add api for subscribe and unsubscribe other users

src/main/java/com/smartcalendar/controller/FriendshipController.java

@@ -0,0 +1,55 @@
+package com.smartcalendar.controller;
+
+import com.smartcalendar.dto.SubscriptionRequest;
+import com.smartcalendar.model.Friendship;
+import com.smartcalendar.service.FriendshipService;
+import jakarta.validation.Valid;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.security.core.annotation.AuthenticationPrincipal;
+import org.springframework.security.core.userdetails.UserDetails;
+import org.springframework.web.bind.annotation.*;
+
+import java.util.List;
+
+@RestController
+@RequestMapping("/api/friendships")
+public class FriendshipController {
+
+    private final FriendshipService friendshipService;
+
+    @Autowired
+    public FriendshipController(FriendshipService friendshipService) {
+        this.friendshipService = friendshipService;
+    }
+
+    @GetMapping("/my-subscriptions")
+    public ResponseEntity<List<Friendship>> getMySubscriptions(
+            @AuthenticationPrincipal UserDetails userDetails
+    ) {
+        Long currentUserId = Long.parseLong(userDetails.getUsername());
+        List<Friendship> subscriptions = friendshipService.getSubscriptions(currentUserId);
+        return ResponseEntity.ok(subscriptions);
+    }
+
+    @PostMapping("/subscribe")
+    public ResponseEntity<Friendship> subscribe(
+            @AuthenticationPrincipal UserDetails userDetails,
+            @RequestBody @Valid SubscriptionRequest request
+    ) {
+        Long currentUserId = Long.parseLong(userDetails.getUsername());
+        Friendship subscription = friendshipService.createSubscription(currentUserId, request.getUser2Id());
+        return ResponseEntity.status(HttpStatus.CREATED).body(subscription);
+    }
+
+    @DeleteMapping("/unsubscribe/{followingId}")
+    public ResponseEntity<Void> unsubscribe(
+            @AuthenticationPrincipal UserDetails userDetails,
+            @PathVariable Long user2Id
+    ) {
+        Long currentUserId = Long.parseLong(userDetails.getUsername());
+        friendshipService.deleteSubscription(currentUserId, user2Id);
+        return ResponseEntity.noContent().build();
+    }
+}

src/main/java/com/smartcalendar/dto/SubscriptionRequest.java

@@ -0,0 +1,14 @@
+package com.smartcalendar.dto;
+
+import jakarta.validation.constraints.NotNull;
+import lombok.Data;
+
+@Data
+public class SubscriptionRequest {
+    private Long user2Id;
+
+    public Long getUser2Id() {
+        return user2Id;
+    }
+}
+

src/main/java/com/smartcalendar/exceptions/ConflictException.java

@@ -0,0 +1,11 @@
+package com.smartcalendar.exceptions;
+
+import org.springframework.http.HttpStatus;
+import org.springframework.web.bind.annotation.ResponseStatus;
+
+@ResponseStatus(HttpStatus.CONFLICT)
+public class ConflictException extends RuntimeException {
+    public ConflictException(String message) {
+        super(message);
+    }
+}

src/main/java/com/smartcalendar/exceptions/ResourceNotFoundException.java

@@ -0,0 +1,12 @@
+package com.smartcalendar.exceptions;
+
+import org.springframework.http.HttpStatus;
+import org.springframework.web.bind.annotation.ResponseStatus;
+
+@ResponseStatus(HttpStatus.NOT_FOUND)
+public class ResourceNotFoundException extends RuntimeException {
+    public ResourceNotFoundException(String message) {
+        super(message);
+    }
+}
+

src/main/java/com/smartcalendar/model/Friendship.java

@@ -16,7 +16,7 @@
 public class Friendship {
     @Id
     //@GeneratedValue(strategy = GenerationType.IDENTITY)
-    private UUID id;
+    private Long id;
 
     @ManyToOne
     @JoinColumn(name = "user_id1")
@@ -27,4 +27,12 @@ public class Friendship {
     @JoinColumn(name = "user_id2")
     @JsonBackReference(value = "friends2")
     private User user2;
+
+    public void setUser1(User user1) {
+        this.user1 = user1;
+    }
+
+    public void setUser2(User user2) {
+        this.user2 = user2;
+    }
 }

src/main/java/com/smartcalendar/repository/FriendshipRepository.java

@@ -0,0 +1,14 @@
+package com.smartcalendar.repository;
+
+import com.smartcalendar.model.Friendship;
+import com.smartcalendar.model.User;
+import org.springframework.data.jpa.repository.JpaRepository;
+
+import java.util.List;
+import java.util.Optional;
+
+public interface FriendshipRepository extends JpaRepository<Friendship, Long> {
+    List<Friendship> findByUser1(User user1);
+    Optional<Friendship> findByUser1AndUser2(User user1, User user2);
+    boolean existsByUser1AndUser2(User user1, User user2);
+}

src/main/java/com/smartcalendar/service/FriendshipService.java

@@ -0,0 +1,60 @@
+package com.smartcalendar.service;
+
+import com.smartcalendar.exceptions.ConflictException;
+import com.smartcalendar.exceptions.ResourceNotFoundException;
+import com.smartcalendar.model.Friendship;
+import com.smartcalendar.model.User;
+import com.smartcalendar.repository.FriendshipRepository;
+import com.smartcalendar.repository.UserRepository;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Service;
+
+import java.util.List;
+
+@Service
+public class FriendshipService {
+
+    private final FriendshipRepository friendshipRepository;
+    private final UserRepository userRepository;
+
+    @Autowired
+    public FriendshipService(FriendshipRepository friendshipRepository, UserRepository userRepository) {
+        this.friendshipRepository = friendshipRepository;
+        this.userRepository = userRepository;
+    }
+
+    public List<Friendship> getSubscriptions(Long user1Id) {
+        userRepository.findById(user1Id).orElseThrow(() ->
+                new ResourceNotFoundException("User not found with id: " + user1Id));
+        return friendshipRepository.findByUser1(userRepository.findById(user1Id).get());
+    }
+
+    public Friendship createSubscription(Long user1Id, Long user2Id) {
+        userRepository.findById(user1Id).orElseThrow(() ->
+                new ResourceNotFoundException("User not found with id: " + user1Id));
+
+        userRepository.findById(user2Id).orElseThrow(() ->
+                new ResourceNotFoundException("User not found with id: " + user2Id));
+
+        User user1 = userRepository.findById(user1Id).get();
+        User user2 = userRepository.findById(user2Id).get();
+
+        if (friendshipRepository.existsByUser1AndUser2(user1, user2)) {
+            throw new ConflictException("Subscription already exists");
+        }
+
+        Friendship subscription = new Friendship();
+        subscription.setUser1(user1);
+        subscription.setUser2(user2);
+
+        return friendshipRepository.save(subscription);
+    }
+
+    public void deleteSubscription(Long user1Id, Long user2Id) {
+        Friendship subscription = friendshipRepository
+                .findByUser1AndUser2(userRepository.findById(user1Id).get(), userRepository.findById(user2Id).get())
+                .orElseThrow(() -> new ResourceNotFoundException("Subscription not found"));
+
+        friendshipRepository.delete(subscription);
+    }
+}