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

function MultiColumnSettings() {
        this.extraHeight=30;                //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=2;         //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-1;i++) {
                        var currentColumn=columns.item(i);
                        currentColumn.style.width=availableWidth+'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);
        }
}