split({
  source: messageReceived,
  match: {
    text: msg => msg.type === 'text',
    audio: msg => msg.type === 'audio',
  },
  cases: createApi(textContent, {
    text: (list, {value}) => [...list, value],
    audio: (list, {duration}) => [...list, `audio ${duration} ms`],
    __: list => [...list, 'unknown message'],
  }),
})