using System.IdentityModel.Tokens.Jwt;
using System.Net;
using System.Security.Claims;
using System.Text;
using FluentValidation;
using Galaeth.Core.Configuration;
using Galaeth.Core.Constants;
using Galaeth.Core.Entities;
using Galaeth.Core.Extensions;
using Galaeth.Core.Infrastructure;
using Galaeth.Core.RepositoryInterfaces;
using Galaeth.Services.Constants;
using Galaeth.Services.Dtos;
using Galaeth.Services.Exceptions;
using Galaeth.Services.Interfaces;
using Injectio.Attributes;
using Microsoft.Extensions.Options;
using Microsoft.IdentityModel.Tokens;
using MyCSharp.HttpUserAgentParser;

namespace Galaeth.Services.Services;

/// <inheritdoc />
[RegisterScoped]
public class AuthenticationService : IAuthenticationService
{
    /// <summary>
    /// The length of the refresh token.
    /// </summary>
    private const int RefreshTokenLength = 128;

    private readonly ICryptographyService _cryptographyService;
    private readonly IRefreshTokenRepository _refreshTokenRepository;
    private readonly IIdentityProvider _identityProvider;
    private readonly IUserRepository _userRepository;
    private readonly ITransactionProvider _transactionProvider;
    private readonly IValidator<AuthenticateUserDto> _authenticateUserValidator;
    private readonly JwtConfiguration _jwtConfiguration;

    /// <summary>
    /// Initializes a new instance of the <see cref="AuthenticationService"/> class.
    /// </summary>
    /// <param name="cryptographyService">Instance of <see cref="ICryptographyService"/>.</param>
    /// <param name="refreshTokenRepository">Instance of <see cref="IRefreshTokenRepository"/>.</param>
    /// <param name="identityProvider">Instance of <see cref="IIdentityProvider"/>.</param>
    /// <param name="userRepository">Instance of <see cref="IUserRepository"/>.</param>
    /// <param name="transactionProvider">Instance of <see cref="ITransactionProvider"/>.</param>
    /// <param name="authenticateUserValidator">Instance of <see cref="IValidator{AuthenticateUserDto}"/>.</param>
    /// <param name="jwtConfig">Instance of <see cref="IOptions{JwtConfiguration}"/>.</param>
    public AuthenticationService(
        ICryptographyService cryptographyService,
        IRefreshTokenRepository refreshTokenRepository,
        IIdentityProvider identityProvider,
        IUserRepository userRepository,
        ITransactionProvider transactionProvider,
        IValidator<AuthenticateUserDto> authenticateUserValidator,
        IOptions<JwtConfiguration> jwtConfig)
    {
        _cryptographyService = cryptographyService;
        _refreshTokenRepository = refreshTokenRepository;
        _identityProvider = identityProvider;
        _userRepository = userRepository;
        _transactionProvider = transactionProvider;
        _authenticateUserValidator = authenticateUserValidator;
        _jwtConfiguration = jwtConfig.Value;
    }

    /// <inheritdoc />
    public async Task<AccessTokensDto> AuthenticateUser(AuthenticateUserDto request)
    {
        await _authenticateUserValidator.ValidateAndThrowAsync(request);

        // Find user from provided username.
        var user = await _userRepository.FindByUsername(request.Username);
        if (user is null)
        {
            throw new InvalidCredentialsException();
        }

        if (!_cryptographyService.VerifyPassword(
                request.Password,
                user.PasswordSalt,
                user.PasswordHash))
        {
            // TODO store failed logins in future
            throw new InvalidCredentialsException();
        }

        switch (user.State)
        {
            case UserState.Suspended:
                throw new UserSuspendedException();
            case UserState.Banned:
                throw new UserBannedException();
            case UserState.AwaitingEmailActivation:
                throw new UserNotActivatedException();
        }

        // Record last logged in.
        // TODO store successful login in future
        user.LastLoggedIn = DateTime.UtcNow;
        await _userRepository.UpdateAsync(user);

        var accessToken = await GenerateUserAccessTokens(user, request.UserAgent, request.IpAddress);

        return accessToken;
    }

    /// <inheritdoc />
    public async Task<AccessTokensDto> AuthenticateUser(RefreshAuthenticationDto request)
    {
        if (request.RefreshToken.Length != RefreshTokenLength)
        {
            throw new UnauthorizedException();
        }

        // Attempt to find refresh token.
        var refreshToken = await _refreshTokenRepository.FindByIdAsync(request.RefreshToken);

        if (refreshToken is null || refreshToken.Expires < DateTime.UtcNow ||
            request.UserAgent.UserAgent != refreshToken.UserAgent ||
            refreshToken.TokenContext != RefreshTokenContext.UserAccess)
        {
            throw new UnauthorizedException();
        }

        // Get user to determine state.
        var user = await _userRepository.FindByIdAsync(refreshToken.UserId);

        if (user is null || user.State != UserState.Normal)
        {
            throw new UnauthorizedException();
        }

        // Consider this request valid and delete old refresh token.
        await _refreshTokenRepository.DeleteAsync(refreshToken.Token);

        var newTokens = await GenerateUserAccessTokens(user, request.UserAgent, request.IpAddress);

        return newTokens;
    }

    /// <inheritdoc />
    public async Task<AccessTokensDto> ChangeUserPassword(ChangePasswordDto request)
    {
        // Check to make sure a user is logged in.
        var userId = _identityProvider.GetRequestingUserId();
        if (string.IsNullOrWhiteSpace(userId) || !Guid.TryParse(userId, out var guid))
        {
            throw new UnauthorizedException();
        }

        var user = await _userRepository.FindByIdAsync(guid);

        if (user is null || user.State == UserState.Banned || user.State == UserState.Suspended)
        {
            throw new UnauthorizedException();
        }

        // Verify current password is correct.
        if (!_cryptographyService.VerifyPassword(
                request.OldPassword,
                user.PasswordSalt,
                user.PasswordHash))
        {
            // TODO store failed request in future
            throw new InvalidCredentialsException();
        }

        var salt = _cryptographyService.GenerateSalt();
        var hash = _cryptographyService.HashPassword(request.NewPassword, salt);

        user.PasswordHash = Convert.ToBase64String(hash);
        user.PasswordSalt = Convert.ToBase64String(salt);

        // TODO store log in future
        using var transaction = await _transactionProvider.BeginTransactionAsync();

        await _userRepository.UpdateAsync(user);
        await _refreshTokenRepository.RevokeAllForUser(user.Id);

        var tokens = await GenerateUserAccessTokens(user, request.UserAgent, request.IpAddress);

        transaction.Commit();

        return tokens;
    }

    /// <summary>
    /// Generate a new access token and refresh token for user.
    /// </summary>
    /// <param name="user">Instance of <see cref="User"/>.</param>
    /// <param name="userAgentInformation">Information about the requesting user agent.</param>
    /// <param name="ipAddress">The IP address of the agent requesting a user access token.</param>
    /// <returns>Instance of <see cref="AccessTokensDto"/>.</returns>
    private async Task<AccessTokensDto> GenerateUserAccessTokens(
        User user,
        HttpUserAgentInformation userAgentInformation,
        IPAddress ipAddress)
    {
        var handler = new JwtSecurityTokenHandler();

        var claims = new List<Claim>
        {
            new (ClaimIds.UserId, user.Id.ToString()),
            new (ClaimIds.Role, user.Role.ToString()),
        };

        var key = new SymmetricSecurityKey(Encoding.ASCII.GetBytes(_jwtConfiguration.SecretKey));

        var accessExpires = _jwtConfiguration.AccessTokenExpirationDateTime();
        var refreshExpires = _jwtConfiguration.RefreshTokenExpirationDateTime();

        var descriptor = new SecurityTokenDescriptor
        {
            Subject = new ClaimsIdentity(claims),
            Expires = accessExpires,
            SigningCredentials = new SigningCredentials(key, SecurityAlgorithms.HmacSha256Signature),
            Audience = _jwtConfiguration.Audience,
            Issuer = _jwtConfiguration.Issuer,
        };

        var result = new AccessTokensDto();

        var token = handler.CreateToken(descriptor);
        result.AccessToken = handler.WriteToken(token);
        result.RefreshToken = _cryptographyService.GenerateRandomString(RefreshTokenLength);
        result.AccessTokenExpires = accessExpires;
        result.AccessTokenExpiresTicks = accessExpires.Ticks;
        result.RefreshTokenExpires = refreshExpires;
        result.RefreshTokenExpiresTicks = refreshExpires.Ticks;

        // Make sure the refresh token is unique.
        while (await _refreshTokenRepository.FindByIdAsync(result.RefreshToken) is not null)
        {
            result.RefreshToken = _cryptographyService.GenerateRandomString(RefreshTokenLength);
        }

        // Store refresh token.
        await _refreshTokenRepository.AddAsync(new RefreshToken()
        {
            Token = result.RefreshToken,
            UserId = user.Id,
            TokenContext = RefreshTokenContext.UserAccess,
            Expires = refreshExpires,
            UserAgent = userAgentInformation.UserAgent,
            UserAgentType = userAgentInformation.Type,
            IpAddress = ipAddress.ToString(),
            CreatedAt = DateTime.UtcNow,
        });

        return result;
    }
}