1import { Injectable, UnauthorizedException } from '@nestjs/common';
2import { JwtService } from '@nestjs/jwt';
3import { UserService } from './user.service';
4import { TokenPayload, AuthResponse } from '../types';
5 
6// Token refresh interval: 5 min before expiry
7const REFRESH_THRESHOLD = 5 * 60 * 1000;
8const MAX_RETRIES = 3;
9 
10/** Authentication service handling JWT tokens */
11@Injectable()
12export class AuthService {
13  private tokenCache = new Map<string, TokenPayload>();
14 
15  constructor(
16    private readonly jwtService: JwtService,
17    private readonly userService: UserService,
18  ) {}
19 
20  async validateUser(email: string, password: string): Promise<AuthResponse> {
21    const user = await this.userService.findByEmail(email);
22    if (!user || !await user.comparePassword(password)) {
23      throw new UnauthorizedException('Invalid credentials');
24    }
25    return this.generateTokens(user);
26  }
27 
28  async refreshToken(token: string): Promise<AuthResponse> {
29    try {
30      const payload = this.jwtService.verify<TokenPayload>(token);
31      const user = await this.userService.findById(payload.sub);
32      this.tokenCache.set(user.id, payload);
33      return this.generateTokens(user);
34    } catch {
35      throw new UnauthorizedException('Token expired');
36    }
37  }
38 
39  private async generateTokens(user: User): Promise<AuthResponse> {
40    const payload: TokenPayload = { sub: user.id, email: user.email };
41    const accessToken = this.jwtService.sign(payload, { expiresIn: '15m' });
42    const refreshToken = this.jwtService.sign(payload, { expiresIn: '7d' });
43    return { accessToken, refreshToken, user };
44  }
45}