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    <!-- EN-Revision: 19568 -->
    <!-- Reviewed: no -->
<sect1 id="zend.tool.framework.writing-providers">
    <title>Creando Proveedores para usar con Zend_Tool_Framework</title>
    <para> In general, a provider, on its own, is nothing more than the shell
        for a developer to bundle up some capabilities they wish to dispatch
        with the command line (or other) clients. It is an analogue to what a
        "controller" is inside of your <acronym>MVC</acronym> application. </para>

    <sect2 id="zend.tool.framework.writing-providers.loading">
        <title>How Zend Tool finds your Providers</title>

        <para> By default Zend Tool uses the IncludePathLoader to find all the
            providers that you can run. It recursivly iterates all include path
            directories and opens all files that end with "Manifest.php" or
            "Provider.php". All classes in these files are inspected if they
            implement either
                <classname>Zend_Tool_Framework_Provider_Interface</classname> or
                <classname>Zend_Tool_Framework_Manifest_ProviderManifestable</classname>
            . Instances of the provider interface make up for the real
            functionality and all their public methods are accessible as
            provider actions. The ProviderManifestable interface however
            requires the implementation of a method
                <methodname>getProviders()</methodname> which returns an array
            of instantiated provider interface instances. </para>

        <para> The following naming rules apply on how you can access the
            providers that were found by the IncludePathLoader: </para>

        <itemizedlist>
            <listitem>
                <para> The last part of your classname split by underscore is
                    used for the provider name, e.g. "My_Provider_Hello" leads
                    to your provider being accessible by the name "hello".
                </para>
            </listitem>
            <listitem>
                <para> If your provider has a method
                        <methodname>getName()</methodname> it will be used
                    instead of the previous method to determine the name.
                </para>
            </listitem>
            <listitem>
                <para> If your provider has "Provider" as prefix, e.g. it is
                    called <classname>My_HelloProvider</classname> it will be
                    stripped from the name so that the provider will be called
                    "hello". </para>
            </listitem>
        </itemizedlist>

        <note>
            <para>The IncludePathLoader does not follow symlinks, that means you
                cannot link provider functionality into your include paths, they
                have to be physically present in the include paths.</para>
        </note>

        <example id="zend.tool.framework.writing-providers.loading.example">
            <title>Exposing Your Providers with a Manifest</title>

            <para> You can expose your providers to Zend Tool by offering a
                manifest with a special filename ending with "Manifest.php". A
                Provider Manifest is an implementation of the
                    <interface>Zend_Tool_Framework_Manifest_ProviderManifestable</interface>
                and requires the <methodname>getProviders()</methodname> method
                to return an array of instantiated providers. In anticipation of
                our first own provider
                    <classname>My_Component_HelloProvider</classname> we will
                create the following manifest: </para>

            <programlisting language="php"><![CDATA[
class My_Component_Manifest
    implements Zend_Tool_Framework_Manifest_ProviderManifestable
{
    public function getProviders()
    {
        return array(
            new My_Component_HelloProvider()
        );
    }
}
]]></programlisting>

        </example>
    </sect2>

    <sect2 id="zend.tool.framework.writing-providers.basic">
        <title>Basic Instructions for Creating Providers</title>

        <para> As an example, if a developer wants to add the capability of
            showing the version of a datafile that his 3rd party component is
            working from, there is only one class the developer would need to
            implement. Assuming the component is called
                <classname>My_Component</classname> , he would create a class
            named <classname>My_Component_HelloProvider</classname> in a file
            named <filename>HelloProvider.php</filename> somewhere on the
                <property>include_path</property> . This class would implement
                <classname>Zend_Tool_Framework_Provider_Interface</classname> ,
            and the body of this file would only have to look like the
            following: </para>

        <programlisting language="php"><![CDATA[
class My_Component_HelloProvider
    implements Zend_Tool_Framework_Provider_Interface
{
    public function say()
    {
        echo 'Hello from my provider!';
    }
}
]]></programlisting>

        <para> Given that code above, and assuming the developer wishes to
            access this functionality through the console client, the call would
            look like this: </para>

        <programlisting language="sh"><![CDATA[
% zf say hello
Hello from my provider!
]]></programlisting>
    </sect2>

    <sect2 id="zend.tool.framework.writing-providers.response">
        <title>The response object</title>

        <para> As discussed in the architecture section Zend Tool allows to hook
            different clients for using your Zend Tool providers. To keep
            compliant with different clients you should use the response object
            to return messages from your providers instead of using
                <methodname>echo()</methodname> or a similiar output mechanism.
            Rewritting our hello provider with this knowledge it looks like: </para>

        <programlisting language="php"><![CDATA[
class My_Component_HelloProvider
    extends Zend_Tool_Framework_Provider_Abstract
{
    public function say()
    {
        $this->_registry->getResponse
                        ->appendContent("Hello from my provider!");
    }
}
]]></programlisting>

        <para> As you can see one has to extend the
                <classname>Zend_Tool_Framework_Provider_Abstract</classname> to
            gain access to the Registry which holds the
                <classname>Zend_Tool_Framework_Client_Response</classname>
            instance. </para>
    </sect2>

    <sect2 id="zend.tool.framework.writing-providers.advanced">
        <title>Advanced Development Information</title>

        <sect3 id="zend.tool.framework.writing-providers.advanced.variables">
            <title>Passing Variables to a Provider</title>

            <para> The above "Hello World" example is great for simple commands,
                but what about something more advanced? As your scripting and
                tooling needs grow, you might find that you need the ability to
                accept variables. Much like function signatures have parameters,
                your tooling requests can also accept parameters. </para>

            <para> Just as each tooling request can be isolated to a method
                within a class, the parameters of a tooling request can also be
                isolated in a very well known place. Parameters of the action
                methods of a provider can include the same parameters you want
                your client to utilize when calling that provider and action
                combination. For example, if you wanted to accept a name in the
                above example, you would probably do this in OO code: </para>

            <programlisting language="php"><![CDATA[
class My_Component_HelloProvider
    implements Zend_Tool_Framework_Provider_Interface
{
    public function say($name = 'Ralph')
    {
        echo 'Hello' . $name . ', from my provider!';
    }
}
]]></programlisting>

            <para> The above example can then be called via the command line
                    <command>zf say hello Joe</command> . "Joe" will be supplied
                to the provider as a parameter of the method call. Also note, as
                you see that the parameter is optional, that means it is also
                optional on the command line, so that <command>zf say
                    hello</command> will still work, and default to the name
                "Ralph". </para>

        </sect3>

        <sect3 id="zend.tool.framework.writing-providers.advanced.prompt">
            <title>Prompt the User for Input</title>

            <para> There are cases when the workflow of your provider requires
                to prompt the user for input. This can be done by requesting the
                client to ask for more the required input by calling: </para>

            <programlisting language="php"><![CDATA[
class My_Component_HelloProvider
    extends Zend_Tool_Framework_Provider_Abstract
{
    public function say($name = 'Ralph')
    {
        $nameResponse = $this->_registry
                             ->getClient()
                             ->promptInteractiveInput("Whats your name?");
        $name = $name->getContent();

        echo 'Hello' . $name . ', from my provider!';
    }
}
]]></programlisting>

            <para> This command throws an exception if the current client is not
                able to handle interactive requests. In case of the default
                Console Client however you will be asked to enter the name.
            </para>
        </sect3>

        <sect3 id="zend.tool.framework.writing-providers.advanced.pretendable">
            <title>Pretending to execute a Provider Action</title>

            <para> Another interesting feature you might wish to implement is
                    <emphasis>pretendability</emphasis> . Pretendabilty is the
                ability for your provider to "pretend" as if it is doing the
                requested action and provider combination and give the user as
                much information about what it <emphasis>would</emphasis> do
                without actually doing it. This might be an important notion
                when doing heavy database or filesystem modifications that the
                user might not otherwise want to do. </para>

            <para> Pretendability is easy to implement. There are two parts to
                this feature: 1) marking the provider as having the ability to
                "pretend", and 2) checking the request to ensure the current
                request was indeed asked to be "pretended". This feature is
                demonstrated in the code sample below. </para>

            <programlisting language="php"><![CDATA[
class My_Component_HelloProvider
    extends    Zend_Tool_Framework_Provider_Abstract
    implements Zend_Tool_Framework_Provider_Pretendable
{
    public function say($name = 'Ralph')
    {
        if ($this->_registry->getRequest()->isPretend()) {
            echo 'I would say hello to ' . $name . '.';
        } else {
            echo 'Hello' . $name . ', from my provider!';
        }
    }
}
]]></programlisting>

            <para> To run the provider in pretend mode just call: </para>

            <programlisting language="sh"><![CDATA[
% zf --pretend say hello Ralph
I would say hello Ralph.
]]></programlisting>

        </sect3>

        <sect3 id="zend.tool.framework.writing-providers.advanced.verbosedebug">
            <title>Verbose and Debug modes</title>

            <para> You can also run your provider actions in "verbose" or
                "debug" modes. The semantics in regard to this actions have to
                be implemented by you in the context of your provider. You can
                access debug or verbose modes with: </para>

            <programlisting language="php"><![CDATA[
class My_Component_HelloProvider
    implements Zend_Tool_Framework_Provider_Interface
{
    public function say($name = 'Ralph')
    {
        if($this->_registry->getRequest()->isVerbose()) {
            echo "Hello::say has been called\n";
        }
        if($this->_registry->getRequest()->isDebug()) {
            syslog(LOG_INFO, "Hello::say has been called\n");
        }
    }
}
]]></programlisting>
        </sect3>

        <sect3 id="zend.tool.framework.writing-providers.advanced.configstorage">
            <title>Accessing User Config and Storage</title>

            <para> Using the Enviroment variable
                    <property>ZF_CONFIG_FILE</property> or the .zf.ini in your
                home directory you can inject configuration parameters into any
                Zend Tool provider. Access to this configuration is available
                via the registry that is passed to your provider if you extend
                    <classname>Zend_Tool_Framework_Provider_Abstract</classname>
                . </para>

            <programlisting language="php"><![CDATA[
class My_Component_HelloProvider
    extends Zend_Tool_Framework_Provider_Abstract
{
    public function say()
    {
        $username = $this->_registry->getConfig()->username;
        if(!empty($username)) {
            echo "Hello $username!";
        } else {
            echo "Hello!";
        }
    }
}
]]></programlisting>

            <para> The returned configuration is of the type
                    <classname>Zend_Tool_Framework_Client_Config</classname> but
                internally the <methodname>__get()</methodname> and
                    <methodname>__set()</methodname> magic methods proxy to a
                    <classname>Zend_Config</classname> of the given
                configuration type. </para>

            <para> The storage allows to save arbitrary data for later
                reference. This can be useful for batch processing tasks or for
                re-runs of your tasks. You can access the storage in a similar
                way like the configuration: </para>

            <programlisting language="php"><![CDATA[
class My_Component_HelloProvider
    extends Zend_Tool_Framework_Provider_Abstract
{
    public function say()
    {
        $aValue = $this->_registry->getStorage()->get("myUsername");
        echo "Hello $aValue!";
    }
}
]]></programlisting>

            <para> The API of the storage is very simple: </para>

            <programlisting language="php"><![CDATA[
class Zend_Tool_Framework_Client_Storage
{
    public function setAdapter($adapter);
    public function isEnabled();
    public function put($name, $value);
    public function get($name, $defaultValue=null);
    public function has($name);
    public function remove($name);
    public function getStreamUri($name);
}
]]></programlisting>

            <important>
                <para> When designing your providers that are config or storage
                    aware remember to check if the required user-config or
                    storage keys really exist for a user. You won't run into
                    fatal errors when none of these are provided though, since
                    empty ones are created upon request. </para>
            </important>
        </sect3>

    </sect2>
</sect1>
