add TagEngine singleton feature

Author: LordSimal

src/TagEngine.php

@@ -10,6 +10,11 @@
 
 class TagEngine
 {
+    /**
+     * @var self|null
+     */
+    private static ?TagEngine $instance = null;
+
     /**
      * Holds the options array
      *
@@ -36,6 +41,11 @@ class TagEngine
      */
     protected array $data = [];
 
+    /**
+     * @var array
+     */
+    protected array $discovery_cache = [];
+
     /**
      * Initialize TagEngine
      *
@@ -60,6 +70,18 @@ public function __construct(array $options = [])
         }
     }
 
+    /**
+     * @return self
+     */
+    public static function getInstance(?array $options = null): self
+    {
+        if (self::$instance === null) {
+            self::$instance = new self($options ?? []);
+        }
+
+        return self::$instance;
+    }
+
     /**
      * The regex pattern is quite insane, so let's break it down
      *
@@ -96,6 +118,12 @@ protected function registerTags(): void
     {
         if ($this->options['tag_directories']) {
             foreach ($this->options['tag_directories'] as $tag_directory) {
+                if (isset($this->discovery_cache[$tag_directory])) {
+                    continue;
+                }
+                $this->discovery_cache[$tag_directory] = true;
+
+                // This is quite expensive, so only do it once
                 $classes = Discover::in($tag_directory)->classes()
                     ->extending(CustomTag::class)->get();
                 /** @var \LordSimal\CustomHtmlElements\CustomTag|string $class */

tests/TagEngine/TagEngineTest.php

@@ -0,0 +1,33 @@
+<?php
+declare(strict_types=1);
+
+namespace LordSimal\CustomHtmlElements\Test\TagEngine;
+
+use LordSimal\CustomHtmlElements\TagEngine;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * @see \LordSimal\CustomHtmlElements\TagEngine
+ */
+class TagEngineTest extends TestCase
+{
+    /**
+     * Test singleton instance creation
+     *
+     * @return void
+     */
+    public function testGetInstance(): void
+    {
+        $options = [
+            'tag_directories' => [
+                dirname(__DIR__) . DIRECTORY_SEPARATOR . 'Tags' . DIRECTORY_SEPARATOR,
+                dirname(__DIR__) . DIRECTORY_SEPARATOR . 'plugins' . DIRECTORY_SEPARATOR,
+            ],
+        ];
+        $instance = TagEngine::getInstance($options);
+        $this->assertInstanceOf(TagEngine::class, $instance);
+
+        $sameInstance = TagEngine::getInstance();
+        $this->assertSame($instance, $sameInstance);
+    }
+}