Memoize the hydrated PublicSuffixList in-process

config/services.yaml

@@ -22,7 +22,11 @@ services:
             $namespace: 'jeremykendall_php-domain-parser'
             $directory: '%kernel.cache_dir%'
 
-    Pdp\Storage\PublicSuffixListClient: '@Pdp\Storage\RulesStorage'
+    Pdp\Storage\PublicSuffixListClient: '@AssoConnect\ValidatorBundle\Cache\MemoizingPublicSuffixListClient'
+
+    AssoConnect\ValidatorBundle\Cache\MemoizingPublicSuffixListClient:
+        arguments:
+            $decorated: '@Pdp\Storage\RulesStorage'
 
     Pdp\Storage\RulesStorage:
         arguments:

src/Cache/MemoizingPublicSuffixListClient.php

@@ -0,0 +1,31 @@
+<?php
+
+declare(strict_types=1);
+
+namespace AssoConnect\ValidatorBundle\Cache;
+
+use Pdp\PublicSuffixList;
+use Pdp\Storage\PublicSuffixListClient;
+
+/**
+ * Keeps the hydrated PublicSuffixList in memory so repeated lookups in the same
+ * process do not unserialize the list from the PSR-16 cache on every call.
+ */
+final class MemoizingPublicSuffixListClient implements PublicSuffixListClient
+{
+    /** @var array<string, PublicSuffixList> */
+    private array $cache = [];
+
+    public function __construct(private readonly PublicSuffixListClient $decorated)
+    {
+    }
+
+    public function get(string $uri): PublicSuffixList
+    {
+        if (!isset($this->cache[$uri])) {
+            $this->cache[$uri] = $this->decorated->get($uri);
+        }
+
+        return $this->cache[$uri];
+    }
+}

tests/Cache/MemoizingPublicSuffixListClientTest.php

@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+namespace AssoConnect\ValidatorBundle\Tests\Cache;
+
+use AssoConnect\ValidatorBundle\Cache\MemoizingPublicSuffixListClient;
+use Pdp\PublicSuffixList;
+use Pdp\Storage\PublicSuffixListClient;
+use PHPUnit\Framework\TestCase;
+
+class MemoizingPublicSuffixListClientTest extends TestCase
+{
+    public function testGetMemoizesResultForSameUri(): void
+    {
+        $publicSuffixList = self::createStub(PublicSuffixList::class);
+
+        $decorated = $this->createMock(PublicSuffixListClient::class);
+        $decorated->expects(self::once())
+            ->method('get')
+            ->with('https://example.com/public_suffix_list.dat')
+            ->willReturn($publicSuffixList);
+
+        $memoizingPublicSuffixListClient = new MemoizingPublicSuffixListClient($decorated);
+
+        $firstResult = $memoizingPublicSuffixListClient->get('https://example.com/public_suffix_list.dat');
+        $secondResult = $memoizingPublicSuffixListClient->get('https://example.com/public_suffix_list.dat');
+
+        self::assertSame($publicSuffixList, $firstResult);
+        self::assertSame($publicSuffixList, $secondResult);
+    }
+}