serge-web/serge-web

import { INFO_MESSAGE_CLIPPED, MAPPING_MESSAGE, MAPPING_MESSAGE_DELTA } from 'src/config'
import { Message, MessageChannel, MessageCustom, MessageInfoTypeClipped } from 'src/custom-types'

/** helper function to produce unique ids for channel messages
 */
const getIDs = (message: MessageChannel): string => {
  let res
  const generalMessage = message as any as Message
  const isNotMapping = !(generalMessage.messageType === MAPPING_MESSAGE || generalMessage.messageType === MAPPING_MESSAGE_DELTA)
  const customMessage = message as any as MessageCustom
  const emptyNonMappingMessage = isNotMapping && customMessage.message === undefined
  if (message.messageType === INFO_MESSAGE_CLIPPED || ('infoType' in message && message.infoType === true) || emptyNonMappingMessage) {
    const clippedMessage = message as MessageInfoTypeClipped
    res = '' + clippedMessage.gameTurn
  } else {
    const msg = message.message
    if (msg && msg.Reference !== undefined) {
      // note: `Reference` is the id generated by Serge for Collab-style messages
      res = msg.Reference
    } else {
      res = message._id
    }
  }
  
  return res
}
const uniqByKeepLast = (data: MessageChannel[], key: (message: MessageChannel) => string) => {
  return [
    ...new Map(
      data.map(x => [key(x), x])
    ).values()
  ]
}

/** helper function to reduce the list of messages by removing duplicate
 * turn markers & older versions of messages with reference numbers
 */
const mostRecentOnly = (messages: MessageChannel[]): MessageChannel[] => {
  return uniqByKeepLast(messages, getIDs)
}
export default mostRecentOnly