FCM Notifications API Reference

// React Native FCM message handler
import messaging from '@react-native-firebase/messaging';

messaging().setBackgroundMessageHandler(async (remoteMessage) => {
  const { data } = remoteMessage;
  
  // Extract the payload from the stringified default structure
  // FCM sends the nested structure as a JSON string in the 'default' key
  let payload;
  
  if (data.default) {
    try {
      // Parse the stringified JSON to get the nested structure
      const parsedDefault = JSON.parse(data.default);
      payload = parsedDefault.data;
    } catch (error) {
      console.error('Failed to parse FCM default payload:', error);
      return;
    }
  } else {
    // Fallback for legacy flat structure
    payload = data;
  }
  
  // Validate required fields
  if (!payload.message_id || !payload.event_type || !payload.place_id) {
    console.error('Invalid FCM payload:', payload);
    return;
  }
  
  // Process based on event type
  switch (payload.event_type) {
    case 'event_order_created':
      await processOrderCreated(payload);
      break;
    case 'event_order_status_changed':
      await processStatusChange(payload);
      break;
    case 'event_timeslot_started':
      await processTimeslotStarted(payload);
      break;
    case 'event_unpicked_orders_reminder':
      await processUnpickedReminder(payload);
      break;
    default:
      console.warn('Unknown event type:', payload.event_type);
  }
});

function validateFCMPayload(data) {
  // Extract the payload from the stringified default structure
  let payload;
  
  if (data.default) {
    try {
      // Parse the stringified JSON to get the nested structure
      const parsedDefault = JSON.parse(data.default);
      payload = parsedDefault.data;
    } catch (error) {
      throw new Error('Failed to parse FCM default payload: ' + error.message);
    }
  } else {
    // Fallback for legacy flat structure
    payload = data;
  }
  
  const requiredFields = [
    'message_id', 'order_id', 'parent_order_id', 
    'event_type', 'delivery_date', 'start_time', 
    'end_time', 'place_id'
  ];
  
  const missingFields = requiredFields.filter(field => !payload[field]);
  
  if (missingFields.length > 0) {
    throw new Error(`Missing required fields: ${missingFields.join(', ')}`);
  }
  
  // Validate date format
  if (!/^\d{4}-\d{2}-\d{2}$/.test(payload.delivery_date)) {
    throw new Error('Invalid delivery_date format, expected YYYY-MM-DD');
  }
  
  // Validate time format
  if (!/^\d{2}:\d{2}$/.test(payload.start_time) || !/^\d{2}:\d{2}$/.test(payload.end_time)) {
    throw new Error('Invalid time format, expected HH:MM');
  }
  
  return true;
}

async function processStatusChange(data) {
  // Validate status change specific fields
  if (!data.previous_status || !data.new_status) {
    console.error('Missing status change fields:', data);
    return;
  }
  
  // Update local order state
  await updateOrderStatus(data.order_id, data.new_status);
  
  // Show notification to user
  const notification = {
    title: 'Order Status Updated',
    body: `Order #${data.order_number} is now ${data.new_status}`,
    data: {
      orderId: data.order_id,
      previousStatus: data.previous_status,
      newStatus: data.new_status
    }
  };
  
  await showNotification(notification);
}

// Generate test payload for order creation (actual FCM format)
function generateTestOrderCreatedPayload() {
  const data = {
    message_id: `msg-${Date.now()}-${Math.random().toString(36).substr(2, 9)}`,
    order_id: '742ba33c-0c02-43e7-80b0-eb795c14dc6f',
    parent_order_id: '742ba33c-0c02-43e7-80b0-eb795c14dc6f',
    event_type: 'event_order_created',
    delivery_date: '2025-07-07',
    start_time: '14:00',
    end_time: '16:00',
    place_id: '1ee68c4e-7008-4227-a92d-e1b13ac64f30'
  };

  // Return actual FCM format with stringified nested structure
  return {
    default: JSON.stringify({ data })
  };
}

// Helper function to parse received FCM payload
function parseReceivedFCMPayload(fcmData) {
  if (fcmData.default) {
    try {
      const parsedDefault = JSON.parse(fcmData.default);
      return parsedDefault.data;
    } catch (error) {
      console.error('Failed to parse FCM payload:', error);
      return null;
    }
  }
  // Fallback for legacy format
  return fcmData;
}

// Log FCM payload for debugging
function logFCMPayload(data) {
  console.log('FCM Notification Received:', {
    messageId: data.message_id,
    eventType: data.event_type,
    orderId: data.order_id,
    placeId: data.place_id,
    deliveryInfo: `${data.delivery_date} ${data.start_time}-${data.end_time}`,
    additionalFields: Object.keys(data).filter(key => 
      !['message_id', 'event_type', 'order_id', 'place_id', 
        'delivery_date', 'start_time', 'end_time'].includes(key)
    ).reduce((obj, key) => {
      obj[key] = data[key];
      return obj;
    }, {})
  });
}