Ensure every generated code is unique

config/urlshortener.php

@@ -2,6 +2,9 @@
 
 return [
 
+        // Multiplier for pseudo-random codes
+        'multiplier' => 6824219,
+
         // The characters used to generate an unique URL
         'characterset' => env('URLSHORTENER_CHARACTERSET', "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-._~"),
 

src/URL.php

@@ -36,24 +36,42 @@ function ($model) {
         );
     }
 
-    public static function generateCode($url)
+    public static function encode($num, $multiplier, $alphabet, $length_min)
     {
+        if ($num >= pow(strlen($alphabet), $length_min)) {
+            $length_min = ceil(log($num, strlen($alphabet)));
+        }
+
+        $result = '';
+
+        $num = $num * $multiplier % pow(strlen($alphabet), $length_min);
+        do {
+            $result = $alphabet[$num % strlen($alphabet)] . $result;
+            $num = intval($num / strlen($alphabet));
+        } while ($num);
+
+        $result = str_pad($result, $length_min, $alphabet[0], STR_PAD_LEFT);
+
+        return $result;
+    }
 
+    public static function generateCode($url)
+    {
         $code = "";
 
-        $characters = \str_split(config("urlshortener.characterset"));
+        $characters = config("urlshortener.characterset");
         $length = config("urlshortener.length_min");
+        $multiplier = config("urlshortener.multiplier");
 
-        for ($i = 0; $i < $length; $i++) {
-            $code .= $characters[\random_int(0, \count($characters) - 1)];
-        }
+        $number = URL::count() + 1;
+
+        $code = self::encode($number, $multiplier, $characters, $length);
 
         return $code;
     }
 
     public function __toString()
     {
-
         return (string) route('urlshortener.redirect', ['code' => $this->code]);
     }
 }

tests/BasicTest.php

@@ -1,24 +1,33 @@
 <?php
 
-namespace ArieTimmerman\Laravel\OAuth2\Tests;
+namespace ArieTimmerman\Laravel\URLShortener\Tests;
 
-use Orchestra\Testbench\TestCase;
 use ArieTimmerman\Laravel\URLShortener\URL;
 
 class BasicTest extends TestCase
 {
     private static $lengthMin = 4;
     private static $characterset = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-._~';
 
+    protected function setUp(): void
+    {
+        parent::setUp();
+
+        // $this->runDatabaseMigrations();
+        $this->artisan('migrate', ['--database' => 'testbench'])->run();
+    }
+
     protected function getEnvironmentSetUp($app)
     {
+        parent::getEnvironmentSetUp($app);
+
         $app ['config']->set('urlshortener.characterset', self::$characterset);
         $app ['config']->set('urlshortener.length_min', self::$lengthMin);
     }
-    
+
     public function testUrlCode()
     {
-        for ($i = 0;$i<10000;$i++) {
+        for ($i = 0; $i<10000; $i++) {
             $code = URL::generateCode("http://www.example.com");
 
             //Check if the length is correct

tests/RouteTest.php

@@ -1,9 +1,7 @@
 <?php
 
-namespace ArieTimmerman\Laravel\OAuth2\Tests;
+namespace ArieTimmerman\Laravel\URLShortener\Tests;
 
-use Orchestra\Testbench\TestCase;
-use ArieTimmerman\Laravel\URLShortener\URL;
 use ArieTimmerman\Laravel\URLShortener\URLShortener;
 use Illuminate\Support\Facades\Route;
 
@@ -12,7 +10,10 @@ class RouteTest extends TestCase
 
     protected function getEnvironmentSetUp($app)
     {
+        parent::getEnvironmentSetUp($app);
         $app ['config']->set('urlshortener.route_resource_enabled', false);
+        $app ['config']->set('urlshortener.url_prefix_code', '');
+
     }
 
     public function testRoutesRegistered()

tests/TestCase.php

@@ -0,0 +1,41 @@
+<?php
+
+namespace ArieTimmerman\Laravel\URLShortener\Tests;
+
+use Orchestra\Testbench\TestCase as OrchestraTestCase;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use Illuminate\Foundation\Testing\DatabaseMigrations;
+
+class TestCase extends OrchestraTestCase
+{
+    use RefreshDatabase;
+    use DatabaseMigrations;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+
+        $this->runDatabaseMigrations();
+    }
+
+    protected function getEnvironmentSetUp($app)
+    {
+        $app ['config']->set('app.url', 'http://localhost');
+
+        $app['config']->set('app.key', 'base64:1234mRasdLA123F0JiF02Og3bLXbk5qPE8H3+vX2O5M=');
+
+        $app['config']->set('database.default', 'testbench');
+        $app['config']->set('database.connections.testbench', [
+            'driver'   => 'sqlite',
+            'database' => ':memory:',
+            'prefix'   => '',
+        ]);
+    }
+
+    protected function getPackageProviders($app)
+    {
+        return [
+            \ArieTimmerman\Laravel\URLShortener\ServiceProvider::class,
+        ];
+    }
+}

tests/UniqueTest.php

@@ -0,0 +1,30 @@
+<?php
+
+namespace ArieTimmerman\Laravel\URLShortener\Tests;
+
+use ArieTimmerman\Laravel\URLShortener\URLShortener;
+
+class UniqueTest extends TestCase
+{
+    private static $lengthMin = 2;
+    private static $characterset = 'AB';
+
+    protected function getEnvironmentSetUp($app)
+    {
+        parent::getEnvironmentSetUp($app);
+
+        $app ['config']->set('urlshortener.characterset', self::$characterset);
+        $app ['config']->set('urlshortener.length_min', self::$lengthMin);
+    }
+
+    public function testUrlCode()
+    {
+        $all = [];
+        for ($i = 0; $i<12; $i++) {
+            $code = (string)URLShortener::shorten("http://www.example.com/" . $i);
+            $all[] = $code;
+        }
+
+        $this->assertEquals(12, count(array_unique($all)));
+    }
+}