This documentation outlines the implementation of the useAddTopic hook, which handles adding new topics to Firestore in a React Native Firebase application.

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The useAddTopic hook:

1. Manages the input for a topic description.
2. Handles validation and error reporting for adding topics.
3. Saves new topics to Firestore and navigates back to the previous screen after a successful addition.

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• Manages the topic description input.

1. State Variables:

   • description: Stores the topic description entered by the user.

2. Code Snippet:

   const [description, setDescription] = useState<string>('');

3. Process:

   • The description state variable is updated using the setDescription method as the user types.

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• Ensures the topic description is provided and the user is authenticated before saving.

1. Validation Steps:

   • Checks if the description is non-empty.
   • Ensures the user is logged in by verifying the presence of auth.currentUser.

2. Code Snippet:

   if (!description) {
     Alert.alert('Error', 'Please enter a description');
     return;
   }
   
   const currentUser = auth.currentUser;
   
   if (!currentUser) {
     Alert.alert('Error', 'You must be logged in to add a topic');
     return;
   }

3. Process:

   • Displays an alert for missing descriptions or unauthenticated users.
   • Prevents further execution if validation fails.

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• Saves the new topic to the Firestore topics collection with a unique ID.

1. Functionality:

   • Creates a topic document with fields:
     • description: The entered topic description.
     • ownerId: The UID of the current user.
     • ownerName: The display name of the current user or "Anonymous."
     • createdAt: A server-side timestamp.

2. Code Snippet:

   const newTopic = {
     description,
     ownerId: currentUser.uid,
     ownerName: currentUser.displayName || 'Anonymous',
     createdAt: serverTimestamp(),
   };
   
   try {
     const topicDocRef = doc(db, 'topics', `${currentUser.uid}-${Date.now()}`);
     await setDoc(topicDocRef, newTopic);
     Alert.alert('Success', 'Topic added successfully');
     navigation.goBack();
   } catch (error) {
     console.error('Error saving topic:', error);
     Alert.alert('Error', 'Failed to save topic. Please try again.');
   }

3. Process:

   • Generates a unique document ID using the user's UID and the current timestamp.
   • Saves the topic document using setDoc.

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• Navigates back to the previous screen (e.g., FeedScreen) after a successful topic addition.

1. Functionality:

   • Uses the navigation.goBack() method to return to the previous screen.

2. Code Snippet:

   navigation.goBack();

3. Process:

   • Triggered after a successful Firestore write operation.

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Property/Method	Description
description	Stores the topic description entered by the user.
setDescription	Updates the description state variable.
handleAddTopic	Validates input, saves the topic to Firestore, and navigates back.

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• Input Errors:

  • Displays alerts if the description is missing or the user is not logged in.

• Firestore Errors:

  • Logs errors and displays an alert if saving the topic to Firestore fails.

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• The document ID is generated using the current user's UID and a timestamp to ensure uniqueness.

• If the current user has no display name, the owner name defaults to "Anonymous."

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For more details on Firebase Firestore methods, visit the Firebase Firestore Documentation. For React Navigation, refer to the React Navigation Documentation.