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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.

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 further details). In addition Horde_Cli_Modular allows a module to modify the global usage string and add basic options valid for all modules.

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 option. In contrast the --register-only option is specific to the install command provided by pear.

Obviously not all command line interfaces match this scheme. 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

The Horde_Cli_Modular class is the 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 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:

$modular = new Horde_Cli_Modular(
  array(
    'parser' => array('usage' => '[options] MODULE'),
    'modules' => array('directory' => __DIR__ . '/Module'),
    'provider' => array('prefix' => 'Horde_Something_Module_')
  )
);

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 CLI script.

The modules part defines the directory that contains the various modules which are part of 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:

lib/
  Horde/
    Something.php
    Something/
      Module/
        One.php
        Two.php        

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.

$parser = $modular->createParser();
list($options, $arguments) = $parser->parseArgs();

This is the main action you will need.

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

$modules = $modular->getModules();

And you can retrieve a module instance using:

$module = $modular->getProvider()->getModule('one');

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:

interface Horde_Cli_Modular_Module
{
    public function getUsage();
    public function getBaseOptions();
    public function hasOptionGroup();
    public function getOptionGroupTitle();
    public function getOptionGroupDescription();
    public function getOptionGroupOptions();
}

There are two functions 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.