From 9808ff5923e787b3346e6503dbb8e012aef169c8 Mon Sep 17 00:00:00 2001
From: Sam Mousa <sam@mousa.nl>
Date: Mon, 12 Nov 2018 16:58:56 +0100
Subject: [PATCH 1/4] Refactor singleton functionality into trait

---
 server/libs/FileDownloader.php | 13 -------------
 server/libs/FileManager.php    |  1 +
 server/libs/FileUploader.php   | 10 ----------
 server/libs/MailSender.php     | 10 +---------
 server/libs/SingletonTrait.php | 18 ++++++++++++++++++
 server/models/Session.php      | 11 ++---------
 6 files changed, 22 insertions(+), 41 deletions(-)
 create mode 100644 server/libs/SingletonTrait.php

diff --git a/server/libs/FileDownloader.php b/server/libs/FileDownloader.php
index 3d069029..2671c9a3 100755
--- a/server/libs/FileDownloader.php
+++ b/server/libs/FileDownloader.php
@@ -1,19 +1,6 @@
 <?php
 
 class FileDownloader extends FileManager {
-
-    private static $instance = null;
-
-    public static function getInstance() {
-        if (self::$instance === null) {
-            self::$instance = new FileDownloader();
-        }
-
-        return self::$instance;
-    }
-
-    private function __construct() {}
-
     public function download() {
         $fullFilePath = $this->getFullFilePath();
 
diff --git a/server/libs/FileManager.php b/server/libs/FileManager.php
index d1b9f147..86c7be0f 100755
--- a/server/libs/FileManager.php
+++ b/server/libs/FileManager.php
@@ -1,6 +1,7 @@
 <?php
 
 abstract class FileManager {
+    use SingletonTrait;
     private $fileName;
     private $localPath = 'files/';
 
diff --git a/server/libs/FileUploader.php b/server/libs/FileUploader.php
index c2eb6417..9af41d61 100755
--- a/server/libs/FileUploader.php
+++ b/server/libs/FileUploader.php
@@ -8,16 +8,6 @@ class FileUploader extends FileManager {
     private $permission;
     private $storage;
 
-    private static $instance = null;
-
-    public static function getInstance() {
-        if (self::$instance === null) {
-            self::$instance = new FileUploader();
-        }
-
-        return self::$instance;
-    }
-
     private function __construct() {
         $this->storage = new \Upload\Storage\FileSystem($this->getLocalPath());
     }
diff --git a/server/libs/MailSender.php b/server/libs/MailSender.php
index 1d6b2172..1f0b9c7b 100755
--- a/server/libs/MailSender.php
+++ b/server/libs/MailSender.php
@@ -1,17 +1,9 @@
 <?php
 class MailSender {
+    use SingletonTrait;
 
     private $mailOptions = [];
     private $mailerInstance;
-    private static $instance = NULL;
-
-    public static function getInstance() {
-        if(MailSender::$instance === NULL) {
-            MailSender::$instance = new MailSender();
-        }
-
-        return MailSender::$instance;
-    }
 
     private function __construct() {
         $this->setConnectionSettings(
diff --git a/server/libs/SingletonTrait.php b/server/libs/SingletonTrait.php
new file mode 100644
index 00000000..6655915c
--- /dev/null
+++ b/server/libs/SingletonTrait.php
@@ -0,0 +1,18 @@
+<?php
+
+trait SingletonTrait
+{
+    private static $instance;
+
+    private function __construct()
+    {
+    }
+
+    public static function getInstance()
+    {
+        if (!isset(static::$instance)) {
+            static::$instance = new static();
+        }
+        return static::$instance;
+    }
+}
\ No newline at end of file
diff --git a/server/models/Session.php b/server/models/Session.php
index d5268a20..bf6d6531 100755
--- a/server/models/Session.php
+++ b/server/models/Session.php
@@ -1,7 +1,8 @@
 <?php
 
 class Session {
-    static $instance = null;
+    use SingletonTrait;
+
     private $sessionPrefix = '';
     
     private function __construct() {
@@ -17,14 +18,6 @@ class Session {
         session_destroy();
     }
 
-    public static function getInstance() {
-        if (!self::$instance) {
-            self::$instance = new Session();
-        }
-
-        return self::$instance;
-    }
-
     public function createSession($userId, $staff = false) {
         $this->store('userId', $userId);
         $this->store('staff', $staff);

From f5d77bdd5489afea7d8dab12ab4ac4e0922785e4 Mon Sep 17 00:00:00 2001
From: Sam Mousa <sam@mousa.nl>
Date: Mon, 12 Nov 2018 17:18:19 +0100
Subject: [PATCH 2/4] Add `SingletonTrait` to composers' autoloader

---
 server/composer.json | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/server/composer.json b/server/composer.json
index 33104af1..385b094c 100755
--- a/server/composer.json
+++ b/server/composer.json
@@ -11,5 +11,10 @@
     },
     "require-dev": {
         "phpunit/phpunit": "^5.7"
+    },
+    "autoload": {
+        "classmap": [
+            "libs/SingletonTrait.php"
+        ]
     }
 }

From 5c88c8ac2a5b601ab389f456fb9fa7e1018818c2 Mon Sep 17 00:00:00 2001
From: Sam Mousa <sam@mousa.nl>
Date: Mon, 19 Nov 2018 14:14:27 +0100
Subject: [PATCH 3/4] Make constructor protected

---
 server/libs/FileUploader.php   | 3 ++-
 server/libs/SingletonTrait.php | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/server/libs/FileUploader.php b/server/libs/FileUploader.php
index 382e25d4..e6cb6fcc 100755
--- a/server/libs/FileUploader.php
+++ b/server/libs/FileUploader.php
@@ -6,7 +6,8 @@ class FileUploader extends FileManager {
     private $permission;
     private $storage;
 
-    private function __construct() {
+    protected function __construct() {
+        parent::__construct();
         $this->storage = new \Upload\Storage\FileSystem($this->getLocalPath());
     }
 
diff --git a/server/libs/SingletonTrait.php b/server/libs/SingletonTrait.php
index 6655915c..9443e150 100644
--- a/server/libs/SingletonTrait.php
+++ b/server/libs/SingletonTrait.php
@@ -4,7 +4,7 @@ trait SingletonTrait
 {
     private static $instance;
 
-    private function __construct()
+    protected function __construct()
     {
     }
 

From 1a5f38f6dec0b7a3af3c810402bc016270dd2c91 Mon Sep 17 00:00:00 2001
From: Sam Mousa <sam@mousa.nl>
Date: Mon, 19 Nov 2018 14:27:42 +0100
Subject: [PATCH 4/4] Improved singleton implementation

---
 server/libs/FileDownloader.php | 2 ++
 server/libs/FileManager.php    | 1 -
 server/libs/FileUploader.php   | 5 +++--
 server/libs/SingletonTrait.php | 9 +++++++--
 4 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/server/libs/FileDownloader.php b/server/libs/FileDownloader.php
index 2671c9a3..4ea3bcf2 100755
--- a/server/libs/FileDownloader.php
+++ b/server/libs/FileDownloader.php
@@ -1,6 +1,8 @@
 <?php
 
 class FileDownloader extends FileManager {
+    use SingletonTrait;
+
     public function download() {
         $fullFilePath = $this->getFullFilePath();
 
diff --git a/server/libs/FileManager.php b/server/libs/FileManager.php
index 86c7be0f..d1b9f147 100755
--- a/server/libs/FileManager.php
+++ b/server/libs/FileManager.php
@@ -1,7 +1,6 @@
 <?php
 
 abstract class FileManager {
-    use SingletonTrait;
     private $fileName;
     private $localPath = 'files/';
 
diff --git a/server/libs/FileUploader.php b/server/libs/FileUploader.php
index e6cb6fcc..e93a031a 100755
--- a/server/libs/FileUploader.php
+++ b/server/libs/FileUploader.php
@@ -1,13 +1,14 @@
 <?php
 
 class FileUploader extends FileManager {
+    use SingletonTrait;
+
     private $maxSize = 1;
     private $fileName;
     private $permission;
     private $storage;
 
-    protected function __construct() {
-        parent::__construct();
+    private function __construct() {
         $this->storage = new \Upload\Storage\FileSystem($this->getLocalPath());
     }
 
diff --git a/server/libs/SingletonTrait.php b/server/libs/SingletonTrait.php
index 9443e150..429ebddf 100644
--- a/server/libs/SingletonTrait.php
+++ b/server/libs/SingletonTrait.php
@@ -1,10 +1,15 @@
 <?php
 
+/**
+ * Trait SingletonTrait
+ * This trait helps implementing singleton classes
+ * It must be used on each class in a hierarchy that needs to be a singleton
+ */
 trait SingletonTrait
 {
-    private static $instance;
+    protected static $instance;
 
-    protected function __construct()
+    private function __construct()
     {
     }