# Controller binding configuration
By default the controller searches for a config filename with the same 'middlename' as the daemon process. As an example if your process name is afb-daemon then middle name is 'daemon'. In addition, if your process name is afb-daemon-audio the middle name is also 'daemon'. Moreover the prefix is chosen when you call the [CtlConfigSearch](<#4)_Do_controller_config_parsing_at_binding_pre-init>) function, see below:
```bash
CtlConfigSearch(AFB_ApiT apiHandle, const char *dirList, const char *prefix)
```
```bash
# Middlename is taken from process middlename.
(prefix-)middlename*.json
```
You may overload the config search path with environment variables
* **CONTROL_CONFIG_PATH**: change default reserch path for configuration. You may provide multiple directories separated by ':'.
* **CONTROL_LUA_PATH**: same as CONTROL_CONFIG_PATH but for Lua script files.
Example: to load a config named '(prefix-)myconfig-test.json' do
```bash
afb-daemon --name myconfig --verbose ...'
```
The configuration is loaded dynamically during startup time. The controller scans **CONTROL_CONFIG_PATH** for a file corresponding to the pattern
"(prefix-)bindermiddlename*.json". The first file found in the path is loaded,
any other file corresponding to the same path is ignored and only generates a warning.
Each block in the configuration file is defined with
* **uid**: mandatory, it is used either for debugging or as input for the action
(eg: signal name, control name, ...)
* **info**: optional, it is used for documentation purpose only
> **Note**: by default the controller config search path is defined at
> compilation time, but the path might be overloaded with the
> **CONTROL_CONFIG_PATH** environment variable.
## Configuration is organised in sections
* **metadata**: describes the configuration
* **plugins or resources**: defines the plugins to be loaded as additionnal
resources (compiled C or lua).
* **onload**: a collection of actions meant to be executed at startup time
* **control**: sets the controls with a collection of actions, in dynamic api it
could also specify the verbs of the api
* **event**: a collection of actions meant to be executed when receiving a given
signal
* **personnal sections**: personnal section
Callbacks to parse sections are documented in [Declare your controller config section in your binding](<#3_Declare_your_controller_config_section_in_your_binding>)
section. You can use the callback defined in controller or define your own
callback.
## Metadata
As today metadata is only used for documentation purpose.
* **uid**: mandatory
* **version**: mandatory
* **api**: mandatory, string which named the API to be created
* **info**: optional
* **require**: optional, string or array of strings of dependants API's names.
* **author**: optional
* **date**: optional
## OnLoad section
Onload section defines startup time configuration. Onload may provide multiple
initialisation profiles, each with a different uid.
You can define the following keys or arrays of the following keys:
* **uid**: mandatory.
* **info**: optional
* **action**: mandatory, an object or array of object describing an action and
explained in the later [Action Elements](<#Action Elements>) chapter.
* **args**: optionnal, action's arguments.
## Control section
Control section defines a list of controls that are accessible.
You can define the following keys or arrays of the following keys, moreover
this section could be verb api:
* **uid**: mandatory, used as the verb's name.
* **info**: optional
* **action**: mandatory, an object or array of object describing an action and
explained in the later [Action Elements](<#Action Elements>) chapter.
* **args**: optionnal, action's arguments.
## Events section
Events section defines a list of actions to be executed on event reception.
Event can do anything a controller can (change state, send back signal, ...)
eg: if a controller subscribes to vehicle speed, then speed-event may adjust
master-volume to speed.
You can define the following keys or arrays of the following keys, moreover you
can define an event from an another API with the following syntax "API/event".
* **uid**: mandatory must match an event name with format **api/event_name**,
i.e: **low-can/messages.engine.speed**
* **info**: optional
* **action**: mandatory, an object or array of object describing an action and
explained in the later [Action Elements](<#Action Elements>) chapter.
* **args**: optionnal, action's arguments.
## Plugin section
Plugin section defines plugins used with this controller. A plugin is a C/C++
program meant to execute some tasks after an event or on demand. This easily
extends intrinsec binding logic for ad-hoc needs.
You can define the following keys or arrays of the following keys:
* **uid**: mandatory
* **info**: optionnal
* **spath**: optionnal, semicolon separated paths where to find the plugin. This
could be a compiled shared library or LUA scripts. Could be specified using
**CONTROL_PLUGIN_PATH** environment variable also.
* **libs**: mandatory, Plugin file or LUA scripts to load
* **lua**: optionnal, a JSON object listing C functions that could be called
from a LUA script and could prefixed.
* **function**: string or array of string of C functions
* **prefix**: a prefix to be used with the listed C functions
## Personnal sections
* **uid**: mandatory
* **info**: optionnal
* **action**: mandatory, an object or array of object describing an action and
explained in the later [Action Elements](<#Action Elements>) chapter.
* **args**: optionnal, action's arguments.
* **any keys wanted**: optionnal
You can define your own sections and add your own callbacks into the CtlSectionT
structure, see [Declare your controller config section in your binding](<#3_Declare_your_controller_config_section_in_your_binding>)
section.
## Action Elements
Controller supports three categories of actions. Each action returns a status
where 0=success and 1=failure.
* **AppFw API** provides a generic model to request other bindings. Requested
bindings can be local (eg: ALSA/UCM) or external (eg: vehicle signalling).
* `"action": "api://API_NAME#verb_name"`
* C-API, when defined in the onload section, the plugin may provide C native API
with `CTLP-CAPI(apiname, uid, args, query, context)`. Plugin may also create
Lua command with `CTLP-LUA2C(LuaFuncName, uid, args, query, context)`. Where
`args`+`query` are JSON-C object and context is the returned value from
`CTLP_ONLOAD` function. Any missing value is set to NULL.
* `"action": "plugin://plugin_name#function_name"`
* Lua-API, when compiled with Lua option, the controller supports action defined
directly in Lua script. During "*onload*" phase, the controller searches in
`CONTROL_LUA_PATH` file with pattern "(prefix-)bindermiddlename*.lua". Any file
corresponding to this pattern is automatically loaded. Any function defined in
those Lua scripts can be called through a controller action. Lua functions
receive three parameters (uid, args, query).
* `"action": "lua://plugin_name#function_name"`
You also can add the **privileges** property that handles AGL permission
needed to be able to call this action.
> **Note**: Lua added functions are systematically prefixed. AGL standard AppFw
functions are prefixed with AGL: (eg: AFB:notice(), AFB:success(), ...).
> User Lua functions added through the plugin and CTLP_LUA2C are prefixed with
the plugin uid or the one you defined in your config (eg: MyPlug:HelloWorld1).
## Available Application Framework Commands
Each LUA AppFw commands should be prefixed by AFB:
* `AFB:notice ("format", arg1,... argn)` directly printed LUA tables as json
string with '%s'. `AFB:error`, `AFB:warning`, `AFB:info`, `AFB:debug` work on
the same model. Printed messages are limited to 512 characters.
* `AFB:service ('API', 'VERB', {query}, "Lua_Callback_Name", {context})` is an
asynchronous call to another binding. When empty, query/context should be set
to '{}' and not to 'nil'. When 'nil', Lua does not send 'NULL' value but
removes arguments to calling stack. WARNING:"Callback" is the name of the
callback as a string and not a pointer to the callback. (If someone as a
solution to fix this, please let me known). Callback is call as LUA
"function Alsa_Get_Hal_CB (error, result, context)" where:
* error is a Boolean
* result is the full answer from AppFw (do not forget to extract the response)
* context is a copy of the Lua table pass as an argument (warning it's a copy
not a pointer to original table)
* `error,result=AFB:servsync('API', 'VERB', {query})` is saved as previous but
for synchronous call. Note that Lua accepts multiple returns. AFB:servsync
returns both the error message and the response as a Lua table. Like for
AFB:service, the user should not forget to extract response from result.
* `AFB:success(request, response)` is the success request. request is the opaque
handle passes when Lua is called from (api="control", verb="docall"). Response
is a Lua table that will be returned to the client.
* `AFB:fail(request, response)` is the same as for success. Note that LUA
generates automatically the error code from Lua function name. The response
is transformed into a json string before being returned to the client.
* `EventHandle=AFB:evtmake("MyEventName")` creates an event and returns the
handle as an opaque handle. Note that due to a limitation of json_object, this
opaque handle cannot be passed as an argument in a callback context.
* `AFB:subscribe(request, MyEventHandle)` subscribes a given client to a
previously created event.
* `AFB:evtpush (MyEventHandle, MyEventData)` pushes an event to every subscribed
client. MyEventData is a Lua table that will be sent as a json object to the
corresponding clients.
* `timerHandle=AFB:timerset (MyTimer, "Timer_Test_CB", context)` initialises a
timer from MyTimer Lua table. This table should contains 3 elements:
MyTimer={[l"abel"]="MyTimerName", ["delay"]=timeoutInMs, ["count"]=nBOfCycles}
Note that if count==0 then timer is cycled infinitely. Context is a standard
Lua table. This function returns an opaque handle to be used to further
control the timer.
* `AFB:timerclear(timerHandle)` kills an existing timer. Returns an error when
timer does not exit.
* `MyTimer=AFB:timerget(timerHandle)` returns uid, delay and count of an active
timer. Returns an error when timerHandle does not point on an active timer.
* `AFB:GetEventLoop()` retrieves the common systemd's event loop of AFB.
* `AFB:RootDirGetFD()` gets the root directory file descriptor. This file
descriptor can be used with functions 'openat', 'fstatat', ...
> **Note**: Except for functions call during binding initialisation period. Lua
> calls are protected and should returned clean messages even when they are
> improperly used. If you find bug please report.
## Adding Lua command from User Plugin
User Plugin is optional and may provide either native C-action accessible
directly from controller actions as defined in JSON config file, or
alternatively may provide a set of Lua commands usable inside any script (onload
, control,event). A simple plugin that provides both notice C API and Lua
commands is provided as example (see ctl-plugin-sample.c). Technically a plugin
is a simple sharelibrary and any code fitting in sharelib might be used as a
plugin. Developer should nevertheless forget that except when no-concurrency
flag was at binding construction time, any binding should to be thread safe.
A plugin must be declared with `CTLP_REGISTER("MyCtlSamplePlugin")`. This
entry point defines a special structure that is checked at plugin load time by
the controller. Then you have an optional init routine declare with
`CTLP_ONLOAD(plugin, handle)`. The init routine may create a plugin context that
is later presented to every plugin API, this for both LUA and native C ones.
Then each:
* C API declare with `CTLP_CAPI(MyCFunction, source, argsJ, queryJ) {your code}`.
Where:
* **MyFunction** is your function
* **source** is the structure config
* **argsJ** a json_object containing the argument attaches to this control in
JSON config file
* **queryJ** a json_object
* Lua API declare with `CTLP_LUA2C(MyLuaCFunction, source, argsJ, responseJ) {your code}`.
Where:
* **MyLuaCFunction** is both the name of your C function and Lua command
* **source** is the structure config
* **argsJ** the arguments passed this time from Lua script and not from JSON
config file.
* **responseJ** if success the argument is passed into the request.
> **Warning**: Lua samples use with controller enforce strict mode. As a result
> every variable should be declared either as local or as global. Unfortunately
> "luac" is not smart enough to handle strict mode at build time and errors only
> appear at run time. Because of this strict mode every global variables (which
> include functions) should be prefixed by '_'. Note that LUA requires an
> initialisation value for every variables and declaring something like
> "local myvar" will not allocate "myvar".
## Debugging Facilities
Controller Lua scripts are checked for syntax from CMAKE template with Luac.
When needed to go further, a developer API should be allowed to execute directly
Lua commands within the controller context from Rest/Ws (api=control,
verb=lua_doscript). DoScript API takes two other optional arguments func=xxxx
where xxxx is the function to execute within Lua script and args, a JSON object
to provide input parameters. When funcname is not given by default, the
controller tries to execute middle filename doscript-xxxx-????.lua.
When executed from the controller, Lua script may use any AppFw Apis as well as
any L2C user defines commands in plugin.
## Running as Standalone Controller
The controller is a standard binding. It can be started with the following
command:
```bash
afb-daemon --name=yourname --port=1234 --workdir=. --roothttp=./htdocs --tracereq=common --token= --verbose --binding=pathtoyourbinding.so --monitoring
```
afb-daemon only loads controller bindings without searching for the other
binding. In this case, the controller binding will search for a configuration
file name '(prefix-)bindermiddlename*.json'. This model can be used to implement
for testing purpose or simply to act as the glue between a UI and other
binder/services.