# Creating Providers to use with Zend_Tool_Framework

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 MVC application.

## How Zend_Tool finds your Providers

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 Zend_Tool_Framework_Provider_Interface or Zend_Tool_Framework_Manifest_ProviderManifestable. 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 getProviders() which returns an array of instantiated provider interface instances.

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

- 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".

- If your provider has a method getName() it will be used instead of the previous method to determine the name.

- If your provider has "Provider" as prefix, e.g. it is called My_HelloProvider it will be stripped from the name so that the provider will be called "hello".

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.

Exposing Your Providers with a Manifest

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 Zend_Tool_Framework_Manifest_ProviderManifestable and requires the getProviders() method to return an array of instantiated providers. In anticipation of our first own provider My_Component_HelloProvider we will create the following manifest:

    class My_Component_Manifest
        implements Zend_Tool_Framework_Manifest_ProviderManifestable
    {
        public function getProviders()
        {
            return array(
                new My_Component_HelloProvider()
            );
        }
    }

## Basic Instructions for Creating Providers

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 My_Component, he would create a class named My_Component_HelloProvider in a file named `HelloProvider.php` somewhere on the include_path. This class would implement Zend_Tool_Framework_Provider_Interface, and the body of this file would only have to look like the following:

    class My_Component_HelloProvider
        implements Zend_Tool_Framework_Provider_Interface
    {
        public function say()
        {
            echo 'Hello from my provider!';
        }
    }

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

    % zf say hello
    Hello from my provider!

## The response object

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 echo() or a similiar output mechanism. Rewritting our hello provider with this knowledge it looks like:

    class My_Component_HelloProvider
        extends Zend_Tool_Framework_Provider_Abstract
    {
        public function say()
        {
            $this->_registry->getResponse
                            ->appendContent("Hello from my provider!");
        }
    }

As you can see one has to extend the Zend_Tool_Framework_Provider_Abstract to gain access to the Registry which holds the Zend_Tool_Framework_Client_Response instance.

## Advanced Development Information

### Passing Variables to a Provider

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.

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:

    class My_Component_HelloProvider
        implements Zend_Tool_Framework_Provider_Interface
    {
        public function say($name = 'Ralph')
        {
            echo 'Hello' . $name . ', from my provider!';
        }
    }

The above example can then be called via the command line `zf say hello Joe`. "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 `zf say hello` will still work, and default to the name "Ralph".

### Prompt the User for Input

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:

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

            echo 'Hello' . $name . ', from my provider!';
        }
    }

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.

### Pretending to execute a Provider Action

Another interesting feature you might wish to implement is pretendability. 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 would 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.

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.

    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!';
            }
        }
    }

To run the provider in pretend mode just call:

    % zf --pretend say hello Ralph
    I would say hello Ralph.

### Verbose and Debug modes

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:

    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");
            }
        }
    }

### Accessing User Config and Storage

Using the Enviroment variable ZF_CONFIG_FILE 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 Zend_Tool_Framework_Provider_Abstract.

    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!";
            }
        }
    }

The returned configuration is of the type Zend_Tool_Framework_Client_Config but internally the __get() and __set() magic methods proxy to a Zend_Config of the given configuration type.

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:

    class My_Component_HelloProvider
        extends Zend_Tool_Framework_Provider_Abstract
    {
        public function say()
        {
            $aValue = $this->_registry->getStorage()->get("myUsername");
            echo "Hello $aValue!";
        }
    }

The API of the storage is very simple:

    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);
    }

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.