source: ChapterX.Application/Auth/LoginHandler.cs@ 3ae4bab

using ChapterX.Domain.Repositories;
using MediatR;

namespace ChapterX.Application.Auth
{
    public class LoginHandler : IRequestHandler<LoginRequest, LoginResponse>
    {
        private readonly IUserRepository _userRepository;
        private readonly IJwtTokenService _jwtTokenService;

        public LoginHandler(IUserRepository userRepository, IJwtTokenService jwtTokenService)
        {
            _userRepository = userRepository;
            _jwtTokenService = jwtTokenService;
        }

        public async Task<LoginResponse> Handle(LoginRequest request, CancellationToken cancellationToken)
        {
            var user = await _userRepository.GetByEmailAsync(request.Email, cancellationToken)
                ?? throw new UnauthorizedAccessException("No account found with this email. Please register first.");

            if (!BCrypt.Net.BCrypt.Verify(request.Password, user.Password))
                throw new UnauthorizedAccessException("Incorrect password. Please try again.");

            var token = _jwtTokenService.GenerateToken(user);

            var role = user.Admin != null ? "admin"
                : user.Writer != null ? "writer"
                : "regular";

            return new LoginResponse(token, user.Id, user.Username, user.Email, user.Name, user.Surname, role);
        }
    }
}