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<html>
<head>
  <link rel="stylesheet" type="text/css" href="doc.css">
  <meta charset="UTF-8">
</head>
<body>
<a name="HOWTO.WRITE.an.APPLICATION.above.AGL.FRAMEWORK"></a>
<h1>HOWTO WRITE an APPLICATION above AGL FRAMEWORK</h1>

<pre><code>version: 1
Date:    30 mai 2016
Author:  José Bollo
</code></pre>

<p><ul>
 <li><a href="#HOWTO.WRITE.an.APPLICATION.above.AGL.FRAMEWORK">HOWTO WRITE an APPLICATION above AGL FRAMEWORK</a>
 <ul>
  <li><a href="#Programmation.Languages.for.Applications">Programmation Languages for Applications</a>
  <ul>
   <li><a href="#Writing.an.HTML5.application">Writing an HTML5 application</a></li>
   <li><a href="#Writing.a.Qt.application">Writing a Qt application</a></li>
   <li><a href="#Writing..C..application">Writing "C" application</a></li>
  </ul>
  </li>
  <li><a href="#Handling.sessions.within.applications">Handling sessions within applications</a>
  <ul>
   <li><a href="#Handling.sessions">Handling sessions</a></li>
   <li><a href="#Exchanging.tokens">Exchanging tokens</a></li>
   <li><a href="#Example.of.session.management">Example of session management</a>
   <ul>
    <li><a href="#Using.curl">Using curl</a></li>
    <li><a href="#Using.afb-client-demo">Using afb-client-demo</a>
</li>
   </ul>
   </li>
  </ul>
  </li>
  <li><a href="#Format.of.replies">Format of replies</a>
  <ul>
   <li><a href="#Field.jtype">Field jtype</a></li>
   <li><a href="#Field.request">Field request</a>
   <ul>
    <li><a href="#Subfield.request.status">Subfield request.status</a></li>
    <li><a href="#Subfield.request.info">Subfield request.info</a></li>
    <li><a href="#Subfield.request.token">Subfield request.token</a></li>
    <li><a href="#Subfield.request.uuid">Subfield request.uuid</a></li>
    <li><a href="#Subfield.request.reqid">Subfield request.reqid</a></li>
   </ul>
   </li>
   <li><a href="#Field.response">Field response</a></li>
   <li><a href="#Template">Template</a></li>
  </ul>
  </li>
 </ul>
 </li>
</ul></p>

<a name="Programmation.Languages.for.Applications"></a>
<h2>Programmation Languages for Applications</h2>

<a name="Writing.an.HTML5.application"></a>
<h3>Writing an HTML5 application</h3>

<p>Developers of HTML5 applications (client side) can easily create
applications for AGL framework using their preferred
HTML5 framework.</p>

<p>Developers may also take advantage of powerful server side plugins to improve
application behavior. Server side plugins return an application/json mine-type
and can be accessed though either HTTP or Websockets.</p>

<p>In a near future, JSON-RPC protocol should be added to complete current x-afb-json1 protocol.</p>

<p>Two examples of HTML5 applications are given:</p>

<ul>
<li><p><a href="https://github.com/iotbzh/afb-client">afb-client</a> a simple &ldquo;hello world&rdquo; application template</p></li>
<li><p><a href="https://github.com/iotbzh/afm-client">afm-client</a> a simple &ldquo;Home screen&rdquo; application template</p></li>
</ul>


<a name="Writing.a.Qt.application"></a>
<h3>Writing a Qt application</h3>

<p>Writing Qt applications is also supported. Qt offers standard API to send request through HTTP or WebSockets.</p>

<p>It is also possible to write QML applications. A sample QML application [token-websock] is avaliable..</p>

<ul>
<li><a href="https://github.com/iotbzh/afb-daemon/blob/master/test/token-websock.qml">token-websock</a>
a simple &ldquo;hello world&rdquo; application in QML</li>
</ul>


<a name="Writing..C..application"></a>
<h3>Writing &ldquo;C&rdquo; application</h3>

<p>C applications can use afb-daemon binder through a websocket connection.</p>

<p>The library <strong>libafbwsc</strong> is provided for C clients that need
to connect with an afb-daemon binder.</p>

<p>The program <strong>afb-client-demo</strong> is the C example that use
<strong>libafbwsc</strong> library.
Source code is available here
<a href="https://github.com/iotbzh/afb-daemon/blob/master/src/afb-client-demo.c">src/afb-client-demo.c</a>.</p>

<p>Current implementation relies on libsystemd and file descriptors.
This model might be review in the future to support secure sockets
and free the dependency with libsystemd.</p>

<a name="Handling.sessions.within.applications"></a>
<h2>Handling sessions within applications</h2>

<p>Applications should understand sessions and tokens management when interacting with afb-daemon binder.</p>

<p>Applications are communicating with their private binder(afb-daemon) using
a network connection or potentially any other connection channel. While current version
does not yet implement unix domain this feature might be added in a near future.
Developers need to be warn that HTTP protocol is a none connected protocol. This prevents
from using HTTP socket connection to authenticate clients.</p>

<p>For this reason, the binder should authenticate the application
by using a shared secret. The secret is named &ldquo;token&rdquo; and the identification
of client is named &ldquo;session&rdquo;.</p>

<p>The examples <strong>token-websock.qml</strong> and <strong>afb-client</strong> are demonstrating
how authentication and sessions are managed.</p>

<a name="Handling.sessions"></a>
<h3>Handling sessions</h3>

<p>Plugins and other binder feature need to keep track of client
instances. This is especially important for plugins running as services
as they may typically have to keep each client&rsquo;s data separated.</p>

<p>For HTML5 applications, the web runtime handles the cookie of session
that the binder afb-daemon automatically sets.</p>

<p>Session identifier can be set using the parameter
<strong>uuid</strong> or <strong>x-afb-uuid</strong> in URI requests. Within current version of the
framework session UUID is supported by both HTTP requests and websocket negotiation.</p>

<a name="Exchanging.tokens"></a>
<h3>Exchanging tokens</h3>

<p>At application start, AGL framework communicates a shared secret to both binder
and client application. This initial secret is called the &ldquo;initial token&rdquo;.</p>

<p>For each of its client application, the binder manages a current active
token for session management. This authentication token can be use to restrict
access to some plugin&rsquo;s methods.</p>

<p>The token must be included in URI request on HTTP or during websockets
connection using parameter <strong>token</strong> or <strong>x-afb-token</strong>.</p>

<p>To ensure security, tokens must be refreshed periodically.</p>

<a name="Example.of.session.management"></a>
<h3>Example of session management</h3>

<p>In following examples, we suppose that <strong>afb-daemon</strong> is launched with something equivalent to:</p>

<pre><code>$ afb-daemon --port=1234 --token=123456 [...]
</code></pre>

<p>making the expectation that <strong>AuthLogin</strong> plugin is requested as default.</p>

<a name="Using.curl"></a>
<h4>Using curl</h4>

<p>First, connects with the initial token, 123456:</p>

<pre><code>$ curl http://localhost:1234/api/auth/connect?token=123456
{
  "jtype": "afb-reply",
  "request": {
 "status": "success",
 "token": "0aef6841-2ddd-436d-b961-ae78da3b5c5f",
 "uuid": "850c4594-1be1-4e9b-9fcc-38cc3e6ff015"
  },
  "response": {"token": "A New Token and Session Context Was Created"}
}
</code></pre>

<p>It returns an answer containing session UUID, 850c4594-1be1-4e9b-9fcc-38cc3e6ff015,
and a refreshed token, 850c4594-1be1-4e9b-9fcc-38cc3e6ff015.</p>

<p>Check if session and token is valid:</p>

<pre><code>$ curl http://localhost:1234/api/auth/check?token=0aef6841-2ddd-436d-b961-ae78da3b5c5f&amp;uuid=850c4594-1be1-4e9b-9fcc-38cc3e6ff015
{
  "jtype": "afb-reply",
  "request": {"status":"success"},
  "response": {"isvalid":true}
}
</code></pre>

<p>Refresh the token:</p>

<pre><code>$ curl http://localhost:1234/api/auth/refresh?token=0aef6841-2ddd-436d-b961-ae78da3b5c5f&amp;uuid=850c4594-1be1-4e9b-9fcc-38cc3e6ff015
{
  "jtype": "afb-reply",
  "request": {
 "status":"success",
 "token":"b8ec3ec3-6ffe-448c-9a6c-efda69ad7bd9"
  },
  "response": {"token":"Token was refreshed"}
}
</code></pre>

<p>Close the session:</p>

<pre><code>curl http://localhost:1234/api/auth/logout?token=b8ec3ec3-6ffe-448c-9a6c-efda69ad7bd9&amp;uuid=850c4594-1be1-4e9b-9fcc-38cc3e6ff015
{
  "jtype": "afb-reply",
  "request": {"status": "success"},
  "response": {"info":"Token and all resources are released"}
}
</code></pre>

<p>Checking on closed session for uuid should be refused:</p>

<pre><code>curl http://localhost:1234/api/auth/check?token=b8ec3ec3-6ffe-448c-9a6c-efda69ad7bd9&amp;uuid=850c4594-1be1-4e9b-9fcc-38cc3e6ff015
{
  "jtype": "afb-reply",
  "request": {
 "status": "failed",
 "info": "invalid token's identity"
  }
}
</code></pre>

<a name="Using.afb-client-demo"></a>
<h4>Using afb-client-demo</h4>

<p>Here is an example of exchange using <strong>afb-client-demo</strong>:</p>

<pre><code>$ afb-client-demo ws://localhost:1234/api?token=123456
auth connect
ON-REPLY 1:auth/connect: {"jtype":"afb-reply","request":{"status":"success",
   "token":"63f71a29-8b52-4f9b-829f-b3028ba46b68","uuid":"5fcc3f3d-4b84-4fc7-ba66-2d8bd34ae7d1"},
   "response":{"token":"A New Token and Session Context Was Created"}}
auth check
ON-REPLY 2:auth/check: {"jtype":"afb-reply","request":{"status":"success"},"response":{"isvalid":true}}
auth refresh
ON-REPLY 4:auth/refresh: {"jtype":"afb-reply","request":{"status":"success",
   "token":"8b8ba8f4-1b0c-48fa-962d-4a00a8c9157e"},"response":{"token":"Token was refreshed"}}
auth check
ON-REPLY 5:auth/check: {"jtype":"afb-reply","request":{"status":"success"},"response":{"isvalid":true}}
auth refresh
ON-REPLY 6:auth/refresh: {"jtype":"afb-reply","request":{"status":"success",
   "token":"e83b36f8-d945-463d-b983-5d8ed73ba529"},"response":{"token":"Token was refreshed"}}
</code></pre>

<p>After closing connection, reconnect as here after:</p>

<pre><code>$ afb-client-demo ws://localhost:1234/api?token=e83b36f8-d945-463d-b983-5d8ed73ba529&amp;uuid=5fcc3f3d-4b84-4fc7-ba66-2d8bd34ae7d1 auth check
ON-REPLY 1:auth/check: {"jtype":"afb-reply","request":{"status":"success"},"response":{"isvalid":true}}
</code></pre>

<p>Same connection check using <strong>curl</strong>:</p>

<pre><code>$ curl http://localhost:1234/api/auth/check?token=e83b36f8-d945-463d-b983-5d8ed73ba529&amp;uuid=5fcc3f3d-4b84-4fc7-ba66-2d8bd34ae7d1
{"jtype":"afb-reply","request":{"status":"success"},"response":{"isvalid":true}}
</code></pre>

<a name="Format.of.replies"></a>
<h2>Format of replies</h2>

<p>Replies use javascript object returned as serialized JSON.</p>

<p>This object contains at least 2 mandatory fields of name <strong>jtype</strong> and <strong>request</strong>
and one optional field of name <strong>response</strong>.</p>

<a name="Field.jtype"></a>
<h3>Field jtype</h3>

<p>The field <strong>jtype</strong> must have a value of type string equal to <strong>&ldquo;afb-reply&rdquo;</strong>.</p>

<a name="Field.request"></a>
<h3>Field request</h3>

<p>The field <strong>request</strong> must have a value of type object. This request object
has at least one field named <strong>status</strong> and four optional fields named
<strong>info</strong>, <strong>token</strong>, <strong>uuid</strong>, <strong>reqid</strong>.</p>

<a name="Subfield.request.status"></a>
<h4>Subfield request.status</h4>

<p><strong>status</strong> must have a value of type string. This string is equal to <strong>&ldquo;success&rdquo;</strong>
only in case of success.</p>

<a name="Subfield.request.info"></a>
<h4>Subfield request.info</h4>

<p><strong>info</strong> is of type string and represent optional information added to the reply.</p>

<a name="Subfield.request.token"></a>
<h4>Subfield request.token</h4>

<p><strong>token</strong> is of type string. It is sent either at session creation
or when the token is refreshed.</p>

<a name="Subfield.request.uuid"></a>
<h4>Subfield request.uuid</h4>

<p><strong>uuid</strong> is of type string. It is sent at session creation.</p>

<a name="Subfield.request.reqid"></a>
<h4>Subfield request.reqid</h4>

<p><strong>reqid</strong> is of type string. It is sent in response to HTTP requests
that added a parameter of name <strong>reqid</strong> or <strong>x-afb-reqid</strong> at request time.
Value returns in the reply has the exact same value as the one received in the request.</p>

<a name="Field.response"></a>
<h3>Field response</h3>

<p>This field response optionally contains an object returned when request succeeded.</p>

<a name="Template"></a>
<h3>Template</h3>

<p>This is a template of replies:</p>

<pre><code>{
  "jtype": "afb-reply",
  "request": {
   "status": "success",
   "info": "informationnal text",
   "token": "e83b36f8-d945-463d-b983-5d8ed73ba52",
   "uuid": "5fcc3f3d-4b84-4fc7-ba66-2d8bd34ae7d1",
   "reqid": "application-generated-id-23456"
 },
  "response": ....any response object....
}
</code></pre>
</body>
</html>