import { Injectable, UnauthorizedException } from '@nestjs/common';
import { JwtService } from '@nestjs/jwt';
import { PrismaService } from '../prisma/prisma.service';
import * as argon2 from 'argon2';

@Injectable()
export class AuthService {
  constructor(
    private readonly prisma: PrismaService,
    private readonly jwtService: JwtService,
  ) {}

  /**
   * Verifies user credentials and generates a JWT.
   * Uses Argon2 for secure password verification.
   * Throws an UnauthorizedException if the user is not found or the password does not match.
   */
  async login(email: string, pass: string) {
    const user = await this.prisma.user.findUnique({ where: { email } });
    if (!user) {
      throw new UnauthorizedException('Invalid credentials');
    }

    const isPasswordValid = await argon2.verify(user.password, pass);
    if (!isPasswordValid) {
      throw new UnauthorizedException('Invalid credentials');
    }

    const payload = { email: user.email, sub: user.id };
    return {
      access_token: this.jwtService.sign(payload),
    };
  }
}