Forum tree model, i18n, and frontend updates

2025-12-24 13:15:02 +01:00
parent 98a2f1d536
commit 193273c843
29 changed files with 1115 additions and 218 deletions
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -0,0 +1,8 @@
+# Changelog
+
+## 2025-12-24
+- Reworked the domain model into a single forum tree (category/forum types) with parent/child hierarchy and threads restricted to forum nodes.
+- Updated API Platform resources, filters, migrations, and JSON format support.
+- Added shared i18n: Symfony serves PO-based translations via `/api/i18n/{locale}` and React consumes them.
+- Refactored the React UI to browse forums, show sub-forums, and post threads only in forum nodes.
+- Added Apache rewrite rules for Symfony routing.
--- a/api/composer.json
+++ b/api/composer.json
@@ -26,6 +26,7 @@
        "symfony/runtime": "8.0.*",
        "symfony/security-bundle": "8.0.*",
        "symfony/serializer": "8.0.*",
+        "symfony/translation": "8.0.*",
        "symfony/twig-bundle": "8.0.*",
        "symfony/validator": "8.0.*",
        "symfony/yaml": "8.0.*"
--- a/api/composer.lock
+++ b/api/composer.lock
@@ -4,7 +4,7 @@
        "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
        "This file is @generated automatically"
    ],
-    "content-hash": "7c78a734d525250702b4a298784f81dd",
+    "content-hash": "678b66a22585eb57ff21a981f084502f",
    "packages": [
        {
            "name": "api-platform/doctrine-common",
@@ -6233,6 +6233,99 @@
            ],
            "time": "2025-12-01T09:13:36+00:00"
        },
+        {
+            "name": "symfony/translation",
+            "version": "v8.0.1",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/symfony/translation.git",
+                "reference": "770e3b8b0ba8360958abedcabacd4203467333ca"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/symfony/translation/zipball/770e3b8b0ba8360958abedcabacd4203467333ca",
+                "reference": "770e3b8b0ba8360958abedcabacd4203467333ca",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=8.4",
+                "symfony/polyfill-mbstring": "^1.0",
+                "symfony/translation-contracts": "^3.6.1"
+            },
+            "conflict": {
+                "nikic/php-parser": "<5.0",
+                "symfony/http-client-contracts": "<2.5",
+                "symfony/service-contracts": "<2.5"
+            },
+            "provide": {
+                "symfony/translation-implementation": "2.3|3.0"
+            },
+            "require-dev": {
+                "nikic/php-parser": "^5.0",
+                "psr/log": "^1|^2|^3",
+                "symfony/config": "^7.4|^8.0",
+                "symfony/console": "^7.4|^8.0",
+                "symfony/dependency-injection": "^7.4|^8.0",
+                "symfony/finder": "^7.4|^8.0",
+                "symfony/http-client-contracts": "^2.5|^3.0",
+                "symfony/http-kernel": "^7.4|^8.0",
+                "symfony/intl": "^7.4|^8.0",
+                "symfony/polyfill-intl-icu": "^1.21",
+                "symfony/routing": "^7.4|^8.0",
+                "symfony/service-contracts": "^2.5|^3",
+                "symfony/yaml": "^7.4|^8.0"
+            },
+            "type": "library",
+            "autoload": {
+                "files": [
+                    "Resources/functions.php"
+                ],
+                "psr-4": {
+                    "Symfony\\Component\\Translation\\": ""
+                },
+                "exclude-from-classmap": [
+                    "/Tests/"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Fabien Potencier",
+                    "email": "fabien@symfony.com"
+                },
+                {
+                    "name": "Symfony Community",
+                    "homepage": "https://symfony.com/contributors"
+                }
+            ],
+            "description": "Provides tools to internationalize your application",
+            "homepage": "https://symfony.com",
+            "support": {
+                "source": "https://github.com/symfony/translation/tree/v8.0.1"
+            },
+            "funding": [
+                {
+                    "url": "https://symfony.com/sponsor",
+                    "type": "custom"
+                },
+                {
+                    "url": "https://github.com/fabpot",
+                    "type": "github"
+                },
+                {
+                    "url": "https://github.com/nicolas-grekas",
+                    "type": "github"
+                },
+                {
+                    "url": "https://tidelift.com/funding/github/packagist/symfony/symfony",
+                    "type": "tidelift"
+                }
+            ],
+            "time": "2025-12-01T09:13:36+00:00"
+        },
        {
            "name": "symfony/translation-contracts",
            "version": "v3.6.1",
--- a/api/config/packages/api_platform.yaml
+++ b/api/config/packages/api_platform.yaml
@@ -1,6 +1,9 @@
 api_platform:
    title: speedBB API
    version: 1.0.0
+    formats:
+        json: ['application/json']
+        jsonld: ['application/ld+json']
    defaults:
        stateless: true
        cache_headers:
--- a/api/config/packages/translation.yaml
+++ b/api/config/packages/translation.yaml
@@ -0,0 +1,5 @@
+framework:
+    default_locale: en
+    translator:
+        default_path: '%kernel.project_dir%/translations'
+        providers:
--- a/api/config/reference.php
+++ b/api/config/reference.php
@@ -297,7 +297,7 @@ namespace Symfony\Component\DependencyInjection\Loader\Configurator;
 *         },
 *     },
 *     translator?: bool|array{ // Translator configuration
- *         enabled?: bool, // Default: false
+ *         enabled?: bool, // Default: true
 *         fallbacks?: list<scalar|null>,
 *         logging?: bool, // Default: false
 *         formatter?: scalar|null, // Default: "translator.formatter.default"
--- a/api/migrations/Version20251224115331.php
+++ b/api/migrations/Version20251224115331.php
@@ -0,0 +1,24 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DoctrineMigrations;
+
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\Migrations\AbstractMigration;
+
+final class Version20251224115331 extends AbstractMigration
+{
+    public function getDescription(): string
+    {
+        return 'Initial schema (executed previously).';
+    }
+
+    public function up(Schema $schema): void
+    {
+    }
+
+    public function down(Schema $schema): void
+    {
+    }
+}
--- a/api/migrations/Version20251224120510.php
+++ b/api/migrations/Version20251224120510.php
@@ -0,0 +1,46 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DoctrineMigrations;
+
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\Migrations\AbstractMigration;
+
+/**
+ * Auto-generated Migration: Please modify to your needs!
+ */
+final class Version20251224120510 extends AbstractMigration
+{
+    public function getDescription(): string
+    {
+        return '';
+    }
+
+    public function up(Schema $schema): void
+    {
+        // this up() migration is auto-generated, please modify it to your needs
+        $this->addSql('CREATE TABLE forum (id INT AUTO_INCREMENT NOT NULL, name VARCHAR(100) NOT NULL, description LONGTEXT DEFAULT NULL, type VARCHAR(20) NOT NULL, created_at DATETIME NOT NULL, updated_at DATETIME NOT NULL, parent_id INT DEFAULT NULL, INDEX IDX_852BBECD727ACA70 (parent_id), PRIMARY KEY (id)) DEFAULT CHARACTER SET utf8mb4');
+        $this->addSql('ALTER TABLE forum ADD CONSTRAINT FK_852BBECD727ACA70 FOREIGN KEY (parent_id) REFERENCES forum (id)');
+        $this->addSql('ALTER TABLE thread DROP FOREIGN KEY `FK_31204C8312469DE2`');
+        $this->addSql('DROP INDEX IDX_31204C8312469DE2 ON thread');
+        $this->addSql('INSERT INTO forum (id, name, description, type, created_at, updated_at) SELECT id, name, description, \'forum\', created_at, updated_at FROM category');
+        $this->addSql('ALTER TABLE thread CHANGE category_id forum_id INT NOT NULL');
+        $this->addSql('ALTER TABLE thread ADD CONSTRAINT FK_31204C8329CCBAD0 FOREIGN KEY (forum_id) REFERENCES forum (id)');
+        $this->addSql('CREATE INDEX IDX_31204C8329CCBAD0 ON thread (forum_id)');
+        $this->addSql('DROP TABLE category');
+    }
+
+    public function down(Schema $schema): void
+    {
+        // this down() migration is auto-generated, please modify it to your needs
+        $this->addSql('CREATE TABLE category (id INT AUTO_INCREMENT NOT NULL, name VARCHAR(100) CHARACTER SET utf8mb4 NOT NULL COLLATE `utf8mb4_general_ci`, description LONGTEXT CHARACTER SET utf8mb4 DEFAULT NULL COLLATE `utf8mb4_general_ci`, created_at DATETIME NOT NULL, updated_at DATETIME NOT NULL, PRIMARY KEY (id)) DEFAULT CHARACTER SET utf8mb4 COLLATE `utf8mb4_general_ci` ENGINE = InnoDB COMMENT = \'\' ');
+        $this->addSql('ALTER TABLE forum DROP FOREIGN KEY FK_852BBECD727ACA70');
+        $this->addSql('DROP TABLE forum');
+        $this->addSql('ALTER TABLE thread DROP FOREIGN KEY FK_31204C8329CCBAD0');
+        $this->addSql('DROP INDEX IDX_31204C8329CCBAD0 ON thread');
+        $this->addSql('ALTER TABLE thread CHANGE forum_id category_id INT NOT NULL');
+        $this->addSql('ALTER TABLE thread ADD CONSTRAINT `FK_31204C8312469DE2` FOREIGN KEY (category_id) REFERENCES category (id)');
+        $this->addSql('CREATE INDEX IDX_31204C8312469DE2 ON thread (category_id)');
+    }
+}
--- a/api/public/.htaccess
+++ b/api/public/.htaccess
@@ -0,0 +1,11 @@
+<IfModule mod_rewrite.c>
+    RewriteEngine On
+
+    RewriteCond %{REQUEST_FILENAME} -f
+    RewriteRule ^ - [L]
+
+    RewriteCond %{REQUEST_FILENAME} -d
+    RewriteRule ^ - [L]
+
+    RewriteRule ^ index.php [L]
+</IfModule>
--- a/api/src/Controller/I18nController.php
+++ b/api/src/Controller/I18nController.php
@@ -0,0 +1,55 @@
+<?php
+
+namespace App\Controller;
+
+use Symfony\Component\DependencyInjection\Attribute\Autowire;
+use Symfony\Component\HttpFoundation\JsonResponse;
+use Symfony\Component\Routing\Attribute\Route;
+use Symfony\Contracts\Translation\TranslatorInterface;
+
+class I18nController
+{
+    public function __construct(
+        private TranslatorInterface $translator,
+        #[Autowire('%kernel.default_locale%')]
+        private string $defaultLocale
+    ) {
+    }
+
+    #[Route(
+        '/api/i18n/{locale}',
+        name: 'api_i18n',
+        methods: ['GET'],
+        requirements: ['locale' => '[A-Za-z0-9_-]+']
+    )]
+    public function __invoke(string $locale): JsonResponse
+    {
+        $messages = $this->getMessagesForLocale($locale);
+
+        if (!$messages && $locale !== $this->defaultLocale) {
+            $messages = $this->getMessagesForLocale($this->defaultLocale);
+        }
+
+        return new JsonResponse($messages);
+    }
+
+    private function getMessagesForLocale(string $locale): array
+    {
+        $catalogue = $this->translator->getCatalogue($locale);
+        $messages = $catalogue->all('messages');
+
+        $fallback = $catalogue->getFallbackCatalogue();
+        while ($fallback) {
+            foreach ($fallback->all('messages') as $key => $value) {
+                if (!array_key_exists($key, $messages)) {
+                    $messages[$key] = $value;
+                }
+            }
+            $fallback = $fallback->getFallbackCatalogue();
+        }
+
+        ksort($messages);
+
+        return $messages;
+    }
+}
--- a/api/src/Entity/Category.php
+++ b/api/src/Entity/Category.php
@@ -2,6 +2,9 @@

 namespace App\Entity;

+use ApiPlatform\Doctrine\Orm\Filter\ExistsFilter;
+use ApiPlatform\Doctrine\Orm\Filter\SearchFilter;
+use ApiPlatform\Metadata\ApiFilter;
 use ApiPlatform\Metadata\ApiResource;
 use ApiPlatform\Metadata\Delete;
 use ApiPlatform\Metadata\Get;
@@ -16,48 +19,67 @@ use Symfony\Component\Validator\Constraints as Assert;

 #[ORM\Entity]
 #[ORM\HasLifecycleCallbacks]
+#[ApiFilter(SearchFilter::class, properties: ['parent' => 'exact', 'type' => 'exact'])]
+#[ApiFilter(ExistsFilter::class, properties: ['parent'])]
 #[ApiResource(
-    operations            : [
+    normalizationContext: ['groups' => ['forum:read']],
+    denormalizationContext: ['groups' => ['forum:write']],
+    operations: [
        new Get(),
        new GetCollection(),
        new Post(security: "is_granted('ROLE_ADMIN')"),
        new Patch(security: "is_granted('ROLE_ADMIN')"),
        new Delete(security: "is_granted('ROLE_ADMIN')")
-    ],
-    normalizationContext  : ['groups' => ['category:read']],
-    denormalizationContext: ['groups' => ['category:write']]
+    ]
 )]
-class Category
+class Forum
 {
+    public const TYPE_CATEGORY = 'category';
+    public const TYPE_FORUM = 'forum';
+
    #[ORM\Id]
    #[ORM\GeneratedValue]
    #[ORM\Column]
-    #[Groups(['category:read', 'thread:read'])]
+    #[Groups(['forum:read', 'thread:read'])]
    private ?int $id = null;

    #[ORM\Column(length: 100)]
    #[Assert\NotBlank]
-    #[Groups(['category:read', 'category:write', 'thread:read'])]
+    #[Groups(['forum:read', 'forum:write', 'thread:read'])]
    private ?string $name = null;

    #[ORM\Column(type: 'text', nullable: true)]
-    #[Groups(['category:read', 'category:write'])]
+    #[Groups(['forum:read', 'forum:write'])]
    private ?string $description = null;

+    #[ORM\Column(length: 20)]
+    #[Assert\Choice(choices: [self::TYPE_CATEGORY, self::TYPE_FORUM])]
+    #[Groups(['forum:read', 'forum:write'])]
+    private string $type = self::TYPE_CATEGORY;
+
+    #[ORM\ManyToOne(targetEntity: self::class, inversedBy: 'children')]
+    #[Groups(['forum:read', 'forum:write'])]
+    private ?self $parent = null;
+
+    #[ORM\OneToMany(mappedBy: 'parent', targetEntity: self::class)]
+    #[Groups(['forum:read'])]
+    private Collection $children;
+
+    #[ORM\OneToMany(mappedBy: 'forum', targetEntity: Thread::class)]
+    #[Groups(['forum:read'])]
+    private Collection $threads;
+
    #[ORM\Column]
-    #[Groups(['category:read'])]
+    #[Groups(['forum:read'])]
    private ?\DateTimeImmutable $createdAt = null;

    #[ORM\Column]
-    #[Groups(['category:read'])]
+    #[Groups(['forum:read'])]
    private ?\DateTimeImmutable $updatedAt = null;

-    #[ORM\OneToMany(mappedBy: 'category', targetEntity: Thread::class)]
-    #[Groups(['category:read'])]
-    private Collection $threads;
-
    public function __construct()
    {
+        $this->children = new ArrayCollection();
        $this->threads = new ArrayCollection();
    }

@@ -104,14 +126,36 @@ class Category
        return $this;
    }

-    public function getCreatedAt(): ?\DateTimeImmutable
+    public function getType(): string
    {
-        return $this->createdAt;
+        return $this->type;
    }

-    public function getUpdatedAt(): ?\DateTimeImmutable
+    public function setType(string $type): self
    {
-        return $this->updatedAt;
+        $this->type = $type;
+
+        return $this;
+    }
+
+    public function getParent(): ?self
+    {
+        return $this->parent;
+    }
+
+    public function setParent(?self $parent): self
+    {
+        $this->parent = $parent;
+
+        return $this;
+    }
+
+    /**
+     * @return Collection<int, Forum>
+     */
+    public function getChildren(): Collection
+    {
+        return $this->children;
    }

    /**
@@ -121,4 +165,14 @@ class Category
    {
        return $this->threads;
    }
+
+    public function isCategory(): bool
+    {
+        return $this->type === self::TYPE_CATEGORY;
+    }
+
+    public function isForum(): bool
+    {
+        return $this->type === self::TYPE_FORUM;
+    }
 }
--- a/api/src/Entity/Thread.php
+++ b/api/src/Entity/Thread.php
@@ -9,7 +9,7 @@ use ApiPlatform\Metadata\Delete;
 use ApiPlatform\Metadata\Get;
 use ApiPlatform\Metadata\GetCollection;
 use ApiPlatform\Metadata\Patch;
-use ApiPlatform\Metadata\Post;
+use ApiPlatform\Metadata\Post as PostOperation;
 use App\State\ThreadOwnerProcessor;
 use Doctrine\Common\Collections\ArrayCollection;
 use Doctrine\Common\Collections\Collection;
@@ -19,14 +19,14 @@ use Symfony\Component\Validator\Constraints as Assert;

 #[ORM\Entity]
 #[ORM\HasLifecycleCallbacks]
-#[ApiFilter(SearchFilter::class, properties: ['category' => 'exact'])]
+#[ApiFilter(SearchFilter::class, properties: ['forum' => 'exact'])]
 #[ApiResource(
    normalizationContext: ['groups' => ['thread:read']],
    denormalizationContext: ['groups' => ['thread:write']],
    operations: [
        new Get(),
        new GetCollection(),
-        new Post(
+        new PostOperation(
            security: "is_granted('ROLE_USER')",
            processor: ThreadOwnerProcessor::class
        ),
@@ -39,12 +39,12 @@ class Thread
    #[ORM\Id]
    #[ORM\GeneratedValue]
    #[ORM\Column]
-    #[Groups(['thread:read', 'category:read', 'post:read'])]
+    #[Groups(['thread:read', 'forum:read', 'post:read'])]
    private ?int $id = null;

    #[ORM\Column(length: 200)]
    #[Assert\NotBlank]
-    #[Groups(['thread:read', 'thread:write', 'category:read', 'post:read'])]
+    #[Groups(['thread:read', 'thread:write', 'forum:read', 'post:read'])]
    private ?string $title = null;

    #[ORM\Column(type: 'text')]
@@ -52,11 +52,12 @@ class Thread
    #[Groups(['thread:read', 'thread:write'])]
    private ?string $body = null;

-    #[ORM\ManyToOne(targetEntity: Category::class, inversedBy: 'threads')]
+    #[ORM\ManyToOne(targetEntity: Forum::class, inversedBy: 'threads')]
    #[ORM\JoinColumn(nullable: false)]
    #[Assert\NotNull]
+    #[Assert\Expression("this.getForum() and this.getForum().isForum()", message: "Thread must belong to a forum.")]
    #[Groups(['thread:read', 'thread:write'])]
-    private ?Category $category = null;
+    private ?Forum $forum = null;

    #[ORM\ManyToOne(targetEntity: User::class, inversedBy: 'threads')]
    #[ORM\JoinColumn(nullable: true, onDelete: 'SET NULL')]
@@ -123,14 +124,14 @@ class Thread
        return $this;
    }

-    public function getCategory(): ?Category
+    public function getForum(): ?Forum
    {
-        return $this->category;
+        return $this->forum;
    }

-    public function setCategory(?Category $category): self
+    public function setForum(?Forum $forum): self
    {
-        $this->category = $category;
+        $this->forum = $forum;

        return $this;
    }
--- a/api/src/Entity/User.php
+++ b/api/src/Entity/User.php
@@ -7,7 +7,7 @@ use ApiPlatform\Metadata\Delete;
 use ApiPlatform\Metadata\Get;
 use ApiPlatform\Metadata\GetCollection;
 use ApiPlatform\Metadata\Patch;
-use ApiPlatform\Metadata\Post;
+use ApiPlatform\Metadata\Post as PostOperation;
 use App\State\UserPasswordHasherProcessor;
 use Doctrine\Common\Collections\ArrayCollection;
 use Doctrine\Common\Collections\Collection;
@@ -29,7 +29,7 @@ use Symfony\Component\Validator\Constraints as Assert;
    operations: [
        new Get(security: "is_granted('ROLE_ADMIN')"),
        new GetCollection(security: "is_granted('ROLE_ADMIN')"),
-        new Post(
+        new PostOperation(
            security: "is_granted('PUBLIC_ACCESS')",
            processor: UserPasswordHasherProcessor::class,
            validationContext: ['groups' => ['Default', 'user:create']]
--- a/api/symfony.lock
+++ b/api/symfony.lock
@@ -144,6 +144,19 @@
            "config/routes/security.yaml"
        ]
    },
+    "symfony/translation": {
+        "version": "8.0",
+        "recipe": {
+            "repo": "github.com/symfony/recipes",
+            "branch": "main",
+            "version": "6.3",
+            "ref": "620a1b84865ceb2ba304c8f8bf2a185fbf32a843"
+        },
+        "files": [
+            "config/packages/translation.yaml",
+            "translations/.gitignore"
+        ]
+    },
    "symfony/twig-bundle": {
        "version": "8.0",
        "recipe": {
--- a/api/translations/.gitignore
+++ b/api/translations/.gitignore
--- a/api/translations/messages.de.po
+++ b/api/translations/messages.de.po
@@ -0,0 +1,166 @@
+msgid ""
+msgstr ""
+"Language: de\n"
+"Content-Type: text/plain; charset=UTF-8\n"
+
+msgid "app.brand"
+msgstr "speedBB"
+
+msgid "nav.forums"
+msgstr "Foren"
+
+msgid "nav.login"
+msgstr "Anmelden"
+
+msgid "nav.register"
+msgstr "Registrieren"
+
+msgid "nav.logout"
+msgstr "Abmelden"
+
+msgid "nav.language"
+msgstr "Sprache"
+
+msgid "home.hero_title"
+msgstr "Foren"
+
+msgid "home.hero_body"
+msgstr "Entdecke Diskussionen, stelle Fragen und teile Ideen in Kategorien und Foren."
+
+msgid "home.browse"
+msgstr "Foren durchsuchen"
+
+msgid "home.loading"
+msgstr "Foren werden geladen..."
+
+msgid "home.empty"
+msgstr "Noch keine Foren vorhanden. Lege das erste Forum in der API an."
+
+msgid "forum.threads"
+msgstr "Threads"
+
+msgid "forum.start_thread"
+msgstr "Thread starten"
+
+msgid "forum.loading"
+msgstr "Forum wird geladen..."
+
+msgid "forum.type_category"
+msgstr "Kategorie"
+
+msgid "forum.type_forum"
+msgstr "Forum"
+
+msgid "forum.no_description"
+msgstr "Noch keine Beschreibung vorhanden."
+
+msgid "forum.empty_threads"
+msgstr "Noch keine Threads vorhanden. Starte unten einen."
+
+msgid "forum.login_hint"
+msgstr "Melde dich an, um einen neuen Thread zu erstellen."
+
+msgid "forum.open"
+msgstr "Forum öffnen"
+
+msgid "forum.children"
+msgstr "Unterforen"
+
+msgid "forum.empty_children"
+msgstr "Noch keine Unterforen vorhanden."
+
+msgid "forum.only_forums"
+msgstr "Threads können nur in Foren erstellt werden."
+
+msgid "thread.replies"
+msgstr "Antworten"
+
+msgid "thread.reply"
+msgstr "Antworten"
+
+msgid "thread.loading"
+msgstr "Thread wird geladen..."
+
+msgid "thread.label"
+msgstr "Thread"
+
+msgid "thread.category"
+msgstr "Forum:"
+
+msgid "thread.back_to_category"
+msgstr "Zurück zum Forum"
+
+msgid "thread.empty"
+msgstr "Sei die erste Person, die antwortet."
+
+msgid "thread.anonymous"
+msgstr "Anonym"
+
+msgid "thread.login_hint"
+msgstr "Melde dich an, um auf diesen Thread zu antworten."
+
+msgid "thread.view"
+msgstr "Thread ansehen"
+
+msgid "auth.login_title"
+msgstr "Anmelden"
+
+msgid "auth.login_hint"
+msgstr "Melde dich an, um neue Threads zu starten und zu antworten."
+
+msgid "auth.register_title"
+msgstr "Konto erstellen"
+
+msgid "auth.register_hint"
+msgstr "Registriere dich mit E-Mail und einem eindeutigen Benutzernamen."
+
+msgid "footer.copy"
+msgstr "speedBB Forum. Powered by API Platform und React-Bootstrap."
+
+msgid "form.title"
+msgstr "Titel"
+
+msgid "form.body"
+msgstr "Inhalt"
+
+msgid "form.message"
+msgstr "Nachricht"
+
+msgid "form.email"
+msgstr "E-Mail"
+
+msgid "form.username"
+msgstr "Benutzername"
+
+msgid "form.password"
+msgstr "Passwort"
+
+msgid "form.thread_title_placeholder"
+msgstr "Thema"
+
+msgid "form.thread_body_placeholder"
+msgstr "Teile den Kontext und deine Frage."
+
+msgid "form.reply_placeholder"
+msgstr "Schreibe deine Antwort."
+
+msgid "form.posting"
+msgstr "Wird gesendet..."
+
+msgid "form.create_thread"
+msgstr "Thread erstellen"
+
+msgid "form.post_reply"
+msgstr "Antwort posten"
+
+msgid "form.signing_in"
+msgstr "Anmeldung läuft..."
+
+msgid "form.sign_in"
+msgstr "Anmelden"
+
+msgid "form.registering"
+msgstr "Registrierung läuft..."
+
+msgid "form.create_account"
+msgstr "Konto erstellen"
--- a/api/translations/messages.en.po
+++ b/api/translations/messages.en.po
@@ -0,0 +1,166 @@
+msgid ""
+msgstr ""
+"Language: en\n"
+"Content-Type: text/plain; charset=UTF-8\n"
+
+msgid "app.brand"
+msgstr "speedBB"
+
+msgid "nav.forums"
+msgstr "Forums"
+
+msgid "nav.login"
+msgstr "Login"
+
+msgid "nav.register"
+msgstr "Register"
+
+msgid "nav.logout"
+msgstr "Logout"
+
+msgid "nav.language"
+msgstr "Language"
+
+msgid "home.hero_title"
+msgstr "Forums"
+
+msgid "home.hero_body"
+msgstr "Explore conversations, ask questions, and share ideas across categories and forums."
+
+msgid "home.browse"
+msgstr "Browse forums"
+
+msgid "home.loading"
+msgstr "Loading forums..."
+
+msgid "home.empty"
+msgstr "No forums yet. Create the first one in the API."
+
+msgid "forum.threads"
+msgstr "Threads"
+
+msgid "forum.start_thread"
+msgstr "Start a thread"
+
+msgid "forum.loading"
+msgstr "Loading forum..."
+
+msgid "forum.type_category"
+msgstr "Category"
+
+msgid "forum.type_forum"
+msgstr "Forum"
+
+msgid "forum.no_description"
+msgstr "No description added yet."
+
+msgid "forum.empty_threads"
+msgstr "No threads here yet. Start one below."
+
+msgid "forum.login_hint"
+msgstr "Log in to create a new thread."
+
+msgid "forum.open"
+msgstr "Open forum"
+
+msgid "forum.children"
+msgstr "Sub-forums"
+
+msgid "forum.empty_children"
+msgstr "No sub-forums yet."
+
+msgid "forum.only_forums"
+msgstr "Threads can only be created in forums."
+
+msgid "thread.replies"
+msgstr "Replies"
+
+msgid "thread.reply"
+msgstr "Reply"
+
+msgid "thread.loading"
+msgstr "Loading thread..."
+
+msgid "thread.label"
+msgstr "Thread"
+
+msgid "thread.category"
+msgstr "Forum:"
+
+msgid "thread.back_to_category"
+msgstr "Back to forum"
+
+msgid "thread.empty"
+msgstr "Be the first to reply."
+
+msgid "thread.anonymous"
+msgstr "Anonymous"
+
+msgid "thread.login_hint"
+msgstr "Log in to reply to this thread."
+
+msgid "thread.view"
+msgstr "View thread"
+
+msgid "auth.login_title"
+msgstr "Log in"
+
+msgid "auth.login_hint"
+msgstr "Access your account to start new threads and reply."
+
+msgid "auth.register_title"
+msgstr "Create account"
+
+msgid "auth.register_hint"
+msgstr "Register with an email and a unique username."
+
+msgid "footer.copy"
+msgstr "speedBB forum. Powered by API Platform and React-Bootstrap."
+
+msgid "form.title"
+msgstr "Title"
+
+msgid "form.body"
+msgstr "Body"
+
+msgid "form.message"
+msgstr "Message"
+
+msgid "form.email"
+msgstr "Email"
+
+msgid "form.username"
+msgstr "Username"
+
+msgid "form.password"
+msgstr "Password"
+
+msgid "form.thread_title_placeholder"
+msgstr "Topic headline"
+
+msgid "form.thread_body_placeholder"
+msgstr "Share the context and your question."
+
+msgid "form.reply_placeholder"
+msgstr "Share your reply."
+
+msgid "form.posting"
+msgstr "Posting..."
+
+msgid "form.create_thread"
+msgstr "Create thread"
+
+msgid "form.post_reply"
+msgstr "Post reply"
+
+msgid "form.signing_in"
+msgstr "Signing in..."
+
+msgid "form.sign_in"
+msgstr "Sign in"
+
+msgid "form.registering"
+msgstr "Registering..."
+
+msgid "form.create_account"
+msgstr "Create account"
--- a/frontend/package-lock.json
+++ b/frontend/package-lock.json
@@ -9,9 +9,12 @@
      "version": "0.0.0",
      "dependencies": {
        "bootstrap": "^5.3.8",
+        "i18next": "^25.7.3",
+        "i18next-http-backend": "^3.0.2",
        "react": "^19.2.0",
        "react-bootstrap": "^2.10.10",
        "react-dom": "^19.2.0",
+        "react-i18next": "^16.5.0",
        "react-router-dom": "^7.11.0"
      },
      "devDependencies": {
@@ -1659,6 +1662,14 @@
        "url": "https://opencollective.com/express"
      }
    },
+    "node_modules/cross-fetch": {
+      "version": "4.0.0",
+      "resolved": "https://registry.npmjs.org/cross-fetch/-/cross-fetch-4.0.0.tgz",
+      "integrity": "sha512-e4a5N8lVvuLgAWgnCrLr2PP0YyDOTHa9H/Rj54dirp61qXnNq46m82bRhNqIA5VccJtWBvPTFRV3TtvHUKPB1g==",
+      "dependencies": {
+        "node-fetch": "^2.6.12"
+      }
+    },
    "node_modules/cross-spawn": {
      "version": "7.0.6",
      "resolved": "https://registry.npmjs.org/cross-spawn/-/cross-spawn-7.0.6.tgz",
@@ -2113,6 +2124,52 @@
        "hermes-estree": "0.25.1"
      }
    },
+    "node_modules/html-parse-stringify": {
+      "version": "3.0.1",
+      "resolved": "https://registry.npmjs.org/html-parse-stringify/-/html-parse-stringify-3.0.1.tgz",
+      "integrity": "sha512-KknJ50kTInJ7qIScF3jeaFRpMpE8/lfiTdzf/twXyPBLAGrLRTmkz3AdTnKeh40X8k9L2fdYwEp/42WGXIRGcg==",
+      "dependencies": {
+        "void-elements": "3.1.0"
+      }
+    },
+    "node_modules/i18next": {
+      "version": "25.7.3",
+      "resolved": "https://registry.npmjs.org/i18next/-/i18next-25.7.3.tgz",
+      "integrity": "sha512-2XaT+HpYGuc2uTExq9TVRhLsso+Dxym6PWaKpn36wfBmTI779OQ7iP/XaZHzrnGyzU4SHpFrTYLKfVyBfAhVNA==",
+      "funding": [
+        {
+          "type": "individual",
+          "url": "https://locize.com"
+        },
+        {
+          "type": "individual",
+          "url": "https://locize.com/i18next.html"
+        },
+        {
+          "type": "individual",
+          "url": "https://www.i18next.com/how-to/faq#i18next-is-awesome.-how-can-i-support-the-project"
+        }
+      ],
+      "dependencies": {
+        "@babel/runtime": "^7.28.4"
+      },
+      "peerDependencies": {
+        "typescript": "^5"
+      },
+      "peerDependenciesMeta": {
+        "typescript": {
+          "optional": true
+        }
+      }
+    },
+    "node_modules/i18next-http-backend": {
+      "version": "3.0.2",
+      "resolved": "https://registry.npmjs.org/i18next-http-backend/-/i18next-http-backend-3.0.2.tgz",
+      "integrity": "sha512-PdlvPnvIp4E1sYi46Ik4tBYh/v/NbYfFFgTjkwFl0is8A18s7/bx9aXqsrOax9WUbeNS6mD2oix7Z0yGGf6m5g==",
+      "dependencies": {
+        "cross-fetch": "4.0.0"
+      }
+    },
    "node_modules/ignore": {
      "version": "5.3.2",
      "resolved": "https://registry.npmjs.org/ignore/-/ignore-5.3.2.tgz",
@@ -2346,6 +2403,25 @@
      "integrity": "sha512-OWND8ei3VtNC9h7V60qff3SVobHr996CTwgxubgyQYEpg290h9J0buyECNNJexkFm5sOajh5G116RYA1c8ZMSw==",
      "dev": true
    },
+    "node_modules/node-fetch": {
+      "version": "2.7.0",
+      "resolved": "https://registry.npmjs.org/node-fetch/-/node-fetch-2.7.0.tgz",
+      "integrity": "sha512-c4FRfUm/dbcWZ7U+1Wq0AwCyFL+3nt2bEw05wfxSz+DWpWsitgmSgYmy2dQdWyKC1694ELPqMs/YzUSNozLt8A==",
+      "dependencies": {
+        "whatwg-url": "^5.0.0"
+      },
+      "engines": {
+        "node": "4.x || >=6.0.0"
+      },
+      "peerDependencies": {
+        "encoding": "^0.1.0"
+      },
+      "peerDependenciesMeta": {
+        "encoding": {
+          "optional": true
+        }
+      }
+    },
    "node_modules/node-releases": {
      "version": "2.0.27",
      "resolved": "https://registry.npmjs.org/node-releases/-/node-releases-2.0.27.tgz",
@@ -2572,6 +2648,32 @@
        "react": "^19.2.3"
      }
    },
+    "node_modules/react-i18next": {
+      "version": "16.5.0",
+      "resolved": "https://registry.npmjs.org/react-i18next/-/react-i18next-16.5.0.tgz",
+      "integrity": "sha512-IMpPTyCTKxEj8klCrLKUTIUa8uYTd851+jcu2fJuUB9Agkk9Qq8asw4omyeHVnOXHrLgQJGTm5zTvn8HpaPiqw==",
+      "dependencies": {
+        "@babel/runtime": "^7.27.6",
+        "html-parse-stringify": "^3.0.1",
+        "use-sync-external-store": "^1.6.0"
+      },
+      "peerDependencies": {
+        "i18next": ">= 25.6.2",
+        "react": ">= 16.8.0",
+        "typescript": "^5"
+      },
+      "peerDependenciesMeta": {
+        "react-dom": {
+          "optional": true
+        },
+        "react-native": {
+          "optional": true
+        },
+        "typescript": {
+          "optional": true
+        }
+      }
+    },
    "node_modules/react-is": {
      "version": "16.13.1",
      "resolved": "https://registry.npmjs.org/react-is/-/react-is-16.13.1.tgz",
@@ -2781,6 +2883,11 @@
        "url": "https://github.com/sponsors/SuperchupuDev"
      }
    },
+    "node_modules/tr46": {
+      "version": "0.0.3",
+      "resolved": "https://registry.npmjs.org/tr46/-/tr46-0.0.3.tgz",
+      "integrity": "sha512-N3WMsuqV66lT30CrXNbEjx4GEwlow3v6rr4mCcv6prnfwhS01rkgyFdjPNBYd9br7LpXV1+Emh01fHnq2Gdgrw=="
+    },
    "node_modules/tslib": {
      "version": "2.8.1",
      "resolved": "https://registry.npmjs.org/tslib/-/tslib-2.8.1.tgz",
@@ -2851,6 +2958,14 @@
        "punycode": "^2.1.0"
      }
    },
+    "node_modules/use-sync-external-store": {
+      "version": "1.6.0",
+      "resolved": "https://registry.npmjs.org/use-sync-external-store/-/use-sync-external-store-1.6.0.tgz",
+      "integrity": "sha512-Pp6GSwGP/NrPIrxVFAIkOQeyw8lFenOHijQWkUTrDvrF4ALqylP2C/KCkeS9dpUM3KvYRQhna5vt7IL95+ZQ9w==",
+      "peerDependencies": {
+        "react": "^16.8.0 || ^17.0.0 || ^18.0.0 || ^19.0.0"
+      }
+    },
    "node_modules/vite": {
      "version": "7.3.0",
      "resolved": "https://registry.npmjs.org/vite/-/vite-7.3.0.tgz",
@@ -2925,6 +3040,14 @@
        }
      }
    },
+    "node_modules/void-elements": {
+      "version": "3.1.0",
+      "resolved": "https://registry.npmjs.org/void-elements/-/void-elements-3.1.0.tgz",
+      "integrity": "sha512-Dhxzh5HZuiHQhbvTW9AMetFfBHDMYpo23Uo9btPXgdYP+3T5S+p+jgNy7spra+veYhBP2dCSgxR/i2Y02h5/6w==",
+      "engines": {
+        "node": ">=0.10.0"
+      }
+    },
    "node_modules/warning": {
      "version": "4.0.3",
      "resolved": "https://registry.npmjs.org/warning/-/warning-4.0.3.tgz",
@@ -2933,6 +3056,20 @@
        "loose-envify": "^1.0.0"
      }
    },
+    "node_modules/webidl-conversions": {
+      "version": "3.0.1",
+      "resolved": "https://registry.npmjs.org/webidl-conversions/-/webidl-conversions-3.0.1.tgz",
+      "integrity": "sha512-2JAn3z8AR6rjK8Sm8orRC0h/bcl/DqL7tRPdGZ4I1CjdF+EaMLmYxBHyXuKL849eucPFhvBoxMsflfOb8kxaeQ=="
+    },
+    "node_modules/whatwg-url": {
+      "version": "5.0.0",
+      "resolved": "https://registry.npmjs.org/whatwg-url/-/whatwg-url-5.0.0.tgz",
+      "integrity": "sha512-saE57nupxk6v3HY35+jzBwYa0rKSy0XR8JSxZPwgLr7ys0IBzhGviA1/TUGJLmSVqs8pb9AnvICXEuOHLprYTw==",
+      "dependencies": {
+        "tr46": "~0.0.3",
+        "webidl-conversions": "^3.0.0"
+      }
+    },
    "node_modules/which": {
      "version": "2.0.2",
      "resolved": "https://registry.npmjs.org/which/-/which-2.0.2.tgz",
--- a/frontend/package.json
+++ b/frontend/package.json
@@ -12,9 +12,12 @@
  },
  "dependencies": {
    "bootstrap": "^5.3.8",
+    "i18next": "^25.7.3",
+    "i18next-http-backend": "^3.0.2",
    "react": "^19.2.0",
    "react-bootstrap": "^2.10.10",
    "react-dom": "^19.2.0",
+    "react-i18next": "^16.5.0",
    "react-router-dom": "^7.11.0"
  },
  "devDependencies": {
--- a/frontend/src/App.jsx
+++ b/frontend/src/App.jsx
@@ -1,43 +1,58 @@
 import { BrowserRouter, Link, Route, Routes } from 'react-router-dom'
-import { Container, Nav, Navbar } from 'react-bootstrap'
+import { Container, Nav, Navbar, NavDropdown } from 'react-bootstrap'
 import { AuthProvider, useAuth } from './context/AuthContext'
 import Home from './pages/Home'
-import CategoryView from './pages/CategoryView'
+import ForumView from './pages/ForumView'
 import ThreadView from './pages/ThreadView'
 import Login from './pages/Login'
 import Register from './pages/Register'
+import { useTranslation } from 'react-i18next'

 function Navigation() {
  const { token, email, logout } = useAuth()
+  const { t, i18n } = useTranslation()
+
+  const handleLanguageChange = (locale) => {
+    i18n.changeLanguage(locale)
+    localStorage.setItem('speedbb_lang', locale)
+  }

  return (
    <Navbar expand="lg" className="bb-nav">
      <Container>
        <Navbar.Brand as={Link} to="/" className="fw-semibold">
-          speedBB
+          {t('app.brand')}
        </Navbar.Brand>
        <Navbar.Toggle aria-controls="bb-nav" />
        <Navbar.Collapse id="bb-nav">
          <Nav className="ms-auto align-items-lg-center gap-2">
            <Nav.Link as={Link} to="/">
-              Categories
+              {t('nav.forums')}
            </Nav.Link>
            {!token && (
              <>
                <Nav.Link as={Link} to="/login">
-                  Login
+                  {t('nav.login')}
                </Nav.Link>
                <Nav.Link as={Link} to="/register">
-                  Register
+                  {t('nav.register')}
                </Nav.Link>
              </>
            )}
            {token && (
              <>
                <span className="bb-chip">{email}</span>
-                <Nav.Link onClick={logout}>Logout</Nav.Link>
+                <Nav.Link onClick={logout}>{t('nav.logout')}</Nav.Link>
              </>
            )}
+            <NavDropdown title={t('nav.language')} align="end">
+              <NavDropdown.Item onClick={() => handleLanguageChange('en')}>
+                English
+              </NavDropdown.Item>
+              <NavDropdown.Item onClick={() => handleLanguageChange('de')}>
+                Deutsch
+              </NavDropdown.Item>
+            </NavDropdown>
          </Nav>
        </Navbar.Collapse>
      </Container>
@@ -46,19 +61,21 @@ function Navigation() {
 }

 function AppShell() {
+  const { t } = useTranslation()
+
  return (
    <div className="bb-shell">
      <Navigation />
      <Routes>
        <Route path="/" element={<Home />} />
-        <Route path="/category/:id" element={<CategoryView />} />
+        <Route path="/forum/:id" element={<ForumView />} />
        <Route path="/thread/:id" element={<ThreadView />} />
        <Route path="/login" element={<Login />} />
        <Route path="/register" element={<Register />} />
      </Routes>
      <footer className="bb-footer">
        <Container>
-          speedBB forum. Powered by API Platform and React-Bootstrap.
+          {t('footer.copy')}
        </Container>
      </footer>
    </div>
--- a/frontend/src/api/client.js
+++ b/frontend/src/api/client.js
@@ -50,16 +50,20 @@ export async function registerUser({ email, username, plainPassword }) {
  })
 }

-export async function listCategories() {
-  return getCollection('/categories')
+export async function listRootForums() {
+  return getCollection('/forums?parent[exists]=false')
 }

-export async function getCategory(id) {
-  return apiFetch(`/categories/${id}`)
+export async function listForumsByParent(parentId) {
+  return getCollection(`/forums?parent=/api/forums/${parentId}`)
 }

-export async function listThreadsByCategory(categoryId) {
-  return getCollection(`/threads?category=/api/categories/${categoryId}`)
+export async function getForum(id) {
+  return apiFetch(`/forums/${id}`)
+}
+
+export async function listThreadsByForum(forumId) {
+  return getCollection(`/threads?forum=/api/forums/${forumId}`)
 }

 export async function getThread(id) {
@@ -70,13 +74,13 @@ export async function listPostsByThread(threadId) {
  return getCollection(`/posts?thread=/api/threads/${threadId}`)
 }

-export async function createThread({ title, body, categoryId }) {
+export async function createThread({ title, body, forumId }) {
  return apiFetch('/threads', {
    method: 'POST',
    body: JSON.stringify({
      title,
      body,
-      category: `/api/categories/${categoryId}`,
+      forum: `/api/forums/${forumId}`,
    }),
  })
 }
--- a/frontend/src/i18n.js
+++ b/frontend/src/i18n.js
@@ -0,0 +1,25 @@
+import i18n from 'i18next'
+import HttpBackend from 'i18next-http-backend'
+import { initReactI18next } from 'react-i18next'
+
+const storedLanguage = localStorage.getItem('speedbb_lang') || 'en'
+
+i18n
+  .use(HttpBackend)
+  .use(initReactI18next)
+  .init({
+    lng: storedLanguage,
+    fallbackLng: 'en',
+    supportedLngs: ['en', 'de'],
+    backend: {
+      loadPath: '/api/i18n/{{lng}}',
+    },
+    react: {
+      useSuspense: false,
+    },
+    interpolation: {
+      escapeValue: false,
+    },
+  })
+
+export default i18n
--- a/frontend/src/main.jsx
+++ b/frontend/src/main.jsx
@@ -2,6 +2,7 @@ import { StrictMode } from 'react'
 import { createRoot } from 'react-dom/client'
 import 'bootstrap/dist/css/bootstrap.min.css'
 import './index.css'
+import './i18n'
 import App from './App.jsx'

 createRoot(document.getElementById('root')).render(
--- a/frontend/src/pages/CategoryView.jsx
+++ b/frontend/src/pages/CategoryView.jsx
@@ -1,121 +0,0 @@
-import { useEffect, useState } from 'react'
-import { Button, Card, Col, Container, Form, Row } from 'react-bootstrap'
-import { Link, useParams } from 'react-router-dom'
-import { createThread, getCategory, listThreadsByCategory } from '../api/client'
-import { useAuth } from '../context/AuthContext'
-
-export default function CategoryView() {
-  const { id } = useParams()
-  const { token } = useAuth()
-  const [category, setCategory] = useState(null)
-  const [threads, setThreads] = useState([])
-  const [error, setError] = useState('')
-  const [loading, setLoading] = useState(true)
-  const [title, setTitle] = useState('')
-  const [body, setBody] = useState('')
-  const [saving, setSaving] = useState(false)
-
-  useEffect(() => {
-    setLoading(true)
-    Promise.all([getCategory(id), listThreadsByCategory(id)])
-      .then(([categoryData, threadData]) => {
-        setCategory(categoryData)
-        setThreads(threadData)
-      })
-      .catch((err) => setError(err.message))
-      .finally(() => setLoading(false))
-  }, [id])
-
-  const handleSubmit = async (event) => {
-    event.preventDefault()
-    setSaving(true)
-    setError('')
-    try {
-      await createThread({ title, body, categoryId: id })
-      setTitle('')
-      setBody('')
-      const updated = await listThreadsByCategory(id)
-      setThreads(updated)
-    } catch (err) {
-      setError(err.message)
-    } finally {
-      setSaving(false)
-    }
-  }
-
-  return (
-    <Container className="py-5">
-      {loading && <p className="bb-muted">Loading category...</p>}
-      {error && <p className="text-danger">{error}</p>}
-      {category && (
-        <>
-          <div className="bb-hero mb-4">
-            <p className="bb-chip">Category</p>
-            <h2 className="mt-3">{category.name}</h2>
-            <p className="bb-muted mb-0">
-              {category.description || 'No description added yet.'}
-            </p>
-          </div>
-
-          <Row className="g-4">
-            <Col lg={7}>
-              <h4 className="bb-section-title mb-3">Threads</h4>
-              {threads.length === 0 && (
-                <p className="bb-muted">No threads here yet. Start one below.</p>
-              )}
-              {threads.map((thread) => (
-                <Card className="bb-card mb-3" key={thread.id}>
-                  <Card.Body>
-                    <Card.Title>{thread.title}</Card.Title>
-                    <Card.Text className="bb-muted">
-                      {thread.body.length > 160 ? `${thread.body.slice(0, 160)}...` : thread.body}
-                    </Card.Text>
-                    <Link to={`/thread/${thread.id}`} className="stretched-link">
-                      View thread
-                    </Link>
-                  </Card.Body>
-                </Card>
-              ))}
-            </Col>
-            <Col lg={5}>
-              <h4 className="bb-section-title mb-3">Start a thread</h4>
-              <div className="bb-form">
-                {!token && (
-                  <p className="bb-muted mb-3">Log in to create a new thread.</p>
-                )}
-                <Form onSubmit={handleSubmit}>
-                  <Form.Group className="mb-3">
-                    <Form.Label>Title</Form.Label>
-                    <Form.Control
-                      type="text"
-                      placeholder="Topic headline"
-                      value={title}
-                      onChange={(event) => setTitle(event.target.value)}
-                      disabled={!token || saving}
-                      required
-                    />
-                  </Form.Group>
-                  <Form.Group className="mb-3">
-                    <Form.Label>Body</Form.Label>
-                    <Form.Control
-                      as="textarea"
-                      rows={5}
-                      placeholder="Share the context and your question."
-                      value={body}
-                      onChange={(event) => setBody(event.target.value)}
-                      disabled={!token || saving}
-                      required
-                    />
-                  </Form.Group>
-                  <Button type="submit" variant="dark" disabled={!token || saving}>
-                    {saving ? 'Posting...' : 'Create thread'}
-                  </Button>
-                </Form>
-              </div>
-            </Col>
-          </Row>
-        </>
-      )}
-    </Container>
-  )
-}
--- a/frontend/src/pages/ForumView.jsx
+++ b/frontend/src/pages/ForumView.jsx
@@ -0,0 +1,180 @@
+import { useEffect, useState } from 'react'
+import { Button, Card, Col, Container, Form, Row } from 'react-bootstrap'
+import { Link, useParams } from 'react-router-dom'
+import { createThread, getForum, listForumsByParent, listThreadsByForum } from '../api/client'
+import { useAuth } from '../context/AuthContext'
+import { useTranslation } from 'react-i18next'
+
+export default function ForumView() {
+  const { id } = useParams()
+  const { token } = useAuth()
+  const [forum, setForum] = useState(null)
+  const [children, setChildren] = useState([])
+  const [threads, setThreads] = useState([])
+  const [error, setError] = useState('')
+  const [loading, setLoading] = useState(true)
+  const [title, setTitle] = useState('')
+  const [body, setBody] = useState('')
+  const [saving, setSaving] = useState(false)
+  const { t } = useTranslation()
+
+  useEffect(() => {
+    let active = true
+
+    const loadData = async () => {
+      setLoading(true)
+      setError('')
+      try {
+        const forumData = await getForum(id)
+        if (!active) return
+        setForum(forumData)
+        const childData = await listForumsByParent(id)
+        if (!active) return
+        setChildren(childData)
+        if (forumData.type === 'forum') {
+          const threadData = await listThreadsByForum(id)
+          if (!active) return
+          setThreads(threadData)
+        } else {
+          setThreads([])
+        }
+      } catch (err) {
+        if (active) setError(err.message)
+      } finally {
+        if (active) setLoading(false)
+      }
+    }
+
+    loadData()
+
+    return () => {
+      active = false
+    }
+  }, [id])
+
+  const handleSubmit = async (event) => {
+    event.preventDefault()
+    setSaving(true)
+    setError('')
+    try {
+      await createThread({ title, body, forumId: id })
+      setTitle('')
+      setBody('')
+      const updated = await listThreadsByForum(id)
+      setThreads(updated)
+    } catch (err) {
+      setError(err.message)
+    } finally {
+      setSaving(false)
+    }
+  }
+
+  return (
+    <Container className="py-5">
+      {loading && <p className="bb-muted">{t('forum.loading')}</p>}
+      {error && <p className="text-danger">{error}</p>}
+      {forum && (
+        <>
+          <div className="bb-hero mb-4">
+            <p className="bb-chip">
+              {forum.type === 'forum' ? t('forum.type_forum') : t('forum.type_category')}
+            </p>
+            <h2 className="mt-3">{forum.name}</h2>
+            <p className="bb-muted mb-0">
+              {forum.description || t('forum.no_description')}
+            </p>
+          </div>
+
+          <Row className="g-4">
+            <Col lg={7}>
+              <h4 className="bb-section-title mb-3">{t('forum.children')}</h4>
+              {children.length === 0 && (
+                <p className="bb-muted">{t('forum.empty_children')}</p>
+              )}
+              {children.map((child) => (
+                <Card className="bb-card mb-3" key={child.id}>
+                  <Card.Body>
+                    <Card.Title>{child.name}</Card.Title>
+                    <Card.Text className="bb-muted">
+                      {child.description || t('forum.no_description')}
+                    </Card.Text>
+                    <Link to={`/forum/${child.id}`} className="stretched-link">
+                      {t('forum.open')}
+                    </Link>
+                  </Card.Body>
+                </Card>
+              ))}
+
+              {forum.type === 'forum' && (
+                <>
+                  <h4 className="bb-section-title mb-3 mt-4">{t('forum.threads')}</h4>
+                  {threads.length === 0 && (
+                    <p className="bb-muted">{t('forum.empty_threads')}</p>
+                  )}
+                  {threads.map((thread) => (
+                    <Card className="bb-card mb-3" key={thread.id}>
+                      <Card.Body>
+                        <Card.Title>{thread.title}</Card.Title>
+                        <Card.Text className="bb-muted">
+                          {thread.body.length > 160
+                            ? `${thread.body.slice(0, 160)}...`
+                            : thread.body}
+                        </Card.Text>
+                        <Link to={`/thread/${thread.id}`} className="stretched-link">
+                          {t('thread.view')}
+                        </Link>
+                      </Card.Body>
+                    </Card>
+                  ))}
+                </>
+              )}
+            </Col>
+            <Col lg={5}>
+              <h4 className="bb-section-title mb-3">{t('forum.start_thread')}</h4>
+              <div className="bb-form">
+                {forum.type !== 'forum' && (
+                  <p className="bb-muted mb-3">{t('forum.only_forums')}</p>
+                )}
+                {forum.type === 'forum' && !token && (
+                  <p className="bb-muted mb-3">{t('forum.login_hint')}</p>
+                )}
+                <Form onSubmit={handleSubmit}>
+                  <Form.Group className="mb-3">
+                    <Form.Label>{t('form.title')}</Form.Label>
+                    <Form.Control
+                      type="text"
+                      placeholder={t('form.thread_title_placeholder')}
+                      value={title}
+                      onChange={(event) => setTitle(event.target.value)}
+                      disabled={!token || saving || forum.type !== 'forum'}
+                      required
+                    />
+                  </Form.Group>
+                  <Form.Group className="mb-3">
+                    <Form.Label>{t('form.body')}</Form.Label>
+                    <Form.Control
+                      as="textarea"
+                      rows={5}
+                      placeholder={t('form.thread_body_placeholder')}
+                      value={body}
+                      onChange={(event) => setBody(event.target.value)}
+                      disabled={!token || saving || forum.type !== 'forum'}
+                      required
+                    />
+                  </Form.Group>
+                  <Button
+                    type="submit"
+                    variant="dark"
+                    disabled={!token || saving || forum.type !== 'forum'}
+                  >
+                    {saving ? t('form.posting') : t('form.create_thread')}
+                  </Button>
+                </Form>
+              </div>
+            </Col>
+          </Row>
+        </>
+      )}
+    </Container>
+  )
+}
--- a/frontend/src/pages/Home.jsx
+++ b/frontend/src/pages/Home.jsx
@@ -1,16 +1,18 @@
 import { useEffect, useState } from 'react'
 import { Card, Col, Container, Row } from 'react-bootstrap'
 import { Link } from 'react-router-dom'
-import { listCategories } from '../api/client'
+import { listRootForums } from '../api/client'
+import { useTranslation } from 'react-i18next'

 export default function Home() {
-  const [categories, setCategories] = useState([])
+  const [forums, setForums] = useState([])
  const [error, setError] = useState('')
  const [loading, setLoading] = useState(true)
+  const { t } = useTranslation()

  useEffect(() => {
-    listCategories()
-      .then(setCategories)
+    listRootForums()
+      .then(setForums)
      .catch((err) => setError(err.message))
      .finally(() => setLoading(false))
  }, [])
@@ -18,31 +20,30 @@ export default function Home() {
  return (
    <Container className="py-5">
      <div className="bb-hero mb-4">
-        <p className="bb-chip">speedBB</p>
-        <h1 className="mt-3">Forum categories</h1>
+        <p className="bb-chip">{t('app.brand')}</p>
+        <h1 className="mt-3">{t('home.hero_title')}</h1>
        <p className="bb-muted mb-0">
-          Explore conversations, ask questions, and share ideas. Start in a category
-          that matches your topic.
+          {t('home.hero_body')}
        </p>
      </div>

-      <h3 className="bb-section-title mb-3">Browse categories</h3>
-      {loading && <p className="bb-muted">Loading categories...</p>}
+      <h3 className="bb-section-title mb-3">{t('home.browse')}</h3>
+      {loading && <p className="bb-muted">{t('home.loading')}</p>}
      {error && <p className="text-danger">{error}</p>}
-      {!loading && categories.length === 0 && (
-        <p className="bb-muted">No categories yet. Create the first one in the API.</p>
+      {!loading && forums.length === 0 && (
+        <p className="bb-muted">{t('home.empty')}</p>
      )}
      <Row xs={1} md={2} lg={3} className="g-4">
-        {categories.map((category) => (
-          <Col key={category.id}>
+        {forums.map((forum) => (
+          <Col key={forum.id}>
            <Card className="bb-card h-100">
              <Card.Body>
-                <Card.Title>{category.name}</Card.Title>
+                <Card.Title>{forum.name}</Card.Title>
                <Card.Text className="bb-muted">
-                  {category.description || 'No description yet.'}
+                  {forum.description || t('forum.no_description')}
                </Card.Text>
-                <Link to={`/category/${category.id}`} className="stretched-link">
-                  Open category
+                <Link to={`/forum/${forum.id}`} className="stretched-link">
+                  {t('forum.open')}
                </Link>
              </Card.Body>
            </Card>
--- a/frontend/src/pages/Login.jsx
+++ b/frontend/src/pages/Login.jsx
@@ -2,6 +2,7 @@ import { useState } from 'react'
 import { Button, Card, Container, Form } from 'react-bootstrap'
 import { useNavigate } from 'react-router-dom'
 import { useAuth } from '../context/AuthContext'
+import { useTranslation } from 'react-i18next'

 export default function Login() {
  const { login } = useAuth()
@@ -10,6 +11,7 @@ export default function Login() {
  const [password, setPassword] = useState('')
  const [error, setError] = useState('')
  const [loading, setLoading] = useState(false)
+  const { t } = useTranslation()

  const handleSubmit = async (event) => {
    event.preventDefault()
@@ -29,14 +31,12 @@ export default function Login() {
    <Container className="py-5">
      <Card className="bb-card mx-auto" style={{ maxWidth: '480px' }}>
        <Card.Body>
-          <Card.Title className="mb-3">Log in</Card.Title>
-          <Card.Text className="bb-muted">
-            Access your account to start new threads and reply.
-          </Card.Text>
+          <Card.Title className="mb-3">{t('auth.login_title')}</Card.Title>
+          <Card.Text className="bb-muted">{t('auth.login_hint')}</Card.Text>
          {error && <p className="text-danger">{error}</p>}
          <Form onSubmit={handleSubmit}>
            <Form.Group className="mb-3">
-              <Form.Label>Email</Form.Label>
+              <Form.Label>{t('form.email')}</Form.Label>
              <Form.Control
                type="email"
                value={email}
@@ -45,7 +45,7 @@ export default function Login() {
              />
            </Form.Group>
            <Form.Group className="mb-4">
-              <Form.Label>Password</Form.Label>
+              <Form.Label>{t('form.password')}</Form.Label>
              <Form.Control
                type="password"
                value={password}
@@ -54,7 +54,7 @@ export default function Login() {
              />
            </Form.Group>
            <Button type="submit" variant="dark" disabled={loading}>
-              {loading ? 'Signing in...' : 'Sign in'}
+              {loading ? t('form.signing_in') : t('form.sign_in')}
            </Button>
          </Form>
        </Card.Body>
--- a/frontend/src/pages/Register.jsx
+++ b/frontend/src/pages/Register.jsx
@@ -2,6 +2,7 @@ import { useState } from 'react'
 import { Button, Card, Container, Form } from 'react-bootstrap'
 import { useNavigate } from 'react-router-dom'
 import { registerUser } from '../api/client'
+import { useTranslation } from 'react-i18next'

 export default function Register() {
  const navigate = useNavigate()
@@ -10,6 +11,7 @@ export default function Register() {
  const [plainPassword, setPlainPassword] = useState('')
  const [error, setError] = useState('')
  const [loading, setLoading] = useState(false)
+  const { t } = useTranslation()

  const handleSubmit = async (event) => {
    event.preventDefault()
@@ -29,14 +31,12 @@ export default function Register() {
    <Container className="py-5">
      <Card className="bb-card mx-auto" style={{ maxWidth: '520px' }}>
        <Card.Body>
-          <Card.Title className="mb-3">Create account</Card.Title>
-          <Card.Text className="bb-muted">
-            Register with an email and a unique username.
-          </Card.Text>
+          <Card.Title className="mb-3">{t('auth.register_title')}</Card.Title>
+          <Card.Text className="bb-muted">{t('auth.register_hint')}</Card.Text>
          {error && <p className="text-danger">{error}</p>}
          <Form onSubmit={handleSubmit}>
            <Form.Group className="mb-3">
-              <Form.Label>Email</Form.Label>
+              <Form.Label>{t('form.email')}</Form.Label>
              <Form.Control
                type="email"
                value={email}
@@ -45,7 +45,7 @@ export default function Register() {
              />
            </Form.Group>
            <Form.Group className="mb-3">
-              <Form.Label>Username</Form.Label>
+              <Form.Label>{t('form.username')}</Form.Label>
              <Form.Control
                type="text"
                value={username}
@@ -54,7 +54,7 @@ export default function Register() {
              />
            </Form.Group>
            <Form.Group className="mb-4">
-              <Form.Label>Password</Form.Label>
+              <Form.Label>{t('form.password')}</Form.Label>
              <Form.Control
                type="password"
                value={plainPassword}
@@ -64,7 +64,7 @@ export default function Register() {
              />
            </Form.Group>
            <Button type="submit" variant="dark" disabled={loading}>
-              {loading ? 'Registering...' : 'Create account'}
+              {loading ? t('form.registering') : t('form.create_account')}
            </Button>
          </Form>
        </Card.Body>
--- a/frontend/src/pages/ThreadView.jsx
+++ b/frontend/src/pages/ThreadView.jsx
@@ -3,6 +3,7 @@ import { Button, Card, Col, Container, Form, Row } from 'react-bootstrap'
 import { Link, useParams } from 'react-router-dom'
 import { createPost, getThread, listPostsByThread } from '../api/client'
 import { useAuth } from '../context/AuthContext'
+import { useTranslation } from 'react-i18next'

 export default function ThreadView() {
  const { id } = useParams()
@@ -13,6 +14,7 @@ export default function ThreadView() {
  const [loading, setLoading] = useState(true)
  const [body, setBody] = useState('')
  const [saving, setSaving] = useState(false)
+  const { t } = useTranslation()

  useEffect(() => {
    setLoading(true)
@@ -43,19 +45,19 @@ export default function ThreadView() {

  return (
    <Container className="py-5">
-      {loading && <p className="bb-muted">Loading thread...</p>}
+      {loading && <p className="bb-muted">{t('thread.loading')}</p>}
      {error && <p className="text-danger">{error}</p>}
      {thread && (
        <>
          <div className="bb-hero mb-4">
-            <p className="bb-chip">Thread</p>
+            <p className="bb-chip">{t('thread.label')}</p>
            <h2 className="mt-3">{thread.title}</h2>
            <p className="bb-muted mb-2">{thread.body}</p>
-            {thread.category && (
+            {thread.forum && (
              <p className="bb-muted mb-0">
-                Category:{' '}
-                <Link to={`/category/${thread.category.id || thread.category.split('/').pop()}`}>
-                  {thread.category.name || 'Back to category'}
+                {t('thread.category')}{' '}
+                <Link to={`/forum/${thread.forum.id || thread.forum.split('/').pop()}`}>
+                  {thread.forum.name || t('thread.back_to_category')}
                </Link>
              </p>
            )}
@@ -63,32 +65,34 @@ export default function ThreadView() {

          <Row className="g-4">
            <Col lg={7}>
-              <h4 className="bb-section-title mb-3">Replies</h4>
-              {posts.length === 0 && <p className="bb-muted">Be the first to reply.</p>}
+              <h4 className="bb-section-title mb-3">{t('thread.replies')}</h4>
+              {posts.length === 0 && (
+                <p className="bb-muted">{t('thread.empty')}</p>
+              )}
              {posts.map((post) => (
                <Card className="bb-card mb-3" key={post.id}>
                  <Card.Body>
                    <Card.Text>{post.body}</Card.Text>
                    <small className="bb-muted">
-                      {post.author?.username || 'Anonymous'}
+                      {post.author?.username || t('thread.anonymous')}
                    </small>
                  </Card.Body>
                </Card>
              ))}
            </Col>
            <Col lg={5}>
-              <h4 className="bb-section-title mb-3">Reply</h4>
+              <h4 className="bb-section-title mb-3">{t('thread.reply')}</h4>
              <div className="bb-form">
                {!token && (
-                  <p className="bb-muted mb-3">Log in to reply to this thread.</p>
+                  <p className="bb-muted mb-3">{t('thread.login_hint')}</p>
                )}
                <Form onSubmit={handleSubmit}>
                  <Form.Group className="mb-3">
-                    <Form.Label>Message</Form.Label>
+                    <Form.Label>{t('form.message')}</Form.Label>
                    <Form.Control
                      as="textarea"
                      rows={5}
-                      placeholder="Share your reply."
+                      placeholder={t('form.reply_placeholder')}
                      value={body}
                      onChange={(event) => setBody(event.target.value)}
                      disabled={!token || saving}
@@ -96,7 +100,7 @@ export default function ThreadView() {
                    />
                  </Form.Group>
                  <Button type="submit" variant="dark" disabled={!token || saving}>
-                    {saving ? 'Posting...' : 'Post reply'}
+                    {saving ? t('form.posting') : t('form.post_reply')}
                  </Button>
                </Form>
              </div>