action-cable-unread-messages-selector.js

// src/features/messages/messagesSlice.js

... // omitted other imports
import { selectTeamById } from '../teams/teamsSlice'
import { isAfter, parseISO, subYears } from 'date-fns'

export const selectUnreadMessages = createSelector(
  [selectMessagesByTeam, selectTeamById],
  (messages, team) => {
    const lastReadAt = parseISO(team.lastReadAt) || subYears(Date.now(), 1)
    return messages.filter((message) =>
      isAfter(parseISO(message.created_at), lastReadAt)
    )
  }
)