Added user block / unblock logic

src/main/java/UserService.java

@@ -1,10 +1,38 @@
+import java.util.HashMap;
+import java.util.Map;
+
 public class UserService {
 
+    private Map<String, Integer> failedAttempts = new HashMap();
+    private static final int MAX_FAILED_ATTEMPTS = 4;
+
     public String authenticate(String username, String password) {
-        if ("admin".equals(username) && "password123".equals(password)) {
+        if (isUserBlocked(username)) {
+            return "User is blocked due to too many failed login attempts.";
+        }
+
+        if ("admin".equals(username) && "password1234".equals(password)) {
+            resetFailedAttempts(username); // Reset attempts on successful login
             return "Login successful";
         } else {
-            return "Login failed";
+            incrementFailedAttempts(username);
+            if (failedAttempts.get(username) >= MAX_FAILED_ATTEMPTS) {
+                return "User is blocked due to too many failed login attempts.";
+            } else {
+                return "Login failed. You have " + (MAX_FAILED_ATTEMPTS - failedAttempts.get(username)) + " attempts left.";
+            }
         }
     }
-}
+
+    private void incrementFailedAttempts(String username) {
+        failedAttempts.put(username, failedAttempts.getOrDefault(username, 0) + 1);
+    }
+
+    private void resetFailedAttempts(String username) {
+        failedAttempts.put(username, 0);
+    }
+
+    private boolean isUserBlocked(String username) {
+        return failedAttempts.getOrDefault(username, 0) >= MAX_FAILED_ATTEMPTS;
+    }
+}