feat: register admin routes

Made-with: Cursor

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "samreshu_docs"]
+	path = samreshu_docs
+	url = https://git.vakanaut.ru/admin/samreshu_docs.git

src/app.ts

@@ -5,7 +5,11 @@ import redisPlugin from './plugins/redis.js';
 import securityPlugin from './plugins/security.js';
 import rateLimitPlugin from './plugins/rateLimit.js';
 import authPlugin from './plugins/auth.js';
+import subscriptionPlugin from './plugins/subscription.js';
 import { authRoutes } from './routes/auth.js';
+import { profileRoutes } from './routes/profile.js';
+import { testsRoutes } from './routes/tests.js';
+import { adminQuestionsRoutes } from './routes/admin/questions.js';
 import { env } from './config/env.js';
 import { randomUUID } from 'node:crypto';
 
@@ -72,7 +76,11 @@ export async function buildApp(): Promise<FastifyInstance> {
   await app.register(securityPlugin);
   await app.register(rateLimitPlugin);
   await app.register(authPlugin);
+  await app.register(subscriptionPlugin);
   await app.register(authRoutes, { prefix: '/auth' });
+  await app.register(profileRoutes, { prefix: '/profile' });
+  await app.register(testsRoutes, { prefix: '/tests' });
+  await app.register(adminQuestionsRoutes, { prefix: '/admin' });
 
   app.get('/health', async () => ({ status: 'ok', timestamp: new Date().toISOString() }));
 

src/config/env.ts

@@ -14,9 +14,11 @@ const envSchema = z.object({
 
   LLM_BASE_URL: z.string().url().default('http://localhost:11434/v1'),
   LLM_MODEL: z.string().default('qwen2.5:14b'),
+  LLM_FALLBACK_MODEL: z.string().optional(),
   LLM_API_KEY: z.string().optional(),
   LLM_TIMEOUT_MS: z.coerce.number().default(15000),
   LLM_MAX_RETRIES: z.coerce.number().min(0).default(1),
+  LLM_RETRY_DELAY_MS: z.coerce.number().min(0).default(1000),
   LLM_TEMPERATURE: z.coerce.number().min(0).max(2).default(0.7),
   LLM_MAX_TOKENS: z.coerce.number().default(2048),
 

src/plugins/auth.ts

@@ -1,11 +1,14 @@
 import type { FastifyInstance, FastifyRequest, FastifyReply } from 'fastify';
 import fp from 'fastify-plugin';
+import { eq } from 'drizzle-orm';
 import { verifyToken, isAccessPayload } from '../utils/jwt.js';
-import { unauthorized } from '../utils/errors.js';
+import { unauthorized, forbidden } from '../utils/errors.js';
+import { users } from '../db/schema/users.js';
 
 declare module 'fastify' {
   interface FastifyInstance {
     authenticate: (req: FastifyRequest, reply: FastifyReply) => Promise<void>;
+    authenticateAdmin: (req: FastifyRequest, reply: FastifyReply) => Promise<void>;
   }
   interface FastifyRequest {
     user?: { id: string; email: string };
@@ -34,9 +37,22 @@ export async function authenticate(req: FastifyRequest, _reply: FastifyReply): P
   }
 }
 
+export async function authenticateAdmin(req: FastifyRequest, _reply: FastifyReply): Promise<void> {
+  if (!req.user) {
+    throw unauthorized('Authentication required');
+  }
+
+  const [user] = await req.server.db.select({ role: users.role }).from(users).where(eq(users.id, req.user.id));
+
+  if (!user || user.role !== 'admin') {
+    throw forbidden('Admin access required');
+  }
+}
+
 const authPlugin = async (app: FastifyInstance) => {
   app.decorateRequest('user', undefined);
   app.decorate('authenticate', authenticate);
+  app.decorate('authenticateAdmin', authenticateAdmin);
 };
 
-export default fp(authPlugin, { name: 'auth' });
+export default fp(authPlugin, { name: 'auth', dependencies: ['database'] });

src/plugins/subscription.ts

@@ -0,0 +1,71 @@
+import type { FastifyInstance, FastifyRequest, FastifyReply } from 'fastify';
+import fp from 'fastify-plugin';
+import { eq } from 'drizzle-orm';
+import { subscriptions } from '../db/schema/subscriptions.js';
+import { forbidden } from '../utils/errors.js';
+
+export type SubscriptionInfo = {
+  plan: 'free' | 'pro';
+  status: 'active' | 'trialing' | 'cancelled' | 'expired';
+  isPro: boolean;
+  expiresAt: Date | null;
+};
+
+declare module 'fastify' {
+  interface FastifyRequest {
+    subscription?: SubscriptionInfo | null;
+  }
+  interface FastifyInstance {
+    withSubscription: (req: FastifyRequest, reply: FastifyReply) => Promise<void>;
+    requirePro: (req: FastifyRequest, reply: FastifyReply) => Promise<void>;
+  }
+}
+
+async function loadSubscription(db: FastifyInstance['db'], userId: string): Promise<SubscriptionInfo | null> {
+  const [sub] = await db
+    .select()
+    .from(subscriptions)
+    .where(eq(subscriptions.userId, userId))
+    .limit(1);
+
+  if (!sub) return null;
+
+  const now = new Date();
+  const isExpired = sub.expiresAt && sub.expiresAt < now;
+  const isPro =
+    sub.plan === 'pro' &&
+    (sub.status === 'active' || sub.status === 'trialing') &&
+    !isExpired;
+
+  return {
+    plan: sub.plan as 'free' | 'pro',
+    status: sub.status as SubscriptionInfo['status'],
+    isPro,
+    expiresAt: sub.expiresAt,
+  };
+}
+
+export async function requirePro(req: FastifyRequest, _reply: FastifyReply): Promise<void> {
+  const sub = req.subscription;
+
+  if (!sub?.isPro) {
+    throw forbidden('Pro subscription required');
+  }
+}
+
+const subscriptionPlugin = async (app: FastifyInstance) => {
+  app.decorateRequest('subscription', undefined);
+
+  app.decorate('withSubscription', async (req: FastifyRequest, _reply: FastifyReply) => {
+    if (!req.user?.id) return;
+    const sub = await loadSubscription(app.db, req.user.id);
+    req.subscription = sub;
+  });
+
+  app.decorate('requirePro', requirePro);
+};
+
+export default fp(subscriptionPlugin, {
+  name: 'subscription',
+  dependencies: ['database', 'auth'],
+});

src/routes/admin/questions.ts

@@ -0,0 +1,131 @@
+import type { FastifyInstance } from 'fastify';
+import { AdminQuestionService } from '../../services/admin/admin-question.service.js';
+import type { EditQuestionInput } from '../../services/admin/admin-question.service.js';
+
+const STACKS = ['html', 'css', 'js', 'ts', 'react', 'vue', 'nodejs', 'git', 'web_basics'] as const;
+const LEVELS = ['basic', 'beginner', 'intermediate', 'advanced', 'expert'] as const;
+const QUESTION_TYPES = ['single_choice', 'multiple_select', 'true_false', 'short_text'] as const;
+
+const listPendingQuerySchema = {
+  querystring: {
+    type: 'object',
+    properties: {
+      limit: { type: 'integer', minimum: 1, maximum: 100 },
+      offset: { type: 'integer', minimum: 0 },
+    },
+    additionalProperties: false,
+  },
+};
+
+const questionIdParamsSchema = {
+  params: {
+    type: 'object',
+    required: ['questionId'],
+    properties: {
+      questionId: { type: 'string', format: 'uuid' },
+    },
+  },
+};
+
+const editQuestionSchema = {
+  params: {
+    type: 'object',
+    required: ['questionId'],
+    properties: {
+      questionId: { type: 'string', format: 'uuid' },
+    },
+  },
+  body: {
+    type: 'object',
+    properties: {
+      stack: { type: 'string', enum: [...STACKS] },
+      level: { type: 'string', enum: [...LEVELS] },
+      type: { type: 'string', enum: [...QUESTION_TYPES] },
+      questionText: { type: 'string', minLength: 1 },
+      options: {
+        type: 'array',
+        items: {
+          type: 'object',
+          required: ['key', 'text'],
+          properties: {
+            key: { type: 'string' },
+            text: { type: 'string' },
+          },
+        },
+      },
+      correctAnswer: {
+        oneOf: [
+          { type: 'string' },
+          { type: 'array', items: { type: 'string' } },
+        ],
+      },
+      explanation: { type: 'string', minLength: 1 },
+    },
+    additionalProperties: false,
+  },
+};
+
+export async function adminQuestionsRoutes(app: FastifyInstance) {
+  const adminQuestionService = new AdminQuestionService(app.db);
+  const { rateLimitOptions } = app;
+
+  app.get(
+    '/questions/pending',
+    {
+      schema: listPendingQuerySchema,
+      config: { rateLimit: rateLimitOptions.apiAuthed },
+      preHandler: [app.authenticate, app.authenticateAdmin],
+    },
+    async (req, reply) => {
+      const { limit, offset } = (req.query as { limit?: number; offset?: number }) ?? {};
+      const result = await adminQuestionService.listPending(limit, offset);
+      return reply.send(result);
+    },
+  );
+
+  app.post(
+    '/questions/:questionId/approve',
+    {
+      schema: questionIdParamsSchema,
+      config: { rateLimit: rateLimitOptions.apiAuthed },
+      preHandler: [app.authenticate, app.authenticateAdmin],
+    },
+    async (req, reply) => {
+      const adminId = req.user!.id;
+      const { questionId } = req.params as { questionId: string };
+      await adminQuestionService.approve(questionId, adminId);
+      return reply.status(204).send();
+    },
+  );
+
+  app.post(
+    '/questions/:questionId/reject',
+    {
+      schema: questionIdParamsSchema,
+      config: { rateLimit: rateLimitOptions.apiAuthed },
+      preHandler: [app.authenticate, app.authenticateAdmin],
+    },
+    async (req, reply) => {
+      const adminId = req.user!.id;
+      const { questionId } = req.params as { questionId: string };
+      await adminQuestionService.reject(questionId, adminId);
+      return reply.status(204).send();
+    },
+  );
+
+  app.patch(
+    '/questions/:questionId',
+    {
+      schema: editQuestionSchema,
+      config: { rateLimit: rateLimitOptions.apiAuthed },
+      preHandler: [app.authenticate, app.authenticateAdmin],
+    },
+    async (req, reply) => {
+      const adminId = req.user!.id;
+      const { questionId } = req.params as { questionId: string };
+      const body = req.body as EditQuestionInput;
+      const question = await adminQuestionService.edit(questionId, body, adminId);
+      return reply.send(question);
+    },
+  );
+}

src/routes/profile.ts

@@ -0,0 +1,73 @@
+import type { FastifyInstance } from 'fastify';
+import { UserService } from '../services/user/user.service.js';
+
+const patchProfileSchema = {
+  body: {
+    type: 'object',
+    properties: {
+      nickname: { type: 'string', minLength: 2, maxLength: 30 },
+      avatarUrl: { type: ['string', 'null'], maxLength: 500 },
+      country: { type: ['string', 'null'], maxLength: 100 },
+      city: { type: ['string', 'null'], maxLength: 100 },
+      selfLevel: { type: ['string', 'null'], enum: ['jun', 'mid', 'sen'] },
+      isPublic: { type: 'boolean' },
+    },
+    additionalProperties: false,
+  },
+};
+
+const usernameParamsSchema = {
+  params: {
+    type: 'object',
+    required: ['username'],
+    properties: {
+      username: { type: 'string', minLength: 2, maxLength: 30 },
+    },
+  },
+};
+
+export async function profileRoutes(app: FastifyInstance) {
+  const userService = new UserService(app.db);
+  const { rateLimitOptions } = app;
+
+  app.get(
+    '/',
+    {
+      config: { rateLimit: rateLimitOptions.apiAuthed },
+      preHandler: [app.authenticate, app.withSubscription],
+    },
+    async (req, reply) => {
+      const userId = req.user!.id;
+      const profile = await userService.getPrivateProfile(userId);
+      return reply.send(profile);
+    },
+  );
+
+  app.patch(
+    '/',
+    {
+      schema: patchProfileSchema,
+      config: { rateLimit: rateLimitOptions.apiAuthed },
+      preHandler: [app.authenticate],
+    },
+    async (req, reply) => {
+      const userId = req.user!.id;
+      const body = req.body as Parameters<UserService['updateProfile']>[1];
+      const profile = await userService.updateProfile(userId, body);
+      return reply.send(profile);
+    },
+  );
+
+  app.get(
+    '/:username',
+    {
+      schema: usernameParamsSchema,
+      config: { rateLimit: rateLimitOptions.apiGuest },
+    },
+    async (req, reply) => {
+      const { username } = req.params as { username: string };
+      const profile = await userService.getPublicProfile(username);
+      return reply.send(profile);
+    },
+  );
+}

src/routes/tests.ts

@@ -0,0 +1,185 @@
+import type { FastifyInstance } from 'fastify';
+import { LlmService } from '../services/llm/llm.service.js';
+import { QuestionService } from '../services/questions/question.service.js';
+import { TestsService } from '../services/tests/tests.service.js';
+import { notFound } from '../utils/errors.js';
+import type { CreateTestInput } from '../services/tests/tests.service.js';
+import type { TestSnapshot } from '../services/tests/tests.service.js';
+
+const STACKS = ['html', 'css', 'js', 'ts', 'react', 'vue', 'nodejs', 'git', 'web_basics'] as const;
+const LEVELS = ['basic', 'beginner', 'intermediate', 'advanced', 'expert'] as const;
+
+const createTestSchema = {
+  body: {
+    type: 'object',
+    required: ['stack', 'level', 'questionCount'],
+    properties: {
+      stack: { type: 'string', enum: STACKS },
+      level: { type: 'string', enum: LEVELS },
+      questionCount: { type: 'integer', minimum: 1, maximum: 50 },
+      mode: { type: 'string', enum: ['fixed', 'infinite', 'marathon'] },
+    },
+    additionalProperties: false,
+  },
+};
+
+const testIdParamsSchema = {
+  params: {
+    type: 'object',
+    required: ['testId'],
+    properties: {
+      testId: { type: 'string', format: 'uuid' },
+    },
+  },
+};
+
+const answerSchema = {
+  params: {
+    type: 'object',
+    required: ['testId'],
+    properties: {
+      testId: { type: 'string', format: 'uuid' },
+    },
+  },
+  body: {
+    type: 'object',
+    required: ['questionId', 'answer'],
+    properties: {
+      questionId: { type: 'string', format: 'uuid' },
+      answer: {
+        oneOf: [
+          { type: 'string' },
+          { type: 'array', items: { type: 'string' } },
+        ],
+      },
+    },
+    additionalProperties: false,
+  },
+};
+
+const historyQuerySchema = {
+  querystring: {
+    type: 'object',
+    properties: {
+      limit: { type: 'integer', minimum: 1, maximum: 100 },
+      offset: { type: 'integer', minimum: 0 },
+    },
+    additionalProperties: false,
+  },
+};
+
+function stripAnswersForClient(
+  q: TestSnapshot
+): Omit<TestSnapshot, 'correctAnswer' | 'explanation'> {
+  const { correctAnswer: _, explanation: __, ...rest } = q;
+  return rest;
+}
+
+export async function testsRoutes(app: FastifyInstance) {
+  const llmService = new LlmService();
+  const questionService = new QuestionService(app.db, llmService);
+  const testsService = new TestsService(app.db, questionService);
+  const { rateLimitOptions } = app;
+
+  app.get(
+    '/',
+    {
+      schema: historyQuerySchema,
+      config: { rateLimit: rateLimitOptions.apiAuthed },
+      preHandler: [app.authenticate],
+    },
+    async (req, reply) => {
+      const userId = req.user!.id;
+      const { limit, offset } = (req.query as { limit?: number; offset?: number }) ?? {};
+      const { tests: testList, total } = await testsService.getHistory(
+        userId,
+        { limit, offset }
+      );
+      return reply.send({ tests: testList, total });
+    }
+  );
+
+  app.post(
+    '/',
+    {
+      schema: createTestSchema,
+      config: { rateLimit: rateLimitOptions.apiAuthed },
+      preHandler: [app.authenticate, app.withSubscription],
+    },
+    async (req, reply) => {
+      const userId = req.user!.id;
+      const body = req.body as CreateTestInput;
+      const test = await testsService.createTest(userId, body);
+      const hideAnswers = test.status === 'in_progress';
+      const response = {
+        ...test,
+        questions: hideAnswers
+          ? test.questions.map(stripAnswersForClient)
+          : test.questions,
+      };
+      return reply.status(201).send(response);
+    }
+  );
+
+  app.post(
+    '/:testId/answer',
+    {
+      schema: answerSchema,
+      config: { rateLimit: rateLimitOptions.apiAuthed },
+      preHandler: [app.authenticate],
+    },
+    async (req, reply) => {
+      const userId = req.user!.id;
+      const { testId } = req.params as { testId: string };
+      const { questionId, answer } = req.body as { questionId: string; answer: string | string[] };
+      const snapshot = await testsService.answerQuestion(
+        userId,
+        testId,
+        questionId,
+        answer
+      );
+      return reply.send(snapshot);
+    }
+  );
+
+  app.post(
+    '/:testId/finish',
+    {
+      schema: testIdParamsSchema,
+      config: { rateLimit: rateLimitOptions.apiAuthed },
+      preHandler: [app.authenticate],
+    },
+    async (req, reply) => {
+      const userId = req.user!.id;
+      const { testId } = req.params as { testId: string };
+      const test = await testsService.finishTest(userId, testId);
+      return reply.send(test);
+    }
+  );
+
+  app.get(
+    '/:testId',
+    {
+      schema: testIdParamsSchema,
+      config: { rateLimit: rateLimitOptions.apiAuthed },
+      preHandler: [app.authenticate],
+    },
+    async (req, reply) => {
+      const userId = req.user!.id;
+      const { testId } = req.params as { testId: string };
+      const test = await testsService.getById(userId, testId);
+      if (!test) {
+        throw notFound('Test not found');
+      }
+      const hideAnswers = test.status === 'in_progress';
+      const response = {
+        ...test,
+        questions: hideAnswers
+          ? test.questions.map(stripAnswersForClient)
+          : test.questions,
+      };
+      return reply.send(response);
+    }
+  );
+
+}

src/services/admin/admin-question.service.ts

@@ -0,0 +1,194 @@
+import { eq, asc, count } from 'drizzle-orm';
+import type { NodePgDatabase } from 'drizzle-orm/node-postgres';
+import type * as schema from '../../db/schema/index.js';
+import { questionBank, auditLogs } from '../../db/schema/index.js';
+import { notFound } from '../../utils/errors.js';
+import type { Stack, Level, QuestionType } from '../../db/schema/enums.js';
+
+type Db = NodePgDatabase<typeof schema>;
+
+export type PendingQuestion = {
+  id: string;
+  stack: Stack;
+  level: Level;
+  type: QuestionType;
+  questionText: string;
+  options: Array<{ key: string; text: string }> | null;
+  correctAnswer: string | string[];
+  explanation: string;
+  source: string;
+  createdAt: Date;
+};
+
+export type EditQuestionInput = {
+  stack?: Stack;
+  level?: Level;
+  type?: QuestionType;
+  questionText?: string;
+  options?: Array<{ key: string; text: string }> | null;
+  correctAnswer?: string | string[];
+  explanation?: string;
+};
+
+export type ListPendingResult = {
+  questions: PendingQuestion[];
+  total: number;
+};
+
+export class AdminQuestionService {
+  constructor(private readonly db: Db) {}
+
+  async listPending(limit = 50, offset = 0): Promise<ListPendingResult> {
+    const questions = await this.db
+      .select({
+        id: questionBank.id,
+        stack: questionBank.stack,
+        level: questionBank.level,
+        type: questionBank.type,
+        questionText: questionBank.questionText,
+        options: questionBank.options,
+        correctAnswer: questionBank.correctAnswer,
+        explanation: questionBank.explanation,
+        source: questionBank.source,
+        createdAt: questionBank.createdAt,
+      })
+      .from(questionBank)
+      .where(eq(questionBank.status, 'pending'))
+      .orderBy(asc(questionBank.createdAt))
+      .limit(limit)
+      .offset(offset);
+
+    const [{ count: totalCount }] = await this.db
+      .select({ count: count() })
+      .from(questionBank)
+      .where(eq(questionBank.status, 'pending'));
+
+    return {
+      questions: questions.map((q) => ({
+        id: q.id,
+        stack: q.stack,
+        level: q.level,
+        type: q.type,
+        questionText: q.questionText,
+        options: q.options,
+        correctAnswer: q.correctAnswer,
+        explanation: q.explanation,
+        source: q.source,
+        createdAt: q.createdAt,
+      })),
+      total: totalCount ?? 0,
+    };
+  }
+
+  async approve(questionId: string, adminId: string): Promise<void> {
+    const [updated] = await this.db
+      .update(questionBank)
+      .set({
+        status: 'approved',
+        approvedAt: new Date(),
+      })
+      .where(eq(questionBank.id, questionId))
+      .returning({ id: questionBank.id });
+
+    if (!updated) {
+      throw notFound('Question not found');
+    }
+
+    await this.db.insert(auditLogs).values({
+      adminId,
+      action: 'question_approved',
+      targetType: 'question',
+      targetId: questionId,
+    });
+  }
+
+  async reject(questionId: string, adminId: string): Promise<void> {
+    const [updated] = await this.db
+      .update(questionBank)
+      .set({ status: 'rejected' })
+      .where(eq(questionBank.id, questionId))
+      .returning({ id: questionBank.id });
+
+    if (!updated) {
+      throw notFound('Question not found');
+    }
+
+    await this.db.insert(auditLogs).values({
+      adminId,
+      action: 'question_rejected',
+      targetType: 'question',
+      targetId: questionId,
+    });
+  }
+
+  async edit(questionId: string, input: EditQuestionInput, adminId: string): Promise<PendingQuestion> {
+    const updates: Partial<{
+      stack: Stack;
+      level: Level;
+      type: QuestionType;
+      questionText: string;
+      options: Array<{ key: string; text: string }> | null;
+      correctAnswer: string | string[];
+      explanation: string;
+    }> = {};
+
+    if (input.stack !== undefined) updates.stack = input.stack;
+    if (input.level !== undefined) updates.level = input.level;
+    if (input.type !== undefined) updates.type = input.type;
+    if (input.questionText !== undefined) updates.questionText = input.questionText;
+    if (input.options !== undefined) updates.options = input.options;
+    if (input.correctAnswer !== undefined) updates.correctAnswer = input.correctAnswer;
+    if (input.explanation !== undefined) updates.explanation = input.explanation;
+
+    if (Object.keys(updates).length === 0) {
+      const [existing] = await this.db
+        .select()
+        .from(questionBank)
+        .where(eq(questionBank.id, questionId));
+      if (!existing) throw notFound('Question not found');
+      return {
+        id: existing.id,
+        stack: existing.stack,
+        level: existing.level,
+        type: existing.type,
+        questionText: existing.questionText,
+        options: existing.options,
+        correctAnswer: existing.correctAnswer,
+        explanation: existing.explanation,
+        source: existing.source,
+        createdAt: existing.createdAt,
+      };
+    }
+
+    const [updated] = await this.db
+      .update(questionBank)
+      .set(updates)
+      .where(eq(questionBank.id, questionId))
+      .returning();
+
+    if (!updated) {
+      throw notFound('Question not found');
+    }
+
+    await this.db.insert(auditLogs).values({
+      adminId,
+      action: 'question_edited',
+      targetType: 'question',
+      targetId: questionId,
+      details: updates as Record<string, unknown>,
+    });
+
+    return {
+      id: updated.id,
+      stack: updated.stack,
+      level: updated.level,
+      type: updated.type,
+      questionText: updated.questionText,
+      options: updated.options,
+      correctAnswer: updated.correctAnswer,
+      explanation: updated.explanation,
+      source: updated.source,
+      createdAt: updated.createdAt,
+    };
+  }
+}

src/services/llm/llm.service.ts

@@ -0,0 +1,237 @@
+import { z } from 'zod';
+import { createHash } from 'node:crypto';
+import { env } from '../../config/env.js';
+import type { Stack, Level, QuestionType } from '../../db/schema/enums.js';
+
+export interface LlmConfig {
+  baseUrl: string;
+  model: string;
+  fallbackModel?: string;
+  apiKey?: string;
+  timeoutMs: number;
+  temperature: number;
+  maxTokens: number;
+  maxRetries: number;
+  retryDelayMs: number;
+}
+
+export interface ChatMessage {
+  role: 'system' | 'user' | 'assistant';
+  content: string;
+}
+
+export interface ChatCompletionResponse {
+  choices: Array<{
+    message?: { content: string };
+    text?: string;
+  }>;
+}
+
+const QUESTION_TYPES: QuestionType[] = ['single_choice', 'multiple_select', 'true_false', 'short_text'];
+
+const optionSchema = z.object({
+  key: z.string().min(1),
+  text: z.string().min(1),
+});
+
+const generatedQuestionSchema = z.object({
+  questionText: z.string().min(1),
+  type: z.enum(QUESTION_TYPES as [string, ...string[]]),
+  options: z.array(optionSchema).optional(),
+  correctAnswer: z.union([z.string(), z.array(z.string())]),
+  explanation: z.string().min(1),
+});
+
+const generateQuestionsResponseSchema = z.object({
+  questions: z.array(generatedQuestionSchema),
+});
+
+export type GeneratedQuestion = z.infer<typeof generatedQuestionSchema> & {
+  stack: Stack;
+  level: Level;
+};
+
+export interface GenerateQuestionsInput {
+  stack: Stack;
+  level: Level;
+  count: number;
+  types?: QuestionType[];
+}
+
+/** Metadata for persisting to question_cache_meta (used by QuestionService) */
+export interface LlmGenerationMeta {
+  llmModel: string;
+  promptHash: string;
+  generationTimeMs: number;
+  rawResponse: unknown;
+}
+
+export interface GenerateQuestionsResult {
+  questions: GeneratedQuestion[];
+  meta: LlmGenerationMeta;
+}
+
+export class LlmService {
+  private readonly config: LlmConfig;
+
+  constructor(config?: Partial<LlmConfig>) {
+    this.config = {
+      baseUrl: config?.baseUrl ?? env.LLM_BASE_URL,
+      model: config?.model ?? env.LLM_MODEL,
+      fallbackModel: config?.fallbackModel ?? env.LLM_FALLBACK_MODEL,
+      apiKey: config?.apiKey ?? env.LLM_API_KEY,
+      timeoutMs: config?.timeoutMs ?? env.LLM_TIMEOUT_MS,
+      temperature: config?.temperature ?? env.LLM_TEMPERATURE,
+      maxTokens: config?.maxTokens ?? env.LLM_MAX_TOKENS,
+      maxRetries: config?.maxRetries ?? env.LLM_MAX_RETRIES,
+      retryDelayMs: config?.retryDelayMs ?? env.LLM_RETRY_DELAY_MS,
+    };
+  }
+
+  async chat(messages: ChatMessage[]): Promise<string> {
+    const { content } = await this.chatWithMeta(messages);
+    return content;
+  }
+
+  /** Returns content and model used (for logging to question_cache_meta) */
+  async chatWithMeta(messages: ChatMessage[]): Promise<{ content: string; model: string }> {
+    let lastError: Error | null = null;
+
+    const modelsToTry = [this.config.model];
+    if (this.config.fallbackModel) {
+      modelsToTry.push(this.config.fallbackModel);
+    }
+
+    for (const model of modelsToTry) {
+      for (let attempt = 0; attempt <= this.config.maxRetries; attempt++) {
+        try {
+          const content = await this.executeChat(messages, model);
+          return { content, model };
+        } catch (err) {
+          lastError = err instanceof Error ? err : new Error('LLM request failed');
+          if (attempt < this.config.maxRetries) {
+            const delayMs = this.config.retryDelayMs * Math.pow(2, attempt);
+            await sleep(delayMs);
+          }
+        }
+      }
+    }
+
+    throw lastError ?? new Error('LLM request failed');
+  }
+
+  private async executeChat(messages: ChatMessage[], model: string): Promise<string> {
+    const url = `${this.config.baseUrl.replace(/\/$/, '')}/chat/completions`;
+
+    const headers: Record<string, string> = {
+      'Content-Type': 'application/json',
+    };
+    if (this.config.apiKey) {
+      headers['Authorization'] = `Bearer ${this.config.apiKey}`;
+    }
+
+    const body = {
+      model,
+      messages: messages.map((m) => ({ role: m.role, content: m.content })),
+      temperature: this.config.temperature,
+      max_tokens: this.config.maxTokens,
+    };
+
+    const controller = new AbortController();
+    const timeoutId = setTimeout(() => controller.abort(), this.config.timeoutMs);
+
+    try {
+      const res = await fetch(url, {
+        method: 'POST',
+        headers,
+        body: JSON.stringify(body),
+        signal: controller.signal,
+      });
+
+      clearTimeout(timeoutId);
+
+      if (!res.ok) {
+        const text = await res.text();
+        throw new Error(`LLM request failed: ${res.status} ${res.statusText} - ${text}`);
+      }
+
+      const data = (await res.json()) as ChatCompletionResponse;
+
+      const choice = data.choices?.[0];
+      const content = choice?.message?.content ?? choice?.text ?? '';
+
+      return content.trim();
+    } catch (err) {
+      clearTimeout(timeoutId);
+      if (err instanceof Error) {
+        throw err;
+      }
+      throw new Error('LLM request failed');
+    }
+  }
+
+  async generateQuestions(input: GenerateQuestionsInput): Promise<GenerateQuestionsResult> {
+    const { stack, level, count, types = QUESTION_TYPES } = input;
+
+    const typeList = types.join(', ');
+    const systemPrompt = `You are a technical interview question generator. Generate exactly ${count} programming/tech questions.
+Return ONLY valid JSON in this exact format (no markdown, no code blocks):
+{"questions":[{"questionText":"...","type":"single_choice|multiple_select|true_false|short_text","options":[{"key":"a","text":"..."}],"correctAnswer":"a" or ["a","b"],"explanation":"..."}]}
+Rules: type must be one of: ${typeList}. For single_choice/multiple_select: options array required with key (a,b,c,d). For true_false: options [{"key":"true","text":"True"},{"key":"false","text":"False"}]. For short_text: options omitted, correctAnswer is string.`;
+
+    const userPrompt = `Generate ${count} questions for stack="${stack}", level="${level}". Use types: ${typeList}.`;
+
+    const promptForHash = systemPrompt + '\n---\n' + userPrompt;
+    const promptHash = createHash('sha256').update(promptForHash).digest('hex');
+
+    const start = Date.now();
+    const { content: raw, model } = await this.chatWithMeta([
+      { role: 'system', content: systemPrompt },
+      { role: 'user', content: userPrompt },
+    ]);
+    const generationTimeMs = Date.now() - start;
+
+    const jsonStr = extractJson(raw);
+    const parsed = JSON.parse(jsonStr) as unknown;
+
+    const result = generateQuestionsResponseSchema.safeParse(parsed);
+    if (!result.success) {
+      throw new Error(`LLM response validation failed: ${result.error.message}`);
+    }
+
+    const questions: GeneratedQuestion[] = result.data.questions.map((q) => ({
+      ...q,
+      stack,
+      level,
+    }));
+
+    for (const q of questions) {
+      if ((q.type === 'single_choice' || q.type === 'multiple_select') && (!q.options || q.options.length === 0)) {
+        throw new Error(`Question validation failed: ${q.type} requires options`);
+      }
+      if (q.type === 'true_false' && (!q.options || q.options.length < 2)) {
+        throw new Error(`Question validation failed: true_false requires true/false options`);
+      }
+    }
+
+    return {
+      questions,
+      meta: {
+        llmModel: model,
+        promptHash,
+        generationTimeMs,
+        rawResponse: parsed,
+      },
+    };
+  }
+}
+
+function sleep(ms: number): Promise<void> {
+  return new Promise((resolve) => setTimeout(resolve, ms));
+}
+
+function extractJson(text: string): string {
+  const trimmed = text.trim();
+  const match = trimmed.match(/\{[\s\S]*\}/);
+  return match ? match[0]! : trimmed;
+}

src/services/questions/question.service.ts

@@ -0,0 +1,197 @@
+import { eq, and, sql, asc, inArray } from 'drizzle-orm';
+import type { NodePgDatabase } from 'drizzle-orm/node-postgres';
+import type * as schema from '../../db/schema/index.js';
+import {
+  questionBank,
+  questionCacheMeta,
+  userQuestionLog,
+} from '../../db/schema/index.js';
+import { internalError, AppError, ERROR_CODES } from '../../utils/errors.js';
+import type { Stack, Level, QuestionType } from '../../db/schema/enums.js';
+import type {
+  GeneratedQuestion,
+  GenerateQuestionsResult,
+} from '../llm/llm.service.js';
+
+type Db = NodePgDatabase<typeof schema>;
+
+export type QuestionForTest = {
+  questionBankId: string;
+  type: QuestionType;
+  questionText: string;
+  options: Array<{ key: string; text: string }> | null;
+  correctAnswer: string | string[];
+  explanation: string;
+};
+
+export interface LlmServiceInterface {
+  generateQuestions(input: {
+    stack: Stack;
+    level: Level;
+    count: number;
+    types?: QuestionType[];
+  }): Promise<GenerateQuestionsResult>;
+}
+
+function shuffle<T>(arr: T[]): T[] {
+  const result = [...arr];
+  for (let i = result.length - 1; i > 0; i--) {
+    const j = Math.floor(Math.random() * (i + 1));
+    [result[i], result[j]] = [result[j]!, result[i]!];
+  }
+  return result;
+}
+
+export class QuestionService {
+  constructor(
+    private readonly db: Db,
+    private readonly llmService: LlmServiceInterface
+  ) {}
+
+  /**
+   * Get questions for a test. Fetches approved questions from question_bank.
+   * If not enough, generates via LLM, persists to question_bank and question_cache_meta.
+   */
+  async getQuestionsForTest(
+    userId: string,
+    stack: Stack,
+    level: Level,
+    count: number
+  ): Promise<QuestionForTest[]> {
+    const approved = await this.db
+      .select({
+        id: questionBank.id,
+        type: questionBank.type,
+        questionText: questionBank.questionText,
+        options: questionBank.options,
+        correctAnswer: questionBank.correctAnswer,
+        explanation: questionBank.explanation,
+      })
+      .from(questionBank)
+      .where(
+        and(eq(questionBank.stack, stack), eq(questionBank.level, level), eq(questionBank.status, 'approved'))
+      )
+      .orderBy(asc(questionBank.usageCount));
+
+    const seenIds = await this.db
+      .select({ questionBankId: userQuestionLog.questionBankId })
+      .from(userQuestionLog)
+      .where(eq(userQuestionLog.userId, userId));
+
+    const seenSet = new Set(seenIds.map((r) => r.questionBankId));
+    const preferred = approved.filter((q) => !seenSet.has(q.id));
+    const pool = preferred.length >= count ? preferred : approved;
+    const shuffled = shuffle(pool);
+
+    const fromBank: QuestionForTest[] = shuffled.slice(0, count).map((q) => ({
+      questionBankId: q.id,
+      type: q.type,
+      questionText: q.questionText,
+      options: q.options,
+      correctAnswer: q.correctAnswer,
+      explanation: q.explanation,
+    }));
+
+    let result = fromBank;
+
+    if (result.length < count) {
+      const generated = await this.generateAndPersistQuestions(
+        stack,
+        level,
+        count - result.length
+      );
+      result = [...result, ...generated];
+    }
+
+    if (result.length < count) {
+      throw new AppError(
+        ERROR_CODES.QUESTIONS_UNAVAILABLE,
+        'Not enough questions available for this stack and level',
+        422
+      );
+    }
+
+    if (result.length > 0) {
+      await this.db.insert(userQuestionLog).values(
+        result.map((q) => ({
+          userId,
+          questionBankId: q.questionBankId,
+        }))
+      );
+
+      const ids = result.map((q) => q.questionBankId);
+      await this.db
+        .update(questionBank)
+        .set({
+          usageCount: sql`${questionBank.usageCount} + 1`,
+        })
+        .where(inArray(questionBank.id, ids));
+    }
+
+    return result;
+  }
+
+  private async generateAndPersistQuestions(
+    stack: Stack,
+    level: Level,
+    count: number
+  ): Promise<QuestionForTest[]> {
+    let generated: GeneratedQuestion[];
+    let meta: GenerateQuestionsResult['meta'];
+
+    try {
+      const result = await this.llmService.generateQuestions({
+        stack,
+        level,
+        count,
+      });
+      generated = result.questions;
+      meta = result.meta;
+    } catch (err) {
+      throw internalError(
+        'Failed to generate questions',
+        err instanceof Error ? err : undefined
+      );
+    }
+
+    const inserted: QuestionForTest[] = [];
+
+    for (const q of generated) {
+      const [row] = await this.db
+        .insert(questionBank)
+        .values({
+          stack,
+          level,
+          type: q.type as QuestionType,
+          questionText: q.questionText,
+          options: q.options ?? null,
+          correctAnswer: q.correctAnswer,
+          explanation: q.explanation,
+          status: 'approved',
+          source: 'llm_generated',
+        })
+        .returning();
+
+      if (row) {
+        await this.db.insert(questionCacheMeta).values({
+          questionBankId: row.id,
+          llmModel: meta.llmModel,
+          promptHash: meta.promptHash,
+          generationTimeMs: meta.generationTimeMs,
+          rawResponse: meta.rawResponse,
+        });
+
+        inserted.push({
+          questionBankId: row.id,
+          type: row.type,
+          questionText: row.questionText,
+          options: row.options,
+          correctAnswer: row.correctAnswer,
+          explanation: row.explanation,
+        });
+      }
+    }
+
+    return inserted;
+  }
+}

src/services/tests/tests.service.ts

@@ -0,0 +1,399 @@
+import { eq, and, desc } from 'drizzle-orm';
+import type { NodePgDatabase } from 'drizzle-orm/node-postgres';
+import type * as schema from '../../db/schema/index.js';
+import { tests, testQuestions, userStats } from '../../db/schema/index.js';
+import { notFound, conflict, AppError, ERROR_CODES } from '../../utils/errors.js';
+import type { Stack, Level, TestMode } from '../../db/schema/enums.js';
+import type { QuestionService } from '../questions/question.service.js';
+
+type Db = NodePgDatabase<typeof schema>;
+
+export type CreateTestInput = {
+  stack: Stack;
+  level: Level;
+  questionCount: number;
+  mode?: TestMode;
+};
+
+export type TestSnapshot = {
+  id: string;
+  testId: string;
+  questionBankId: string | null;
+  orderNumber: number;
+  type: string;
+  questionText: string;
+  options: Array<{ key: string; text: string }> | null;
+  correctAnswer: string | string[];
+  explanation: string;
+  userAnswer?: string | string[] | null;
+  isCorrect?: boolean | null;
+  answeredAt?: string | null;
+};
+
+export type TestWithQuestions = {
+  id: string;
+  userId: string;
+  stack: string;
+  level: string;
+  questionCount: number;
+  mode: string;
+  status: string;
+  score: number | null;
+  startedAt: string;
+  finishedAt: string | null;
+  timeLimitSeconds: number | null;
+  questions: TestSnapshot[];
+};
+
+export class TestsService {
+  constructor(
+    private readonly db: Db,
+    private readonly questionService: QuestionService
+  ) {}
+
+  /**
+   * Create a new test: fetch questions, create test record, snapshot questions into test_questions.
+   */
+  async createTest(userId: string, input: CreateTestInput): Promise<TestWithQuestions> {
+    const { stack, level, questionCount, mode = 'fixed' } = input;
+
+    if (questionCount < 1 || questionCount > 50) {
+      throw new AppError(
+        ERROR_CODES.BAD_REQUEST,
+        'questionCount must be between 1 and 50',
+        400
+      );
+    }
+
+    const questions = await this.questionService.getQuestionsForTest(
+      userId,
+      stack,
+      level,
+      questionCount
+    );
+
+    const [test] = await this.db
+      .insert(tests)
+      .values({
+        userId,
+        stack,
+        level,
+        questionCount,
+        mode,
+        status: 'in_progress',
+      })
+      .returning();
+
+    if (!test) {
+      throw new AppError(
+        ERROR_CODES.INTERNAL_ERROR,
+        'Failed to create test',
+        500
+      );
+    }
+
+    const tqValues = questions.map((q, i) => ({
+      testId: test.id,
+      questionBankId: q.questionBankId,
+      orderNumber: i + 1,
+      type: q.type,
+      questionText: q.questionText,
+      options: q.options,
+      correctAnswer: q.correctAnswer,
+      explanation: q.explanation,
+    }));
+
+    await this.db.insert(testQuestions).values(tqValues);
+
+    const questionsRows = await this.db
+      .select()
+      .from(testQuestions)
+      .where(eq(testQuestions.testId, test.id))
+      .orderBy(testQuestions.orderNumber);
+
+    return this.toTestWithQuestions(test, questionsRows);
+  }
+
+  /**
+   * Submit an answer for a question in an in-progress test.
+   */
+  async answerQuestion(
+    userId: string,
+    testId: string,
+    testQuestionId: string,
+    userAnswer: string | string[]
+  ): Promise<TestSnapshot> {
+    const [test] = await this.db
+      .select()
+      .from(tests)
+      .where(and(eq(tests.id, testId), eq(tests.userId, userId)))
+      .limit(1);
+
+    if (!test) {
+      throw notFound('Test not found');
+    }
+    if (test.status !== 'in_progress') {
+      throw conflict(ERROR_CODES.TEST_ALREADY_FINISHED, 'Test is already finished');
+    }
+
+    const [tq] = await this.db
+      .select()
+      .from(testQuestions)
+      .where(
+        and(
+          eq(testQuestions.id, testQuestionId),
+          eq(testQuestions.testId, testId)
+        )
+      )
+      .limit(1);
+
+    if (!tq) {
+      throw conflict(ERROR_CODES.WRONG_QUESTION, 'Question does not belong to this test');
+    }
+    if (tq.userAnswer !== null && tq.userAnswer !== undefined) {
+      throw conflict(ERROR_CODES.QUESTION_ALREADY_ANSWERED, 'Question already answered');
+    }
+
+    const isCorrect = this.checkAnswer(tq.correctAnswer, userAnswer);
+
+    const [updated] = await this.db
+      .update(testQuestions)
+      .set({
+        userAnswer,
+        isCorrect,
+        answeredAt: new Date(),
+      })
+      .where(eq(testQuestions.id, testQuestionId))
+      .returning();
+
+    if (!updated) {
+      throw notFound('Question not found');
+    }
+
+    return {
+      id: updated.id,
+      testId: updated.testId,
+      questionBankId: updated.questionBankId,
+      orderNumber: updated.orderNumber,
+      type: updated.type,
+      questionText: updated.questionText,
+      options: updated.options,
+      correctAnswer: updated.correctAnswer,
+      explanation: updated.explanation,
+      userAnswer: updated.userAnswer,
+      isCorrect: updated.isCorrect,
+      answeredAt: updated.answeredAt?.toISOString() ?? null,
+    };
+  }
+
+  private checkAnswer(
+    correct: string | string[],
+    user: string | string[]
+  ): boolean {
+    if (Array.isArray(correct) && Array.isArray(user)) {
+      if (correct.length !== user.length) return false;
+      const a = [...correct].sort();
+      const b = [...user].sort();
+      return a.every((v, i) => v === b[i]);
+    }
+    if (typeof correct === 'string' && typeof user === 'string') {
+      return correct.trim().toLowerCase() === user.trim().toLowerCase();
+    }
+    return false;
+  }
+
+  /**
+   * Finish a test: calculate score, update user_stats.
+   */
+  async finishTest(userId: string, testId: string): Promise<TestWithQuestions> {
+    const [test] = await this.db
+      .select()
+      .from(tests)
+      .where(and(eq(tests.id, testId), eq(tests.userId, userId)))
+      .limit(1);
+
+    if (!test) {
+      throw notFound('Test not found');
+    }
+    if (test.status !== 'in_progress') {
+      throw conflict(ERROR_CODES.TEST_ALREADY_FINISHED, 'Test is already finished');
+    }
+
+    const questions = await this.db
+      .select()
+      .from(testQuestions)
+      .where(eq(testQuestions.testId, testId));
+
+    const unanswered = questions.filter(
+      (q) => q.userAnswer === null || q.userAnswer === undefined
+    );
+    if (unanswered.length > 0) {
+      throw new AppError(
+        ERROR_CODES.NO_ANSWERS,
+        `Cannot finish: ${unanswered.length} question(s) not answered`,
+        422
+      );
+    }
+
+    const correctCount = questions.filter((q) => q.isCorrect === true).length;
+    const score = Math.round((correctCount / questions.length) * 100);
+
+    const [updatedTest] = await this.db
+      .update(tests)
+      .set({
+        status: 'completed',
+        score,
+        finishedAt: new Date(),
+      })
+      .where(eq(tests.id, testId))
+      .returning();
+
+    if (!updatedTest) {
+      throw notFound('Test not found');
+    }
+
+    await this.upsertUserStats(userId, test.stack as Stack, test.level as Level, {
+      totalQuestions: questions.length,
+      correctAnswers: correctCount,
+      testsTaken: 1,
+    });
+
+    const questionsRows = await this.db
+      .select()
+      .from(testQuestions)
+      .where(eq(testQuestions.testId, testId))
+      .orderBy(testQuestions.orderNumber);
+
+    return this.toTestWithQuestions(updatedTest, questionsRows);
+  }
+
+  private async upsertUserStats(
+    userId: string,
+    stack: Stack,
+    level: Level,
+    delta: { totalQuestions: number; correctAnswers: number; testsTaken: number }
+  ): Promise<void> {
+    const [existing] = await this.db
+      .select()
+      .from(userStats)
+      .where(
+        and(
+          eq(userStats.userId, userId),
+          eq(userStats.stack, stack),
+          eq(userStats.level, level)
+        )
+      )
+      .limit(1);
+
+    const now = new Date();
+
+    if (existing) {
+      await this.db
+        .update(userStats)
+        .set({
+          totalQuestions: existing.totalQuestions + delta.totalQuestions,
+          correctAnswers: existing.correctAnswers + delta.correctAnswers,
+          testsTaken: existing.testsTaken + delta.testsTaken,
+          lastTestAt: now,
+        })
+        .where(eq(userStats.id, existing.id));
+    } else {
+      await this.db.insert(userStats).values({
+        userId,
+        stack,
+        level,
+        totalQuestions: delta.totalQuestions,
+        correctAnswers: delta.correctAnswers,
+        testsTaken: delta.testsTaken,
+        lastTestAt: now,
+      });
+    }
+  }
+
+  /**
+   * Get a single test by ID (must belong to user).
+   */
+  async getById(userId: string, testId: string): Promise<TestWithQuestions | null> {
+    const [test] = await this.db
+      .select()
+      .from(tests)
+      .where(and(eq(tests.id, testId), eq(tests.userId, userId)))
+      .limit(1);
+
+    if (!test) return null;
+
+    const questionsRows = await this.db
+      .select()
+      .from(testQuestions)
+      .where(eq(testQuestions.testId, testId))
+      .orderBy(testQuestions.orderNumber);
+
+    return this.toTestWithQuestions(test, questionsRows);
+  }
+
+  /**
+   * Get test history for a user (most recent first).
+   */
+  async getHistory(
+    userId: string,
+    options?: { limit?: number; offset?: number }
+  ): Promise<{ tests: TestWithQuestions[]; total: number }> {
+    const limit = Math.min(options?.limit ?? 20, 100);
+    const offset = options?.offset ?? 0;
+
+    const all = await this.db
+      .select()
+      .from(tests)
+      .where(eq(tests.userId, userId))
+      .orderBy(desc(tests.startedAt));
+
+    const total = all.length;
+    const page = all.slice(offset, offset + limit);
+
+    const result: TestWithQuestions[] = [];
+
+    for (const test of page) {
+      const questionsRows = await this.db
+        .select()
+        .from(testQuestions)
+        .where(eq(testQuestions.testId, test.id))
+        .orderBy(testQuestions.orderNumber);
+      result.push(this.toTestWithQuestions(test, questionsRows));
+    }
+
+    return { tests: result, total };
+  }
+
+  private toTestWithQuestions(
+    test: (typeof tests.$inferSelect),
+    questionsRows: (typeof testQuestions.$inferSelect)[]
+  ): TestWithQuestions {
+    return {
+      id: test.id,
+      userId: test.userId,
+      stack: test.stack,
+      level: test.level,
+      questionCount: test.questionCount,
+      mode: test.mode,
+      status: test.status,
+      score: test.score,
+      startedAt: test.startedAt.toISOString(),
+      finishedAt: test.finishedAt?.toISOString() ?? null,
+      timeLimitSeconds: test.timeLimitSeconds,
+      questions: questionsRows.map((q) => ({
+        id: q.id,
+        testId: q.testId,
+        questionBankId: q.questionBankId,
+        orderNumber: q.orderNumber,
+        type: q.type,
+        questionText: q.questionText,
+        options: q.options,
+        correctAnswer: q.correctAnswer,
+        explanation: q.explanation,
+        userAnswer: q.userAnswer,
+        isCorrect: q.isCorrect,
+        answeredAt: q.answeredAt?.toISOString() ?? null,
+      })),
+    };
+  }
+}

src/services/user/user.service.ts

@@ -0,0 +1,175 @@
+import { eq } from 'drizzle-orm';
+import type { NodePgDatabase } from 'drizzle-orm/node-postgres';
+import type * as schema from '../../db/schema/index.js';
+import { users, userStats } from '../../db/schema/index.js';
+import { notFound, conflict, ERROR_CODES } from '../../utils/errors.js';
+import type { User } from '../../db/schema/users.js';
+import type { SelfLevel } from '../../db/schema/index.js';
+
+type Db = NodePgDatabase<typeof schema>;
+
+export type UserStatItem = {
+  stack: string;
+  level: string;
+  totalQuestions: number;
+  correctAnswers: number;
+  testsTaken: number;
+  lastTestAt: string | null;
+};
+
+export type ProfileStats = {
+  byStack: UserStatItem[];
+  totalTestsTaken: number;
+  totalQuestions: number;
+  correctAnswers: number;
+  accuracy: number | null;
+};
+
+export type ProfileUpdateInput = {
+  nickname?: string;
+  avatarUrl?: string | null;
+  country?: string | null;
+  city?: string | null;
+  selfLevel?: SelfLevel | null;
+  isPublic?: boolean;
+};
+
+export type PublicProfile = {
+  id: string;
+  nickname: string;
+  avatarUrl: string | null;
+  country: string | null;
+  city: string | null;
+  selfLevel: string | null;
+  isPublic: boolean;
+  stats: ProfileStats;
+};
+
+export type PrivateProfile = PublicProfile & {
+  email: string;
+  emailVerifiedAt: string | null;
+  createdAt: string;
+  updatedAt: string;
+};
+
+async function getStatsForUser(db: Db, userId: string): Promise<ProfileStats> {
+  const rows = await db
+    .select()
+    .from(userStats)
+    .where(eq(userStats.userId, userId));
+
+  const byStack: UserStatItem[] = rows.map((r) => ({
+    stack: r.stack,
+    level: r.level,
+    totalQuestions: r.totalQuestions,
+    correctAnswers: r.correctAnswers,
+    testsTaken: r.testsTaken,
+    lastTestAt: r.lastTestAt?.toISOString() ?? null,
+  }));
+
+  const totalTestsTaken = rows.reduce((sum, r) => sum + r.testsTaken, 0);
+  const totalQuestions = rows.reduce((sum, r) => sum + r.totalQuestions, 0);
+  const correctAnswers = rows.reduce((sum, r) => sum + r.correctAnswers, 0);
+  const accuracy = totalQuestions > 0 ? correctAnswers / totalQuestions : null;
+
+  return { byStack, totalTestsTaken, totalQuestions, correctAnswers, accuracy };
+}
+
+function toPublicProfile(user: User, stats: ProfileStats): PublicProfile {
+  return {
+    id: user.id,
+    nickname: user.nickname,
+    avatarUrl: user.avatarUrl,
+    country: user.country,
+    city: user.city,
+    selfLevel: user.selfLevel,
+    isPublic: user.isPublic,
+    stats,
+  };
+}
+
+function toPrivateProfile(user: User, stats: ProfileStats): PrivateProfile {
+  return {
+    ...toPublicProfile(user, stats),
+    email: user.email,
+    emailVerifiedAt: user.emailVerifiedAt?.toISOString() ?? null,
+    createdAt: user.createdAt.toISOString(),
+    updatedAt: user.updatedAt.toISOString(),
+  };
+}
+
+export class UserService {
+  constructor(private readonly db: Db) {}
+
+  async getById(userId: string): Promise<User | null> {
+    const [user] = await this.db.select().from(users).where(eq(users.id, userId)).limit(1);
+    return user ?? null;
+  }
+
+  async getByNickname(nickname: string): Promise<User | null> {
+    const [user] = await this.db
+      .select()
+      .from(users)
+      .where(eq(users.nickname, nickname.trim()))
+      .limit(1);
+    return user ?? null;
+  }
+
+  async getPrivateProfile(userId: string): Promise<PrivateProfile> {
+    const [user, stats] = await Promise.all([this.getById(userId), getStatsForUser(this.db, userId)]);
+    if (!user) {
+      throw notFound('User not found');
+    }
+    return toPrivateProfile(user, stats);
+  }
+
+  async getPublicProfile(username: string): Promise<PublicProfile> {
+    const user = await this.getByNickname(username);
+    if (!user) {
+      throw notFound('User not found');
+    }
+    if (!user.isPublic) {
+      throw notFound('User not found');
+    }
+    const stats = await getStatsForUser(this.db, user.id);
+    return toPublicProfile(user, stats);
+  }
+
+  async updateProfile(userId: string, input: ProfileUpdateInput): Promise<PrivateProfile> {
+    const updateData: Partial<typeof users.$inferInsert> = {
+      updatedAt: new Date(),
+    };
+
+    if (input.nickname !== undefined) {
+      const trimmed = input.nickname.trim();
+      const [existing] = await this.db
+        .select({ id: users.id })
+        .from(users)
+        .where(eq(users.nickname, trimmed))
+        .limit(1);
+
+      if (existing && existing.id !== userId) {
+        throw conflict(ERROR_CODES.NICKNAME_TAKEN, 'Nickname already taken');
+      }
+      updateData.nickname = trimmed;
+    }
+    if (input.avatarUrl !== undefined) updateData.avatarUrl = input.avatarUrl;
+    if (input.country !== undefined) updateData.country = input.country;
+    if (input.city !== undefined) updateData.city = input.city;
+    if (input.selfLevel !== undefined) updateData.selfLevel = input.selfLevel;
+    if (input.isPublic !== undefined) updateData.isPublic = input.isPublic;
+
+    const [updated] = await this.db
+      .update(users)
+      .set(updateData)
+      .where(eq(users.id, userId))
+      .returning();
+
+    if (!updated) {
+      throw notFound('User not found');
+    }
+
+    const stats = await getStatsForUser(this.db, userId);
+    return toPrivateProfile(updated, stats);
+  }
+}