/**
 * Convert a single file-input element into a 'multiple' input list
 *
 * Usage:
 *
 *   1. Create a file input element (no name)
 *      eg. <input type="file" id="first_file_element">
 *
 *   2. Create a DIV for the output to be written to
 *      eg. <div id="files_list"></div>
 *
 *   3. Instantiate a MultiSelector object, passing in the DIV and an (optional) maximum number of files
 *      eg. var multi_selector = new MultiSelector( document.getElementById( 'files_list' ), 3 );
 *
 *   4. Add the first element
 *      eg. multi_selector.addElement( document.getElementById( 'first_file_element' ) );
 *
 *   5. That's it.
 *
 *   You might (will) want to play around with the addListRow() method to make the output prettier.
 *
 *   You might also want to change the line 
 *       element.name = 'file_' + this.count;
 *   ...to a naming convention that makes more sense to you.
 * 
 * Licence:
 *   Use this however/wherever you like, just don't blame me if it breaks anything.
 *
 * Credit:
 *   If you're nice, you'll leave this bit:
 *  
 *   Class by Stickman -- http://www.the-stickman.com
 *      with thanks to:
 *      [for Safari fixes]
 *         Luis Torrefranca -- http://www.law.pitt.edu
 *         and
 *         Shawn Parker & John Pennypacker -- http://www.fuzzycoconut.com
 *      [for duplicate name bug]
 *         'neal'
 */
function MultiSelector( list_target, max ){

        // Where to write the list
        this.list_target = list_target;
        // How many elements?
        this.count = 0;
        // How many elements?
        this.id = 0;
        // Is there a maximum?
        if( max ){
                this.max = max;
        } else {
                this.max = -1;
        };
        
        /**
         * Add a new file input element
         */
        this.addElement = function( element ){

                // Make sure it's a file input element
                if( element.tagName == 'INPUT' && element.type == 'file' ){

                        // Element name -- what number am I?
                        element.name = 'file_' + this.id++;

                        // Add reference to this object
                        element.multi_selector = this;

                        // What to do when a file is selected
                        element.onchange = function(){

                                // New file input
                                var new_element = document.createElement( 'input' );
                                new_element.type = 'file';

                                // Add new element
                                this.parentNode.insertBefore( new_element, this );

                                // Apply 'update' to element
                                this.multi_selector.addElement( new_element );

                                // Update list
                                this.multi_selector.addListRow( this );

                                // Hide this: we can't use display:none because Safari doesn't like it
                                this.style.position = 'absolute';
                                this.style.left = '-1000px';

                        };
                        // If we've reached maximum number, disable input element
                        if( this.max != -1 && this.count >= this.max ){
                                element.disabled = true;
                        };

                        // File element counter
                        this.count++;
                        // Most recent element
                        this.current_element = element;
                        
                } else {
                        // This can only be applied to file input elements!
                        alert( 'Error: not a file input element' );
                };

        };

        /**
         * Add a new row to the list of files
         */
        this.addListRow = function( element ){

                // Row div
                var new_row = document.createElement( 'div' );
                new_row.className = 'file_upload_div';

                // Delete button
                var new_row_button = document.createElement( 'input' );
                new_row_button.type = 'button';
                new_row_button.value = ' ';
                new_row_button.className = 'button delete_one_nf';

                // References
                new_row.element = element;

                // Delete function
                new_row_button.onclick= function(){

                        // Remove element from form
                        this.parentNode.element.parentNode.removeChild( this.parentNode.element );

                        // Remove this row from the list
                        this.parentNode.parentNode.removeChild( this.parentNode );

                        // Decrement counter
                        this.parentNode.element.multi_selector.count--;

                        // Re-enable input element (if it's disabled)
                        this.parentNode.element.multi_selector.current_element.disabled = false;

                        // Appease Safari
                        //    without it Safari wants to reload the browser window
                        //    which nixes your already queued uploads
                        return false;
                };

                // Set row value
                new_row.innerHTML = element.value;

                // Add button
                new_row.appendChild( new_row_button );

                // Add it to the list
                this.list_target.appendChild( new_row );
                
        };

};