HOWTO WRITE an APPLICATION above AGL FRAMEWORK
==============================================
version: 1
- Date: 29 mai 2016
+ Date: 30 mai 2016
Author: José Bollo
TABLE-OF-CONTENT-HERE
+Programmation Languages for Applications
+-----------------------------------------
-Writing a C application
------------------------
+### Writing an HTML5 application
-C applications can use the binder afb-daemon through a websocket connection.
+Developers of HTML5 applications (client side) can easily create
+applications for AGL framework using their preferred
+HTML5 framework.
-The library **libafbwsc** is made for C clients that want
-to connect to the afb-daemon binder.
+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.
-The program **afb-client-demo** is the C program that use
-the provided library **libafbwsc**.
-Its source code is here
+In a near future, JSON-RPC protocol should be added to complete current x-afb-json1 protocol.
+
+Two examples of HTML5 applications are given:
+
+- [afb-client](https://github.com/iotbzh/afb-client) a simple "hello world" application template
+
+- [afm-client](https://github.com/iotbzh/afm-client) a simple "Home screen" application template
+
+### Writing a Qt application
+
+Writing Qt applications is also supported. Qt offers standard API to send request through HTTP or WebSockets.
+
+It is also possible to write QML applications. A sample QML application [token-websock] is avaliable..
+
+- [token-websock](https://github.com/iotbzh/afb-daemon/blob/master/test/token-websock.qml)
+a simple "hello world" application in QML
+
+### Writing "C" application
+
+C applications can use afb-daemon binder through a websocket connection.
+
+The library **libafbwsc** is provided for C clients that need
+to connect with an afb-daemon binder.
+
+The program **afb-client-demo** is the C example that use
+**libafbwsc** library.
+Source code is available here
[src/afb-client-demo.c](https://github.com/iotbzh/afb-daemon/blob/master/src/afb-client-demo.c).
-The current implementation use libsystemd and file descriptors.
-This may be changed in the future to also support secure sockets
-and being less dependant of libsystemd.
+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.
+
+Handling sessions within applications
+-------------------------------------
+
+Applications should understand sessions and tokens management when interacting with afb-daemon binder.
+
+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.
+
+For this reason, the binder should authenticate the application
+by using a shared secret. The secret is named "token" and the identification
+of client is named "session".
+
+The examples **token-websock.qml** and **afb-client** are demonstrating
+how authentication and sessions are managed.
+
+### Handling sessions
+
+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's data separated.
+
+For HTML5 applications, the web runtime handles the cookie of session
+that the binder afb-daemon automatically sets.
+
+Session identifier can be set using the parameter
+**uuid** or **x-afb-uuid** in URI requests. Within current version of the
+framework session UUID is supported by both HTTP requests and websocket negotiation.
+
+### Exchanging tokens
+
+At application start, AGL framework communicates a shared secret to both binder
+and client application. This initial secret is called the "initial token".
+
+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's methods.
+
+The token must be included in URI request on HTTP or during websockets
+connection using parameter **token** or **x-afb-token**.
+
+To ensure security, tokens must be refreshed periodically.
+
+### Example of session management
+
+In following examples, we suppose that **afb-daemon** is launched with something equivalent to:
+
+ $ afb-daemon --port=1234 --token=123456 [...]
+
+making the expectation that **AuthLogin** plugin is requested as default.
+
+#### Using curl
+
+First, connects with the initial token, 123456:
+
+ $ 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"}
+ }
+
+It returns an answer containing session UUID, 850c4594-1be1-4e9b-9fcc-38cc3e6ff015,
+and a refreshed token, 850c4594-1be1-4e9b-9fcc-38cc3e6ff015.
+
+Check if session and token is valid:
+
+ $ curl http://localhost:1234/api/auth/check?token=0aef6841-2ddd-436d-b961-ae78da3b5c5f\&uuid=850c4594-1be1-4e9b-9fcc-38cc3e6ff015
+ {
+ "jtype": "afb-reply",
+ "request": {"status":"success"},
+ "response": {"isvalid":true}
+ }
+
+Refresh the token:
+
+ $ curl http://localhost:1234/api/auth/refresh?token=0aef6841-2ddd-436d-b961-ae78da3b5c5f\&uuid=850c4594-1be1-4e9b-9fcc-38cc3e6ff015
+ {
+ "jtype": "afb-reply",
+ "request": {
+ "status":"success",
+ "token":"b8ec3ec3-6ffe-448c-9a6c-efda69ad7bd9"
+ },
+ "response": {"token":"Token was refreshed"}
+ }
+
+Close the session:
+
+ curl http://localhost:1234/api/auth/logout?token=b8ec3ec3-6ffe-448c-9a6c-efda69ad7bd9\&uuid=850c4594-1be1-4e9b-9fcc-38cc3e6ff015
+ {
+ "jtype": "afb-reply",
+ "request": {"status": "success"},
+ "response": {"info":"Token and all resources are released"}
+ }
+
+Checking on closed session for uuid should be refused:
+
+ curl http://localhost:1234/api/auth/check?token=b8ec3ec3-6ffe-448c-9a6c-efda69ad7bd9\&uuid=850c4594-1be1-4e9b-9fcc-38cc3e6ff015
+ {
+ "jtype": "afb-reply",
+ "request": {
+ "status": "failed",
+ "info": "invalid token's identity"
+ }
+ }
+
+#### Using afb-client-demo
+
+Here is an example of exchange using **afb-client-demo**:
+
+ $ 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"}}
+
+After closing connection, reconnect as here after:
+
+ $ afb-client-demo ws://localhost:1234/api?token=e83b36f8-d945-463d-b983-5d8ed73ba529\&uuid=5fcc3f3d-4b84-4fc7-ba66-2d8bd34ae7d1 auth check
+ ON-REPLY 1:auth/check: {"jtype":"afb-reply","request":{"status":"success"},"response":{"isvalid":true}}
+
+Same connection check using **curl**:
+
+ $ curl http://localhost:1234/api/auth/check?token=e83b36f8-d945-463d-b983-5d8ed73ba529\&uuid=5fcc3f3d-4b84-4fc7-ba66-2d8bd34ae7d1
+ {"jtype":"afb-reply","request":{"status":"success"},"response":{"isvalid":true}}
+
+Format of replies
+-----------------
+
+Replies use javascript object returned as serialized JSON.
+
+This object contains at least 2 mandatory fields of name **jtype** and **request**
+and one optional field of name **response**.
+
+### Field jtype
+
+The field **jtype** must have a value of type string equal to **"afb-reply"**.
+
+### Field request
+
+The field **request** must have a value of type object. This request object
+has at least one field named **status** and four optional fields named
+**info**, **token**, **uuid**, **reqid**.
+
+#### Subfield request.status
+
+**status** must have a value of type string. This string is equal to **"success"**
+only in case of success.
+
+#### Subfield request.info
+
+**info** is of type string and represent optional information added to the reply.
+
+#### Subfield request.token
+
+**token** is of type string. It is sent either at session creation
+or when the token is refreshed.
+
+#### Subfield request.uuid
+
+**uuid** is of type string. It is sent at session creation.
+
+#### Subfield request.reqid
+
+**reqid** is of type string. It is sent in response to HTTP requests
+that added a parameter of name **reqid** or **x-afb-reqid** at request time.
+Value returns in the reply has the exact same value as the one received in the request.
+
+### Field response
+
+This field response optionally contains an object returned when request succeeded.
+
+### Template
+
+This is a template of replies:
+ {
+ "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....
+ }
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