Implement a 'Deferred type loader' example

Introducing an `AuthorTypeLoader`, to be used in `BlogType`.

Note: The (SQLite) repository implementation to get all authors is simple,
focus for this example application is showcasing the GraphQL framework.

Author: jerowork

src/Domain/Author/AuthorRepository.php

@@ -13,5 +13,10 @@ interface AuthorRepository
 {
     public function getById(string $authorId): Author;
 
+    /**
+     * @return list<Author>
+     */
+    public function getByIds(string ...$authorIds): array;
+
     public function save(Author $author): void;
 }

src/Infrastructure/Api/Http/GraphQL/Loader/AuthorTypeLoader.php

@@ -0,0 +1,30 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Jerowork\ExampleApplicationGraphqlAttributeSchema\Infrastructure\Api\Http\GraphQL\Loader;
+
+use Jerowork\ExampleApplicationGraphqlAttributeSchema\Domain\Author\AuthorRepository;
+use Jerowork\ExampleApplicationGraphqlAttributeSchema\Infrastructure\Api\Http\GraphQL\Type\AuthorType;
+use Jerowork\GraphqlAttributeSchema\Type\Loader\DeferredType;
+use Jerowork\GraphqlAttributeSchema\Type\Loader\DeferredTypeLoader;
+use Symfony\Component\DependencyInjection\Attribute\Autoconfigure;
+
+#[Autoconfigure(public: true)]
+final readonly class AuthorTypeLoader implements DeferredTypeLoader
+{
+    public function __construct(
+        private AuthorRepository $authorRepository,
+    ) {}
+
+    /**
+     * @param list<string> $references
+     */
+    public function load(array $references): array
+    {
+        return array_map(
+            fn($author) => new DeferredType($author->id, new AuthorType($author)),
+            $this->authorRepository->getByIds(...$references),
+        );
+    }
+}

src/Infrastructure/Api/Http/GraphQL/Type/BlogType.php

@@ -5,9 +5,8 @@
 namespace Jerowork\ExampleApplicationGraphqlAttributeSchema\Infrastructure\Api\Http\GraphQL\Type;
 
 use DateTimeImmutable;
-use Jerowork\ExampleApplicationGraphqlAttributeSchema\Domain\Author\AuthorRepository;
 use Jerowork\ExampleApplicationGraphqlAttributeSchema\Domain\Blog\Blog;
-use Jerowork\GraphqlAttributeSchema\Attribute\Autowire;
+use Jerowork\ExampleApplicationGraphqlAttributeSchema\Infrastructure\Api\Http\GraphQL\Loader\AuthorTypeLoader;
 use Jerowork\GraphqlAttributeSchema\Attribute\Cursor;
 use Jerowork\GraphqlAttributeSchema\Attribute\Field;
 use Jerowork\GraphqlAttributeSchema\Attribute\Option\ListType;
@@ -42,12 +41,10 @@ public function getTitle(): string
         return $this->blog->title;
     }
 
-    #[Field]
-    public function getAuthor(
-        #[Autowire]
-        AuthorRepository $authorRepository,
-    ): AuthorType {
-        return new AuthorType($authorRepository->getById($this->blog->authorId));
+    #[Field(type: AuthorType::class, deferredTypeLoader: AuthorTypeLoader::class)]
+    public function getAuthor(): string
+    {
+        return $this->blog->authorId;
     }
 
     /**

src/Infrastructure/Persistence/Author/SQLite/SQLiteAuthorRepository.php

@@ -61,6 +61,61 @@ public function getById(string $authorId): Author
         );
     }
 
+    public function getByIds(string ...$authorIds): array
+    {
+        $sqlite = $this->sqliteFactory->create();
+
+        $idBinds = [];
+        for ($i = 0; $i < count($authorIds); ++$i) {
+            $idBinds[] = sprintf(':id_%d', $i);
+        }
+
+        $idBinds = implode(', ', $idBinds);
+
+        $statement = $sqlite->prepare(
+            <<<SQL
+                SELECT * 
+                FROM author 
+                WHERE id IN({$idBinds})
+                SQL
+        );
+
+        if ($statement === false) {
+            throw new RuntimeException('Failed to prepare statement');
+        }
+
+        $i = 0;
+        foreach ($authorIds as $authorId) {
+            $statement->bindValue(sprintf('id_%d', $i), $authorId);
+            ++$i;
+        }
+
+        $result = $statement->execute();
+
+        if ($result === false) {
+            throw new RuntimeException('Failed to execute statement');
+        }
+
+        $authors = [];
+
+        while ($row = $result->fetchArray(SQLITE3_ASSOC)) {
+            /**
+             * @var array{
+             *     id: string,
+             *     name: string,
+             *     email: null|string
+             * } $row
+             */
+            $authors[] = new Author(
+                $row['id'],
+                $row['name'],
+                $row['email'],
+            );
+        }
+
+        return $authors;
+    }
+
     public function save(Author $author): void
     {
         $sqlite = $this->sqliteFactory->create();