/*
* AjaxObject is a an object that encapsulates the transaction
*     request and callback logic.
*
* handleSuccess( ) provides success case logic
* handleFailure( ) provides failure case logic
* processResult( ) displays the results of the response from both the
* success and failure handlers
* startRequest( ) calling this member starts the transaction request.
*
* Usage Example:
*
* // The location to the php script that process the JS request
* var php_script_location = 'ajax/ajax.php';
*
* // Create a new ajax object instance, pass in true to enable error catching
* var ajaxObj = new AjaxObject();
* 
* //Initializes the object to hold the query string formatted arguments
* //to be passed to the ajax object for processing
* var queryStringArgs = new Object();
* 
* //Will call the PHP script function getData().
* //Also passes arg1 and arg2 to the PHP script with keys: arg1, arg2, respectively
* queryStringArgs['func']    = 'getData';
* queryStringArgs['arg1']    = arg1;
* queryStringArgs['arg2']    = arg2;
* 
* //This defines what to do with the resuls of the ajax call to the 
* //designated script function
* ajaxObj.processResult = function (o)
* {
*   //Creates an array of output
* 	var result = o.responseText.split('&');
* 	alert(result)
* }
* 
* //This defines what to do with the resuls of the ajax call to the 
* //designated script function on failure
* ajaxObj.processFailure = function (o)
* {
*     alert('Yahoo connection manager failed.\n' + 
* 	           'Click OK to see the results.');
*     
*     var result = '';
*     
*     for (var i in o)
*     {
*         result += i + ' => ' + o[i] + '\n';
*     }
*     
*     alert(result);
* }
* 
* //Start the transaction.
* ajaxObj.startRequest(php_script_location, queryStringArgs);    
*
*/

function AjaxObject(errorReporting)
{
    //Initializes the errorReporting
    if (errorReporting !== undefined)
    {
        this.errorReporting = errorReporting;
    }
    else
    {
        this.errorReporting = false;
    }
     
	this.handleSuccess = function(o)
	{
	    //Parse out the error codes from the response
	    var output = o.responseText.split('%$^%ERROR%^$%');
	    
	    //If there were errors...
	    if (output.length > 1)
	    {
		    var error         = output[1];
    		o.responseText    = output[2];
	    }
	    //If error reporting is turned on...
		if (this.errorReporting)
		{
		    if (error !== undefined)
		    {
        		alert(error);
		    }
		}
		
		// This member handles the success response
		// and passes the response object o to AjaxObject's
		// processResult member.
		this.processResult(o);
	};

	this.handleFailure = function(o)
	{
		// Failure handler
		this.processFailure(o);
	};

	this.processResult = function(o)
	{
		// This member is called by handleSuccess
		// THIS METHOD SHOULD BE REDEFINED TO DO WHATEVER IS NEEDED
		// BY THE JS THAT IS INSTANTIATING THE AjaxObject
		// Example: AjaxObject.processResult = fuction (o) { alert('hello world'); }
	};

	this.processFailure = function(o)
	{
		// This member is called by handleFailure
		// THIS METHOD SHOULD BE REDEFINED TO DO WHATEVER IS NEEDED
		// BY THE JS THAT IS INSTANTIATING THE AjaxObject
		// Example: AjaxObject.processFailure = fuction (o) { alert('failure'); }
	};

	this.startRequest = function(phpScriptLoc, queryStringArgs, method)
	{
        /*
        * Define the callback object for success and failure
        * handlers as well as object scope.
        */
        var callback =
        {
        	success:   this.handleSuccess,
        	failure:   this.handleFailure,
        	scope:     this,
        	argument:  this
        };
        
        //Defaults the method to POST
        if (method === undefined)
        {
            method = 'POST';
        }
        
		var sendStr = this.postEncode(queryStringArgs);
		YAHOO.util.Connect.asyncRequest(method, phpScriptLoc, callback, sendStr);
	};
	
	/**
	 * Encodes a variable in a form acceptable to PHP
	 * 
	 * @param mixed variable       A variable of any type (functions gracefully ignored)
	 * @param string varname       Optional variable name; needed for scalars
	 *
	 * @return string              The encoded string
	 */
	this.postEncode = function(variable, varname)
    {
        var enc    = '';
        var prefix = '';
        
        switch (typeof(variable))
        {
            case 'array':
                prefix = '_';       // prefix this to the key names
                // drop through
            case 'object':
                if (undefined !== variable.innerHTML)        // uh-oh, must be a DOM object
                {
                    // just store the object's ID
                    enc += prefix + encodeURIComponent(varname) + '=' + encodeURIComponent(variable.id) + '&';
                }
                else
                {
                    for (var i in variable)
                    {
                        enc += this.postEncode(variable[i], (varname == null) ? i : varname + '[' + i + ']');
                    }
                }
                break;
                
            case 'boolean':
                enc += encodeURIComponent(varname) + '=' + (variable ? '1' : '') + '&';
                break;
                
            case 'function':
                break;
                
            default:
                // should we check for missing varname here?
                enc += encodeURIComponent(varname) + '=' + encodeURIComponent(variable) + '&';
                break;
        }
        
        if (varname === null)
        {
            enc = enc.substr(0, enc.length - 1);        // remove last '&'
        }
        return enc;
    };
}