/**
  * 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;

     /**
      * The textbox to capture.
      * @scope private
      */
     this.textbox /*:HTMLInputElement*/ = oTextbox;

     //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.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") {
             oThis.textbox.value = 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();
             break;
         case 40: //down arrow
             this.nextSuggestion();
             break;
         case 13: //enter
             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 || iKeyCode == 13) {
         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)) {
         //ignore
     } else {
         //request suggestions from the suggestion provider with typeahead
         this.provider.requestSuggestions(this, true);
     }
 };

 AutoSuggestControl.prototype.handleFocus = function () {
     this.provider.requestSuggestions(this, false);
 };

 /**
  * Hides the suggestion dropdown.
  * @scope private
  */
 AutoSuggestControl.prototype.hideSuggestions = function () {
     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) {
             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();
     };

     this.textbox.onfocus = function () {
         oThis.handleFocus();
     }

     //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];
         this.highlightSuggestion(oNode);
         this.textbox.value = oNode.firstChild.nodeValue;
     }
 };

 /**
  * 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];
         this.highlightSuggestion(oNode);
         this.textbox.value = oNode.firstChild.nodeValue;
     }
 };

 /**
  * 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 iLen = this.textbox.value.length;
         this.textbox.value = sSuggestion;
         this.selectRange(iLen, sSuggestion.length);
     }
 };