/* Finds the index of the first occurence of item in the array, or -1 if not found */
Array.prototype.indexOf = function(item) {
	for (var i = 0; i < this.length; i++) {
		if (this[i] == item) {
			return i;
		}
	}
	return -1;
};
/* Returns an array of items judged 'true' by the passed in test function */
Array.prototype.filter = function(test) {
	var matches = [];
	for (var i = 0; i < this.length; i++) {
		if (test(this[i])) {
			matches[matches.length] = this[i];
		}
	}
	return matches;
};

var monthNames = "January February March April May June July August September October November December".split(" ");
var weekdayNames = "Sunday Monday Tuesday Wednesday Thursday Friday Saturday".split(" ");

/* Takes a string, returns the index of the month matching that string, throws
an error if 0 or more than 1 matches
*/
function parseMonth(month) {
	var matches = monthNames.filter(function(item) { 
		return new RegExp("^" + month, "i").test(item);
	});

	if (matches.length == 0) {
		throw new Error("Invalid month string");
	}
	if (matches.length > 1) {
		throw new Error("Ambiguous month");
	}
	return monthNames.indexOf(matches[0]);
}
/* Same as parseMonth but for days of the week */
function parseWeekday(weekday) {
	var matches = weekdayNames.filter(function(item) {
		return new RegExp("^" + weekday, "i").test(item);
	});

	if (matches.length == 0) {
		throw new Error("Invalid day string");
	}
	if (matches.length > 1) {
		throw new Error("Ambiguous weekday");
	}
	return weekdayNames.indexOf(matches[0]);
}


/* Array of objects, each has 're', a regular expression and 'handler', a 
function for creating a date from something that matches the regular 
expression. Handlers may throw errors if string is unparseable. 
*/
var dateParsePatterns = [
	// Today
	{   re: /^tod/i,
		handler: function() { 
			return new Date();
		} 
	},
	// Tomorrow
	{   re: /^tom/i,
		handler: function() {
			var d = new Date(); 
			d.setDate(d.getDate() + 1); 
			return d;
		}
	},
	// Yesterday
	{   re: /^yes/i,
		handler: function() {
			var d = new Date();
			d.setDate(d.getDate() - 1);
			return d;
		}
	},
	// 4th
	{   re: /^(\d{1,2})(st|nd|rd|th)?$/i, 
		handler: function(bits) {
			var d = new Date();
			d.setDate(parseInt(bits[1], 10));
			return d;
		}
	},
	// 4th Jan
	{   re: /^(\d{1,2})(?:st|nd|rd|th)? (\w+)$/i, 
		handler: function(bits) {
			var d = new Date();
			d.setDate(1);
			d.setMonth(parseMonth(bits[2]));
			d.setDate(parseInt(bits[1], 10));
			return d;
		}
	},
	// 4th Jan 2003
	{   re: /^(\d{1,2})(?:st|nd|rd|th)? (\w+),? (\d{4})$/i,
		handler: function(bits) {
			var d = new Date();
			d.setDate(1);
			d.setYear(bits[3]);
			d.setMonth(parseMonth(bits[2]));
			d.setDate(parseInt(bits[1], 10));
			return d;
		}
	},
	// Jan 4th
	{   re: /^(\w+) (\d{1,2})(?:st|nd|rd|th)?$/i, 
		handler: function(bits) {
			var d = new Date();
			d.setDate(1);
			d.setMonth(parseMonth(bits[1]));
			d.setDate(parseInt(bits[2], 10));
			return d;
		}
	},
	// Jan 4th 2003
	{   re: /^(\w+) (\d{1,2})(?:st|nd|rd|th)?,? (\d{4})$/i,
		handler: function(bits) {
			var d = new Date();
			d.setDate(1);
			d.setYear(bits[3]);
			d.setMonth(parseMonth(bits[1]));
			d.setDate(parseInt(bits[2], 10));
			return d;
		}
	},
	// next Tuesday - this is suspect due to weird meaning of "next"
	{   re: /^ne(?:xt)* (\w+)$/i,
		handler: function(bits) {
			var d = new Date();
			var wd = d.getDay();
			var nwd = parseWeekday(bits[1]);
			var addDays = nwd - wd;

			// It can't be before today or this week.
			if (nwd <= wd || (addDays + wd < 7) ) {
				addDays += 7;
			}
			
			// Next is not tomorrow.
			if (1 == addDays) {
				addDays += 7;
			}

			d.setDate(d.getDate() + addDays);
			return d;
		}
	},
	// last Tuesday
	{   re: /^la(?:st)* (\w+)$/i,
		handler: function(bits) {
			var d = new Date();
			var wd = d.getDay();
			var nwd = parseWeekday(bits[1]);

			// determine the number of days to subtract to get last weekday
			var addDays = (-1 * (wd + 7 - nwd)) % 7;
			// above calculate 0 if weekdays are the same so we have to change this to 7
			if (0 == addDays) {
				addDays = -7;
			} else if (-1 == addDays) {	// Last is not yesterday.
				addDays -= 7;
			}

			// adjust date and return
			d.setDate(d.getDate() + addDays);
			return d;
			}
	},
	// this coming Tuesday
	{   re: /^th(?:is)* (\w+)$/i,
		handler: function(bits) {
			var d = new Date();
			var wd = d.getDay();
			var nwd = parseWeekday(bits[1]);
			var addDays = nwd - wd;

			// It can't be before today.
			if (nwd <= wd) {
				addDays += 7;
			}
			
			d.setDate(d.getDate() + addDays);
			return d;
		}
	},
	// first Tuesday
	{   re: /^fir(?:st)* (\w+)$/i,
		handler: function(bits) {
			var d = new Date();
			d.setDate(1);
			var day = d.getDay();
			var newDay = parseWeekday(bits[1]);
			if(day == newDay) {
				return d;
			}
			
			var addDays = newDay - day;
			if (newDay < day) {
				addDays += 7;
			}
			d.setDate(d.getDate() + addDays);
			return d;
		}
	},
	// second Tuesday
	{   re: /^sec(?:ond)* (\w+)$/i,
		handler: function(bits) {
			var d = new Date();
			d.setDate(1);
			var day = d.getDay();
			var newDay = parseWeekday(bits[1]);
			var addDays = newDay - day;
			if (newDay < day) {
				addDays += 7;
			}
			addDays += 7;
			d.setDate(d.getDate() + addDays);
			return d;
		}
	},
	// third Tuesday
	{   re: /^thi(?:rd)* (\w+)$/i,
		handler: function(bits) {
			var d = new Date();
			d.setDate(1);
			var day = d.getDay();
			var newDay = parseWeekday(bits[1]);
			var addDays = newDay - day;
			if (newDay < day) {
				addDays += 7;
			}
			addDays += 14;
			d.setDate(d.getDate() + addDays);
			return d;
		}
	},
	// fourth Tuesday
	{   re: /^fo(?:urth)* (\w+)$/i,
		handler: function(bits) {
			var d = new Date();
			d.setDate(1);
			var day = d.getDay();
			var newDay = parseWeekday(bits[1]);
			var addDays = newDay - day;
			if (newDay < day) {
				addDays += 7;
			}
			addDays += 21;
			d.setDate(d.getDate() + addDays);
			return d;
		}
	},
	// fifth Tuesday
	{   re: /^fi(?:fth)* (\w+)$/i,
		handler: function(bits) {
			var d = new Date();
			d.setDate(1);
			var day = d.getDay();
			var newDay = parseWeekday(bits[1]);
			var addDays = newDay - day;
			if (newDay < day) {
				addDays += 7;
			}
			addDays += 28;
			d.setDate(d.getDate() + addDays);
			return d;
		}
	},
	// mm/dd/yyyy (American style)
	{   re: /(\d{1,2})\/(\d{1,2})\/(\d{4})/,
		handler: function(bits) {
			var d = new Date();
			d.setDate(1);
			if(!dp_dateFormat || dp_dateFormat.substr(0,1) == 'm') {
				d.setYear(bits[3]);
				d.setMonth(parseInt(bits[1], 10) - 1); // Because months indexed from 0
				d.setDate(parseInt(bits[2], 10));
			} else {
				d.setYear(bits[3]);
				d.setMonth(parseInt(bits[2], 10) - 1); // Because months indexed from 0
				d.setDate(parseInt(bits[1], 10));
			}
			return d;
		}
	},
	// mm-dd-yyyy (American style) or dd-mm-yyyy
	{   re: /(\d{1,2})-(\d{1,2})-(\d{4})/,
		handler: function(bits) {
			var d = new Date();
			d.setDate(1);
			if(!dp_dateFormat || dp_dateFormat.substr(0,1) == 'm') {
				d.setYear(bits[3]);
				d.setMonth(parseInt(bits[1], 10) - 1); // Because months indexed from 0
				d.setDate(parseInt(bits[2], 10));
			} else {
				d.setYear(bits[3]);
				d.setMonth(parseInt(bits[2], 10) - 1); // Because months indexed from 0
				d.setDate(parseInt(bits[1], 10));
			}
			return d;
		}
	},
	// mm.dd.yyyy (American style) or dd.mm.yyyy
	{   re: /(\d{1,2})\.(\d{1,2})\.(\d{4})/,
		handler: function(bits) {
			var d = new Date();
			d.setDate(1);
			if(!dp_dateFormat || dp_dateFormat.substr(0,1) == 'm') {
				d.setYear(bits[3]);
				d.setMonth(parseInt(bits[1], 10) - 1); // Because months indexed from 0
				d.setDate(parseInt(bits[2], 10));
			} else {
				d.setYear(bits[3]);
				d.setMonth(parseInt(bits[2], 10) - 1); // Because months indexed from 0
				d.setDate(parseInt(bits[1], 10));
			}
			return d;
		}
	},
	// yyyy-mm-dd (ISO style)
	{   re: /(\d{4})-(\d{1,2})-(\d{1,2})/,
		handler: function(bits) {
			var d = new Date();
			d.setDate(1);
			d.setYear(parseInt(bits[1],10));
			d.setMonth(parseInt(bits[2], 10) - 1);
			d.setDate(parseInt(bits[3], 10));
			return d;
		}
	}
];

function parseDateString(s) {
	for (var i = 0; i < dateParsePatterns.length; i++) {
		var re = dateParsePatterns[i].re;
		var handler = dateParsePatterns[i].handler;
		var bits = re.exec(s);
		if (bits) {
			return handler(bits);
		}
	}
	throw new Error("You have inserted an Invalid Date");
}

var dp_dateFormat;

function dp_DateString(d) {
	var dateDelim, delim;

	dp_dateFormat = dp_dateFormat || 'mm/dd/yyyy';
	if(dp_dateFormat.indexOf('/') != -1) {
		delim = eval('/\\//g');
		dateDelim = '/';
	} else if(dp_dateFormat.indexOf('-') != -1) {
		delim = eval('/\\-/g');
		dateDelim = '-';
	} else if(dp_dateFormat.indexOf('.') != -1) {
		delim = eval('/\\./g');
		dateDelim = '.';
	} else {
		delim = eval('/\\ /g');
		dateDelim = ' ';
	}

	var month, day, year;
	
	month = d.getMonth();
	day = d.getDate();
	year = d.getFullYear();

	switch (dp_dateFormat.replace(delim,"")){
	case 'ddmmmyyyy':
		return dp_padZero(day) + dateDelim + monthNames[month].substr(0,3) + dateDelim + year;
	case 'dmmmyyyy':
		return day + dateDelim + monthNames[month].substr(0,3) + dateDelim + year;
	case 'ddmmyyyy':
		return dp_padZero(day) + dateDelim + dp_padZero(month+1) + dateDelim + year;
	case 'dmmyyyy':
		return day + dateDelim + dp_padZero(month+1) + dateDelim + year;
	case 'mmddyyyy':
		return dp_padZero((month+1)) + dateDelim + dp_padZero(day) + dateDelim + year;
	case 'mddyyyy':
		return (month+1) + dateDelim + dp_padZero(day) + dateDelim + year;
	case 'mdyyyy':
		return (month+1) + dateDelim + day + dateDelim + year;
	case 'yyyymmdd':
		return year + dateDelim + dp_padZero(month+1) + dateDelim + dp_padZero(day);
	default:
		return (month+1) + dateDelim + day + dateDelim + year;
	}
}

function dp_padZero(n) {
	return ((n <= 9) ? ("0" + n) : n);
}

function magicDate(input, required) {
	if(!required && input.value == '') {
		return true;
	}
	var bRet = true;
	var messagespan = input.id + 'Msg';
	try {
		var d = parseDateString(input.value);
		input.value = dp_DateString(d);
		input.className = '';
		// Human readable date
		var el = document.getElementById(messagespan);
		if(el) {
			el.firstChild.nodeValue = d.toDateString();
			el.className = 'normal';
		} else {
			d.toDateString();
		}
	}
	catch (e) {
		input.className = 'error';
		var message = e.message;

		// Fix for IE6 bug
		if (!message.length || message.indexOf('is null or not an object') > -1) {
			message = 'Invalid date string';
		}
		var el = document.getElementById(messagespan);
		if(el) {
			el.firstChild.nodeValue = message;
			el.className = 'error';
		} else {
			alert(message);
		}
		bRet = false;
	}
//	if(!bRet)
//		input.focus();
	return bRet;
}

// If there is an addEvent function add an event to add the dateparse functions to
// an input field with a className of dateparse. If you don't have an addEvent function,
// please use mine at http://tanny.ica.com, search for DOMContentLoaded.
try {
	if(addEvent){
		// If there is an addDOMLoadEvent function use it as it runs as soon as the
		// DOM (html) has loaded. This is faster than load (onload) since it doesn't
		// have to wait for images and other stuff (technical term).
		var sEventType;;
		try {
			if(addDOMLoadEvent)
				sEventType = "DOMContentLoaded";
		}
		catch(e) {
			sEventType = "load";
		}

		// Let's add an event to run the add date parse behavior function.
		addEvent(window, sEventType, function() {
			// Get an array of input elements.
			var els = document.getElementsByTagName("input");

			// Check each input element.
			for(var i = 0; i < els.length; i++) {
				// If the className has the word dateparse in it, add the behavior.
				if(/\bdateparse\b/.test(els[i].className)) {
					addEvent(els[i], "blur", function() { magicDate(this); });
					addEvent(els[i], "focus", function() { if (this.className != 'error') this.select(); });
				}
			}
		});
	}
}
catch(e) {
	// We could add the function to the onload event here, but the user might overright it
	// in body onload attribute. Therefore, we're not going to add the functionality.
}