Add new Collections component, with a first Set implementation

Author: beberlei

composer.json

@@ -26,7 +26,8 @@
     "autoload": {
         "psr-0": {
             "QafooLabs\\Refactoring": "src/main/",
-            "QafooLabs\\Patches": "src/main/"
+            "QafooLabs\\Patches": "src/main/",
+            "QafooLabs\\Collections": "src/main/"
         }
     },
 

src/main/QafooLabs/Collections/Hashable.php

@@ -0,0 +1,19 @@
+<?php
+
+namespace QafooLabs\Collections;
+
+/**
+ * Allows to span a hash over all identifing values of an object.
+ *
+ * This is used by some data structures to compute the uniqueness of
+ * an object, for example in the Set.
+ */
+interface Hashable
+{
+    /**
+     * Return a hash over identifying values of this object.
+     *
+     * @return string
+     */
+    public function hashCode();
+}

src/main/QafooLabs/Collections/Set.php

@@ -0,0 +1,52 @@
+<?php
+
+namespace QafooLabs\Collections;
+
+use Countable;
+use IteratorAggregate;
+use ArrayIterator;
+
+/**
+ * Unique Set of Elements
+ */
+class Set implements Countable, IteratorAggregate
+{
+    private $items = array();
+
+    /**
+     * Add a new item to the set.
+     *
+     * Overrides values that were previously set that have the same value
+     * or hashCode. If you pass an object make sure it implements either
+     * {__toString()} or the {@see Hashable} interface.
+     *
+     * @param mixed $item
+     * @return void
+     */
+    public function add($item)
+    {
+        if ($item instanceof Hashable) {
+            $this->items[$item->hashCode()] = $item;
+
+            return;
+        }
+
+        $this->items[(string)$item] = $item;
+    }
+
+    /**
+     * @return int
+     */
+    public function count()
+    {
+        return count($this->items);
+    }
+
+    /**
+     * @return Iterator
+     */
+    public function getIterator()
+    {
+        return new ArrayIterator(array_values($this->items));
+    }
+}

src/test/QafooLabs/Collections/SetTest.php

@@ -0,0 +1,89 @@
+<?php
+
+namespace QafooLabs\Collections;
+
+class SetTest extends \PHPUnit_Framework_TestCase
+{
+    /**
+     * @test
+     */
+    public function whenAddingItemMultipleTimes_ThenOnlyAddItOnce()
+    {
+        $item = 'A';
+
+        $set = new Set();
+        $set->add($item);
+        $set->add($item);
+
+        $this->assertEquals(1, count($set));
+    }
+
+    /**
+     * @test
+     */
+    public function whenAddingMultipleItems_ThenCountThemUniquely()
+    {
+        $item1 = 'A';
+        $item2 = 'B';
+
+        $set = new Set();
+        $set->add($item1);
+        $set->add($item1);
+        $set->add($item2);
+
+        $this->assertEquals(2, count($set));
+    }
+
+    /**
+     * @test
+     */
+    public function whenAddingHashableObjectMultipleTimes_ThenOnlyAddItOnce()
+    {
+        $item1 = new FooObject(1);
+        $item2 = new FooObject(2);
+
+        $set = new Set();
+        $set->add($item1);
+        $set->add($item1);
+        $set->add($item2);
+        $set->add($item2);
+
+        $this->assertEquals(2, count($set));
+    }
+
+    /**
+     * @test
+     */
+    public function whenIteratingOverSet_ThenReturnAllUniqueItems()
+    {
+        $item1 = 'A';
+        $item2 = 'B';
+
+        $set = new Set();
+        $set->add($item1);
+        $set->add($item2);
+
+        $values = array();
+
+        foreach ($set as $key => $value) {
+            $values[$key] = $value;
+        }
+
+        $this->assertEquals(array(0 => 'A', 1 => 'B'), $values);
+    }
+}
+
+class FooObject implements Hashable
+{
+    private $value;
+
+    public function __construct($value)
+    {
+        $this->value = $value;
+    }
+
+    public function hashCode()
+    {
+        return md5($this->value);
+    }
+}