Added Specification pattern

Author: memsb

README.md

@@ -41,6 +41,7 @@ The patterns can be structured in roughly three different categories. Please cli
 * [Mediator](Mediator) [:notebook:](http://en.wikipedia.org/wiki/Mediator_pattern)
 * [NullObject](NullObject) [:notebook:](http://en.wikipedia.org/wiki/Null_Object_pattern)
 * [Observer](Observer) [:notebook:](http://en.wikipedia.org/wiki/Observer_pattern)
+* [Specification](Specification) [:notebook:](http://en.wikipedia.org/wiki/Specification_pattern)
 * [State](State) [:notebook:](http://en.wikipedia.org/wiki/State_pattern)
 * [Strategy](Strategy) [:notebook:](http://en.wikipedia.org/wiki/Strategy_pattern)
 * [TemplateMethod](TemplateMethod) [:notebook:](http://en.wikipedia.org/wiki/Template_method_pattern)

Specification/AbstractSpecification.php

@@ -0,0 +1,53 @@
+<?php
+namespace DesignPatterns\Specification;
+
+/**
+ * An abstract specification allows the creation of wrapped specifications
+ */
+abstract class AbstractSpecification implements SpecificationInterface
+{
+    /**
+     * Checks if given item meets all criteria
+     * 
+     * @param Item $item
+     * 
+     * @return bool
+     */
+    public function isSatisfiedBy(Item $item)
+    {
+    }
+
+    /**
+     * Creates a new logical AND specification
+     * 
+     * @param SpecificationInterface $spec
+     * 
+     * @return SpecificationInterface
+     */
+    public function plus(SpecificationInterface $spec)
+    {
+        return new Plus($this, $spec);
+    }
+
+    /**
+     * Creates a new logical OR composite specification
+     * 
+     * @param SpecificationInterface $spec
+     * 
+     * @return SpecificationInterface
+     */
+    public function either(SpecificationInterface $spec)
+    {
+        return new Either($this, $spec);
+    }
+
+    /**
+     * Creates a new logical NOT specification
+     * 
+     * @return SpecificationInterface
+     */
+    public function not()
+    {
+        return new Not($this);
+    }
+}

Specification/Either.php

@@ -0,0 +1,37 @@
+<?php
+namespace DesignPatterns\Specification;
+
+/**
+ * A logical AND specification
+ */
+class Either extends AbstractSpecification
+{
+
+    protected $left;
+    protected $right;
+
+    /**
+     * A composite wrapper of two specifications
+     * 
+     * @param SpecificationInterface $left
+     * @param SpecificationInterface $right
+
+     */
+    public function __construct(SpecificationInterface $left, SpecificationInterface $right)
+    {
+        $this->left = $left;
+        $this->right = $right;
+    }
+
+    /**
+     * Returns the evaluation of both wrapped specifications as a logical AND
+     * 
+     * @param Item $item
+     * 
+     * @return bool
+     */
+    public function isSatisfiedBy(Item $item)
+    {
+        return $this->left->isSatisfiedBy($item) || $this->right->isSatisfiedBy($item);
+    }
+}

Specification/Item.php

@@ -0,0 +1,31 @@
+<?php
+namespace DesignPatterns\Specification;
+
+/**
+ * An trivial item
+ */
+class Item
+{
+    protected $price;
+
+    /**
+     * An item must have a price
+     * 
+     * @param int $price
+
+     */
+    public function __construct($price)
+    {
+        $this->price = $price;
+    }
+
+    /**
+     * Get the items price
+     * 
+     * @return int
+     */
+    public function getPrice()
+    {
+        return $this->price;
+    }
+}

Specification/Not.php

@@ -0,0 +1,34 @@
+<?php
+namespace DesignPatterns\Specification;
+
+/**
+ * A logical Not specification
+ */
+class Not extends AbstractSpecification
+{
+
+    protected $spec;
+
+    /**
+     * Creates a new specification wrapping another
+     * 
+     * @param SpecificationInterface $spec
+
+     */
+    public function __construct(SpecificationInterface $spec)
+    {
+        $this->spec = $spec;
+    }
+
+    /**
+     * Returns the negated result of the wrapped specification
+     * 
+     * @param Item $item
+     * 
+     * @return bool
+     */
+    public function isSatisfiedBy(Item $item)
+    {
+        return !$this->spec->isSatisfiedBy($item);
+    }
+}

Specification/Plus.php

@@ -0,0 +1,37 @@
+<?php
+namespace DesignPatterns\Specification;
+
+/**
+ * A logical AND specification
+ */
+class Plus extends AbstractSpecification
+{
+
+    protected $left;
+    protected $right;
+
+    /**
+     * Creation of a locical AND of two specifications
+     * 
+     * @param SpecificationInterface $left
+     * @param SpecificationInterface $right
+
+     */
+    public function __construct(SpecificationInterface $left, SpecificationInterface $right)
+    {
+        $this->left = $left;
+        $this->right = $right;
+    }
+
+    /**
+     * Checks if the composite AND of specifications passes
+     * 
+     * @param Item $item
+     * 
+     * @return bool
+     */
+    public function isSatisfiedBy(Item $item)
+    {
+        return $this->left->isSatisfiedBy($item) && $this->right->isSatisfiedBy($item);
+    }
+}

Specification/PriceSpecification.php

@@ -0,0 +1,50 @@
+<?php
+namespace DesignPatterns\Specification;
+
+/**
+ * A specification to check an Item is priced between min and max
+ */
+class PriceSpecification extends AbstractSpecification
+{
+    protected $maxPrice;
+    protected $minPrice;
+
+    /**
+     * Sets the optional maximum price
+     *
+     * @param int $maxPrice
+     */
+    public function setMaxPrice($maxPrice)
+    {
+        $this->maxPrice = $maxPrice;
+    }
+
+    /**
+     * Sets the optional minimum price
+     *
+     * @param int $minPrice
+     */
+    public function setMinPrice($minPrice)
+    {
+        $this->minPrice = $minPrice;
+    }
+
+    /**
+     * Checks if Item price falls between bounds
+     * 
+     * @param Item $item
+     * 
+     * @return bool
+     */
+    public function isSatisfiedBy(Item $item)
+    {
+        if ( !empty($this->maxPrice) && $item->getPrice() > $this->maxPrice) {
+            return false;
+        }
+        if ( !empty($this->minPrice) && $item->getPrice() < $this->minPrice) {
+            return false;
+        }
+
+        return true;
+    }
+}

Specification/SpecificationInterface.php

@@ -0,0 +1,38 @@
+<?php
+namespace DesignPatterns\Specification;
+
+/**
+ * An interface for a specification
+ */
+interface SpecificationInterface
+{
+    /**
+     * A boolean evaluation indicating if the object meets the specification
+     * 
+     * @param Item $item
+     * 
+     * @return bool
+     */
+    public function isSatisfiedBy(Item $item);
+
+    /**
+     * Creates a logical AND specification
+     * 
+     * @param SpecificationInterface $spec
+
+     */
+    public function plus(SpecificationInterface $spec);
+
+    /**
+     * Creates a logical OR specification
+     * 
+     * @param SpecificationInterface $spec
+
+     */
+    public function either(SpecificationInterface $spec);
+
+    /**
+     * Creates a logical not specification
+     */
+    public function not();
+}