//Some stuff needs to be maintained in a global variable.
MultiColumnResizeTimer=null;
MultiColumnList=null;

var MultiColumnPadding = 10;

function MultiColumnSettings() {
	this.extraHeight=20;		//Add extra height to a column. Increase this if the last column 'sticks out' too much.
	this.minSplitHeight=0;		//If the base column is smaller than minSplitHeight, the column does not split.
	this.minHeight=0;			//Minimum height of a column
	this.readOnText=null;		//Add the "read on" notice a the bottom of each column
	this.classNameScreen=null;	//Set the classname of *container* of the rendered columns for screen-media. Use to differentiate between JS/non-JS base column widths.
	this.classNamePrint=null;	//Set the classname of *container* of the rendered columns for print-media. (optional, may be null)
	this.numberOfColumns=null; 	//null: calculate number of columns based on minimum width. Number >0: use specified number of columns, always adapt width.
}

function MultiColumn(columnContainerIn,settingsIn) {
	//IE6 doesn't support HTMLElement prototyping. IE7 probably won't too. Let's aim for IE8! *sigh*	
	//But thank you, www.quirksmode.org!
	this.getStyle= function (element,stylePropW3,stylePropIE) {
		var y = null;
		if (element.currentStyle)
			y = element.currentStyle[stylePropIE];
		else if (window.getComputedStyle && document.defaultView.getComputedStyle(element,null)) {
			y = document.defaultView.getComputedStyle(element,null).getPropertyValue(stylePropW3);
		}
		return y;
	}
		
	this.generateColumns= function () {
		var i=0;
		var numColumns;
		
		//Obtain the base column. This column contains the original text.
		var baseColumn=this.columnContainer.getElementsByTagName('div').item(0);
		
		//Add a node with style: "clear: both;" to stretch the container-node.
		var clearingNode=document.createElement('span');
		clearingNode.style.display="block";
		clearingNode.style.clear="both";
		clearingNode.style.zoom="1"; //yet another work-around for a certain obsolete browser.
		this.columnContainer.appendChild(clearingNode);
		
		//Use specified number of columns, or calculate number based on minimum width?
		if (this.settings.numberOfColumns!=null) {
			//Use specified number of columns
			numColumns=this.settings.numberOfColumns;
		}	else {
			//Calculate the number of columns that can be added, based on width.
			numColumns=Math.floor(this.columnContainer.offsetWidth/(baseColumn.offsetWidth)); //baseColumn.getStyle('width') gives wrong value in Opera
		}
		
		//Calculate the available width for one column.
		var availableWidth=Math.floor((this.columnContainer.offsetWidth-10)/numColumns)-parseInt(this.getStyle(baseColumn,'padding-right','paddingRight'))-parseInt(this.getStyle(baseColumn,'padding-left','paddingLeft'));
		
		//Add new columns
		for (i=1;i<numColumns;i++) {
			this.columnContainer.insertBefore(baseColumn.cloneNode(false),this.columnContainer.firstChild);
		}
				
		//First, set the new width for the existing column..
		baseColumn.style.width=availableWidth+'px';
		
		//Get all columns in the container
		var columns=this.columnContainer.getElementsByTagName('div');
		
		//..then calculate the average needed height for other .
		var minHeight;
		
		if (baseColumn.offsetHeight<=this.settings.minSplitHeight) {
			var minHeight=baseColumn.offsetHeight;
		} else {
			var minHeight=Math.max(parseInt((baseColumn.offsetHeight+numColumns*this.settings.extraHeight)/columns.length),this.settings.minHeight);
		}
		
		//Cut/paste blocks from the baseColumn to the new columns, until the reached the minHeight.
		for (i=0;i<columns.length;i++) {
			var currentColumn=columns.item(i);		

		    var appendedPadding = 0;

			if(i == 0) {
				appendedPadding = MultiColumnPadding;
				currentColumn.style.paddingRight = MultiColumnPadding + "px";	
			} else 	if(i > 0 && i < columns.length-1) {
				appendedPadding = MultiColumnPadding * 2;
				currentColumn.style.paddingLeft = MultiColumnPadding + "px";
				currentColumn.style.paddingRight = MultiColumnPadding + "px";
			} else {
				appendedPadding = MultiColumnPadding;
				currentColumn.style.paddingLeft = MultiColumnPadding + "px";
			}						
						
		}

		//Cut/paste blocks from the baseColumn to the new columns, until the reached the minHeight.
		for (i=0;i<columns.length-1;i++) {
			var currentColumn=columns.item(i);
			currentColumn.style.width=(availableWidth - appendedPadding) +'px';

			//Cut/paste blocks from the baseColumn to the current column, while the
			//current column has not reach the minHeight
			while (currentColumn.offsetHeight<minHeight && baseColumn.hasChildNodes()) {
				if (baseColumn.firstChild.nodeType==1) { //Node.ELEMENT_NODE Doesn't work in ^%@$#@$!!! IE6
					currentColumn.appendChild(baseColumn.firstChild);
				} else {
					baseColumn.removeChild(baseColumn.firstChild);
				}
			}
			
			//Some elements can be split and wrapped to the next column
			
			var lastChild=currentColumn.lastChild;
			var nextColumn=columns.item(i+1);
			switch (lastChild.nodeName.toLowerCase()) {
				case 'p': 
					new ParapgraphWrapper(currentColumn,lastChild,nextColumn,minHeight);
					break;
				case 'ul':
				case 'ol':
					new ListWrapper(currentColumn,lastChild,nextColumn,minHeight);					
					break;				
				default:
					//don't know what to do with this element. Let it stick out.
			}
			
			//Move headings at the bottom to next column. (this implies a proper usage of headings!)
			new HeadingWrapper(currentColumn,nextColumn);

			//add the 'read on' text.
			if (this.settings.readOnText!=null) {
				currentColumn.appendChild(this.readOnNode.cloneNode(true));
			}
		}
			
		//Stretch all columns to equal height
		var maxHeight=0;
		
		for (i=0;i<columns.length;i++) {
			maxHeight=Math.max(maxHeight,columns.item(i).offsetHeight);
		}			
		for (i=0;i<columns.length;i++) {
			columns.item(i).style.height=maxHeight+"px";
		}
	}
	
	//Initialisation starts here
	this.settings=settingsIn;
	
	if (this.settings.readOnText!=null) {					
		this.readOnNode=document.createElement('p');
		this.readOnNode.className="readOn";
		this.readOnNode.appendChild(document.createTextNode(this.settings.readOnText));
	}
	
	this.columnContainer=columnContainerIn;
	
	//If a screen class name is set, 
	if (this.settings.classNameScreen!=null) {
		//assign the classname.
		this.columnContainer.className=this.settings.classNameScreen;
	}
	
	//Store a copy of the original column	
	this.originalContent=columnContainerIn.cloneNode(true);
		
	//If a print class name is set, 
	if (this.settings.classNamePrint!=null) {
		//make a copy of the original node,
		var printNode=this.originalContent.cloneNode(true);
		//assign the classname
		printNode.className=this.settings.classNamePrint;
		//and insert it into the dom.
		this.columnContainer.parentNode.insertBefore(printNode,this.columnContainer);
	}	
	
	//Add this MultiColumn to the listener.
	if (MultiColumnList === null) {		
		MultiColumnList = new Array;
		if (window.addEventListener) {
			window.addEventListener('resize',multiColumnSetResizeTimer,false);		
		} else {
			window.attachEvent('onresize',multiColumnSetResizeTimer);
		}
	}
	
	MultiColumnList.push(this);
	
	//And do the magic!
	this.generateColumns();
}

//Regenerates the columns after a short delay after the user stopped resizing.
function multiColumnSetResizeTimer() {
	if (MultiColumnResizeTimer) {
		clearTimeout(MultiColumnResizeTimer);
	}
	MultiColumnResizeTimer=setTimeout(multiColumnResize,100);	
}
	
//Called when window is resized.
function multiColumnResize() {
	if (!window.addEventListener && window.attachEvent) { //Damned IE keeps fireing events when reflowing the text!
		window.detachEvent('onresize',multiColumnSetResizeTimer);
	}
	for (var i=0; i<MultiColumnList.length;i++) {
		var object = MultiColumnList[i];
		
		//Restore original situation
		var newCopy=object.originalContent.cloneNode(true);
		object.columnContainer.parentNode.replaceChild(newCopy,object.columnContainer);
		object.columnContainer=newCopy;
		
		//Regenerate columns
		object.generateColumns();
	}
	
	if (!window.addEventListener && window.attachEvent) { 
		setTimeout("window.attachEvent('onresize',multiColumnSetResizeTimer)",0);
	}
}

function ParapgraphWrapper(sourceColumnIn, sourceParagraphIn, destinationColumnIn, heightIn) {
	this.sourceColumn=sourceColumnIn;
	this.height=heightIn;
	
	/**
	* Recursively loops over given <source>, moving text from <source> to <dest>
	* until the column height is less or equal to the target height.
	*
	* Preconditions: <source> and <dest> are element nodes.
	*/
	this.processElement=function (source,dest) {
		var lastSourceChild;
		
		while (lastSourceChild=source.lastChild) {
			if (lastSourceChild.nodeType==1) {
				//Make a shalow clone copy of this element to the destination
				//node, to preserve styles and attributes.
				var newDest=lastSourceChild.cloneNode(false);
				dest.insertBefore(newDest,dest.firstChild);				
				//recursively process this node.
				if (this.processElement(lastSourceChild,newDest)) {
					return true;
				}							
			} else if (lastSourceChild.nodeType==3) {
				//Wrap this text node..
				if (this.wrapTextNode(lastSourceChild,dest)) {
					//..and return when the target has been reached.
					return true;
				}
			}
			
			//This node has been cleaned out. Remove it.
			source.removeChild(lastSourceChild);
		} 
				
		return false;
	}
	
	/**
	* Cuts words at the end of <source>, until the column height
	* is less or equal to target-height.
	* Cut words are then placed into <dest>
	*
	* Preconditions: <source> is a text node. <dest> is an element node.
	*/
	this.wrapTextNode=function (source,dest) {	
		var sourceText=source.nodeValue;
		
		//Split the text at spaces.
		var sourceTextAray=sourceText.split(/\s/);
		var destTextArray=new Array();
		
		//Keep removing words form the source until the column fits.
		while (this.sourceColumn.offsetHeight>this.height && sourceTextAray.length>0) {
			destTextArray.push(sourceTextAray.pop());
			source.nodeValue=sourceTextAray.join(' ');
		}
		
		//Add spaces at the front and end, if there are spaces in the original.
		var newText=(/^\s/.test(sourceText)?' ':'') + (destTextArray.reverse().join(' ')) + (/\s$/.test(sourceText)?' ':'');
		
		//Put the text into the destination node in the next column.
		dest.insertBefore(document.createTextNode(newText),dest.firstChild);		
		
		//return true if the target has been reached.
		return this.sourceColumn.offsetHeight<=this.height;
	}

	//Duplicate the current paragraph by shallow copy
	destinationColumnIn.insertBefore(sourceParagraphIn.cloneNode(false),destinationColumnIn.firstChild);	
	
	this.processElement(sourceParagraphIn,destinationColumnIn.firstChild);
	
	//check if the origal paragraph is emtpy
	if (sourceParagraphIn.offsetHeight==0) { //Check to see if normalized text is "" would be better..
		//Yes it's empty. Remove the empty paragraph.
		this.sourceColumn.removeChild(sourceParagraphIn);		
	}
}

function ListWrapper(sourceColumnIn, sourceListIn, destinationColumnIn, heightIn) {
	//Duplicate the current paragraph by shallow copy
	var newList=sourceListIn.cloneNode(false);
	
	destinationColumnIn.insertBefore(newList,destinationColumnIn.firstChild);
		
	//Loop over all elements in this list.
	while (currentElement=sourceListIn.lastChild) {
		if (sourceColumnIn.offsetHeight<=heightIn) {
			break;
		}
		
		if (currentElement.nodeName.toLowerCase()=='li') {
			newList.insertBefore(currentElement,newList.firstChild);			
		} else {		
			//remove the last element.
			sourceListIn.removeChild(currentElement);
		}
	}
		
	//Count current number of items.
	var numItems=1;
	var elementList=sourceListIn.childNodes;
	//count remaining items.
	for (var i=0;i<elementList.length;i++) {
		if (elementList[i].nodeName.toLowerCase()=='li') {
			numItems++;
		}
	}
	
	newList.start=numItems;
	
	//check if the origal list is emtpy
	if (sourceListIn.offsetHeight==0) { //Check to see if normalized text is "" would be better..
		//Yes it's empty. Remove the empty list.
		sourceColumnIn.removeChild(sourceListIn);		
	}
}

function HeadingWrapper(currentColumn,nextColumn) {
	//Wrap a heading, if there was one. 
	if (/^h[1-6]$/i.test(currentColumn.lastChild.nodeName)) {			
		nextColumn.insertBefore(currentColumn.lastChild,nextColumn.firstChild);	
	}
}