main.ts

/**
 * Retrieves or creates a Firestore document for the user and manages their session ID.
 * @param from - The 'From' phone number from the Twilio request (e.g., 'whatsapp:+1234567890').
 * @returns An object containing the session ID, whether a session existed, and the customer data.
 */
async function getUserSessionInfo(from: string) {
  // Get the Firestore database instance using the Firebase Admin SDK app.
  const db = getFirestore(getFirebaseAdminApp());

  // Fetch the customer document.
  const customerRef = db.collection('customers').doc(from);
  const customerDoc = await customerRef.get();
  const existingCustomer =  customerDoc.data();

  // Check if a session ID already exists in the customer data.
  const existingSessionIdExists =  !!existingCustomer?.sessionId;

  // Generate a new UUID for a potential new session.
  const newSessionId = crypto.randomUUID();

  // Prepare the updated customer data.
  const updatedCustomer = {
    sessionId: existingCustomer?.sessionId ?? newSessionId,
    phoneNumber: existingCustomer?.phoneNumber ?? from.replace('whatsapp:', ""),
    name: existingCustomer?.name ??'',
  }

  // Update the updated customer data back into the Firestore document.
  await customerRef.set(updatedCustomer, {merge: true});

  return {
    sessionId: updatedCustomer.sessionId,
    exist: existingSessionIdExists,
    customer: updatedCustomer,
  }

}
/**
 * Gets or creates a Genkit session for the given user.
 * @param from - The user's identifier (Twilio 'From' number).
 * @returns An object containing the Genkit session and a function to clear the session.
 */
async function getSession(from: string) {
  // Get business information, which might be needed by some of the tools.
  const businessInfo = await getBusinessInfo();

  // Get user session information, including their existing session ID if any,
  // and customer details.
  const { sessionId, exist, customer } = await getUserSessionInfo(from);

  // Initialize a session store (e.g., using Firebase Realtime Database).
  const sessionStore = new RtdbSessionStore();
  let session;

  // Check if a session with the retrieved sessionId already exists.
  if (exist) {
    // If it exists, load the existing session from the store.
    session = await ai.loadSession(sessionId, {
      store: sessionStore,
    });
  }
  else {
    console.log('session not found, creating new');

    // Create a new session with the generated sessionId and store.
    // Provide initial state 
    session = ai.createSession<AgentSessionState>({
      sessionId: sessionId,
      store: sessionStore,
      initialState: {
        userId: from,
        phoneNumber: customer.phoneNumber,
        name: customer.name,
        businessInfo,
      }
    })
  }
  return {
    session,
    // Provide a utility function to clear the session from the store.
    clearSession: () =>
      sessionStore.delete(sessionId)
  };
}

/**
 * Begin chatting with session
 */
async function onMessaageReceived(from, message){
  const { session, clearSession } = await getSession(from);
  // Load or create a session for the user.
  const chat = session.chat(routingAgent);
  const response = await chat.send(userMessage);
}