namespace MUD.Lib.Daemons
{
    /// <summary>
    /// Handles the details of logging in and out. Yes, I'm playing enums-as-state-machines here. Leave me alone.
    /// </summary>
    internal class Login : VerbProcessor
    {
        private enum LoginState
        {
            Name,
            NameExistsPass,
            NameConfirm,
            NewPassword1,
            NewPassword2,
            Email,
            CharacterSequence
        }

        private delegate bool LoginStateHandler(User user, string input);

        private Dictionary<LoginState, LoginStateHandler> LoginStateMachine;

        private User.ReceiveHandler Listener;

        private LoginState _currentState = LoginState.Name;

        private int InvalidLoginTries = 0;

        public Login(User user)
        {
            LoginStateMachine = new Dictionary<LoginState, LoginStateHandler>();
            Listener = new User.ReceiveHandler(ReceiveInput);
            user.OnExclusiveReceive += Listener;
            InitializeSteps();
        }

        private void InitializeSteps()
        {
            LoginStateMachine.Add(LoginState.Name, new LoginStateHandler(ProcessName));
            LoginStateMachine.Add(LoginState.NameExistsPass, new LoginStateHandler(ValidatePassword));
            LoginStateMachine.Add(LoginState.NameConfirm, new LoginStateHandler(NameConfirm));
            LoginStateMachine.Add(LoginState.NewPassword1, new LoginStateHandler(NewPassword1));
            LoginStateMachine.Add(LoginState.NewPassword2, new LoginStateHandler(NewPassword2));
            LoginStateMachine.Add(LoginState.Email, new LoginStateHandler(EmailHandler));
            LoginStateMachine.Add(LoginState.CharacterSequence, new LoginStateHandler(ToCharacterSequence));
        }

        private bool ReceiveInput(User user, string command)
        {
            if (LoginStateMachine.Keys.Contains(_currentState))
                return LoginStateMachine[_currentState](user, command.TrimNewline());
            else
                return false;
        }

        // First thing we're going to see from the user.
        private bool ProcessName(User user, string input)
        {
            user.Username = input;
            // attempt to load the user;
            user.Load();
            if (!string.IsNullOrEmpty(user.Password))
            {
                // ok, there is a user by this name.
                _currentState = LoginState.NameExistsPass;
                user.Write("Welcome back, " + user.Username + "! Please enter your password:\r\n");
            }
            else
            {
                // this is a new user.
                _currentState = LoginState.NameConfirm;
                user.Write("Are you sure this is the account name you wish to use? (y/n)\r\n");
            }
            return true;
        }

        private bool ValidatePassword(User user, string input)
        {
            MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider();
            if (user.Password == BitConverter.ToString(md5.ComputeHash(ASCIIEncoding.ASCII.GetBytes(input))))
            {
                // password valid, continue to character selection
                // TODO: Move to character creation/selection
                _currentState = LoginState.CharacterSequence;
                ToCharacterSequence(user, "y");
            }
            else
            {
                // password invalid, ask them to try again.
                InvalidLoginTries++;
                if (InvalidLoginTries < 3)
                {
                    user.Write("Password invalid, please try again:\r\n ");
                    return false;
                }
                else
                {
                    user.Write("Maximum login attempts reached, disconnecting.\r\n");
                    user.OnExclusiveReceive -= Listener;
                    user.Disconnect();
                }
            }
            return true;
        }

        private bool NameConfirm(User user, string input)
        {
            if (input.ToLower() == "y")
            {
                // they want this name, move on.
                user.Write("Great! Please enter a password.\r\n");
                _currentState = LoginState.NewPassword1;
            }
            else
            {
                user.Write("Ok, what name would you like to use?\r\n");
                _currentState = LoginState.Name;
            }
            return true;
        }

        private bool NewPassword1(User user, string input)
        {
            MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider();
            user.Password = BitConverter.ToString(md5.ComputeHash(ASCIIEncoding.ASCII.GetBytes(input)));
            _currentState = LoginState.NewPassword2;
            user.Write("Please reenter your password:\r\n");
            return true;
        }

        private bool NewPassword2(User user, string input)
        {
            MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider();
            if (BitConverter.ToString(md5.ComputeHash(ASCIIEncoding.ASCII.GetBytes(input))) == user.Password)
            {
                // Password accepted, move on.
                _currentState = LoginState.Email;
                user.Write("Please enter a valid email address.\r\n");
            }
            else
            {
                // Passwords don't match, reenter.
                _currentState = LoginState.NewPassword1;
                user.Write("Passwords do not match, please choose a password:\r\n");
            }
            return true;
        }

        private bool EmailHandler(User user, string input)
        {
            if (IsEmailValid(input))
            {
                // store it and move on to character selection/creation!
                user.Email = input;
                user.Write("Ok, your new account with username " + user.Username + " and email address: " + user.Email + " is created. Please verify these details before continuing. (y/n)\r\n Warning: entering 'n' will cause the creation process to restart!\r\n");
                _currentState = LoginState.CharacterSequence;
            }
            else
            {
                // oops, need to reenter.
                user.Write("Email invalid, please enter a valid email address.");
            }
            return true;
        }

        private bool ToCharacterSequence(User user, string input)
        {
            if (input.ToLower() == "y")
            {
                // TODO: load character select/creation sequence
                user.OnExclusiveReceive -= Listener;
                user.Save();
                user.Write("Welcome to MUD.Net!!\r\n");
            }
            else
            {
                user.Write("Ok, starting over. Please enter desired username.\r\n");
                _currentState = LoginState.Name;
            }
            return true;
        }

        private bool IsEmailValid(string email)
        {
            if (string.IsNullOrEmpty(email))
                return false;
            // is there more than one "@"?
            int First = email.IndexOf('@');
            int Last = email.IndexOf('@');
            if (First != Last && First < email.Length - 1)
                return false;
            return true;
        }

        // TODO: Should I assign a single Login instance to every user for the duration of their login sequence or handle it via daemon?
        // TODO: Also, should I handle all character creation here as well?
        // enum++ and -- work just fine, btw.



    }
}