/**
 * An autosuggest textbox control.
 * @class
 * @scope public
 * @param oTextbox HTMLInputElement
 * @param oProvider SuggestionProvider
 */
function AutoSuggestControl(oTextbox, oProvider) {
	/**
	 * The currently selected suggestions.
	 * @scope private
	 */   
	this.cur = -1;
	
	/**
	 * The dropdown list layer.
	 * @scope private
	 */
	this.layer = null;
	
	/**
	 * Suggestion provider for the autosuggest feature.
	 * @scope private.
	 */
	this.provider = oProvider;
	
	/**
	 * The textbox to capture.
	 * @scope private
	 */
	this.textbox = 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, bTypeAhead) {
	// 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 () {
	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 () {
	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) {
	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) {
	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, iLength) {
	//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) {
	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) {
	//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);
	}
};