[commits] [Wiki] created: Doc/Dev/HordeCliModular

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Created page: http://wiki.horde.org/Doc/Dev/HordeCliModular

+ Horde_Cli_Modular

Command line interfaces can often be composed of different modules  
responsible for distinct actions. {{Horde_Cli_Modular}} allows each  
such module to influence the overall command line interface.

++ Introduction

The command line of the tool '''{{pear}}''' is a good example of the  
kind of interface {{Horde_Cli_Modular}} supports: There are a number  
of global options available but each command supported by  
'''{{pear}}''' may have its own subset of options. '''{{-c}}'''  
identifies the '''{{pear}}''' configuration file as a global options.  
In contrast the '''{{--register-only}}''' option is an option specific  
to the '''{{install}}''' command '''{{pear}}''' provides.

Obviously not all command line interfaces match this scheme and hence  
{{Horde_Cli_Modular}} shouldn't be considered to be a generic utility  
for all CLI tools. But for all CLI helpers that have such a structure  
the library should provide a decent skeleton that allows to quickly  
start adding modules.

++ Structure

{{Horde_Cli_Modular}} provides four classes as main structural elements:

: {{Horde_Cli_Modular}} : The entry point for generating the command  
line interface.
: {{Horde_Cli_Modular_Modules}} : The handler for the list of modules.
: {{Horde_Cli_Modular_ModuleProvide}} : A module factory.
: {{Horde_Cli_Modular_Module}} : The interface definition for a module.

++ Horde_Cli_Modular

This class is entry point for constructing a modular command line  
interface. The class provides methods to combine and access the  
different modules.

+++ Setup

This class generates the basic setup and you will only have to provide  
a few basic parameters to setup the system. This introduction will  
only focus on the central settings and you will need to lookup the API  
documentation for further details.

The following demonstrates how you could construct the  
{{Horde_Cli_Modular}} instance:

<code type="php">
$modular = new Horde_Cli_Modular(
   array(
     'parser' => array('usage' => '[options] MODULE'),
     'modules' => array('directory' => dirname(__FILE__) . '/Module'),
     'provider' => array('prefix' => 'Horde_Something_Module_')
   )
);
</code>

The '''{{parser}}''' parameter preparse the command line argument  
parser (usually {{Horde_Argv}}. The snippet above only provides the  
'''{{usage}}''' setting that will be displayed as the condensed usage  
instruction when the user requests the help for the command.

The '''{{modules}}''' part defines the '''{{directory}}''' that  
contains the various modules that form the command line interface.

And finally the '''{{provider}}''' setting indicates the common  
'''{{prefix}}''' that the module classes will have.

The file structure for the hypothetical {{Horde_Something}} package  
would look like this in order to match the setup presented above:

<code>
lib/
   Horde/
     Something.php
     Something/
       Module/
         One.php
         Two.php
</code>

There are two modules: {{Horde_Something_Module_One}} in {{One.php}}  
and {{Horde_Something_Module_Two}} in {{Two.php}}.

+++ Usage

After creating the {{Horde_Cli_Modular}} instance you should create  
the command line parser and read the arguments the user provided.

<code type="php">
$parser = $modular->createParser();
list($options, $arguments) = $parser->parseArgs();
</code>

This is the main action you will need.

Beyond that {{Horde_Cli_Modular}} will allow you to retrieve the list  
of modules with:

<code type="php">
$modules = $modular->getModules();
</code>

And you can retrieve a module instance using:

<code type="php">
$module = $modular->getProvider()->getModule('one');
</code>

++ Writing modules

First and foremost each module can add its own option group with a  
specific title, description and a set of module specific options (see  
Horde_Argv_OptionGroup for exact details). In addition  
{{Horde_Cli_Modular}} allows a module to modify the global usage  
string and add basic options valid for all modules.

For that to work all modules are required to implement the  
{{Horde_Cli_Modular_Module}} interface:

<code type="php">
interface Horde_Cli_Modular_Module
{
     public function getUsage();
     public function getBaseOptions();
     public function hasOptionGroup();
     public function getOptionGroupTitle();
     public function getOptionGroupDescription();
     public function getOptionGroupOptions();
}
</code>

There are two function that allow to influence the global setup of the  
command line parser: {{getUsage()}} and {{getBaseOptions()}}. The  
first one returns a string that will be added to the generic usage  
description displayed when the user requests the help screen. The  
second one returns an array of {{Horde_Argv_Option}} instances that  
each define an option valid for all modules.

If the module defines its own option group (that will be displayed as  
a separate section in the help text for the command)  
{{hasOptionGroup()}} needs to return '''{{true}}'''.

An option group needs a title (returned as a string by  
{{getOptionGroupTitle()}}) and a descriptions (returned as a string by  
{{getOptionGroupDescription()}}). And finally an option group needs a  
list of options valid for the specific module defining the option  
group. The corresponding list is returned as an array of  
{{Horde_Argv_Option}} instances by the method  
{{getOptionGroupOptions()}}.

++ Examples

Currently the package {{Horde_Kolab_Cli}} and the {{components}}  
application both use {{Horde_Cli_Modular}}. You are referred to these  
package in order to look at real world examples using the  
{{Horde_Cli_Modular}} library.