overleaf/services/chat/app/js/Features/Messages/MessageFormatter.js

export function formatMessageForClientSide(message) {
  if (message._id) {
    message.id = message._id.toString()
    delete message._id
  }
  const formattedMessage = {
    id: message.id,
    content: message.content,
    timestamp: message.timestamp,
    user_id: message.user_id,
  }
  if (message.edited_at) {
    formattedMessage.edited_at = message.edited_at
  }
  return formattedMessage
}

export function formatMessagesForClientSide(messages) {
  return messages.map(message => formatMessageForClientSide(message))
}

export function groupMessagesByThreads(rooms, messages) {
  let room, thread
  const roomsById = {}
  for (room of rooms) {
    roomsById[room._id.toString()] = room
  }

  const threads = {}
  const getThread = function (room) {
    const threadId = room.thread_id.toString()
    if (threads[threadId]) {
      return threads[threadId]
    } else {
      const thread = { messages: [] }
      if (room.resolved) {
        thread.resolved = true
        thread.resolved_at = room.resolved.ts
        thread.resolved_by_user_id = room.resolved.user_id
      }
      threads[threadId] = thread
      return thread
    }
  }

  for (const message of messages) {
    room = roomsById[message.room_id.toString()]
    if (room) {
      thread = getThread(room)
      thread.messages.push(formatMessageForClientSide(message))
    }
  }

  for (const threadId in threads) {
    thread = threads[threadId]
    thread.messages.sort((a, b) => a.timestamp - b.timestamp)
  }

  return threads
}