data class Match(
    @PrimaryKey var uid: Long? = null,
    @ColumnInfo var homeTeamId: Long? = null,
    @ColumnInfo var awayTeamId: Long? = null,
    @Ignore var homeTeam: Team? = null,
    @Ignore var awayTeam: Team? = null
)

data class Team(
    @PrimaryKey var uid: Long? = null,
    @ColumnInfo var captainId: Long? = null,
    @Ignore var captain: Player? = null
)

data class Player(
    @PrimaryKey var uid: Long? = null,
    @ColumnInfo var name: String? = null,
    var number: Int? = null
)

// inside fragment
matchDao.getLive(matchId).observe(this, Observer {})

fun getMatchLive(id: Long): LiveData<Match> {
    return Transformations.switchMap(matchDao.getLive(id)) { inputMatch ->
        val output1: LiveData<Match>? = inputMatch.homeTeamId?.run {
            Transformations.switchMap(teamDao.getLive(this)) { team ->
                team.captainId?.run {
                    Transformations.map(playerDao.getLive(this)) { player ->
                        team.apply {
                            captain = player
                            inputMatch.homeTeam = team
                        }
                        inputMatch
                    }
                }
            }
        }

        output1?.run {
            Transformations.switchMap(this) { inputMatch1 ->
                inputMatch1.awayTeamId?.run {
                    Transformations.switchMap(teamDao.getLive(this)) { team ->
                        team.captainId?.run {
                            Transformations.map(playerDao.getLive(this)) { player ->
                                team.apply {
                                    captain = player
                                    inputMatch1.awayTeam = team
                                }
                                inputMatch1
                            }
                        }
                    }
                }
            }
        }
    }
}