var request = {
  correlationId: '888',
  commands: [{
    command: 'makeComment',
    contextId: '123',
    text: 'foible',
    commentId: '456'
  }]
}

function makeCommentHandler(events, command) {
  if (events.filter( e => e.commentId === command.commentId) > 0) {
     throw new Error('hey you already assigned this id to a comment (rare)')
  }

  events.push({
      event: 'commentMade',
      text: command.text,
      commentId: command.commentId,
      contextId: command.contextId
  })
  return events
}

function samReadModelUpdater(event) {
   if (event.event === 'commentMade') {
     var context = getContext(event.contextId)
     context.comments[event.commentId] = { text: event.text, commentId: event.commentId, timestamp: 'iso' }
     save(context)
   }
}