Feature/notification

src/main/java/com/hcmus/forumus_backend/controller/NotificationController.java

@@ -0,0 +1,28 @@
+package com.hcmus.forumus_backend.controller;
+
+import com.hcmus.forumus_backend.dto.notification.NotificationTriggerRequest;
+import com.hcmus.forumus_backend.service.NotificationService;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.*;
+
+@RestController
+@RequestMapping("/api/notifications")
+@CrossOrigin
+public class NotificationController {
+
+    private final NotificationService notificationService;
+
+    public NotificationController(NotificationService notificationService) {
+        this.notificationService = notificationService;
+    }
+
+    @PostMapping("")
+    public ResponseEntity<String> triggerNotification(@RequestBody NotificationTriggerRequest request) {
+        boolean success = notificationService.triggerNotification(request);
+        if (success) {
+            return ResponseEntity.ok("Notification triggered successfully");
+        } else {
+            return ResponseEntity.badRequest().body("Failed to trigger notification");
+        }
+    }
+}

src/main/java/com/hcmus/forumus_backend/dto/notification/NotificationTriggerRequest.java

@@ -0,0 +1,70 @@
+package com.hcmus.forumus_backend.dto.notification;
+
+public class NotificationTriggerRequest {
+    private String type; // UPVOTE, COMMENT, REPLY
+    private String actorId;
+    private String actorName;
+    private String targetId; // Post ID or Comment ID
+    private String targetUserId; // The user to notify
+    private String previewText; // Snippet of post title or comment
+
+    public NotificationTriggerRequest() {
+    }
+
+    public NotificationTriggerRequest(String type, String actorId, String actorName, String targetId, String targetUserId, String previewText) {
+        this.type = type;
+        this.actorId = actorId;
+        this.actorName = actorName;
+        this.targetId = targetId;
+        this.targetUserId = targetUserId;
+        this.previewText = previewText;
+    }
+
+    public String getType() {
+        return type;
+    }
+
+    public void setType(String type) {
+        this.type = type;
+    }
+
+    public String getActorId() {
+        return actorId;
+    }
+
+    public void setActorId(String actorId) {
+        this.actorId = actorId;
+    }
+
+    public String getActorName() {
+        return actorName;
+    }
+
+    public void setActorName(String actorName) {
+        this.actorName = actorName;
+    }
+
+    public String getTargetId() {
+        return targetId;
+    }
+
+    public void setTargetId(String targetId) {
+        this.targetId = targetId;
+    }
+
+    public String getTargetUserId() {
+        return targetUserId;
+    }
+
+    public void setTargetUserId(String targetUserId) {
+        this.targetUserId = targetUserId;
+    }
+
+    public String getPreviewText() {
+        return previewText;
+    }
+
+    public void setPreviewText(String previewText) {
+        this.previewText = previewText;
+    }
+}

src/main/java/com/hcmus/forumus_backend/service/FCMService.java

@@ -177,4 +177,52 @@ public void sendMulticastNotification(
             logger.error("Failed to send multicast notification", e);
         }
     }
+    /**
+     * Send a general notification to a specific device
+     * 
+     * @param fcmToken The recipient's FCM token
+     * @param title    The notification title
+     * @param body     The notification body
+     * @param data     Additional data payload
+     * @return true if sent successfully, false otherwise
+     */
+    public boolean sendGeneralNotification(String fcmToken, String title, String body, Map<String, String> data) {
+        try {
+            // Create notification
+            Notification notification = Notification.builder()
+                    .setTitle(title)
+                    .setBody(body)
+                    .build();
+
+            // Build the message
+            Message.Builder messageBuilder = Message.builder()
+                    .setToken(fcmToken)
+                    .setNotification(notification)
+                    .setAndroidConfig(AndroidConfig.builder()
+                            .setPriority(AndroidConfig.Priority.HIGH)
+                            .setNotification(AndroidNotification.builder()
+                                    .setSound("default")
+                                    .setChannelId("general_notifications")
+                                    .build())
+                            .build());
+
+            if (data != null && !data.isEmpty()) {
+                messageBuilder.putAllData(data);
+            }
+
+            Message message = messageBuilder.build();
+
+            // Send the message
+            String response = FirebaseMessaging.getInstance().send(message);
+            logger.info("Successfully sent general notification: {}", response);
+            return true;
+
+        } catch (FirebaseMessagingException e) {
+            logger.error("Failed to send general notification to token: {}", fcmToken, e);
+            return false;
+        } catch (Exception e) {
+            logger.error("Unexpected error sending general notification", e);
+            return false;
+        }
+    }
 }

src/main/java/com/hcmus/forumus_backend/service/NotificationService.java

@@ -0,0 +1,120 @@
+package com.hcmus.forumus_backend.service;
+
+import com.google.cloud.Timestamp;
+import com.google.cloud.firestore.Firestore;
+import com.hcmus.forumus_backend.dto.notification.NotificationTriggerRequest;
+import com.hcmus.forumus_backend.model.User;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.stereotype.Service;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.UUID;
+import java.util.concurrent.ExecutionException;
+
+@Service
+public class NotificationService {
+
+    private static final Logger logger = LoggerFactory.getLogger(NotificationService.class);
+
+    private final Firestore db;
+    private final UserService userService;
+    private final FCMService fcmService;
+
+    public NotificationService(Firestore db, UserService userService, FCMService fcmService) {
+        this.db = db;
+        this.userService = userService;
+        this.fcmService = fcmService;
+    }
+
+    public boolean triggerNotification(NotificationTriggerRequest request) {
+        try {
+            // 1. Validate inputs
+            if (request.getTargetUserId() == null || request.getTargetUserId().isEmpty()) {
+                logger.warn("Notification validation failed: targetUserId is missing");
+                return false;
+            }
+
+            // Don't notify if actor is the same as target user (self-action)
+            if (request.getTargetUserId().equals(request.getActorId())) {
+                logger.info("Skipping notification: Actor is target user");
+                return true; // Use true because it's not an error, just logic
+            }
+
+            // 2. Fetch target user to get FCM token
+            User targetUser;
+            try {
+                targetUser = userService.getUserById(request.getTargetUserId());
+            } catch (Exception e) {
+                logger.error("Failed to fetch target user: {}", request.getTargetUserId(), e);
+                return false;
+            }
+
+            // 3. Prepare Notification Data for Firestore
+            String notificationId = UUID.randomUUID().toString();
+            Map<String, Object> notificationData = new HashMap<>();
+            notificationData.put("id", notificationId);
+            notificationData.put("type", request.getType());
+            notificationData.put("actorId", request.getActorId());
+            notificationData.put("actorName", request.getActorName());
+            notificationData.put("targetId", request.getTargetId());
+            notificationData.put("previewText", request.getPreviewText());
+            notificationData.put("createdAt", Timestamp.now());
+            notificationData.put("isRead", false);
+
+            // 4. Write to Firestore: users/{targetUserId}/notifications/{notificationId}
+            db.collection("users")
+                .document(request.getTargetUserId())
+                .collection("notifications")
+                .document(notificationId)
+                .set(notificationData);
+
+            logger.info("Notification saved to Firestore: {}", notificationId);
+
+            // 5. Send FCM Push Notification
+            if (targetUser.getFcmToken() != null && !targetUser.getFcmToken().isEmpty()) {
+                String title = generateNotificationTitle(request);
+                String body = generateNotificationBody(request);
+
+                Map<String, String> data = new HashMap<>();
+                data.put("type", "general_notification");
+                data.put("notificationId", notificationId);
+                data.put("targetId", request.getTargetId()); // Post/Comment ID for deep link
+                data.put("click_action", "FLUTTER_NOTIFICATION_CLICK"); // Standard, but we handle intent in Android
+
+                fcmService.sendGeneralNotification(targetUser.getFcmToken(), title, body, data);
+            } else {
+                logger.info("Target user has no FCM token, skipping push notification");
+            }
+
+            return true;
+
+        } catch (Exception e) {
+            logger.error("Error triggering notification", e);
+            return false;
+        }
+    }
+
+    private String generateNotificationTitle(NotificationTriggerRequest request) {
+        return switch (request.getType()) {
+            case "UPVOTE" -> "New Upvote";
+            case "COMMENT" -> "New Comment";
+            case "REPLY" -> "New Reply";
+            default -> "New Notification";
+        };
+    }
+
+    private String generateNotificationBody(NotificationTriggerRequest request) {
+        String actor = request.getActorName() != null ? request.getActorName() : "Someone";
+        String preview = request.getPreviewText() != null ? request.getPreviewText() : "";
+        if (preview.length() > 50) preview = preview.substring(0, 50) + "...";
+
+        return switch (request.getType()) {
+            case "UPVOTE" -> actor + " upvoted your post: " + preview;
+            case "COMMENT" -> actor + " commented on your post: " + preview;
+            case "REPLY" -> actor + " replied to your comment: " + preview;
+            default -> actor + " interacted with your content.";
+        };
+    }
+}