Processor

Mechanism to process a work from a request

Installation

You can install Processor with Composer

$ composer require meuhmeuhconcept/processor

How to use it ?

The main interest of this library is the ChainProcessor. It contains multiple processors who can procced a particular work from a request and generate a response.

The ChainProcessor ask to each processors contains on it if it can proceed the job for a particular request. The first processor who awser that it can do it will be use. The response contains several things like the request itself, the status code, name of processor who do the job and obviously the output of the job.

Build a Request

Before use the processor you have to build your request. You request can be what ever you want : a simple string, an array, a object... This object will be use to determine if processor can do the job and to do it.

Example

<?php

$object; // The object is the reason of your request.

$request = ['action' => 'validate', 'item' => $object];

Proceed the job

You just have to use a Processor to try to do the job. The best way is to use a ChainProcessor who contains several processors.

<?php

$chainProcessor; // We considere that this processors is already init with several processors

$request; // We considere that you already build the request

if ($chainProcessor->supports($request) { // Test if the processor can do the job
    $response = $chainProcessor->proccess($request); //Do the job
}

In fact you can directly try to do the job with a ChainProcessor. If the job can't be done the processor return a response with the special status code Mmc\Processor\Component\ResponseStatusCode::NOT_IMPLEMENTED.

Use the Response

The fisrt thing that you have to do with a Response is to consult the status code to know how the job is done.

<?php

use Mmc\Processor\Component\ResponseStatusCode;

if ($response->getStatusCode() == ResponseStatusCode::OK) {
    // the job had been correctly done.
} else {
    $reasonPhrase = $response->getReasonPhrase();
    // The message who explain the cause of the status code
}

You can also know which Processor had done the job (when you use a ChainProcessor) with the next method :

<?php

$response->getExtra('name');

Obviously you can get the initial request (i.e. to get the input) with the method $response->getRequest().

And the more important is to get the result of the job.

<?php

$response->getOutput();

Build your own Processor

This library is not ready to play because there is no Processor define in it. You have to create them to do the job that you want.

To do it you just have to create a class who implements Mmc\Processor\Component\Processor interface.

<?php

use Mmc\Processor\Component\Processor;
use Mmc\Processor\Component\Response;
use Mmc\Processor\Component\ResponseStatusCode;

class CustomProcessor implements Processor
{
    public function supports($request)
    {
        // With the $request you have to decide if this processor can do the job

        // i.e.
        return $request instanceof MyClass;
    }

    public function process($request)
    {
        // Advice : check the method 'supports'
        if (!$this->supports($request)) {
            return new Response($request, null, ResponseStatusCode::NOT_SUPPORTED);
        }

        // do the job

        // and return the Response

        return Response($request, $output); // $output had been create during the job was doing
    }
}

Now, you just have to add it on a ChainProcessor.

<?php

$chainProcessor->add(new CustomProcessor());

Easiers ways

• use Mmc\Processor\Component\ProcessorTrait and implements Mmc\Processor\Component\Processor
• extends Mmc\Processor\Component\AbstractProcessor (who use Mmc\Processor\Component\ProcessTrait)

Why ? Because the process method :

• already test if request is supported by processor before proceed
• create and return a Response with ResponseStatusCode::INTERNAL_ERROR status code if your processor return null
• create and return a Response with ResponseStatusCode::INTERNAL_ERROR status code if your processor throw an exception.
• create and return a Response with ResponseStatusCode::OK status code if your processor return a not null value who is not an instance of Response

The difference with previous method is that 'process' method have to be call 'doProcess' and be protected.

Example with AbstractProcessor

<?php

use Mmc\Processor\Component\AbstractProcessor;

class CustomProcessor extends AbstractProcessor
{
    public function supports($request)
    {
        // With the $request you have to decide if this processor can do the job

        // i.e.
        return $request instanceof MyClass;
    }

    protected function doPocess($request)
    {
        // No need to check if $request is supported

        // do the job

        // and return the Response
        // or nothing for bad response
        // or throw exception for bad response
        // or directly the ouput for bood response
    }
}

Example with ProcessorTrait

<?php

use Mmc\Processor\Component\Processor;
use Mmc\Processor\Component\ProcessorTrait;

class CustomProcessor implements Processor
{
    use ProcessorTrait;

    public function supports($request)
    {
        // With the $request you have to decide if this processor can do the job

        // i.e.
        return $request instanceof MyClass;
    }

    protected function doPocess($request)
    {
        return $this->otherMethod($request);
    }
}

Integration with other libraries

Symfony

meuhmeuhconcept/processor contains a CompilerPass to link automatically Processor to a ChainProcessor.

Configuration

You can use this CompilerPass with class Mmc\Processor\Bridge\Symfony\DependencyInjection\Compiler\ProcessorPass or just add the bundle in your Symfony kernel like this :

// app/AppKernel.php

public function registerBundles()
{
    $bundles = [
        // ...
        new Mmc\Processor\Bridge\Symfony\Bundle\MmcProcessorBundle(),
    ];

    // ...

    return $bundles;
}

To use it you have to require symfony/dependency-injection and symfony/options-resolver packages (if you don't use Symfony fullstack).

Uses

Now you can use the tag mmc.processor.chain on a service (which is instance of ChainProcessor). Every services tagged with the name of this service will be add in it.

You can add priority parameter on the tag to set the priority of the processor (default priority is 10).

services:
    my_chain:
        class: Mmc\Processor\Component\ChainProcessor
        tags:
            - { name: 'mmc.processor.chain' }

    p1:
        class: Foo\Processor
        tags:
            - { name: 'my_chain', priority: 5 }
    p2:
        class: Bar\Processor
        tags:
            - { name: 'my_chain' }

In this example, the ChainProcessor my_chain will receive the two Processor p1 and p2.

What now ?

The input of the Processor if no constraint by a type hinting, so you can use really what you want to create your request. The ChainProcessor can do what you want... if it contains Processor who can do it.