//CONSTRUCTOR FOR THE HRD_AJAXCLIENT OBJECT
function AjaxClient ()
{
	this.DeclareVariables = DeclareVariables;
	this.DeclareFunctions = DeclareFunctions;
	
	this.DeclareVariables();
	this.DeclareFunctions();
	
}//HRD_AjaxClient 

//FUNCTION DECLARING ALL THE VARIABLES NEEDED
function DeclareVariables()
{
	this.baseUrl = ''; //THE URL OF THE SERVER
	this.callType = 'GET';	//THE TYPE OF CALL TO BE MADE
	this.command = '';	//THE COMMAND TO BE EXECUTED ON THE GIVEN URL
	this.async = true;	//BOOLEAN DETERMINING WHETHER OR NOT THE CALL IS MADE ASYNCHRONOUSLY
	
	this.parameters = null;	//ARRAY OF PARAMETER OBJECTS USED IN POST REQUESTS
	this.responseHandler = null;	//DELEGATE FOR THE METHOD WHICH WILL HANDLE THE SERVER RESPONSE
	
	this.returnsXML = false;	//BOOLEAN DETERMINING WHETHER THE REQUEST RETURNS XML OR TEXT
	this.requestObject = null;	//THE REQUEST OBJECT
	
}//DeclareVariables

//FUNCTION DECLARING ALL THE FUNCTIONS AVAILABLE
function DeclareFunctions()
{
	//PROPERTY SETTERS
	this.SetUrl = SetUrl;
	this.SetCallType = SetCallType;
	
	this.SetCommand = SetCommand;	
	this.SetAsync = SetAsync;	
	
	this.AddParameter = AddParameter;
	this.ClearParameters = ClearParameters;
	
	this.SetTypeToPost = SetTypeToPost;
	this.SetTypeToGet = SetTypeToGet;
	
	this.SetResponseHandler = SetResponseHandler;
	
	this.ReturnXML = ReturnXML;
	
	//FUNCTIONAL FUNCTIONS
	this.GetUrl = GetUrl;
	
	this.GetUpperType = GetUpperType;
	this.GetLowerType = GetLowerType;
	
	this.GetParameters = GetParameters;	//FUNCTION USED TO 'COMPILE' THE PARAMETERS IN A SUITABLE QUERY STRING
	
	this.GetResponseXML = GetResponseXML;
	this.GetResponseText = GetResponseText;
	
	this.InitializeRequest = InitializeRequest;// INITIALIZE THE REQUEST OBEJCT
	this.ExecuteRequest = ExecuteRequest;	//EXECUTES THE AJAX REQUEST
	this.HandleServerResponse = HandleServerResponse;	//METHOD HANDLING THE ONREADYSTATECHANGE OF THE REQUEST OBJECT
	
}//DeclareFunctions

/*
------------------------------------------------------------------
		PROPERTY SETTERS OF THE AJAX CLIENT 
------------------------------------------------------------------
*/

function SetUrl ( url ) {	this.baseUrl = url;	}//SetUrl
function SetCallType ( type ) { this.callType = type;	}//SetCallType
function SetCommand ( command )	{	this.command = command;	}//SetCommand 
function SetAsync ( async )	{	this.async = async;	}//SetAsync

function SetTypeToPost()	{	this.SetCallType('POST');	}//SetTypeToPost
function SetTypeToGet()	{	this.SetCallType('GET');	}//SetTypeToGet
	
//FUNCTION USED TO ADD A PARAMETER TO THE ARRAY
function AddParameter ( name, value ) 
{	
	if ( this.parameters === null )
		this.parameters = new Array();
		
	this.parameters[ this.parameters.length ] = new Parameter( name, value );
}//AddParameter

//FUNCTION USED TO CLEAR THE PARAMETER ARRAY
function ClearParameters ()	
{	
	if ( this.parameters !== null )
		this.parameters.length = 0;	
}//ClearParameters

function ReturnXML ( returnXML ) {	this.returnsXML = returnXML;	}//ReturnXML

function SetResponseHandler ( responseHandler ) { 	this.responseHandler = responseHandler; 	}//SetResponseHandler

/*
------------------------------------------------------------------
		PROPERTY GETTERS OF THE AJAX CLIENT 
------------------------------------------------------------------
*/
//FUNCTION USED TO RETRIEVE THE URL. IF A COMMAND IS SPECIFIED, IT IS APPENDED AS A QUERYSTRING TO THE BASE URL
function GetUrl()
{
	var urlFormat = '{0}{1}';
	var sb = new StringBuilder();

	//sb.Append ( this.baseUrl );

	if ( this.command != '' )
	{
		sb.Append ( '?' );
		sb.Append ( this.GetLowerType() );
		sb.Append ( '=' );
		sb.Append ( this.command );
	}//if
	else if ( this.GetUpperType() == 'POST' )
	{
		sb.Append ( '?' );
		sb.Append ( this.GetLowerType() );
		sb.Append ( '=' );
		sb.Append ( 'true' );
	}//else if
	
	var params = this.GetParameters();
	
	if ( params !== null )
	{
		sb.Append ( ( sb.GetLength() > 0 ) ? '&' : '?' );
		sb.Append ( this.GetParameters() );
	}//if
	
	var retUrl = Format( urlFormat, this.baseUrl , sb.ToString() );

	return retUrl;
	
}//GetUrl

function GetUpperType()
{
	return this.callType.toUpperCase();
}//GetUpperType

function GetLowerType()
{
	return this.callType.toLowerCase();
}//GetLowerType
	
//FUNCTION USED TO CONCATINATE THE PARAMETERS IN A STRING, ONLY IF THE CALL TYPE IS 'POST'
function GetParameters()
{
	if ( ( this.parameters === null ) || ( this.parameters.length == 0 ) )
		return null;
	 
	var sBuilder = new StringBuilder();
	
	for ( var i = 0; i < this.parameters.length; i++ )
	{
		if ( i > 0 ) sBuilder.Append('&');
		
		sBuilder.Append (this.parameters[i].name);
		sBuilder.Append ('=');
		sBuilder.Append (this.parameters[i].value);
	}//for
	
	return sBuilder.ToString();

}//GetParameters

function GetResponseXML()
{
	if ( this.requestObject !== null )
		return this.requestObject.responseXML;
	else
		return undefined;
}//GetResponseXML

function GetResponseText()
{
	if ( this.requestObject !== null )
		return this.requestObject.responseText;
	else
		return undefined;
}//GetResponseText

	
/*
------------------------------------------------------------------
		REQUEST EXECUTION FUNCTIONS OF THE AJAX CLIENT 
------------------------------------------------------------------
*/

//FUNCTION USED TO INITIALIZE THE REQUEST OBJECT
function InitializeRequest ( url, responseHandler, command, type )
{
	if ( url !== undefined )
		this.SetUrl ( url );
	
	if ( responseHandler !== undefined )
		this.SetResponseHandler ( responseHandler );
	
	if ( command !== undefined )
		this.SetCommand ( command );
		
	if ( type !== undefined )
		this.SetCallType ( type );
		
}//InitializeRequest

//FUNCTION USED TO EXECUTE A REQUEST USING THE SET PROPERTIES AND VARIABLES
function ExecuteRequest()
{
	window ['ajaxClient'] = this;
	
	var paramString = this.GetParameters();
	var callType = this.GetUpperType();
	
	this.requestObject = GetRequestObject();
	
	this.requestObject.open ( callType , this.GetUrl() , this.async );
	
	if ( callType == 'POST' )
	{
		this.requestObject.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
		this.requestObject.setRequestHeader("Content-length", ( ( paramString === null ) ? 0 : paramString.length ) );
	}//if
	
	if ( this.async )
	{
		this.requestObject.onreadystatechange = HandleServerResponse;
		this.requestObject.send ( paramString );
	}//if
	else
	{
		this.requestObject.send ( paramString );
		
		var retVal = ( ( this.returnsXML ) ? this.requestObject.responseXml : this.requestObject.responseText );
		
		this.responseHandler ( retVal );
		this.ClearParameters();
	}//if	  
}//ExecuteRequest

//FUNCTION USED TO HANDLE THE SERVER RESPONSE
function HandleServerResponse()
{
	var client = window ['ajaxClient'];
	
	if ( client.requestObject.readyState == 4 )
	{
		var retVal = ( ( client.returnsXML )? client.GetResponseXML() : client.GetResponseText() );
		client.responseHandler ( retVal );
		client.ClearParameters();
	}//if is Ready
}//HandleServerResponse

/*
------------------------------------------------------------------
		STATIC FUNCTIONS USED BY THE AJAX CLIENT 
------------------------------------------------------------------
*/

//FUNCTION USED TO CREATE A REQUEST OBJECT
function GetRequestObject()
{
	var requestObject = null;
	
	if (window.ActiveXObject)
		requestObject = new ActiveXObject("Microsoft.XMLHTTP");
	else if (window.XMLHttpRequest)
		requestObject = new XMLHttpRequest();	
	
	return requestObject;
}//GetRequestObject

/*
------------------------------------------------------------------
		SECONDARY OBJECTS USED BY HRD_AjaxClient 
------------------------------------------------------------------
*/

//STRING BUIDLER OBJECT USED TO CONCATINATE STRINGS IN ONE VARIABLE
function StringBuilder() 
{
  this._strings = [];
  this.Append = function(s) { if ( s !== null ) this._strings.push(s); };
  this.GetLength = function() { return ( this.ToString() ).length;	} 
  this.ToString = function() { return this._strings.join(''); };
}//StringBuilder

//PARAMTER OBJECT USED TO CONTAIN THE PARAMETERS TO BE SENT TO THE SERVER
function Parameter ( name, value )
{
	this.name = name;
	this.value = value;
}//Parameter

//FUNCTION PROVIDING THE FUNCTIONALITY SIMILIAR TO THAT OF C# STRING.FORMAT 
function Format(str)
{
  for(i = 1; i < arguments.length; i++)
  	str = str.replace('{' + (i - 1) + '}', arguments[i]);

  return str;
}//StrFormat