import {
  isOfficialChannel,
  OFFICIAL_SENDER_USER_ID,
} from '@linktr.ee/messaging-taxonomy'
import type { Channel } from 'stream-chat'

type ChannelMembers = NonNullable<Channel['state']>['members']
type ChannelMember = ChannelMembers[string]

/**
 * Resolves the member to display as the conversation's "other party".
 *
 * For a normal 1:1 channel this is the member that isn't the current user. The
 * official channel is special: its display identity is always the official
 * sender ("Linktree"), regardless of who is viewing. That matters because an
 * unverified sensitive linker reads the official channel as a guest whose
 * random Stream id isn't a member, so the "not me" heuristic would otherwise
 * fall back to the linker's own member and show their name instead of Linktree.
 */
export function resolveConversationParticipant(
  members: ChannelMembers | undefined,
  currentUserId: string | undefined,
  channelType: string | undefined
): ChannelMember | undefined {
  const memberList = Object.values(members || {})

  if (isOfficialChannel(channelType)) {
    const officialSender = memberList.find(
      (member) => member.user?.id === OFFICIAL_SENDER_USER_ID
    )
    if (officialSender) return officialSender
  }

  return memberList.find(
    (member) => member.user?.id && member.user.id !== currentUserId
  )
}