namespace Diligent.WebAPI.Business.Services
{

    public class UserService : IUserService
    {
        private readonly AuthorizationSettings _authSettings;
        private readonly UserManager<User> _userManager;
        private readonly IMapper _mapper;
        private readonly DatabaseContext _databaseContext;

        public UserService(IOptions<AuthorizationSettings> authSettings, UserManager<User> userManager, IMapper mapper, DatabaseContext databaseContext)
        {
            _authSettings = authSettings.Value;
            _userManager = userManager;
            _mapper = mapper;
            _databaseContext = databaseContext;
        }

        public async Task<IEnumerable<User?>> GetAll() =>
            await _userManager.Users.ToListAsync();

        public async Task<User?> GetById(int id) =>
            await _userManager.FindByIdAsync(id.ToString());

        public async Task CreateUser(CreateUserRequestDto model)
        {
            var user = _mapper.Map<User>(model);

            await _userManager.CreateAsync(user, model.Password);
        }

        public async Task<ServiceResponseDTO<AuthenticateResponseDto>> Authenticate(AuthenticateRequestDto model)
        {
            var user = await _userManager.FindByNameAsync(model.Username);

            // return null if user not found
            if (user == null)
            {
                return new ServiceResponseDTO<AuthenticateResponseDto>
                {
                    IsError = true,
                    ErrorMessage = "Username is not valid"
                };
            }

            var isLocked = await _userManager.IsLockedOutAsync(user);

            if (isLocked)
                return new ServiceResponseDTO<AuthenticateResponseDto>
                {
                    IsError = true,
                    ErrorMessage = "The account is locked out"
                };
               

            var result = await _userManager.CheckPasswordAsync(user, model.Password);

            // password is not correct
            if (!result)
            {
                await _userManager.AccessFailedAsync(user);
                isLocked = await _userManager.IsLockedOutAsync(user);
                
                if(isLocked)
                    return new ServiceResponseDTO<AuthenticateResponseDto>
                    {
                        IsError = true,
                        ErrorMessage = "The account is locked out"
                    };

                return new ServiceResponseDTO<AuthenticateResponseDto>
                {
                    IsError = true,
                    ErrorMessage = "Password is not correct"
                };
            }

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

            var data = new AuthenticateResponseDto
            {
                Id = user.Id,
                Username = user.UserName,
                FirstName = user.FirstName,
                LastName = user.LastName,
                Token = token,
                RefreshToken = token
            };

            return new ServiceResponseDTO<AuthenticateResponseDto>
            {
                Data = data
            };
        }

        private async Task<string> GenerateJwtToken(User user, bool authenticate = false)
        {
            // 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(JwtRegisteredClaimNames.Jti, user.Id.ToString()),
                    new Claim("id", user.Id.ToString())
                }),
                Expires = DateTime.UtcNow.AddMinutes(_authSettings.JwtExpiredTime),
                SigningCredentials = new SigningCredentials(new SymmetricSecurityKey(key), SecurityAlgorithms.HmacSha256Signature)
            };
            var token = tokenHandler.CreateToken(tokenDescriptor);

            var writedToken = tokenHandler.WriteToken(token);

            var refreshToken = new RefreshToken
            {
                Token = writedToken,
                JwtId = user.Id.ToString(),
                UserId = user.Id,
                User = user,
                CreationDate = DateTime.UtcNow,
                ExpiryDate = DateTime.UtcNow.AddMinutes(_authSettings.JwtRefreshExpiredTime)
            };

            var existRefreshToken = await _databaseContext.RefreshTokens.Where(x => x.UserId == user.Id).FirstOrDefaultAsync();

            if(existRefreshToken != null)
            {
                existRefreshToken.Token = writedToken;
                existRefreshToken.JwtId = token.Id;
                existRefreshToken.CreationDate = DateTime.UtcNow;
                existRefreshToken.ExpiryDate = DateTime.UtcNow.AddMinutes(_authSettings.JwtRefreshExpiredTime);

                if (authenticate)
                {
                    existRefreshToken.Used = false;
                    existRefreshToken.Invalidated = false;
                }

                _databaseContext.RefreshTokens.Update(existRefreshToken);
                await UpdateRefreshToken(existRefreshToken);
            }
            else
            {
                await _databaseContext.RefreshTokens.AddAsync(refreshToken);
            }

            await _databaseContext.SaveChangesAsync();

            return writedToken;
        }

        public async Task<RefreshTokenResultDto> RefreshTokenAsync(RefreshTokenRequestDto model)
        {
            var validatedToken = GetPrincipalFromToken(model.Token);

            if (validatedToken == null)
            {
                return new RefreshTokenResultDto { Error = "Invalid token" };
            }

            var jti = validatedToken.Claims.Single(x => x.Type == JwtRegisteredClaimNames.Jti).Value;

            var storedRefreshToken = await _databaseContext.RefreshTokens.SingleOrDefaultAsync(x => x.JwtId == jti);

            if (storedRefreshToken == null)
            {
                return new RefreshTokenResultDto { Error = "This refresh token does not exist" };
            }

            var userk = await _databaseContext.Users.Where(u => u.Id == storedRefreshToken.UserId).FirstOrDefaultAsync();

            if(userk == null)
            {
                return new RefreshTokenResultDto { Error = "There is no user which is associated with refresh token" };
            }

            var expiryDateUnix = long.Parse(validatedToken.Claims.Single(x => x.Type == JwtRegisteredClaimNames.Exp).Value);

            var expiryDateTimeUtc = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc)
                .AddMinutes(expiryDateUnix);

            if (expiryDateTimeUtc < DateTime.UtcNow)
            {
                return new RefreshTokenResultDto
                {
                    Data = new AuthenticateResponseDto
                    {
                        Id = userk.Id,
                        FirstName = userk.FirstName,
                        LastName = userk.LastName,
                        Username = userk.UserName,
                        Token = model.Token,
                        RefreshToken = model.RefreshToken
                    }
                };
            }

            if (DateTime.UtcNow > storedRefreshToken.ExpiryDate)
            {
                return new RefreshTokenResultDto { Error = "This refresh token has expired" };
            }

            if (storedRefreshToken.Invalidated)
            {
                return new RefreshTokenResultDto { Error = "This refresh token has been invalidated" };
            }

            if (storedRefreshToken.JwtId != jti)
            {
                return new RefreshTokenResultDto { Error = "This refresh token does not match this JWT" };
            }

            storedRefreshToken.ExpiryDate = DateTime.UtcNow.AddMinutes(_authSettings.JwtRefreshExpiredTime);

            await _databaseContext.SaveChangesAsync();

            var user = await _userManager.FindByIdAsync(validatedToken.Claims.Single(x => x.Type == "id").Value);

            var token =  await GenerateJwtToken(user);

            return new RefreshTokenResultDto
            {
                Data = new AuthenticateResponseDto
                {
                    Id = userk.Id,
                    FirstName = userk.FirstName,
                    LastName = userk.LastName,
                    Username = userk.UserName,
                    Token = model.Token,
                    RefreshToken = model.RefreshToken
                }
            };
        }

        public async Task<ServiceResponseDTO<string>> DeleteRefreshToken(int userId)
        {
            var refreshToken = await _databaseContext.RefreshTokens.Where(r => r.UserId == userId).FirstOrDefaultAsync();

            if (refreshToken is null)
                return new ServiceResponseDTO<string>
                {
                    IsError = true,
                    ErrorMessage = "There is no refresh token for user"
                };

            _databaseContext.RefreshTokens.Remove(refreshToken);

            var result = await _databaseContext.SaveChangesAsync() > 0;

            if (!result)
                return new ServiceResponseDTO<string>
                {
                    IsError = true,
                    ErrorMessage = "Problem with saving changes into database"
                };

            return new ServiceResponseDTO<string>
            {
                Data = null
            };
        }

        private ClaimsPrincipal? GetPrincipalFromToken(string token)
        {
            var tokenHandler = new JwtSecurityTokenHandler();

            var key = Encoding.ASCII.GetBytes(_authSettings.Secret);
            var tokenValidationParameters = new TokenValidationParameters
            {
                ValidateIssuerSigningKey = true,
                IssuerSigningKey = new SymmetricSecurityKey(key),
                ValidateIssuer = false,
                ValidateAudience = false,
                RequireExpirationTime = false,
                ValidateLifetime = true,
                // set clockskew to zero so tokens expire exactly at token expiration time (instead of 5 minutes later)
                //ClockSkew = TimeSpan.Zero
            };

            try
            {
                var principal = tokenHandler.ValidateToken(token, tokenValidationParameters, out var validatedToken);
                if (!IsJwtWithValidSecurityAlgorithm(validatedToken))
                {
                    return null;
                }

                return principal;
            }
            catch (Exception)
            {
                return null;
            }
        }

        private static bool IsJwtWithValidSecurityAlgorithm(SecurityToken validatedToken)
        {
            return (validatedToken is JwtSecurityToken jwtSecurityToken) &&
                jwtSecurityToken.Header.Alg.Equals(SecurityAlgorithms.HmacSha256,
                    StringComparison.InvariantCultureIgnoreCase);
        }

        public async Task<RefreshToken?> GetRefreshTokenByUserId(int userId)
        {
            return await _databaseContext.RefreshTokens.Where(x => x.UserId == userId).FirstOrDefaultAsync();
        }

        public async Task UpdateRefreshToken(RefreshToken refreshToken)
        {
            _databaseContext.RefreshTokens.Update(refreshToken);

            await _databaseContext.SaveChangesAsync();
        }
    }
}