/**
 * Calendar Script
 * Creates a calendar widget which can be used to select the date more easily than using just a text box
 * http://www.openjs.com/scripts/ui/calendar/
 *
 * Example:
 * <input type="text" name="date" id="date" />
 * <script type="text/javascript">
 * 		calendar.set("date");
 * </script>
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
calendar = {
	month_names: ["January","February","March","April","May","June","July","August","September","October","November","December"],
	weekdays: ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"],
	month_days: [31,28,31,30,31,30,31,31,30,31,30,31],
	//Get today's date - year, month, day and date
	today : new Date(),
	opt : {},
	data: [],

	//Functions
	/// Used to create HTML in a optimized way.
	wrt:function(txt) {
		this.data.push(txt);
	},
	
	/* Inspired by http://www.quirksmode.org/dom/getstyles.html */
	getStyle: function(ele, property){
		if (ele.currentStyle) {
			var alt_property_name = property.replace(/\-(\w)/g,function(m,c){return c.toUpperCase();});//background-color becomes backgroundColor
			var value = ele.currentStyle[property]||ele.currentStyle[alt_property_name];
		
		} else if (window.getComputedStyle) {
			property = property.replace(/([A-Z])/g,"-$1").toLowerCase();//backgroundColor becomes background-color

			var value = document.defaultView.getComputedStyle(ele,null).getPropertyValue(property);
		}
		
		//Some properties are special cases
		if(property == "opacity" && ele.filter) value = (parseFloat( ele.filter.match(/opacity\=([^)]*)/)[1] ) / 100);
		else if(property == "width" && isNaN(value)) value = ele.clientWidth || ele.offsetWidth;
		else if(property == "height" && isNaN(value)) value = ele.clientHeight || ele.offsetHeight;
		return value;
	},
	getPosition:function(ele) {
		var x = 0;
		var y = 0;
		while (ele) {
			x += ele.offsetLeft;
			y += ele.offsetTop;
			ele = ele.offsetParent;
		}
		if (navigator.userAgent.indexOf("Mac") != -1 && typeof document.body.leftMargin != "undefined") {
			x += document.body.leftMargin;
			offsetTop += document.body.topMargin;
		}
	
		var xy = new Array(x,y);
		return xy;
	},
	/// Called when the user clicks on a date in the calendar.
	selectDate:function(year,month,day) {
		var ths = _calendar_active_instance;
		document.getElementById(ths.opt["input"]).innerHTML = year + "-" + month + "-" + day; // Date format is :HARDCODE:
		try{
		document.getElementById("db").value = year + "-" + month + "-" + day; 
		}catch(e){}
		ths.hideCalendar();
	},
	/// Creates a calendar with the date given in the argument as the selected date.
	makeCalendar:function(year, month, day) {
		year = parseInt(year);
		month= parseInt(month);
		day	 = parseInt(day);
		
		//Display the table
		var next_month = month+1;
		var next_month_year = year;
		if(next_month>=12) {
			next_month = 0;
			next_month_year++;
		}
		
		var previous_month = month-1;
		var previous_month_year = year;
		if(previous_month< 0) {
			previous_month = 11;
			previous_month_year--;
		}
		
		this.wrt("<table border=\"1\">");
		this.wrt("<tr><th><a href='javascript:calendar.makeCalendar("+(previous_month_year)+","+(previous_month)+");' title='"+this.month_names[previous_month]+" "+(previous_month_year)+"'>&lt;</a></th>");
		this.wrt("<th colspan='5' class='calendar-title'><select name='calendar-month' class='calendar-month' onChange='calendar.makeCalendar("+year+",this.value);'>");
		for(var i in this.month_names) {
			this.wrt("<option value='"+i+"'");
			if(i == month) this.wrt(" selected='selected'");
			this.wrt(">"+this.month_names[i]+"</option>");
		}
		this.wrt("</select>");
		this.wrt("<select name='calendar-year' class='calendar-year' onChange='calendar.makeCalendar(this.value, "+month+");'>");
		var current_year = this.today.getYear();
		if(current_year < 1900) current_year += 1900;
		
		for(var i=current_year-90; i<current_year+1; i++) {
			this.wrt("<option value='"+i+"'")
			if(i == year) this.wrt(" selected='selected'");
			this.wrt(">"+i+"</option>");
		}
		this.wrt("</select></th>");
		this.wrt("<th><a href='javascript:calendar.makeCalendar("+(next_month_year)+","+(next_month)+");' title='"+this.month_names[next_month]+" "+(next_month_year)+"'>&gt;</a></th></tr>");
		this.wrt("<tr class='header'>");
		for(var weekday=0; weekday<7; weekday++) this.wrt("<td>"+this.weekdays[weekday]+"</td>");
		this.wrt("</tr>");
		
		//Get the first day of this month
		var first_day = new Date(year,month,1);
		var start_day = first_day.getDay();
		
		var d = 1;
		var flag = 0;
		
		//Leap year support
		if(year % 4 == 0) this.month_days[1] = 29;
		else this.month_days[1] = 28;
		
		var days_in_this_month = this.month_days[month];

		//Create the calender
		for(var i=0;i<=5;i++) {
			if(w >= days_in_this_month) break;
			this.wrt("<tr>");
			for(var j=0;j<7;j++) {
				if(d > days_in_this_month) flag=0; //If the days has overshooted the number of days in this month, stop writing
				else if(j >= start_day && !flag) flag=1;//If the first day of this month has come, start the date writing

				if(flag) {
					var w = d, mon = month+1;
					if(w < 10)	w	= "0" + w;
					if(mon < 10)mon = "0" + mon;

					//Is it today?
					var class_name = '';
					var yea = this.today.getYear();
					if(yea < 1900) yea += 1900;

					if(yea == year && this.today.getMonth() == month && this.today.getDate() == d) class_name = " today";
					if(day == d) class_name += " selected";
					
					class_name += " " + this.weekdays[j].toLowerCase();

					this.wrt("<td class='days"+class_name+"'><a href='javascript:calendar.selectDate(\""+year+"\",\""+mon+"\",\""+w+"\")'>"+w+"</a></td>");
					d++;
				} else {
					this.wrt("<td class='days'>&nbsp;</td>");
				}
			}
			this.wrt("</tr>");
		}
		this.wrt("</table>");
		this.wrt("<br /><div align=\"center\"><input type='button' value='Cancel' class='calendar-cancel' onclick='calendar.hideCalendar();' /></div>");

		document.getElementById(this.opt['calendar']).innerHTML = this.data.join("");
		this.data = [];
	},
	
	/// Display the calendar - if a date exists in the input box, that will be selected in the calendar.
	showCalendar: function() {
		var input = document.getElementById(this.opt['input']);
		
		//Position the div in the correct location...
		var div = document.getElementById(this.opt['calendar']);
		var xy = this.getPosition(input);
		var width = parseInt(this.getStyle(input,'width'));
		div.style.left=(xy[0]+width+10)+"px";
		div.style.top=xy[1]+"px";

		// Show the calendar with the date in the input as the selected date
		var existing_date = new Date();
		var date_in_input = input.innerHTML;
		if(date_in_input) {
			var selected_date = false;
			var date_parts = date_in_input.split("-");
			if(date_parts.length == 3) {
				date_parts[1]--; //Month starts with 0
				selected_date = new Date(date_parts[0], date_parts[1], date_parts[2]);
			}
			if(selected_date && !isNaN(selected_date.getYear())) { //Valid date.
				existing_date = selected_date;
			}
		}
		
		var the_year = existing_date.getYear();
		if(the_year < 1900) the_year += 1900;
		this.makeCalendar(the_year, existing_date.getMonth(), existing_date.getDate());
		document.getElementById(this.opt['calendar']).style.display = "block";
		_calendar_active_instance = this;
	},
	
	/// Hides the currently show calendar.
	hideCalendar: function(instance) {
		var active_calendar_id = "";
		if(instance) active_calendar_id = instance.opt['calendar'];
		else active_calendar_id = _calendar_active_instance.opt['calendar'];
		
		if(active_calendar_id) document.getElementById(active_calendar_id).style.display = "none";
		_calendar_active_instance = {};
	},
	
	/// Setup a text input box to be a calendar box.
	set: function(input_id) {
		var input = document.getElementById(input_id);
		if(!input){
			
			return; //If the input field is not there, exit.
		
		}
		if(!this.opt['calendar']) this.init();
		
		var ths = this;
		input.onclick=function(){
			ths.opt['input'] = this.id;
			ths.showCalendar();
		};
	},
	
	/// Will be called once when the first input is set.
	init: function() {
		if(!this.opt['calendar'] || !document.getElementById(this.opt['calendar'])) {
			var div = document.createElement('div');
			if(!this.opt['calendar']) this.opt['calendar'] = 'calender_div_'+ Math.round(Math.random() * 100);

			div.setAttribute('id',this.opt['calendar']);
			div.className="calendar-box";

			document.getElementsByTagName("body")[0].insertBefore(div,document.getElementsByTagName("body")[0].firstChild);
		}
	}
}