function prevent_default_event_handling( e )
{
	if (window.event)
	{
		window.event.returnValue = false;
	}
 	else
	{
 		e.preventDefault();
 	}
}

/**
 * An autosuggest textbox control.
 * @class
 * @scope public
 */
function AutoSuggestControl(oTextbox /*:HTMLInputElement*/,
                            oProvider /*:SuggestionProvider*/) {

    /**
     * The currently selected suggestions.
     * @scope private
     */
    this.cur /*:int*/ = -1;

    /**
     * The dropdown list layer.
     * @scope private
     */
    this.layer = null;

    /**
     * Suggestion provider for the autosuggest feature.
     * @scope private.
     */
    this.provider /*:SuggestionProvider*/ = oProvider;

		this.separator = "---------";

    /**
     * The textbox to capture.
     * @scope private
     */
    this.textbox /*:HTMLInputElement*/ = oTextbox;
		this.textbox.setAttribute("autocomplete","off");
    //initialize the control
    this.init();

}

/**
 * Autosuggests one or more suggestions for what the user has typed.
 * If no suggestions are passed in, then no autosuggest occurs.
 * @scope private
 * @param aSuggestions An array of suggestion strings.
 * @param bTypeAhead If the control should provide a type ahead suggestion.
 */
AutoSuggestControl.prototype.autosuggest = function (aSuggestions /*:Array*/,
                                                     bTypeAhead /*:boolean*/) {

    //make sure there's at least one suggestion
    if (aSuggestions.length > 0) {
        if (bTypeAhead)
				{
           this.typeAhead(aSuggestions[0]);
           this.cur = 0;
        }

        this.showSuggestions(aSuggestions);
    } else {
        this.hideSuggestions();
    }
};

/**
 * Creates the dropdown layer to display multiple suggestions.
 * @scope private
 */
AutoSuggestControl.prototype.createDropDown = function ()
{
  var oThis = this;

  //create the layer and assign styles
  this.layer = document.createElement("div");
  this.layer.className = "suggestions";
  this.layer.style.visibility = "hidden";
  this.layer.style.width = this.textbox.offsetWidth;

  //when the user clicks on the a suggestion, get the text (innerHTML)
  //and place it into a textbox
  this.layer.onmousedown =
  this.layer.onmouseup =
  this.layer.onmouseover = function (oEvent)
	{
    oEvent = oEvent || window.event;
    oTarget = oEvent.target || oEvent.srcElement;

    if (oEvent.type == "mousedown")
		{
			if ( oTarget.firstChild.nodeValue.indexOf( oThis.separator ) == -1 )
			{
				oThis.showSuggestion( oTarget.firstChild.nodeValue );
				oThis.hideSuggestions();
			}
    }
		else if (oEvent.type == "mouseover")
		{
			oThis.highlightSuggestion( oTarget );
    }
		else
		{
			oThis.textbox.focus();
    }
  };

  document.body.appendChild(this.layer);
};

/**
 * Gets the left coordinate of the textbox.
 * @scope private
 * @return The left coordinate of the textbox in pixels.
 */
AutoSuggestControl.prototype.getLeft = function () /*:int*/ {

    var oNode = this.textbox;
    var iLeft = 0;

    while(oNode.tagName != "BODY") {
        iLeft += oNode.offsetLeft;
        oNode = oNode.offsetParent;
    }

    return iLeft;
};

/**
 * Gets the top coordinate of the textbox.
 * @scope private
 * @return The top coordinate of the textbox in pixels.
 */
AutoSuggestControl.prototype.getTop = function () /*:int*/ {

    var oNode = this.textbox;
    var iTop = 0;

    while(oNode.tagName != "BODY") {
        iTop += oNode.offsetTop;
        oNode = oNode.offsetParent;
    }

    return iTop;
};

/**
 * Handles three keydown events.
 * @scope private
 * @param oEvent The event object for the keydown event.
 */
AutoSuggestControl.prototype.handleKeyDown = function (oEvent /*:Event*/) {

    switch(oEvent.keyCode) {
        case 38: //up arrow
          this.previousSuggestion();
          prevent_default_event_handling( oEvent );
          break;
        case 40: //down arrow
          this.nextSuggestion();
          prevent_default_event_handling( oEvent );
          break;
        case 13: //enter
        {
				  if (this.textbox.createTextRange || this.textbox.setSelectionRange)
					{
						if ( this.textbox.setSelectionRange )
						{
							if ( this.suggestionsVisible() || this.textbox.selectionStart != this.textbox.selectionEnd )
							{
								this.textbox.value += ", ";
								this.textbox.selectionStart = this.textbox.selectionEnd;
	          		prevent_default_event_handling( oEvent );
							}
						}
						else
						{
							var oRange = this.textbox.createTextRange();
							if ( this.suggestionsVisible() || oRange.text != "" )
							{
								this.textbox.value += ", ";
				        oRange.moveStart("character", this.textbox.value.length);
				        oRange.moveEnd("character", this.textbox.value.length);
				        oRange.select();
	          		prevent_default_event_handling( oEvent );
							}
						}
			    }

			    //set focus back to the textbox
			    this.textbox.focus();
          this.hideSuggestions();
          break;
        }
    }

};

/**
 * Handles keyup events.
 * @scope private
 * @param oEvent The event object for the keyup event.
 */
AutoSuggestControl.prototype.handleKeyUp = function (oEvent /*:Event*/) {

    var iKeyCode = oEvent.keyCode;

    //for backspace (8) and delete (46), shows suggestions without typeahead
    if (iKeyCode == 8 || iKeyCode == 46) {
        this.provider.requestSuggestions(this, false);

    //make sure not to interfere with non-character keys
    } else if (iKeyCode < 32 || (iKeyCode >= 33 && iKeyCode < 46) || (iKeyCode >= 112 && iKeyCode <= 123)) {
        if ( iKeyCode == 13 )
				{
        	prevent_default_event_handling( oEvent );
        }
    } else {
        //request suggestions from the suggestion provider with typeahead
        this.provider.requestSuggestions(this, true);
    }
};

/**
 * Hides the suggestion dropdown.
 * @scope private
 */
AutoSuggestControl.prototype.hideSuggestions = function () {
    this.layer.style.visibility = "hidden";
};

AutoSuggestControl.prototype.suggestionsVisible = function () {
    return this.layer.style.visibility != "hidden";
};

/**
 * Highlights the given node in the suggestions dropdown.
 * @scope private
 * @param oSuggestionNode The node representing a suggestion in the dropdown.
 */
AutoSuggestControl.prototype.highlightSuggestion = function (oSuggestionNode)
{
  for (var i=0; i < this.layer.childNodes.length; i++)
	{
    var oNode = this.layer.childNodes[i];
    if ( oNode == oSuggestionNode )
		{
			if ( oNode.firstChild.nodeValue.indexOf( this.separator ) == -1 )
			{
				oNode.className = "current"
			}
    } else if (oNode.className == "current")
		{
			oNode.className = "";
    }
  }
};

/**
 * Initializes the textbox with event handlers for
 * auto suggest functionality.
 * @scope private
 */
AutoSuggestControl.prototype.init = function () {

    //save a reference to this object
    var oThis = this;

    //assign the onkeyup event handler
    this.textbox.onkeyup = function (oEvent) {

        //check for the proper location of the event object
        if (!oEvent) {
            oEvent = window.event;
        }

        //call the handleKeyUp() method with the event object
        oThis.handleKeyUp(oEvent);
    };

    //assign onkeydown event handler
    this.textbox.onkeydown = function (oEvent) {

        //check for the proper location of the event object
        if (!oEvent) {
            oEvent = window.event;
        }

        //call the handleKeyDown() method with the event object
        oThis.handleKeyDown(oEvent);
    };

    //assign onblur event handler (hides suggestions)
    this.textbox.onblur = function () {
        oThis.hideSuggestions();
    };

    //create the suggestions dropdown
    this.createDropDown();
};

/**
 * Highlights the next suggestion in the dropdown and
 * places the suggestion into the textbox.
 * @scope private
 */
AutoSuggestControl.prototype.nextSuggestion = function () {
    var cSuggestionNodes = this.layer.childNodes;

    if (cSuggestionNodes.length > 0 && this.cur < cSuggestionNodes.length-1)
		{
      var oNode = cSuggestionNodes[++this.cur];
      if ( oNode.firstChild.nodeValue.indexOf( this.separator ) == -1)
			{
        this.highlightSuggestion(oNode);
				this.showSuggestion( oNode.firstChild.nodeValue );
      }
      else
      {
      	this.nextSuggestion();
      }
    }
};

/**
 * Highlights the previous suggestion in the dropdown and
 * places the suggestion into the textbox.
 * @scope private
 */
AutoSuggestControl.prototype.previousSuggestion = function () {
    var cSuggestionNodes = this.layer.childNodes;

    if (cSuggestionNodes.length > 0 && this.cur > 0)
		{
      var oNode = cSuggestionNodes[--this.cur];
      var strSeparator = "---------";
      if ( oNode.firstChild.nodeValue.indexOf( this.separator ) == -1)
			{
        this.highlightSuggestion(oNode);
				this.showSuggestion( oNode.firstChild.nodeValue );
      }
      else
      {
      	this.previousSuggestion();
      }
    }
};

/**
 * Places the suggestion into the textbox.
 * @scope private
 */
AutoSuggestControl.prototype.showSuggestion = function ( strSuggestion /*:string*/ ) {
		var strTextboxValue = this.textbox.value;
    var iLastComma = strTextboxValue.lastIndexOf( "," );
		var strNewText = strSuggestion;
		var regExp;

		if ( iLastComma != -1 )
		{
			strNewText = strTextboxValue.substring( iLastComma + 1, strTextboxValue.length );
			regExp = new RegExp( strNewText.replace( / /, "" ) + "$" );
			strNewText = strTextboxValue.replace( regExp, "" );
			strNewText += strSuggestion;
		}

    this.textbox.value = strNewText;
};

/**
 * Selects a range of text in the textbox.
 * @scope public
 * @param iStart The start index (base 0) of the selection.
 * @param iLength The number of characters to select.
 */
AutoSuggestControl.prototype.selectRange = function (iStart /*:int*/, iLength /*:int*/) {

    //use text ranges for Internet Explorer
    if (this.textbox.createTextRange) {
        var oRange = this.textbox.createTextRange();
        oRange.moveStart("character", iStart);
        oRange.moveEnd("character", iLength - this.textbox.value.length);
        oRange.select();

    //use setSelectionRange() for Mozilla
    } else if (this.textbox.setSelectionRange) {
        this.textbox.setSelectionRange(iStart, iLength);
    }

    //set focus back to the textbox
    this.textbox.focus();
};

/**
 * Builds the suggestion layer contents, moves it into position,
 * and displays the layer.
 * @scope private
 * @param aSuggestions An array of suggestions for the control.
 */
AutoSuggestControl.prototype.showSuggestions = function (aSuggestions /*:Array*/) {

    var oDiv = null;
    this.layer.innerHTML = "";  //clear contents of the layer

    for (var i=0; i < aSuggestions.length; i++) {
        oDiv = document.createElement("div");
        oDiv.appendChild(document.createTextNode(aSuggestions[i]));
        this.layer.appendChild(oDiv);
    }

    this.layer.style.left = this.getLeft() + "px";
    this.layer.style.top = (this.getTop()+this.textbox.offsetHeight) + "px";
    this.layer.style.visibility = "visible";

};

/**
 * Inserts a suggestion into the textbox, highlighting the
 * suggested part of the text.
 * @scope private
 * @param sSuggestion The suggestion for the textbox.
 */
AutoSuggestControl.prototype.typeAhead = function (sSuggestion /*:String*/) {

    //check for support of typeahead functionality
    if (this.textbox.createTextRange || this.textbox.setSelectionRange)
		{
				var strTextboxValue = this.textbox.value;
        var iLen = strTextboxValue.length;
		    var iLastComma = strTextboxValue.lastIndexOf( "," );
				var strLastTag = "";

				if ( iLastComma != -1 )
				{
					strLastTag = strTextboxValue.substring( iLastComma + 1, strTextboxValue.length );
					strLastTag = strLastTag.replace( / /, "" );
				}
				else
				{
					strLastTag = strTextboxValue;
				}
				strLastTag = sSuggestion.replace( strLastTag, "" );
        this.textbox.value += strLastTag;

				this.selectRange(iLen, this.textbox.value.length );
    }
};