index.tsx

try {
  const response = await fetch('/api/chat', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
    },
    body: JSON.stringify({
      question,
      history,
    }),
  });
  const data = await response.json();
  setMessageState((state) => ({
    ...state,
    messages: [
      ...state.messages,
      {
        type: 'apiMessage',
        message: data.text,
        sourceDocs: data.sourceDocuments,
      },
    ],
    history: [...state.history, [question, data.text]],
  }));
}