/**
 * TableDnD plug-in for JQuery, allows you to drag and drop table rows
 * You can set up various options to control how the system will work
 * Copyright © Denis Howlett <denish@isocra.com>
 * Licensed like jQuery, see http://docs.jquery.com/License.
 *
 * Configuration options:
 * 
 * onDragStyle
 *     This is the style that is assigned to the row during drag. There are limitations to the styles that can be
 *     associated with a row (such as you can't assign a border—well you can, but it won't be
 *     displayed). (So instead consider using onDragClass.) The CSS style to apply is specified as
 *     a map (as used in the jQuery css(...) function).
 * onDropStyle
 *     This is the style that is assigned to the row when it is dropped. As for onDragStyle, there are limitations
 *     to what you can do. Also this replaces the original style, so again consider using onDragClass which
 *     is simply added and then removed on drop.
 * onDragClass
 *     This class is added for the duration of the drag and then removed when the row is dropped. It is more
 *     flexible than using onDragStyle since it can be inherited by the row cells and other content. The default
 *     is class is tDnD_whileDrag. So to use the default, simply customise this CSS class in your
 *     stylesheet.
 * onDrop
 *     Pass a function that will be called when the row is dropped. The function takes 2 parameters: the table
 *     and the row that was dropped. You can work out the new order of the rows by using
 *     table.rows.
 * onDragStart
 *     Pass a function that will be called when the user starts dragging. The function takes 2 parameters: the
 *     table and the row which the user has started to drag.
 * onAllowDrop
 *     Pass a function that will be called as a row is over another row. If the function returns true, allow 
 *     dropping on that row, otherwise not. The function takes 2 parameters: the dragged row and the row under
 *     the cursor. It returns a boolean: true allows the drop, false doesn't allow it.
 * scrollAmount
 *     This is the number of pixels to scroll if the user moves the mouse cursor to the top or bottom of the
 *     window. The page should automatically scroll up or down as appropriate (tested in IE6, IE7, Safari, FF2,
 *     FF3 beta)
 * 
 * Other ways to control behaviour:
 *
 * Add class="nodrop" to any rows for which you don't want to allow dropping, and class="nodrag" to any rows
 * that you don't want to be draggable.
 *
 * Inside the onDrop method you can also call $.tableDnD.serialize() this returns a string of the form
 * <tableID>[]=<rowID1>&<tableID>[]=<rowID2> so that you can send this back to the server. The table must have
 * an ID as must all the rows.
 *
 * Known problems:
 * - Auto-scoll has some problems with IE7  (it scrolls even when it shouldn't), work-around: set scrollAmount to 0
 * 
 * Version 0.2: 2008-02-20 First public version
 * Version 0.3: 2008-02-07 Added onDragStart option
 *                         Made the scroll amount configurable (default is 5 as before)
 * Version 0.4: 2008-03-15 Changed the noDrag/noDrop attributes to nodrag/nodrop classes
 *                         Added onAllowDrop to control dropping
 *                         Fixed a bug which meant that you couldn't set the scroll amount in both directions
 *                         Added serialise method
 */
jQuery.tableDnD = {
    /** Keep hold of the current table being dragged */
    currentTable : null,
    /** Keep hold of the current drag object if any */
    dragObject: null,
    /** The current mouse offset */
    mouseOffset: null,
    /** Remember the old value of Y so that we don't do too much processing */
    oldY: 0,

    /** Actually build the structure */
    build: function(options) {
        // Make sure options exists
        options = options || {};
        // Set up the defaults if any

        this.each(function() {
            // Remember the options
            this.tableDnDConfig = {
                onDragStyle: options.onDragStyle,
                onDropStyle: options.onDropStyle,
				// Add in the default class for whileDragging
				onDragClass: options.onDragClass ? options.onDragClass : "tDnD_whileDrag",
                onDrop: options.onDrop,
                onDragStart: options.onDragStart,
                scrollAmount: options.scrollAmount ? options.scrollAmount : 5
            };
            // Now make the rows draggable
            jQuery.tableDnD.makeDraggable(this);
        });

        // Now we need to capture the mouse up and mouse move event
        // We can use bind so that we don't interfere with other event handlers
        jQuery(document)
            .bind('mousemove', jQuery.tableDnD.mousemove)
            .bind('mouseup', jQuery.tableDnD.mouseup);

        // Don't break the chain
        return this;
    },

    /** This function makes all the rows on the table draggable apart from those marked as "NoDrag" */
    makeDraggable: function(table) {
        // Now initialise the rows
        var rows = table.rows; //getElementsByTagName("tr")
        var config = table.tableDnDConfig;
        for (var i=0; i<rows.length; i++) {
            // To make non-draggable rows, add the nodrag class (eg for Category and Header rows) 
			// inspired by John Tarr and Famic
            var nodrag = $(rows[i]).hasClass("nodrag");
            if (! nodrag) { //There is no NoDnD attribute on rows I want to drag
                jQuery(rows[i]).mousedown(function(ev) {
                    if (ev.target.tagName == "TD") {
                        jQuery.tableDnD.dragObject = this;
                        jQuery.tableDnD.currentTable = table;
                        jQuery.tableDnD.mouseOffset = jQuery.tableDnD.getMouseOffset(this, ev);
                        if (config.onDragStart) {
                            // Call the onDrop method if there is one
                            config.onDragStart(table, this);
                        }
                        return false;
                    }
                }).css("cursor", "move"); // Store the tableDnD object
            }
        }
    },

    /** Get the mouse coordinates from the event (allowing for browser differences) */
    mouseCoords: function(ev){
        if(ev.pageX || ev.pageY){
            return {x:ev.pageX, y:ev.pageY};
        }
        return {
            x:ev.clientX + document.body.scrollLeft - document.body.clientLeft,
            y:ev.clientY + document.body.scrollTop  - document.body.clientTop
        };
    },

    /** Given a target element and a mouse event, get the mouse offset from that element.
        To do this we need the element's position and the mouse position */
    getMouseOffset: function(target, ev) {
        ev = ev || window.event;

        var docPos    = this.getPosition(target);
        var mousePos  = this.mouseCoords(ev);
        return {x:mousePos.x - docPos.x, y:mousePos.y - docPos.y};
    },

    /** Get the position of an element by going up the DOM tree and adding up all the offsets */
    getPosition: function(e){
        var left = 0;
        var top  = 0;
        /** Safari fix -- thanks to Luis Chato for this! */
        if (e.offsetHeight == 0) {
            /** Safari 2 doesn't correctly grab the offsetTop of a table row
            this is detailed here:
            http://jacob.peargrove.com/blog/2006/technical/table-row-offsettop-bug-in-safari/
            the solution is likewise noted there, grab the offset of a table cell in the row - the firstChild.
            note that firefox will return a text node as a first child, so designing a more thorough
            solution may need to take that into account, for now this seems to work in firefox, safari, ie */
            e = e.firstChild; // a table cell
        }

        while (e.offsetParent){
            left += e.offsetLeft;
            top  += e.offsetTop;
            e     = e.offsetParent;
        }

        left += e.offsetLeft;
        top  += e.offsetTop;

        return {x:left, y:top};
    },

    mousemove: function(ev) {
        if (jQuery.tableDnD.dragObject == null) {
            return;
        }

        var dragObj = jQuery(jQuery.tableDnD.dragObject);
        var config = jQuery.tableDnD.currentTable.tableDnDConfig;
        var mousePos = jQuery.tableDnD.mouseCoords(ev);
        var y = mousePos.y - jQuery.tableDnD.mouseOffset.y;
        //auto scroll the window
	    var yOffset = window.pageYOffset;
	 	if (document.all) {
	        // Windows version
	        //yOffset=document.body.scrollTop;
	        if (typeof document.compatMode != 'undefined' &&
	             document.compatMode != 'BackCompat') {
	           yOffset = document.documentElement.scrollTop;
	        }
	        else if (typeof document.body != 'undefined') {
	           yOffset=document.body.scrollTop;
	        }

	    }
		    
		if (mousePos.y-yOffset < config.scrollAmount) {
	    	window.scrollBy(0, -config.scrollAmount);
	    } else {
            var windowHeight = window.innerHeight ? window.innerHeight
                    : document.documentElement.clientHeight ? document.documentElement.clientHeight : document.body.clientHeight;
            if (windowHeight-(mousePos.y-yOffset) < config.scrollAmount) {
                window.scrollBy(0, config.scrollAmount);
            }
        }


        if (y != jQuery.tableDnD.oldY) {
            // work out if we're going up or down...
            var movingDown = y > jQuery.tableDnD.oldY;
            // update the old value
            jQuery.tableDnD.oldY = y;
            // update the style to show we're dragging
			if (config.onDragClass) {
				dragObj.addClass(config.onDragClass);
			} else {
	            dragObj.css(config.onDragStyle);
			}
            // If we're over a row then move the dragged row to there so that the user sees the
            // effect dynamically
            var currentRow = jQuery.tableDnD.findDropTargetRow(dragObj, y);
            if (currentRow) {
                // TODO worry about what happens when there are multiple TBODIES
                if (movingDown && jQuery.tableDnD.dragObject != currentRow) {
                    jQuery.tableDnD.dragObject.parentNode.insertBefore(jQuery.tableDnD.dragObject, currentRow.nextSibling);
                } else if (! movingDown && jQuery.tableDnD.dragObject != currentRow) {
                    jQuery.tableDnD.dragObject.parentNode.insertBefore(jQuery.tableDnD.dragObject, currentRow);
                }
            }
        }

        return false;
    },

    /** We're only worried about the y position really, because we can only move rows up and down */
    findDropTargetRow: function(draggedRow, y) {
        var rows = jQuery.tableDnD.currentTable.rows;
        for (var i=0; i<rows.length; i++) {
            var row = rows[i];
            var rowY    = this.getPosition(row).y;
            var rowHeight = parseInt(row.offsetHeight)/2;
            if (row.offsetHeight == 0) {
                rowY = this.getPosition(row.firstChild).y;
                rowHeight = parseInt(row.firstChild.offsetHeight)/2;
            }
            // Because we always have to insert before, we need to offset the height a bit
            if ((y > rowY - rowHeight) && (y < (rowY + rowHeight))) {
                // that's the row we're over
				// If it's the same as the current row, ignore it
				if (row == draggedRow) {return null;}
                var config = jQuery.tableDnD.currentTable.tableDnDConfig;
                if (config.onAllowDrop) {
                    if (config.onAllowDrop(draggedRow, row)) {
                        return row;
                    } else {
                        return null;
                    }
                } else {
					// If a row has nodrop class, then don't allow dropping (inspired by John Tarr and Famic)
                    var nodrop = $(row).hasClass("nodrop");
                    if (! nodrop) {
                        return row;
                    } else {
                        return null;
                    }
                }
                return row;
            }
        }
        return null;
    },

    mouseup: function(e) {
        if (jQuery.tableDnD.currentTable && jQuery.tableDnD.dragObject) {
            var droppedRow = jQuery.tableDnD.dragObject;
            var config = jQuery.tableDnD.currentTable.tableDnDConfig;
            // If we have a dragObject, then we need to release it,
            // The row will already have been moved to the right place so we just reset stuff
			if (config.onDragClass) {
	            jQuery(droppedRow).removeClass(config.onDragClass);
			} else {
	            jQuery(droppedRow).css(config.onDropStyle);
			}
            jQuery.tableDnD.dragObject   = null;
            if (config.onDrop) {
                // Call the onDrop method if there is one
                config.onDrop(jQuery.tableDnD.currentTable, droppedRow);
            }
            jQuery.tableDnD.currentTable = null; // let go of the table too
        }
    },

    serialize: function() {
        if (jQuery.tableDnD.currentTable) {
            var result = "";
            var tableId = jQuery.tableDnD.currentTable.id;
            var rows = jQuery.tableDnD.currentTable.rows;
            for (var i=0; i<rows.length; i++) {
                if (result.length > 0) result += "&";
                result += tableId + '[]=' + rows[i].id;
            }
            return result;
        } else {
            return "Error: No Table id set, you need to set an id on your table and every row";
        }
    }
}

jQuery.fn.extend(
	{
		tableDnD : jQuery.tableDnD.build
	}
);