constructor regarding the `true` utc-mode param. ~ashaw
//   I'd move the boolean to be the *first* argument. Still optional. Seems cleaner.
//   I'd remove it from the `xdate`, `nativeDate`, and `milliseconds` constructors.
//      (because you can simply call .setUTCMode(true) after)
//   And I'd only leave it for the y/m/d/h/m/s/m and `dateString` constructors
//      (because those are the only constructors that need it for DST-gap data-loss reasons)
//   Should do this for 1.0

function XDate() {
	return init(
		(this instanceof XDate) ? this : new XDate(),
		arguments
	);
}


function init(xdate, args) {
	var len = args.length;
	var utcMode;
	if (isBoolean(args[len-1])) {
		utcMode = args[--len];
		args = slice(args, 0, len);
	}
	if (!len) {
		xdate[0] = new Date();
	}
	else if (len == 1) {
		var arg = args[0];
		if (arg instanceof Date || isNumber(arg)) {
			xdate[0] = new Date(+arg);
		}
		else if (arg instanceof XDate) {
			xdate[0] = _clone(arg);
		}
		else if (isString(arg)) {
			xdate[0] = new Date(0);
			xdate = parse(arg, utcMode || false, xdate);
		}
	}
	else {
		xdate[0] = new Date(UTC.apply(Date, args));
		if (!utcMode) {
			xdate[0] = coerceToLocal(xdate[0]);
		}
	}
	if (isBoolean(utcMode)) {
		setUTCMode(xdate, utcMode);
	}
	return xdate;
}



/* UTC Mode Methods
---------------------------------------------------------------------------------*/


proto.getUTCMode = methodize(getUTCMode);
function getUTCMode(xdate) {
	return xdate[0].toString === toUTCString;
};


proto.setUTCMode = methodize(setUTCMode);
function setUTCMode(xdate, utcMode, doCoercion) {
	if (utcMode) {
		if (!getUTCMode(xdate)) {
			if (doCoercion) {
				xdate[0] = coerceToUTC(xdate[0]);
			}
			xdate[0].toString = toUTCString;
		}
	}else{
		if (getUTCMode(xdate)) {
			if (doCoercion) {
				xdate[0] = coerceToLocal(xdate[0]);
			}else{
				xdate[0] = new Date(+xdate[0]);
			}
			// toString will have been cleared
		}
	}
	return xdate; // for chaining
}


proto.getTimezoneOffset = function() {
	if (getUTCMode(this)) {
		return 0;
	}else{
		return this[0].getTimezoneOffset();
	}
};



/* get / set / add / diff Methods (except for week-related)
---------------------------------------------------------------------------------*/


each(methodSubjects, function(subject, fieldIndex) {

	proto['get' + subject] = function() {
		return _getField(this[0], getUTCMode(this), fieldIndex);
	};
	
	if (fieldIndex != YEAR) { // because there is no getUTCYear
	
		proto['getUTC' + subject] = function() {
			return _getField(this[0], true, fieldIndex);
		};
		
	}

	if (fieldIndex != DAY) { // because there is no setDay or setUTCDay
	                         // and the add* and diff* methods use DATE instead
		
		proto['set' + subject] = function(value) {
			_set(this, fieldIndex, value, arguments, getUTCMode(this));
			return this; // for chaining
		};
		
		if (fieldIndex != YEAR) { // because there is no setUTCYear
		                          // and the add* and diff* methods use FULLYEAR instead
			
			proto['setUTC' + subject] = function(value) {
				_set(this, fieldIndex, value, arguments, true);
				return this; // for chaining
			};
			
			proto['add' + (subjectPlurals[fieldIndex] || subject)] = function(delta, preventOverflow) {
				_add(this, fieldIndex, delta, preventOverflow);
				return this; // for chaining
			};
			
			proto['diff' + (subjectPlurals[fieldIndex] || subject)] = function(otherDate) {
				return _diff(this, otherDate, fieldIndex);
			};
			
		}
		
	}

});


function _set(xdate, fieldIndex, value, args, useUTC) {
	var getField = curry(_getField, xdate[0], useUTC);
	var setField = curry(_setField, xdate[0], useUTC);
	var expectedMonth;
	var preventOverflow = false;
	if (args.length == 2 && isBoolean(args[1])) {
		preventOverflow = args[1];
		args = [ value ];
	}
	if (fieldIndex == MONTH) {
		expectedMonth = (value % 12 + 12) % 12;
	}else{
		expectedMonth = getField(MONTH);
	}
	setField(fieldIndex, args);
	if (preventOverflow && getField(MONTH) != expectedMonth) {
		setField(MONTH, [ getField(MONTH) - 1 ]);
		setField(DATE, [ getDaysInMonth(getField(FULLYEAR), getField(MONTH)) ]);
	}
}


function _add(xdate, fieldIndex, delta, preventOverflow) {
	delta = Number(delta);
	var intDelta = Math.floor(delta);
	xdate['set' + methodSubjects[fieldIndex]](
		xdate['get' + methodSubjects[fieldIndex]]() + intDelta,
		preventOverflow || false
	);
	if (intDelta != delta && fieldIndex < MILLISECONDS) {
		_add(xdate, fieldIndex+1, (delta-intDelta)*unitsWithin[fieldIndex], preventOverflow);
	}
}


function _diff(xdate1, xdate2, fieldIndex) { // fieldIndex=FULLYEAR is for years, fieldIndex=DATE is for days
	xdate1 = xdate1.clone().setUTCMode(true, true);
	xdate2 = XDate(xdate2).setUTCMode(true, true);
	var v = 0;
	if (fieldIndex == FULLYEAR || fieldIndex == MONTH) {
		for (var i=MILLISECONDS, methodName; i>=fieldIndex; i--) {
			v /= unitsWithin[i];
			v += _getField(xdate2, false, i) - _getField(xdate1, false, i);
		}
		if (fieldIndex == MONTH) {
			v += (xdate2.getFullYear() - xdate1.getFullYear()) * 12;
		}
	}
	else if (fieldIndex == DATE) {
		var clear1 = xdate1.toDate().setUTCHours(0, 0, 0, 0); // returns an ms value
		var clear2 = xdate2.toDate().setUTCHours(0, 0, 0, 0); // returns an ms value
		v = Math.round((clear2 - clear1) / DAY_MS) + ((xdate2 - clear2) - (xdate1 - clear1)) / DAY_MS;
	}
	else {
		v = (xdate2 - xdate1) / [
			3600000, // milliseconds in hour
			60000,   // milliseconds in minute
			1000,    // milliseconds in second
			1        //
			][fieldIndex - 3];
	}
	return v;
}



/* Week Methods
---------------------------------------------------------------------------------*/


proto.getWeek = function() {
	return _getWeek(curry(_getField, this, false));
};


proto.getUTCWeek = function() {
	return _getWeek(curry(_getField, this, true));
};


proto.setWeek = function(n, year) {
	_setWeek(this, n, year, false);
	return this; // for chaining
};


proto.setUTCWeek = function(n, year) {
	_setWeek(this, n, year, true);
	return this; // for chaining
};


proto.addWeeks = function(delta) {
	return this.addDays(Number(delta) * 7);
};


proto.diffWeeks = function(otherDate) {
	return _diff(this, otherDate, DATE) / 7;
};


function _getWeek(getField) {
	return getWeek(getField(FULLYEAR), getField(MONTH), getField(DATE));
}


function getWeek(year, month, date) {
	var d = new Date(UTC(year, month, date));
	var week1 = getWeek1(
		getWeekYear(year, month, date)
	);
	return Math.floor(Math.round((d - week1) / DAY_MS) / 7) + 1;
}


function getWeekYear(year, month, date) { // get the year that the date's week # belongs to
	var d = new Date(UTC(year, month, date));
	if (d < getWeek1(year)) {
		return year - 1;
	}
	else if (d >= getWeek1(year + 1)) {
		return year + 1;
	}
	return year;
}


function getWeek1(year) { // returns Date of first week of year, in UTC
	var d = new Date(UTC(year, 0, 4));
	d.setUTCDate(d.getUTCDate() - (d.getUTCDay() + 6) % 7); // make it Monday of the week
	return d;
}


function _setWeek(xdate, n, year, useUTC) {
	var getField = curry(_getField, xdate, useUTC);
	var setField = curry(_setField, xdate, useUTC);

	if (year === undefined) {
		year = getWeekYear(
			getField(FULLYEAR),
			getField(MONTH),
			getField(DATE)
		);
	}

	var week1 = getWeek1(year);
	if (!useUTC) {
		week1 = coerceToLocal(week1);
	}

	xdate.setTime(+week1);
	setField(DATE, [ getField(DATE) + (n-1) * 7 ]); // would have used xdate.addUTCWeeks :(
		// n-1 because n is 1-based
}



/* Parsing
---------------------------------------------------------------------------------*/


XDate.parsers = [
	parseISO
];


XDate.parse = function(str) {
	return +XDate(''+str);
};


function parse(str, utcMode, xdate) {
	var parsers = XDate.parsers;
	var i = 0;
	var res;
	for (; i<parsers.length; i++) {
		res = parsers[i](str, utcMode, xdate);
		if (res) {
			return res;
		}
	}
	xdate[0] = new Date(str);
	return xdate;
}


function parseISO(str, utcMode, xdate) {
	var m = str.match(/^(\d{4})(-(\d{2})(-(\d{2})([T ](\d{2}):(\d{2})(:(\d{2})(\.(\d+))?)?(Z|(([-+])(\d{2})(:?(\d{2}))?))?)?)?)?$/);
	if (m) {
		var d = new Date(UTC(
			m[1],
			m[3] ? m[3] - 1 : 0,
			m[5] || 1,
			m[7] || 0,
			m[8] || 0,
			m[10] || 0,
			m[12] ? Number('0.' + m[12]) * 1000 : 0
		));
		if (m[13]) { // has gmt offset or Z
			if (m[14]) { // has gmt offset
				d.setUTCMinutes(
					d.getUTCMinutes() +
					(m[15] == '-' ? 1 : -1) * (Number(m[16]) * 60 + (m[18] ? Number(m[18]) : 0))
				);
			}
		}else{ // no specified timezone
			if (!utcMode) {
				d = coerceToLocal(d);
			}
		}
		return xdate.setTime(+d);
	}
}



/* Formatting
---------------------------------------------------------------------------------*/


proto.toString = function(formatString, settings, uniqueness) {
	if (formatString === undefined || !valid(this)) {
		return this[0].toString(); // already accounts for utc-mode (might be toUTCString)
	}else{
		return format(this, formatString, settings, uniqueness, getUTCMode(this));
	}
};


proto.toUTCString = proto.toGMTString = function(formatString, settings, uniqueness) {
	if (formatString === undefined || !valid(this)) {
		return this[0].toUTCString();
	}else{
		return format(this, formatString, settings, uniqueness, true);
	}
};


proto.toISOString = function() {
	return this.toUTCString(ISO_FORMAT_STRING_TZ);
};


XDate.defaultLocale = '';
XDate.locales = {
	'': {
		monthNames: ['January','February','March','April','May','June','July','August','September','October','November','December'],
		monthNamesShort: ['Jan','Feb','Mar','Apr','May','Jun','Jul','Aug','Sep','Oct','Nov','Dec'],
		dayNames: ['Sunday','Monday','Tuesday','Wednesday','Thursday','Friday','Saturday'],
		dayNamesShort: ['Sun','Mon','Tue','Wed','Thu','Fri','Sat'],
		amDesignator: 'AM',
		pmDesignator: 'PM'
	}
};
XDate.formatters = {
	i: ISO_FORMAT_STRING,
	u: ISO_FORMAT_STRING_TZ
};


function format(xdate, formatString, settings, uniqueness, useUTC) {

	var locales = XDate.locales;
	var defaultLocaleSettings = locales[XDate.defaultLocale] || {};
	var getField = curry(_getField, xdate, useUTC);
	
	settings = (isString(settings) ? locales[settings] : settings) || {};
	
	function getSetting(name) {
		return settings[name] || defaultLocaleSettings[name];
	}
	
	function getFieldAndTrace(fieldIndex) {
		if (uniqueness) {
			var i = (fieldIndex == DAY ? DATE : fieldIndex) - 1;
			for (; i>=0; i--) {
				uniqueness.push(getField(i));
			}
		}
		return getField(fieldIndex);
	}
	
	return _format(xdate, formatString, getFieldAndTrace, getSetting, useUTC);
}


function _format(xdate, formatString, getField, getSetting, useUTC) {
	var m;
	var subout;
	var out = '';
	while (m = formatString.match(formatStringRE)) {
		out += formatString.substr(0, m.index);
		if (m[1]) { // consecutive alphabetic characters
			out += processTokenString(xdate, m[1], getField, getSetting, useUTC);
		}
		else if (m[3]) { // parenthesis
			subout = _format(xdate, m[4], getField, getSetting, useUTC);
			if (parseInt(subout.replace(/\D/g, ''), 10)) { // if any of the numbers are non-zero. or no numbers at all
				out += subout;
			}
		}
		else { // else if (m[6]) { // single quotes
			out += m[7] || "'"; // if inner is blank, meaning 2 consecutive quotes = literal single quote
		}
		formatString = formatString.substr(m.index + m[0].length);
	}
	return out + formatString;
}


function processTokenString(xdate, tokenString, getField, getSetting, useUTC) {
	var end = tokenString.length;
	var replacement;
	var out = '';
	while (end > 0) {
		replacement = getTokenReplacement(xdate, tokenString.substr(0, end), getField, getSetting, useUTC);
		if (replacement !== undefined) {
			out += replacement;
			tokenString = tokenString.substr(end);
			end = tokenString.length;
		}else{
			end--;
		}
	}
	return out + tokenString;
}


function getTokenReplacement(xdate, token, getField, getSetting, useUTC) {
	var formatter = XDate.formatters[token];
	if (isString(formatter)) {
		return _format(xdate, formatter, getField, getSetting, useUTC);
	}
	else if (isFunction(formatter)) {
		return formatter(xdate, useUTC || false, getSetting);
	}
	switch (token) {
		case 'fff'  : return zeroPad(getField(MILLISECONDS), 3);
		case 's'    : return getField(SECONDS);
		case 'ss'   : return zeroPad(getField(SECONDS));
		case 'm'    : return getField(MINUTES);
		case 'mm'   : return zeroPad(getField(MINUTES));
		case 'h'    : return getField(HOURS) % 12 || 12;
		case 'hh'   : return zeroPad(getField(HOURS) % 12 || 12);
		case 'H'    : return getField(HOURS);
		case 'HH'   : return zeroPad(getField(HOURS));
		case 'd'    : return getField(DATE);
		case 'dd'   : return zeroPad(getField(DATE));
		case 'ddd'  : return getSetting('dayNamesShort')[getField(DAY)] || '';
		case 'dddd' : return getSetting('dayNames')[getField(DAY)] || '';
		case 'M'    : return getField(MONTH) + 1;
		case 'MM'   : return zeroPad(getField(MONTH) + 1);
		case 'MMM'  : return getSetting('monthNamesShort')[getField(MONTH)] || '';
		case 'MMMM' : return getSetting('monthNames')[getField(MONTH)] || '';
		case 'yy'   : return (getField(FULLYEAR)+'').substring(2);
		case 'yyyy' : return getField(FULLYEAR);
		case 't'    : return _getDesignator(getField, getSetting).substr(0, 1).toLowerCase();
		case 'tt'   : return _getDesignator(getField, getSetting).toLowerCase();
		case 'T'    : return _getDesignator(getField, getSetting).substr(0, 1);
		case 'TT'   : return _getDesignator(getField, getSetting);
		case 'z'    :
		case 'zz'   :
		case 'zzz'  : return useUTC ? 'Z' : _getTZString(xdate, token);
		case 'w'    : return _getWeek(getField);
		case 'ww'   : return zeroPad(_getWeek(getField));
		case 'S'    :
			var d = getField(DATE);
			if (d > 10 && d < 20) return 'th';
			return ['st', 'nd', 'rd'][d % 10 - 1] || 'th';
	}
}


function _getTZString(xdate, token) {
	var tzo = xdate.getTimezoneOffset();
	var sign = tzo < 0 ? '+' : '-';
	var hours = Math.floor(Math.abs(tzo) / 60);
	var minutes = Math.abs(tzo) % 60;
	var out = hours;
	if (token == 'zz') {
		out = zeroPad(hours);
	}
	else if (token == 'zzz') {
		out = zeroPad(hours) + ':' + zeroPad(minutes);
	}
	return sign + out;
}


function _getDesignator(getField, getSetting) {
	return getField(HOURS) < 12 ? getSetting('amDesignator') : getSetting('pmDesignator');
}



/* Misc Methods
---------------------------------------------------------------------------------*/


each(
	[ // other getters
		'getTime',
		'valueOf',
		'toDateString',
		'toTimeString',
		'toLocaleString',
		'toLocaleDateString',
		'toLocaleTimeString',
		'toJSON'
	],
	function(methodName) {
		proto[methodName] = function() {
			return this[0][methodName]();
		};
	}
);


proto.setTime = function(t) {
	this[0].setTime(t);
	return this; // for chaining
};


proto.valid = methodize(valid);
function valid(xdate) {
	return !isNaN(+xdate[0]);
}


proto.clone = function() {
	return new XDate(this);
};


proto.clearTime = function() {
	return this.setHours(0, 0, 0, 0); // will return an XDate for chaining
};


proto.toDate = function() {
	return new Date(+this[0]);
};



/* Misc Class Methods
---------------------------------------------------------------------------------*/


XDate.now = function() {
	return +new Date();
};


XDate.today = function() {
	return new XDate().clearTime();
};


XDate.UTC = UTC;


XDate.getDaysInMonth = getDaysInMonth;



/* Internal Utilities
---------------------------------------------------------------------------------*/


function _clone(xdate) { // returns the internal Date object that should be used
	var d = new Date(+xdate[0]);
	if (getUTCMode(xdate)) {
		d.toString = toUTCString;
	}
	return d;
}


function _getField(d, useUTC, fieldIndex) {
	return d['get' + (useUTC ? 'UTC' : '') + methodSubjects[fieldIndex]]();
}


function _setField(d, useUTC, fieldIndex, args) {
	d['set' + (useUTC ? 'UTC' : '') + methodSubjects[fieldIndex]].apply(d, args);
}



/* Date Math Utilities
---------------------------------------------------------------------------------*/


function coerceToUTC(date) {
	return new Date(UTC(
		date.getFullYear(),
		date.getMonth(),
		date.getDate(),
		date.getHours(),
		date.getMinutes(),
		date.getSeconds(),
		date.getMilliseconds()
	));
}


function coerceToLocal(date) {
	return new Date(
		date.getUTCFullYear(),
		date.getUTCMonth(),
		date.getUTCDate(),
		date.getUTCHours(),
		date.getUTCMinutes(),
		date.getUTCSeconds(),
		date.getUTCMilliseconds()
	);
}


function getDaysInMonth(year, month) {
	return 32 - new Date(UTC(year, month, 32)).getUTCDate();
}



/* General Utilities
---------------------------------------------------------------------------------*/


function methodize(f) {
	return function() {
		return f.apply(undefined, [this].concat(slice(arguments)));
	};
}


function curry(f) {
	var firstArgs = slice(arguments, 1);
	return function() {
		return f.apply(undefined, firstArgs.concat(slice(arguments)));
	};
}


function slice(a, start, end) {
	return Array.prototype.slice.call(
		a,
		start || 0, // start and end cannot be undefined for IE
		end===undefined ? a.length : end
	);
}


function each(a, f) {
	for (var i=0; i<a.length; i++) {
		f(a[i], i);
	};
}


function isString(arg) {
	return typeof arg == 'string';
}


function isNumber(arg) {
	return typeof arg == 'number';
}


function isBoolean(arg) {
	return typeof arg == 'boolean';
}


function isFunction(arg) {
	return typeof arg == 'function';
}


function zeroPad(n, len) {
	len = len || 2;
	n += '';
	while (n.length < len) {
		n = '0' + n;
	}
	return n;
}



// Export for Node.js
if (typeof module !== 'undefined' && module.exports) {
	module.exports = XDate;
}

// AMD
if (typeof define === 'function' && define.amd) {
	define([], function() {
		return XDate;
	});
}


return XDate;

})(Date, Math, Array);