User Blocking System

The user blocking feature allows users to prevent unwanted communication by blocking specific users. This document explains how the blocking system is implemented in the chat application.

Overview

When a user blocks another user:

1. The blocked user can no longer send messages to the blocker
2. The blocker will see a "blocked" indicator in the UI
3. Messages from blocked users are hidden (optional configuration)

User Interface

The blocking feature is accessible from two main locations:

Direct Message Panel

In the direct message panel (right sidebar), users can find the block/unblock button:

The UI changes based on the current blocking state:

• For unblocked users: Shows a "Block User" button
• For blocked users: Shows "You've blocked this user" banner and an "Unblock User" button

Chat Area

The chat area displays a banner when viewing a conversation with a blocked user:

The message input area is disabled when viewing a chat with a blocked user, with a message indicating "You can't send messages to blocked users".

Implementation

Database Structure

Blocked users are stored in the Firebase Realtime Database under the user's profile:

/users/{userId}/blockedUsers/{blockedUserId}: true

This structure allows for quick lookups to check if a user is blocked.

Core Functions

The blocking functionality is implemented in the ChatContext.jsx file with three main functions:

1. Block User

// Function to block a user
const blockUser = useCallback(async (userIdToBlock) => {
  if (!user?.uid || !userIdToBlock) return;

  try {
    // Add the user to the blocked list
    const updates = {};
    updates[`users/${user.uid}/blockedUsers/${userIdToBlock}`] = true;
    await update(ref(db), updates);
    
    // Update local state
    console.log(`User ${userIdToBlock} has been blocked`);
    
    return true;
  } catch (error) {
    console.error('Error blocking user:', error);
    throw error;
  }
}, [user]);

2. Unblock User

// Function to unblock a user
const unblockUser = useCallback(async (userIdToUnblock) => {
  if (!user?.uid || !userIdToUnblock) return;

  try {
    // Remove the user from the blocked list
    const updates = {};
    updates[`users/${user.uid}/blockedUsers/${userIdToUnblock}`] = null;
    await update(ref(db), updates);
    
    // Update local state
    console.log(`User ${userIdToUnblock} has been unblocked`);
    
    return true;
  } catch (error) {
    console.error('Error unblocking user:', error);
    throw error;
  }
}, [user]);

3. Check If User Is Blocked

// Function to check if a user is blocked
const isUserBlocked = useCallback((userId) => {
  if (!user?.uid || !userId || !allUsers?.[user.uid]?.blockedUsers) return false;
  
  // Check if userId is in current user's blocked list
  return !!allUsers[user.uid]?.blockedUsers?.[userId];
}, [user, allUsers]);

Message Sending Prevention

The application prevents messages from being sent to users who have blocked the sender by checking the blocking status before allowing message transmission:

// In the sendMessage function
if (currentChat.type === 'private') {
  // Find the other user's ID
  let otherUserId = null;
  
  if (currentChat.participants) {
    otherUserId = Object.keys(currentChat.participants).find(id => id !== user.uid);
  } else if (currentChat.members) {
    otherUserId = Object.keys(currentChat.members).find(id => id !== user.uid);
  }
  
  if (otherUserId) {
    // Check if the recipient has blocked the sender
    const otherUserRef = ref(db, `users/${otherUserId}/blockedUsers/${user.uid}`);
    const blockedSnapshot = await get(otherUserRef);
    
    if (blockedSnapshot.exists() && blockedSnapshot.val() === true) {
      // If the recipient has blocked the sender, don't allow sending the message
      console.log("Cannot send message: recipient has blocked you");
      return;
    }
  }
}

Similar checks are implemented for file messages and voice messages.

User Experience Considerations

The blocking system is designed with these UX principles:

1. Clear Feedback: Users receive immediate feedback when blocking/unblocking
2. Reversible Actions: Blocking can always be undone by unblocking
3. Privacy: Users are not notified when they are blocked
4. Transparency: Blocked users see a clear error message if they try to send messages

Integration with Other Features

The blocking system integrates with:

• Message Display: Optionally filtering out messages from blocked users
• User Search: Preventing blocked users from appearing in search results
• Group Chats: Still allowing blocked users to interact in shared group contexts
• Notifications: Preventing notifications from blocked users

Security Considerations

The blocking system includes these security measures:

1. Database Rules: Firebase security rules prevent unauthorized access to blocking data
2. Client-Side Validation: UI prevents attempts to send messages to blocking users
3. Server-Side Validation: Database rules validate blocking status during message sending

Customization Options

The blocking system can be customized by:

1. Modifying the UI: Changing the appearance of blocking indicators
2. Adjusting Behavior: Configuring whether to hide or show messages from blocked users
3. Extending Functionality: Adding block reporting or abuse notification features