namespace Diligent.WebAPI.Business.Services
{

    public class UserService : IUserService
    {
        private readonly AuthorizationSettings _authSettings;
        private readonly DatabaseContext _context;

        public UserService(IOptions<AuthorizationSettings> authSettings, DatabaseContext context)
        {
            _authSettings = authSettings.Value;
            _context = context;
        }

        public AuthenticateResponseDto? Authenticate(AuthenticateRequestDto model)
        {
            var user = _context.User.SingleOrDefault(x => x.Username == model.Username && x.Password == model.Password);

            // return null if user not found
            if (user == null)
                return null;

            // authentication successful so generate jwt token
            var token = GenerateJwtToken(user);

            return new AuthenticateResponseDto
            {
                Id = user.Id,
                Username = user.Username,
                FirstName = user.FirstName,
                LastName = user.LastName,
                Token = token
            };
        }

        public async Task<IEnumerable<User?>> GetAll()
        {
            return await _context.User.ToListAsync();
        }

        public async Task<User?> GetById(int id)
        {
            return await _context.User.FirstOrDefaultAsync(x => x.Id == id);
        }

        private string GenerateJwtToken(User user)
        {
            // generate token that is valid for 7 days
            var tokenHandler = new JwtSecurityTokenHandler();
            var key = Encoding.ASCII.GetBytes(_authSettings.Secret);
            var tokenDescriptor = new SecurityTokenDescriptor
            {
                Subject = new ClaimsIdentity(new[] { new Claim("id", user.Id.ToString()) }),
                Expires = DateTime.UtcNow.AddMinutes(2),
                SigningCredentials = new SigningCredentials(new SymmetricSecurityKey(key), SecurityAlgorithms.HmacSha256Signature)
            };
            var token = tokenHandler.CreateToken(tokenDescriptor);
            return tokenHandler.WriteToken(token);
        }
    }
}