1. Firebase Setup:

• Create a Firebase Project: Start by creating a new project in the Firebase console.
• Register your app: Download the google-services.json (Android) or GoogleService-Info.plist (iOS) file and place it in the correct directory within your Flutter project.
• Add Firebase dependencies: Include the firebase_messaging package in your pubspec.yaml file.
• Initialize Firebase: Initialize Firebase within your Flutter app’s main function. 

2. Flutter App Integration:

• Request notification permissions: Obtain user permission to receive notifications. 
• Retrieve the FCM token: Get the device’s FCM registration token. You’ll need this token to send notifications to specific devices. 
• Handle incoming messages: Implement logic to handle both foreground and background notifications. 

3. WordPress Plugin Setup:

• Install a FCM plugin:

  Install a WordPress plugin designed for sending FCM notifications (e.g., wp_notify or similar). 
• Configure the plugin:

  Configure the plugin with your Firebase credentials (API key, database URL, etc.). 
• Connect Flutter app to the plugin:

  The plugin will likely provide an endpoint (e.g., /wp-json/fcm/pn/subscribe) to which your Flutter app can send a POST request to register the device’s FCM token. 
• Trigger notifications on post publish:

  The plugin should automatically detect new posts and send a notification to all registered devices using FCM. 

4. Sending Notifications (from WordPress):

• Triggered by new posts: When a new post is published, the WordPress plugin will send a notification to Firebase. 
• Firebase sends to devices: Firebase then sends the notification to all registered devices that match the targeting criteria. 
• Notification displayed: The Flutter app will receive the notification and display it to the user. 

Key Considerations:

• Security:

  Secure your Firebase API keys and ensure proper authentication for your WordPress plugin. 
• Error Handling:

  Implement robust error handling in both the Flutter app and WordPress plugin to manage potential issues during the notification process. 
• Customization:

  Customize the notification content, including title, body, and potentially other data, based on the post content or user preferences. 
• Testing:

  Thoroughly test the notification functionality in both foreground and background scenarios. 
• User Experience:

  Provide a seamless experience for users to subscribe and unsubscribe from notifications.