Feat: Added AuthenticationService object and added new method to chec…

…k if username is taken

helpmehelpapplication/src/main/java/ntnu/systemutvikling/team6/database/DatabaseSetup.java

@@ -42,7 +42,6 @@ public boolean testConnection() {
       System.out.println("Database connection failed.");
       e.printStackTrace();
     }
-
     return false;
   }
 

helpmehelpapplication/src/main/java/ntnu/systemutvikling/team6/database/Readers/UserSelect.java

@@ -30,6 +30,30 @@ public UserSelect(DatabaseConnection connection) {
     this.connection = connection;
   }
 
+  public boolean isUsernameTaken(String username){
+    try (Connection conn = connection.getMySqlConnection();
+         Statement stmt = conn.createStatement()) {
+
+      String mysql =
+              """
+              SELECT UUID_User FROM User WHERE user_name = ?
+              """;
+      PreparedStatement statement = conn.prepareStatement(mysql);
+      statement.setString(1, username);
+      ResultSet rs = statement.executeQuery();
+
+      if (rs.next()) {
+        System.out.println("Username Taken already");
+        return true;
+      }
+
+    } catch (SQLException e) {
+      e.printStackTrace();
+    }
+    return false;
+  }
+
+
   /**
    * Retrieves a single {@link User} from the database matching the given username and password.
    *

helpmehelpapplication/src/main/java/ntnu/systemutvikling/team6/service/AuthenticationService.java

@@ -1 +1,117 @@
+package ntnu.systemutvikling.team6.service;
 
+import ntnu.systemutvikling.team6.database.DAO.UserDAO;
+import ntnu.systemutvikling.team6.database.Readers.UserSelect;
+import ntnu.systemutvikling.team6.models.user.Inbox;
+import ntnu.systemutvikling.team6.models.user.Role;
+import ntnu.systemutvikling.team6.models.user.Settings;
+import ntnu.systemutvikling.team6.models.user.User;
+
+
+/**
+ * Service class responsible for handling user authentication operations,
+ * including login, registration, and logout functionality.
+ * <p>
+ * Maintains the state of the currently authenticated user throughout the session.
+ * </p>
+ */
+public class AuthenticationService {
+    /** Handles read operations for user data from the database. */
+    private final UserSelect userDataReader;
+    /** Handles write operations for user data to the database. */
+    private final UserDAO userDataSender;
+
+    /** The currently authenticated user, or {@code null} if no user is logged in. */
+    private User currentUser;
+
+    /**
+     * Constructs an {@code AuthenticationService} with the specified data access objects.
+     *
+     * @param userDataReader the data reader used to query user information from the database
+     * @param userDataSender the DAO used to persist new user registrations to the database
+     */
+    public AuthenticationService(UserSelect userDataReader, UserDAO  userDataSender) {
+        this.userDataReader = userDataReader;
+        this.userDataSender = userDataSender;
+    }
+
+    /**
+     * Attempts to authenticate a user with the given credentials.
+     * <p>
+     * If a matching user is found in the database, they are set as the current user
+     * and the method returns {@code true}.
+     * </p>
+     *
+     * @param username the username of the user attempting to log in
+     * @param password the password of the user attempting to log in
+     * @return {@code true} if authentication was successful; {@code false} otherwise
+     */
+    public boolean login(String username, String password){
+        User user = userDataReader.getUserFromDBUsernameAndPassword(username, password);
+
+        if (user != null){
+            currentUser = user;
+            return true;
+        }
+
+        return false;
+    }
+
+    /**
+     * Registers a new user account with the provided details.
+     * <p>
+     * The new user is assigned the {@link Role#NORMAL_USER} role and default
+     * {@link Settings} and {@link Inbox}. Registration will fail if the
+     * username is already taken or if the database operation is unsuccessful.
+     * On success, the new user is set as the current user.
+     * </p>
+     *
+     * @param displayName the display name shown on the user's profile
+     * @param username    the unique username for the new account
+     * @param email       the email address associated with the new account
+     * @param password    the password for the new account
+     * @return {@code true} if registration was successful; {@code false} if the
+     *         username is already taken or the database operation failed
+     */
+    public boolean register(String displayName, String username, String email, String password ){
+        User newUser = new User(displayName, username, email, password, Role.NORMAL_USER, new Settings(), new Inbox());
+
+        if(userDataReader.isUsernameTaken(username)){
+            return false;
+        }
+
+        boolean success = userDataSender.registerUser(newUser);
+
+        if (success){
+            currentUser = newUser;
+            return true;
+        }
+        return false;
+    }
+
+    /**
+     * Logs out the currently authenticated user by clearing the current user state.
+     */
+    public void logout (){
+        currentUser = null;
+    }
+
+
+    /**
+     * Returns the currently authenticated user.
+     *
+     * @return the current {@link User}, or {@code null} if no user is logged in
+     */
+    public User getCurrentUser(){
+        return currentUser;
+    }
+
+    /**
+     * Checks whether a user is currently logged in.
+     *
+     * @return {@code true} if a user is authenticated; {@code false} otherwise
+     */
+    public boolean isLoggedin(){
+        return currentUser != null;
+    }
+}