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<com:TContent ID="body">
2 
	<h1 id="18008">Building an AJAX Chat Application</h1>
3 
	<com:RequiresVersion Version="3.1a" />
4 
	<p id="90081" class="block-content">This tutorial introduces the Prado web application framework's
5 
	<a href="?page=Database.ActiveRecord">ActiveRecord</a>
6 
	and <a href="?page=ActiveControls.Home">Active Controls</a> to build a Chat
7 
	web application. It is assumed that you
8 
	are familiar with PHP and you have access to a web server that is able to serve PHP5 scripts.
9 
	This basic chat application will utilize the following ideas/components in Prado.
10 
	</p>
11 
	<ul id="u1" class="block-content">
12 
		<li>Building a custom User Manager class.</li>
13 
		<li>Authenticating and adding a new user to the database.</li>
14 
		<li>Using ActiveRecord to interact with the database.</li>
15 
		<li>Using Active Controls and callbacks to implement the user interface.</li>
16 
		<li>Separating application logic and application flow.</li>
17 
	</ul>
18 
 
19 
	<p id="90082" class="block-content">In this tutorial you will build an AJAX Chat web application that allows
20 
		multiple users to communicate through their web browser.
21 
		The application consists of two pages: a login page
22 
		that asks the user to enter their nickname and the main application chat
23 
		page.
24 
		You can try the application <a href="../chat/index.php">locally</a> or at
25 
		<a href="http://www.pradosoft.com/demos/chat/">Pradosoft.com</a>.
26 
		The main application chat page is shown bellow.
27 
		<img src=<%~ chat1.png %> class="figure" />
28 
	</p>
29 
 
30 
	<h1 id="18009">Download, Install and Create a New Application</h1>
31 
	<p id="90083" class="block-content">The download and installation steps are similar to those in
32 
	the <a href="?page=Tutorial.CurrencyConverter#download">Currency converter tutorial</a>.
33 
	To create the application, we run from the command line the following.
34 
	See the <a href="?page=GettingStarted.CommandLine">Command Line Tool</a>
35 
		for more details.
36 
<com:TTextHighlighter Language="text" CssClass="source block-content" id="code_90027">
37 
php prado/framework/prado-cli.php -c chat
38 
</com:TTextHighlighter>
39 
	</p>
40 
 
41 
	<p id="90084" class="block-content">The above command creates the necessary directory structure and minimal
42 
		files (including "index.php" and "Home.page") to run a Prado  web application.
43 
		Now you can point your browser's URL to the web server to serve up
44 
		the <tt>index.php</tt> script in the <tt>chat</tt> directory.
45 
		You should see the message "Welcome to Prado!"
46 
	</p>
47 
 
48 
	<h1 id="18010">Authentication and Authorization</h1>
49 
	<p id="90085" class="block-content">The first task for this application is to ensure that each user
50 
	of the chat application is assigned with a unique (chosen by the user)
51 
	username. To achieve this, we can secure the main chat application
52 
	page to deny access to anonymous users. First, let us create the <tt>Login</tt>
53 
	page with the following code. We save the <tt>Login.php</tt> and <tt>Login.page</tt>
54 
	in the <tt>chat/protected/pages/</tt> directory (there should be a <tt>Home.page</tt>
55 
	file created by the command line tool).
56 
	</p>
57 
<com:TTextHighlighter Language="php" CssClass="source block-content" id="code_90028">
58 
&lt;?php
59 
class Login extends TPage
60 
{
61 
}
62 
?&gt;
63 
</com:TTextHighlighter>
64 
<com:TTextHighlighter Language="prado" CssClass="source block-content" id="code_90029">
65 
<!doctype html public "-//W3C//DTD XHTML 1.0 Strict//EN"
66 
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
67 
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
68 
<head>
69 
    <title>Prado Chat Demo Login</title>
70 
</head>
71 
<body>
72 
&lt;com:TForm&gt;
73 
    <h1 class="login">Prado Chat Demo Login</h1>
74 
    <fieldset class="login">
75 
        <legend>Please enter your name:</legend>
76 
        <div class="username">
77 
            &lt;com:TLabel ForControl="username" Text="Username:" /&gt;
78 
            &lt;com:TTextBox ID="username" MaxLength="20" /&gt;
79 
            &lt;com:TRequiredFieldValidator
80 
                ControlToValidate="username"
81 
                Display="Dynamic"
82 
                ErrorMessage="Please provide a username." /&gt;
83 
        </div>
84 
        <div class="login-button">
85 
            &lt;com:TButton Text="Login" /&gt;
86 
        </div>
87 
&lt;/com:TForm&gt;
88 
</body>
89 
</html>
90 
</com:TTextHighlighter>
91 
	<p id="90086" class="block-content">The login page contains
92 
	a <com:DocLink ClassPath="System.Web.UI.TForm" Text="TForm" />,
93 
	a <com:DocLink ClassPath="System.Web.UI.WebControls.TTextBox" Text="TTextBox" />,
94 
	a <com:DocLink ClassPath="System.Web.UI.WebControls.TRequiredFieldValidator" Text="TRequiredFieldValidator" />
95 
	and a <com:DocLink ClassPath="System.Web.UI.WebControls.TButton" Text="TButton" />. The resulting
96 
	page looks like the following (after applying some a style sheet).
97 
	<img src=<%~ chat2.png %> class="figure" />
98 
	If you click on the <tt>Login</tt> button without entering any
99 
	text in the username textbox, an error message is displayed. This is
100 
	due to the <com:DocLink ClassPath="System.Web.UI.WebControls.TRequiredFieldValidator" Text="TRequiredFieldValidator" />
101 
	requiring the user to enter some text in the textbox before proceeding.
102 
	</p>
103 
<h2 id="18019">Securing the <tt>Home</tt> page</h2>
104 
<p id="90087" class="block-content">Now we wish that if the user is trying to access the main application
105 
page, <tt>Home.page</tt>, before they have logged in, the user is presented with
106 
the <tt>Login.page</tt> first. We add a <tt>chat/protected/application.xml</tt> configuration
107 
file to import some classes that we shall use later.
108 
<com:TTextHighlighter Language="xml" CssClass="source block-content" id="code_90030">
109 
<?xml version="1.0" encoding="utf-8"?>
110 
<application id="Chat" Mode="Debug">
111 
  <paths>
112 
    <using namespace="System.Data.*" />
113 
    <using namespace="System.Data.ActiveRecord.*" />
114 
    <using namespace="System.Security.*" />
115 
    <using namespace="System.Web.UI.ActiveControls.*" />
116 
  </paths>
117 
</application>
118 
</com:TTextHighlighter>
119 
Next, we add a <tt>chat/protected/pages/config.xml</tt> configuration file to
120 
secure the <tt>pages</tt> directory.
121 
<com:TTextHighlighter Language="xml" CssClass="source block-content" id="code_90031">
122 
<?xml version="1.0" encoding="utf-8"?>
123 
<configuration>
124 
  <modules>
125 
    <module id="users" class="TUserManager" />
126 
    <module id="auth" class="TAuthManager" UserManager="users" LoginPage="Login" />
127 
  </modules>
128 
  <authorization>
129 
    <allow pages="Login" users="?" />
130 
    <allow roles="normal" />
131 
    <deny users="*" />
132 
  </authorization>
133 
</configuration>
134 
</com:TTextHighlighter>
135 
We setup the authentication using the default classes as explained in the
136 
<a href="?page=Advanced.Auth">authentication/authorization quickstart</a>.
137 
In the authorization definition, we allow anonymous users to access the
138 
<tt>Login</tt> page (anonymous users is specified by the <tt>?</tt> question mark).
139 
We allow any users with role equal to "normal" (to be defined later)
140 
to access all the pages, that is, the <tt>Login</tt> and <tt>Home</tt> pages.
141 
Lastly, we deny all users without any roles to access any page. The authorization
142 
rules are executed on first match basis.
143 
</p>
144 
 
145 
<p id="90088" class="block-content">If you now try to access the <tt>Home</tt> page by pointing your browser
146 
to the <tt>index.php</tt> you will be redirected to the <tt>Login</tt> page.
147 
</p>
148 
 
149 
<h1 id="18011">Active Record for <tt>chat_users</tt> table</h1>
150 
<p id="90089" class="block-content">The <com:DocLink ClassPath="System.Secutity.TUserManager" Text="TUserManager" />
151 
class only provides a read-only list of users. We need to be able to add or
152 
login new users dynamically. So we need to create our own user manager class.
153 
First, we shall setup a database with a <tt>chat_users</tt> table and create an ActiveRecord
154 
that can work with the <tt>chat_users</tt> table with ease. For the demo, we
155 
use <tt>sqlite</tt> as our database for ease of distributing the demo. The demo
156 
can be extended to use other databases such as MySQL or Postgres SQL easily.
157 
We define the <tt>chat_users</tt> table as follows.
158 
<com:TTextHighlighter Language="text" CssClass="source block-content" id="code_90032">
159 
CREATE TABLE chat_users
160 
(
161 
	username VARCHAR(20) NOT NULL PRIMARY KEY,
162 
	last_activity INTEGER NOT NULL DEFAULT "0"
163 
);
164 
</com:TTextHighlighter>
165 
Next we define the corresponding <tt>ChatUserRecord</tt> class and save it as
166 
<tt>chat/protected/App_Code/ChatUserRecord.php</tt> (you need to create the
167 
<tt>App_Code</tt> directory as well). We also save the sqlite database file
168 
as <tt>App_Code/chat.db</tt>.
169 
<com:TTextHighlighter Language="php" CssClass="source block-content" id="code_90033">
170 
class ChatUserRecord extends TActiveRecord
171 
{
172 
    const TABLE='chat_users';
173 
 
174 
    public $username;
175 
    public $last_activity;
176 
 
177 
    public static function finder($className=__CLASS__)
178 
    {
179 
        return parent::finder($className);
180 
    }
181 
}
182 
</com:TTextHighlighter>
183 
Before using the <tt>ChatUserRecord</tt> class we to configure a default
184 
database connection for ActiveRecord to function. In the <tt>chat/protected/application.xml</tt>
185 
we import classes from the <tt>App_Code</tt> directory and add an
186 
<a href="?page=Database.ActiveRecord">ActiveRecord configuration module</a>.
187 
<com:TTextHighlighter Language="xml" CssClass="source block-content" id="code_90034">
188 
<?xml version="1.0" encoding="utf-8"?>
189 
<application id="Chat" Mode="Debug">
190 
  <paths>
191 
    <using namespace="Application.App_Code.*" />
192 
    <using namespace="System.Data.*" />
193 
    <using namespace="System.Data.ActiveRecord.*" />
194 
    <using namespace="System.Security.*" />
195 
    <using namespace="System.Web.UI.ActiveControls.*" />
196 
  </paths>
197 
  <modules>
198 
    <module class="TActiveRecordConfig" EnableCache="true"
199 
        Database.ConnectionString="sqlite:protected/App_Code/chat.db" />
200 
  </modules>
201 
</application>
202 
</com:TTextHighlighter>
203 
</p>
204 
 
205 
<h2 id="18020">Custom User Manager class</h2>
206 
<p id="90090" class="block-content">To implement a custom user manager module class we just need
207 
to extends the <tt>TModule</tt> class and implement the <tt>IUserManager</tt>
208 
interface. The <tt>getGuestName()</tt>, <tt>getUser()</tt> and <tt>validateUser()</tt>
209 
methods are required by the <tt>IUserManager</tt> interface.
210 
We save the custom user manager class as <tt>App_Code/ChatUserManager.php</tt>.
211 
</p>
212 
<com:TTextHighlighter Language="php" CssClass="source block-content" id="code_90035">
213 
class ChatUserManager extends TModule implements IUserManager
214 
{
215 
    public function getGuestName()
216 
    {
217 
        return 'Guest';
218 
    }
219 
 
220 
    public function getUser($username=null)
221 
    {
222 
        $user=new TUser($this);
223 
        $user->setIsGuest(true);
224 
        if($username !== null && $this->usernameExists($username))
225 
        {
226 
            $user->setIsGuest(false);
227 
            $user->setName($username);
228 
            $user->setRoles(array('normal'));
229 
        }
230 
        return $user;
231 
    }
232 
 
233 
    public function addNewUser($username)
234 
    {
235 
        $user = new ChatUserRecord();
236 
        $user->username = $username;
237 
        $user->save();
238 
    }
239 
 
240 
    public function usernameExists($username)
241 
    {
242 
        $finder = ChatUserRecord::finder();
243 
        $record = $finder->findByUsername($username);
244 
        return $record instanceof ChatUserRecord;
245 
    }
246 
 
247 
    public function validateUser($username,$password)
248 
    {
249 
        return $this->usernameExists($username);
250 
    }
251 
}
252 
</com:TTextHighlighter>
253 
<p id="90091" class="block-content">
254 
The <tt>getGuestName()</tt>
255 
method simply returns the name for a guest user and is not used in our application.
256 
The <tt>getUser()</tt> method returns a <tt>TUser</tt> object if the username
257 
exists in the database, the <tt>TUser</tt> object is set with role of "normal"
258 
that corresponds to the <tt>&lt;authorization&gt;</tt> rules defined in our
259 
<tt>config.xml</tt> file. </p>
260 
 
261 
<p id="90092" class="block-content">The <tt>addNewUser()</tt> and <tt>usernameExists()</tt>
262 
method uses the ActiveRecord corresponding to the <tt>chat_users</tt> table to
263 
add a new user and to check if a username already exists, respectively.
264 
</p>
265 
 
266 
<p id="90093" class="block-content">The next thing to do is change the <tt>config.xml</tt> configuration to use
267 
our new custom user manager class. We simply change the <tt>&lt;module&gt;</tt>
268 
configuration with <tt>id="users"</tt>.</p>
269 
<com:TTextHighlighter Language="xml" CssClass="source block-content" id="code_90036">
270 
<module id="users" class="ChatUserManager" />
271 
</com:TTextHighlighter>
272 
 
273 
<h1 id="18012">Authentication</h1>
274 
<p id="90094" class="block-content">To perform authentication, we just want the user to enter a unique
275 
username. We add a
276 
<com:DocLink ClassPath="System.Web.UI.WebControls.TCustomValidator" Text="TCustomValidator" />
277 
for validate the uniqueness of the username and add an <tt>OnClick</tt> event handler
278 
for the login button.</p>
279 
<com:TTextHighlighter Language="prado" CssClass="source block-content" id="code_90037">
280 
&lt;com:TCustomValidator
281 
    ControlToValidate="username"
282 
    Display="Dynamic"
283 
    OnServerValidate="checkUsername"
284 
    ErrorMessage="The username is already taken." /&gt;
285 
 
286 
...
287 
 
288 
&lt;com:TButton Text="Login" OnClick="createNewUser" /&gt;
289 
</com:TTextHighlighter>
290 
In the <tt>Login.php</tt> file, we add the following 2 methods.
291 
<com:TTextHighlighter Language="php" CssClass="source block-content" id="code_90038">
292 
function checkUsername($sender, $param)
293 
{
294 
    $manager = $this->Application->Modules['users'];
295 
    if($manager->usernameExists($this->username->Text))
296 
        $param->IsValid = false;
297 
}
298 
 
299 
function createNewUser($sender, $param)
300 
{
301 
    if($this->Page->IsValid)
302 
    {
303 
        $manager = $this->Application->Modules['users'];
304 
        $manager->addNewUser($this->username->Text);
305 
 
306 
        //do manual login
307 
        $user = $manager->getUser($this->username->Text);
308 
        $auth = $this->Application->Modules['auth'];
309 
        $auth->updateSessionUser($user);
310 
        $this->Application->User = $user;
311 
 
312 
        $url = $this->Service->constructUrl($this->Service->DefaultPage);
313 
        $this->Response->redirect($url);
314 
    }
315 
}
316 
</com:TTextHighlighter>
317 
The <tt>checkUserName()</tt> method uses the <tt>ChatUserManager</tt> class
318 
(recall that in the <tt>config.xml</tt> configuration we set the
319 
ID of the custom user manager class as "users") to validate the username
320 
is not taken.
321 
</p>
322 
<p id="90095" class="block-content">
323 
In the <tt>createNewUser</tt> method, when the validation passes (that is,
324 
when the user name is not taken) we add a new user. Afterward we perform
325 
a manual login process:</p>
326 
<ul id="u2" class="block-content">
327 
	<li>First we obtain a <tt>TUser</tt> instance from
328 
our custom user manager class using the <tt>$manager->getUser(...)</tt> method.</li>
329 
	<li>Using the <tt>TAuthManager</tt> we set/update the user object in the
330 
	current session data.</li>
331 
	<li>Then we set/update the <tt>Application</tt>'s user instance with our
332 
	new user object.</li>
333 
</ul>
334 
</p>
335 
<p id="finally" class="block-content">
336 
Finally, we redirect the client to the default <tt>Home</tt> page.
337 
</p>
338 
 
339 
<h2 id="18021">Default Values for ActiveRecord</h2>
340 
<p id="90096" class="block-content">If you try to perform a login now, you will receive an error message like
341 
"<i>Property '<tt>ChatUserRecord::$last_activity</tt>' must not be null as defined
342 
by column '<tt>last_activity</tt>' in table '<tt>chat_users</tt>'.</i>". This means that the <tt>$last_activity</tt>
343 
property value was null when we tried to insert a new record. We need to either
344 
define a default value in the corresponding column in the table and allow null values or set the default
345 
value in the <tt>ChatUserRecord</tt> class. We shall demonstrate the later by
346 
altering the <tt>ChatUserRecord</tt> with the addition of a set getter/setter
347 
methods for the <tt>last_activity</tt> property.
348 
 
349 
<com:TTextHighlighter Language="php" CssClass="source block-content" id="code_90039">
350 
private $_last_activity;
351 
 
352 
public function getLast_Activity()
353 
{
354 
    if($this->_last_activity === null)
355 
        $this->_last_activity = time();
356 
    return $this->_last_activity;
357 
}
358 
 
359 
public function setLast_Activity($value)
360 
{
361 
    $this->_last_activity = $value;
362 
}
363 
</com:TTextHighlighter>
364 
Notice that we renamed <tt>$last_activity</tt> to <tt>$_last_activity</tt> (note
365 
the underscore after the dollar sign).
366 
</p>
367 
 
368 
<h1 id="18013">Main Chat Application</h1>
369 
<p id="90097" class="block-content">Now we are ready to build the main chat application. We use a simple
370 
layout that consist of one panel holding the chat messages, one panel
371 
to hold the users list, a textarea for the user to enter the text message
372 
and a button to send the message.
373 
<com:TTextHighlighter Language="prado" CssClass="source block-content" id="code_90040">
374 
<!doctype html public "-//W3C//DTD XHTML 1.0 Strict//EN"
375 
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
376 
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
377 
<head>
378 
    <title>Prado Chat Demo</title>
379 
<style>
380 
.messages
381 
{
382 
    width: 500px;
383 
    height: 300px;
384 
    float: left;
385 
    border: 1px solid ButtonFace;
386 
    overflow: auto;
387 
}
388 
.user-list
389 
{
390 
    margin-left: 2px;
391 
    float: left;
392 
    width: 180px;
393 
    height: 300px;
394 
    border: 1px solid ButtonFace;
395 
    overflow: auto;
396 
    font-size: 0.85em;
397 
}
398 
.message-input
399 
{
400 
    float: left;
401 
}
402 
 
403 
.message-input textarea
404 
{
405 
    margin-top: 3px;
406 
    padding: 0.4em 0.2em;
407 
    width: 493px;
408 
    font-family: Verdana, Geneva, Arial, Helvetica, sans-serif;
409 
    font-size: 0.85em;
410 
    height: 40px;
411 
}
412 
.send-button
413 
{
414 
    margin: 0.5em;
415 
}
416 
</style>
417 
</head>
418 
<body>
419 
&lt;com:TForm&gt;
420 
<h1 id="18014">Prado Chat Demo</h1>
421 
<div id="messages" class="messages">
422 
    &lt;com:TPlaceHolder ID="messageList" /&gt;
423 
</div>
424 
<div id="users" class="user-list">
425 
    &lt;com:TPlaceHolder ID="userList" /&gt;
426 
</div>
427 
<div class="message-input">
428 
    &lt;com:TActiveTextBox ID="userinput"
429 
        Columns="40" Rows="2" TextMode="MultiLine" /&gt;
430 
    &lt;com:TActiveButton ID="sendButton" CssClass="send-button"
431 
        Text="Send" /&gt;
432 
</div>
433 
&lt;/com:TForm&gt;
434 
&lt;com:TJavascriptLogger /&gt;
435 
</body>
436 
</html>
437 
</com:TTextHighlighter>
438 
We added two Active Control components: a
439 
<com:DocLink ClassPath="System.Web.UI.ActiveControls.TActiveTextBox" Text="TActiveTextBox" />
440 
and a
441 
<com:DocLink ClassPath="System.Web.UI.ActiveControls.TActiveButton" Text="TActiveButton" />.
442 
We also added a
443 
<com:DocLink ClassPath="System.Web.UI.WebControls.TJavascriptLogger" Text="TJavascriptLogger" />
444 
that will be very useful for understanding how the Active Controls work.
445 
</p>
446 
 
447 
<h2 id="18022">Exploring the Active Controls</h2>
448 
<p id="90098" class="block-content">We should have some fun before we proceeding with setting up the chat buffering. We want
449 
to see how we can update the current page when we receive a message. First, we add
450 
an <tt>OnClick</tt> event handler for the <tt>Send</tt> button.
451 
 
452 
<com:TTextHighlighter Language="prado" CssClass="source block-content" id="code_90041">
453 
&lt;com:TActiveButton ID="sendButton" CssClass="send-button"
454 
	Text="Send" OnClick="processMessage"/&gt;
455 
</com:TTextHighlighter>
456 
And the corresponding event handler method in the <tt>Home.php</tt> class (we
457 
need to create this new file too).
458 
<com:TTextHighlighter Language="php" CssClass="source block-content" id="code_90042">
459 
class Home extends TPage
460 
{
461 
    function processMessage($sender, $param)
462 
    {
463 
        echo $this->userinput->Text;
464 
    }
465 
}
466 
</com:TTextHighlighter>
467 
If you now type something in the main application textbox and click the send button
468 
you should see whatever you have typed echoed in the <tt>TJavascriptLogger</tt> console.
469 
</p>
470 
 
471 
<p id="90099" class="block-content">To append or add some content to the message list panel, we need to use
472 
some methods in the
473 
<com:DocLink ClassPath="System.Web.UI.ActiveControls.TCallbackClientScript" Text="TCallbackClientScript" />
474 
class which is available through the <tt>CallbackClient</tt> property of the
475 
current <tt>TPage</tt> object. For example, we do can do
476 
<com:TTextHighlighter Language="php" CssClass="source block-content" id="code_90043">
477 
function processMessage($sender, $param)
478 
{
479 
    $this->CallbackClient->appendContent("messages", $this->userinput->Text);
480 
}
481 
</com:TTextHighlighter>
482 
This is one way to update some part of the existing page during a callback (AJAX style events)
483 
and will be the primary way we will use to implement the chat application.
484 
</p>
485 
 
486 
<h1 id="18015">Active Record for <tt>chat_buffer</tt> table</h1>
487 
<p id="90100" class="block-content">To send a message to all the connected users we need to buffer or store
488 
the message for each user. We can use the database to buffer the messages. The
489 
<tt>chat_buffer</tt> table is defined as follows.
490 
<com:TTextHighlighter Language="text" CssClass="source block-content" id="code_90044">
491 
CREATE TABLE chat_buffer
492 
(
493 
	id INTEGER PRIMARY KEY,
494 
	for_user VARCHAR(20) NOT NULL,
495 
	from_user VARCHAR(20) NOT NULL,
496 
	message TEXT NOT NULL,
497 
	created_on INTEGER NOT NULL DEFAULT "0"
498 
);
499 
</com:TTextHighlighter>
500 
The corresponding <tt>ChatBufferRecord</tt> class is saved as
501 
<tt>App_Code/ChatBufferRecord.php</tt>.
502 
 
503 
<com:TTextHighlighter Language="php" CssClass="source block-content" id="code_90045">
504 
class ChatBufferRecord extends TActiveRecord
505 
{
506 
	const TABLE='chat_buffer';
507 
 
508 
    public $id;
509 
    public $for_user;
510 
    public $from_user;
511 
    public $message;
512 
    private $_created_on;
513 
 
514 
    public function getCreated_On()
515 
    {
516 
        if($this->_created_on === null)
517 
            $this->_created_on = time();
518 
        return $this->_created_on;
519 
    }
520 
 
521 
    public function setCreated_On($value)
522 
    {
523 
        $this->_created_on = $value;
524 
    }
525 
 
526 
    public static function finder($className=__CLASS__)
527 
    {
528 
        return parent::finder($className);
529 
    }
530 
}
531 
</com:TTextHighlighter>
532 
</p>
533 
 
534 
<h1 id="18016">Chat Application Logic</h1>
535 
<p id="90101" class="block-content">We finally arrive at the guts of the chat application logic. First, we
536 
need to save a received message into the chat buffer for <b>all</b> the
537 
current users. We add this logic in the <tt>ChatBufferRecord</tt> class.
538 
 
539 
<com:TTextHighlighter Language="php" CssClass="source block-content" id="code_90046">
540 
public function saveMessage()
541 
{
542 
    foreach(ChatUserRecord::finder()->findAll() as $user)
543 
    {
544 
        $message = new self;
545 
        $message->for_user = $user->username;
546 
        $message->from_user = $this->from_user;
547 
        $message->message = $this->message;
548 
        $message->save();
549 
        if($user->username == $this->from_user)
550 
        {
551 
            $user->last_activity = time(); //update the last activity;
552 
            $user->save();
553 
        }
554 
    }
555 
}
556 
</com:TTextHighlighter>
557 
We first find all the current users using the <tt>ChatUserRecord</tt> finder
558 
methods. Then we duplicate the message and save it into the database. In addition,
559 
we update the message sender's last activity timestamp. The above piece of code
560 
demonstrates the simplicity and succinctness of using ActiveRecords for simple database designs.
561 
</p>
562 
 
563 
<p id="90102" class="block-content">The next piece of the logic is to retrieve the users' messages from the buffer.
564 
We simply load all the messages for a particular username and format that message
565 
appropriately (remember to escape the output to prevent Cross-Site Scripting attacks).
566 
After we load the messages, we delete those loaded messages and any older
567 
messages that may have been left in the buffer.
568 
</p>
569 
<com:TTextHighlighter Language="php" CssClass="source block-content" id="code_90047">
570 
public function getUserMessages($user)
571 
{
572 
    $content = '';
573 
    foreach($this->findAll('for_user = ?', $user) as $message)
574 
        $content .= $this->formatMessage($message);
575 
    $this->deleteAll('for_user = ? OR created_on < ?',
576 
                          $user, time() - 300); //5 min inactivity
577 
    return $content;
578 
}
579 
 
580 
protected function formatMessage($message)
581 
{
582 
    $user = htmlspecialchars($message->from_user);
583 
    $content = htmlspecialchars($message->message);
584 
    return "<div class=\"message\"><strong>{$user}:</strong>"
585 
                  ." <span>{$content}</span></div>";
586 
}
587 
</com:TTextHighlighter>
588 
 
589 
To retrieve a list of current users (formatted), we add this logic to the
590 
<tt>ChatUserRecord</tt> class. We delete any users that may have been inactive
591 
for awhile.
592 
<com:TTextHighlighter Language="php" CssClass="source block-content" id="code_90048">
593 
public function getUserList()
594 
{
595 
    $this->deleteAll('last_activity < ?', time()-300); //5 min inactivity
596 
    $content = '<ul>';
597 
    foreach($this->findAll() as $user)
598 
        $content .= '<li>'.htmlspecialchars($user->username).'</li>';
599 
    $content .= '</ul>';
600 
    return $content;
601 
}
602 
</com:TTextHighlighter>
603 
 
604 
<div class="note"><b class="tip">Note:</b>
605 
For simplicity
606 
we formatted the messages in these Active Record classes. For large applications,
607 
these message formatting tasks should be done using Prado components (e.g. using
608 
a TRepeater in the template or a custom component).
609 
</div>
610 
</p>
611 
 
612 
<h1 id="18017">Putting It Together</h1>
613 
<p id="90103" class="block-content">Now comes to put the application flow together. In the <tt>Home.php</tt> we update
614 
the <tt>Send</tt> buttons <tt>OnClick</tt> event handler to use the application
615 
logic we just implemented.
616 
<com:TTextHighlighter Language="php" CssClass="source block-content" id="code_90049">
617 
function processMessage($sender, $param)
618 
{
619 
    if(strlen($this->userinput->Text) > 0)
620 
    {
621 
        $record = new ChatBufferRecord();
622 
        $record->message = $this->userinput->Text;
623 
        $record->from_user = $this->Application->User->Name;
624 
        $record->saveMessage();
625 
 
626 
        $this->userinput->Text = '';
627 
        $messages = $record->getUserMessages($this->Application->User->Name);
628 
        $this->CallbackClient->appendContent("messages", $messages);
629 
        $this->CallbackClient->focus($this->userinput);
630 
    }
631 
}
632 
</com:TTextHighlighter>
633 
We simply save the message to the chat buffer and then ask for all the messages
634 
for the current user and update the client side message list using a callback
635 
response (AJAX style).
636 
</p>
637 
 
638 
<p id="90104" class="block-content">At this point the application is actually already functional, just not very
639 
user friendly. If you open two different browsers, you should be able to communicate
640 
between the two users whenever the <tt>Send</tt> button is clicked.
641 
</p>
642 
 
643 
<p id="90105" class="block-content">The next part is perhaps the more tricker and fiddly than the other tasks. We
644 
need to improve the user experience. First, we want a list of current users
645 
as well. So we add the following method to <tt>Home.php</tt>, we can call
646 
this method when ever some callback event is raised, e.g. when the <tt>Send</tt>
647 
button is clicked.
648 
<com:TTextHighlighter Language="php" CssClass="source block-content" id="code_90050">
649 
protected function refreshUserList()
650 
{
651 
    $lastUpdate = $this->getViewState('userList','');
652 
    $users = ChatUserRecord::finder()->getUserList();
653 
    if($lastUpdate != $users)
654 
    {
655 
        $this->CallbackClient->update('users', $users);
656 
        $this->setViewstate('userList', $users);
657 
    }
658 
}
659 
</com:TTextHighlighter>
660 
</p>
661 
 
662 
<p id="90106" class="block-content">Actually, we want to periodically update the messages and user list as new
663 
users join in and new message may arrive from other users. So we need to refresh
664 
the message list as well.</p>
665 
<com:TTextHighlighter Language="php" CssClass="source block-content" id="code_90051">
666 
function processMessage($sender, $param)
667 
{
668 
    ...
669 
    $this->refreshUserList();
670 
    $this->refreshMessageList();
671 
    ...
672 
}
673 
 
674 
protected function refreshMessageList()
675 
{
676 
    //refresh the message list
677 
    $finder = ChatBufferRecord::finder();
678 
    $content = $finder->getUserMessages($this->Application->User->Name);
679 
    if(strlen($content) > 0)
680 
    {
681 
        $anchor = (string)time();
682 
        $content .= "<a href=\"#\" id=\"{$anchor}\"> </a>";
683 
        $this->CallbackClient->appendContent("messages", $content);
684 
        $this->CallbackClient->focus($anchor);
685 
    }
686 
}
687 
</com:TTextHighlighter>
688 
The anchor using <tt>time()</tt> as ID for a focus point is so that when the
689 
message list on the client side gets very long, the focus method will
690 
scroll the message list to the latest message (well, it works in most browsers).
691 
</p>
692 
 
693 
<p id="90107" class="block-content">Next, we need to redirect the user back to the login page if the user has
694 
been inactive for some time, say about 5 mins, we can add this check to any stage
695 
of the page life-cycle. Lets add it to the <tt>onLoad()</tt> stage.
696 
<com:TTextHighlighter Language="php" CssClass="source block-content" id="code_90052">
697 
public function onLoad($param)
698 
{
699 
    $username = $this->Application->User->Name;
700 
    if(!$this->Application->Modules['users']->usernameExists($username))
701 
    {
702 
        $auth = $this->Application->Modules['auth'];
703 
        $auth->logout();
704 
 
705 
        //redirect to login page.
706 
        $this->Response->Redirect($this->Service->ConstructUrl($auth->LoginPage));
707 
    }
708 
}
709 
</com:TTextHighlighter>
710 
</p>
711 
 
712 
<h1 id="18018">Improving User Experience</h1>
713 
<p id="90108" class="block-content">The last few details are to periodically check for new messages and
714 
refresh the user list. We can accomplish this by polling the server using a
715 
<com:DocLink ClassPath="System.Web.UI.ActiveControls.TTimeTriggeredCallback" Text="TTimeTriggeredCallback" />
716 
control. We add a <tt>TTimeTriggeredCallback</tt> to the <tt>Home.page</tt>
717 
and call the <tt>refresh</tt> handler method defined in <tt>Home.php</tt>.
718 
We set the polling interval to 2 seconds.
719 
<com:TTextHighlighter Language="prado" CssClass="source block-content" id="code_90053">
720 
&lt;com:TTimeTriggeredCallback OnCallback="refresh"
721 
	Interval="2" StartTimerOnLoad="true" /&gt;
722 
</com:TTextHighlighter>
723 
<com:TTextHighlighter Language="php" CssClass="source block-content" id="code_90054">
724 
function refresh($sender, $param)
725 
{
726 
    $this->refreshUserList();
727 
    $this->refreshMessageList();
728 
}
729 
</com:TTextHighlighter>
730 
</p>
731 
 
732 
<p id="90109" class="block-content">The final piece requires us to use some javascript. We want that when the
733 
user type some text in the textarea and press the <tt>Enter</tt> key, we want it
734 
to send the message without clicking on the <tt>Send</tt> button. We add to the
735 
<tt>Home.page</tt> some javascript.
736 
 
737 
<com:TTextHighlighter Language="javascript" CssClass="source block-content" id="code_90055">
738 
&lt;com:TClientScript&gt;
739 
Event.observe($("&lt;%= $this->userinput->ClientID %&gt;"), "keypress", function(ev)
740 
{
741 
    if(Event.keyCode(ev) == Event.KEY_RETURN)
742 
    {
743 
        if(Event.element(ev).value.length > 0)
744 
            new Prado.Callback("&lt;%= $this->sendButton->UniqueID %&gt;");
745 
        Event.stop(ev);
746 
    }
747 
});
748 
&lt;/com:TClientScript&gt;
749 
</com:TTextHighlighter>
750 
Details regarding the javascript can be explored in the
751 
<a href="?page=Advanced.Scripts">Introduction to Javascript</a> section of the quickstart.
752 
</p>
753 
 
754 
<p id="90110" class="block-content">This completes the tutorial on making a basic chat web application using
755 
the Prado framework. Hope you have enjoyed it.
756 
</p>
757 
 
758 
<div class="last-modified">$Id: AjaxChat.page 1846 2007-04-07 10:35:16Z wei $</div></com:TContent>