From 314fc18556b46a0fc5e409a9e139c6ecef8c6e20 Mon Sep 17 00:00:00 2001
From: X25 <job@x25.ru>
Date: Sun, 13 Apr 2014 19:51:37 +0400
Subject: [PATCH] Implemented Memento Pattern

---
 Memento/Caretaker.php         | 33 ++++++++++++++++++++++++++++++++
 Memento/Memento.php           | 25 ++++++++++++++++++++++++
 Memento/Originator.php        | 33 ++++++++++++++++++++++++++++++++
 Memento/README.md             | 18 ++++++++++++++++++
 README.md                     |  1 +
 Tests/Memento/MementoTest.php | 36 +++++++++++++++++++++++++++++++++++
 6 files changed, 146 insertions(+)
 create mode 100644 Memento/Caretaker.php
 create mode 100644 Memento/Memento.php
 create mode 100644 Memento/Originator.php
 create mode 100644 Memento/README.md
 create mode 100644 Tests/Memento/MementoTest.php

diff --git a/Memento/Caretaker.php b/Memento/Caretaker.php
new file mode 100644
index 0000000..9c24357
--- /dev/null
+++ b/Memento/Caretaker.php
@@ -0,0 +1,33 @@
+<?php
+
+namespace DesignPatterns\Memento;
+
+class Caretaker
+{
+    public static function run()
+    {
+        /* @var $savedStates Memento[] */
+
+        $savedStates = array();
+
+        $originator = new Originator();
+
+        //Setting state to State1
+        $originator->setState("State1");
+        //Setting state to State2
+        $originator->setState("State2");
+        //Saving State2 to Memento
+        $savedStates[] = $originator->saveToMemento();
+        //Setting state to State3
+        $originator->setState("State3");
+
+        // We can request multiple mementos, and choose which one to roll back to.
+        // Saving State3 to Memento
+        $savedStates[] = $originator->saveToMemento();
+        //Setting state to State4
+        $originator->setState("State4");
+
+        $originator->restoreFromMemento($savedStates[1]);
+        //State after restoring from Memento: State3
+    }
+}
diff --git a/Memento/Memento.php b/Memento/Memento.php
new file mode 100644
index 0000000..33e0dca
--- /dev/null
+++ b/Memento/Memento.php
@@ -0,0 +1,25 @@
+<?php
+
+namespace DesignPatterns\Memento;
+
+class Memento
+{
+    /* @var string */
+    private $state;
+
+    /**
+     * @param string $stateToSave
+     */
+    public function __construct($stateToSave)
+    {
+        $this->state = $stateToSave;
+    }
+
+    /**
+     * @return string
+     */
+    public function getState()
+    {
+        return $this->state;
+    }
+}
diff --git a/Memento/Originator.php b/Memento/Originator.php
new file mode 100644
index 0000000..6f1b9a7
--- /dev/null
+++ b/Memento/Originator.php
@@ -0,0 +1,33 @@
+<?php
+
+namespace DesignPatterns\Memento;
+
+class Originator
+{
+    /* @var string */
+    private $state;
+
+    // The class could also contain additional data that is not part of the
+    // state saved in the memento..
+
+    /**
+     * @param string $state
+     */
+    public function setState($state)
+    {
+        $this->state = $state;
+    }
+
+    /**
+     * @return Memento
+     */
+    public function saveToMemento()
+    {
+        return new Memento($this->state);
+    }
+
+    public function restoreFromMemento(Memento $memento)
+    {
+        $this->state = $memento->getState();
+    }
+}
diff --git a/Memento/README.md b/Memento/README.md
new file mode 100644
index 0000000..83ca2c0
--- /dev/null
+++ b/Memento/README.md
@@ -0,0 +1,18 @@
+# Memento
+
+## Purpose
+
+Provide the ability to restore an object to its previous state (undo via rollback).
+
+The memento pattern is implemented with three objects: the originator, a caretaker and a memento.
+The originator is some object that has an internal state.
+The caretaker is going to do something to the originator, but wants to be able to undo the change.
+The caretaker first asks the originator for a memento object. Then it does whatever operation (or sequence of operations) it was going to do.
+To roll back to the state before the operations, it returns the memento object to the originator.
+The memento object itself is an opaque object (one which the caretaker cannot, or should not, change).
+When using this pattern, care should be taken if the originator may change other objects or resources - the memento pattern operates on a single object.
+
+## Examples
+
+* The seed of a pseudorandom number generator
+* The state in a finite state machine
diff --git a/README.md b/README.md
index 56fd4df..2f9ba16 100644
--- a/README.md
+++ b/README.md
@@ -40,6 +40,7 @@ The patterns can be structured in roughly three different categories. Please cli
 * [Command](Command) [:notebook:](http://en.wikipedia.org/wiki/Command_pattern)
 * [Iterator](Iterator) [:notebook:](http://en.wikipedia.org/wiki/Iterator_pattern)
 * [Mediator](Mediator) [:notebook:](http://en.wikipedia.org/wiki/Mediator_pattern)
+* [Memento](Memento) [:notebook:](http://http://en.wikipedia.org/wiki/Memento_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)
diff --git a/Tests/Memento/MementoTest.php b/Tests/Memento/MementoTest.php
new file mode 100644
index 0000000..5fc8213
--- /dev/null
+++ b/Tests/Memento/MementoTest.php
@@ -0,0 +1,36 @@
+<?php
+
+namespace DesignPatterns\Tests\Memento;
+
+use DesignPatterns\Memento;
+
+/**
+ * MementoTest tests memento design pattern
+ */
+class MementoTest extends \PHPUnit_Framework_TestCase
+{
+
+    public function testOriginator()
+    {
+        $originator = new Memento\Originator();
+        $originator->setState("State1");
+
+        $this->assertAttributeEquals("State1", "state", $originator);
+
+        $originator->setState("State2");
+
+        $this->assertAttributeEquals("State2", "state", $originator);
+
+        $savedState = $originator->saveToMemento();
+
+        $this->assertAttributeEquals("State2", "state", $savedState);
+
+        $originator->setState("State3");
+
+        $this->assertAttributeEquals("State3", "state", $originator);
+
+        $originator->restoreFromMemento($savedState);
+
+        $this->assertAttributeEquals("State2", "state", $originator);
+    }
+}