/*
 * This function should be called when handling a redirect from facebook.
 * 
 *
 */
function tvg_HandleFacebookRedirect(referrer, target, callback, userid)
{
    var accessToken = window.location.hash.substring(1);
    var path = "https://graph.facebook.com/me?";
    var query = accessToken+"&callback=?";
    var url = path + query;

    // use jsonp to call the graph
    getJSONP(url, function(data){

        //store the access token, call add contact with a userid if one is found 
        var contact = data.id;
        var token = accessToken.split('=')[1];
        token = token.replace('&expires_in', '');
        
        //call add contact to add contact if needed (will not add contact if not needed)
        tvgAddContact(contact, token, 'FB', referrer, target, userid);

        //update the parent 
        if(target!='_self') {
            window.opener.tvgSetCookie('tvgContact', contact);
            window.opener.tvgSetCookie('tvgPasswordHash', contact);
            
            //fire a custom call back function on the parent window
            var elem = window.opener.window[callback](contact, 'FB', referrer);           
            
            //close window 
            setTimeout(function() { window.close()}, 200);
        }
        else 
        {
            //handle case when this is self (redirected)
        }
        
    });       
}

/**
 * function to call the add contact component
 */
function tvgAddContact(contact, token, type, referrer, target, userid)
{
    if(target!='_self') {
        tvgHostUrl = window.opener.tvgHostUrl;
    }
    
    var params = "&tvgReferrer="+referrer+"&tvgContact="+contact+"&tvgType="+type+"&tvgAccessToken="+token;
    if(userid != undefined)
        params += "&tvgUserID="+userid;
        
    //Add the contact
    tvgLoadComponent ("?name=addcontact"+params, "tvgConnect");
}

/*
 * Call a url in JSONP format.
 *
 */
function getJSONP(url, success) {

    var ud = '_' + +new Date,
        script = document.createElement('script'),
        head = document.getElementsByTagName('head')[0] 
               || document.documentElement;

    window[ud] = function(data) {
        head.removeChild(script);
        success && success(data);
    };

    script.src = url.replace('callback=?', 'callback=' + ud);
    head.appendChild(script);
}