start a restructure

Structural/Decorator/Decorator.php

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+<?php
+
+namespace DesignPatterns\Decorator;
+
+/**
+ * the Decorator MUST implement the RendererInterface contract, this is the key-feature
+ * of this design pattern. If not, this is no longer a Decorator but just a dumb
+ * wrapper.
+ */
+
+/**
+ * class Decorator
+ */
+abstract class Decorator implements RendererInterface
+{
+    /**
+     * @var RendererInterface
+     */
+    protected $wrapped;
+
+    /**
+     * You must type-hint the wrapped component :
+     * It ensures you can call renderData() in the subclasses !
+     * 
+     * @param RendererInterface $wrappable
+     */
+    public function __construct(RendererInterface $wrappable)
+    {
+        $this->wrapped = $wrappable;
+    }
+}

Structural/Decorator/README.md

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+# Decorator
+
+## Purpose
+
+To dynamically add new functionality to class instances.
+
+## Examples
+
+* Zend Framework: decorators for `Zend_Form_Element` instances
+* Web Service Layer: Decorators JSON and XML for a REST service (in this case, only one of these should be allowed of course)

Structural/Decorator/RenderInJson.php

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+<?php
+
+namespace DesignPatterns\Decorator;
+
+/**
+ * Class RenderInJson
+ */
+class RenderInJson extends Decorator
+{
+    /**
+     * render data as JSON
+     *
+     * @return mixed|string
+     */
+    public function renderData()
+    {
+        $output = $this->wrapped->renderData();
+
+        return json_encode($output);
+    }
+}

Structural/Decorator/RenderInXml.php

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+<?php
+
+namespace DesignPatterns\Decorator;
+
+/**
+ * Class RenderInXml
+ */
+class RenderInXml extends Decorator
+{
+    /**
+     * render data as XML
+     *
+     * @return mixed|string
+     */
+    public function renderData()
+    {
+        $output = $this->wrapped->renderData();
+
+        // do some fancy conversion to xml from array ...
+
+        $doc = new \DOMDocument();
+
+        foreach ($output as $key => $val) {
+            $doc->appendChild($doc->createElement($key, $val));
+        }
+
+        return $doc->saveXML();
+    }
+}

Structural/Decorator/RendererInterface.php

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+<?php
+
+namespace DesignPatterns\Decorator;
+
+/**
+ * Class RendererInterface
+ */
+interface RendererInterface
+{
+    /**
+     * render data
+     *
+     * @return mixed
+     */
+    public function renderData();
+}

Structural/Decorator/Test/DecoratorTest.php

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+<?php
+
+namespace DesignPatterns\Tests\Decorator;
+
+use DesignPatterns\Decorator;
+
+/**
+ * DecoratorTest tests the decorator pattern
+ */
+class DecoratorTest extends \PHPUnit_Framework_TestCase
+{
+
+    protected $service;
+
+    protected function setUp()
+    {
+        $this->service = new Decorator\Webservice(array('foo' => 'bar'));
+    }
+
+    public function testJsonDecorator()
+    {
+        // Wrap service with a JSON decorator for renderers
+        $service = new Decorator\RenderInJson($this->service);
+        // Our Renderer will now output JSON instead of an array
+        $this->assertEquals('{"foo":"bar"}', $service->renderData());
+    }
+
+    public function testXmlDecorator()
+    {
+        // Wrap service with a JSON decorator for renderers
+        $service = new Decorator\RenderInXml($this->service);
+        // Our Renderer will now output XML instead of an array
+        $this->assertXmlStringEqualsXmlString('<?xml version="1.0"?><foo>bar</foo>', $service->renderData());
+    }
+
+    /**
+     * The first key-point of this pattern :
+     */
+    public function testDecoratorMustImplementsRenderer()
+    {
+        $this->assertTrue(is_subclass_of('DesignPatterns\Decorator\Decorator', 'DesignPatterns\Decorator\RendererInterface'));
+    }
+
+    /**
+     * Second key-point of this pattern : the decorator is type-hinted
+     * 
+     * @expectedException \PHPUnit_Framework_Error
+     */
+    public function testDecoratorTypeHinted()
+    {
+        $this->getMockForAbstractClass('DesignPatterns\Decorator\Decorator', array(new \stdClass()));
+    }
+
+    /**
+     * The decorator implements and wraps the same interface
+     */
+    public function testDecoratorOnlyAcceptRenderer()
+    {
+        $mock = $this->getMock('DesignPatterns\Decorator\RendererInterface');
+        $dec = $this->getMockForAbstractClass('DesignPatterns\Decorator\Decorator', array($mock));
+        $this->assertNotNull($dec);
+    }
+}

Structural/Decorator/Webservice.php

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+<?php
+
+namespace DesignPatterns\Decorator;
+
+/**
+ * Class Webservice
+ */
+class Webservice implements RendererInterface
+{
+    /**
+     * @var mixed
+     */
+    protected $data;
+
+    /**
+     * @param mixed $data
+     */
+    public function __construct($data)
+    {
+        $this->data = $data;
+    }
+
+    /**
+     * @return string
+     */
+    public function renderData()
+    {
+        return $this->data;
+    }
+}