/**
 * 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
      try
         {
            if (aSuggestions.length > 0) 
               {
                  if (bTypeAhead) 
                     {
                        this.typeAhead(aSuggestions[0]);
                     }
                  this.showSuggestions(aSuggestions);
               } 
            else 
               {
                  this.hideSuggestions();
               }
         }
      catch(e) 
         {
            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) 
         {
            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);
         }
   };

/**
 * 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();
         };
    
      //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);
         }
   };