UserService

UserService.cs

    public class UserService : IUserService
    {
        /// <summary>
        /// The cached user for re-use once fetched.
        /// </summary>
        private static User _cachedUser;

        /// <summary>
        /// The filename used when saving the users session token.
        /// </summary>
        private const string tokenFilename = "session";

        /// <summary>
        /// The key name used to save the key/value pair associated with the session token.
        /// </summary>
        private const string tokenKey = "token";

        /// <summary>
        /// The user repository
        /// </summary>
        private IUserRepository userRepository;

        /// <summary>
        /// The storage service
        /// </summary>
        private IStorageService storageService;

        /// <summary>
        /// Initializes a new instance of the <see cref="UserService"/> class.
        /// </summary>
        /// <param name="repository">The repository.</param>
        /// <param name="storageService">The storage service.</param>
        public UserService(IUserRepository repository, IStorageService storageService)
        {
            this.userRepository = repository;
            this.storageService = storageService;
        }

        /// <summary>
        /// Asks the data store to create a new user with the given data..
        /// </summary>
        /// <param name="user"></param>
        /// <param name="password">The password.</param>
        /// <returns>
        /// Returns true if the user was created.
        /// </returns>
        public async Task<bool> CreateUser(User user, string password)
        {
            // Convert the user object to a dictionary for the repository.
            var data = new Dictionary<string, string>
            { 
                { user.GetPropertyName(p => p.Username), user.Username },
                { user.GetPropertyName(p => p.Email), user.Email },
                { "password", password},
            };
            string sessionToken = await this.userRepository.CreateUser(data, password);

            // Save the encrypted token and return.
            await this.storageService.SaveValueByKey(tokenFilename, new KeyValuePair<string, string>(tokenKey, sessionToken));

            _cachedUser = user;
            return true;
        }

        /// <summary>
        /// Retrieves user data for a user who has a matching username and password.
        /// </summary>
        /// <param name="username">The username.</param>
        /// <param name="password">The password.</param>
        /// <returns>
        /// Returns a restored user.
        /// </returns>
        public async Task<User> RetrieveUser(string username, string password)
        {
            Dictionary<string, string> data = await this.userRepository.RetrieveUser(username, password);
            User user = this.RestoreUserFromData(data);
            _cachedUser = user;

            return user;
        }

        /// <summary>
        /// Retrieves the user associated with the provided session token.
        /// </summary>
        /// <returns>
        /// Returns a restored user.
        /// </returns>
        /// <exception cref="Entities.Exceptions.UserNotAuthenticatedException">Session Token does not exist. Use must re-authenticate with a username and password.</exception>
        public async Task<User> RetrieveUser()
        {
            // Check if our cache is valid and return it.
            if (_cachedUser != null)
            {
                return _cachedUser;
            }

            // Load the session token.
            string sessionToken = await this.storageService.LoadValueFromKey(tokenFilename, tokenKey);

            if (string.IsNullOrWhiteSpace(sessionToken))
            {
                throw new UserNotAuthenticatedException("Session Token does not exist. Use must re-authenticate with a username and password.");
            }

            Dictionary<string, string> data = await this.userRepository.RetrieveUser(sessionToken);
            User user = this.RestoreUserFromData(data);
            _cachedUser = user;

            return user;
        }

        /// <summary>
        /// Logs the current user out, closing their session.
        /// </summary>
        public void Logout()
        {
            _cachedUser = null;
        }

        /// <summary>
        /// Restores the user from data provided by the repository.
        /// </summary>
        /// <param name="data">The data retrieved from the repository.</param>
        /// <returns>Returns a user instance.</returns>
        private User RestoreUserFromData(Dictionary<string, string> data)
        {
            var user = new User();
            user.UserId = data[user.GetPropertyName(p => p.UserId)];
            user.Email = data[user.GetPropertyName(p => p.Email)];
            user.Username = data[user.GetPropertyName(p => p.Username)];
            user.CreatedDate = Convert.ToDateTime(data[user.GetPropertyName(p => p.CreatedDate)]);
            user.UpdatedDate = Convert.ToDateTime(data[user.GetPropertyName(p => p.UpdatedDate)]);

            return user;
        }
    }