ws-handler5.ts

if (eventType === 'MESSAGE') {
  const message = JSON.parse(event.body);

  // Handshake with Apollo
  if (message.type === 'connection_init') {
    // Write connection to persistence
    const connection = Object.assign(new Connection(), {
      id: connectionId,
      requestContext: event.requestContext,
      payload: event.body.payload
    });
    await mapper.put(connection);

    // Acknowledges connection
    await gateway
      .postToConnection({
        ConnectionId: connectionId,
        Data: JSON.stringify({ type: 'connection_ack', payload: {} })
      })
      .promise();

    return {
      statusCode: 200,
      body: ''
    };
  }

  // Subscription start event
  if (message.type === 'subscribe') {
    const connection = await mapper.get(Object.assign(new Connection(), {
      id: connectionId
    }));

    // Write subscription to persistence
    const sub = Object.assign(new Subscription(), {
      id: `${connectionId}|${message.id}`,
      connectionId,
      topic: 'NEW_MESSAGE',
      requestContext: event.requestContext,
      connectionRef: connection,
      subscription: {
        ...message.payload
      }
    });
    await mapper.put(sub);

    return {
      statusCode: 200,
      body: ''
    };
  }

  // Subscription stop event
  if (message.type === 'complete') {
    // Remove subscription from persistence
    const sub = assign(new Subscription(), {
      id: `${connectionId}|${message.id}`
    });
    await mapper.delete(sub);

    return {
      statusCode: 200,
      body: '',
    };
  }
}