@startuml team-join-sequence
title CR-Core — Player joins a public team (sequence diagram)

actor Player
participant "BaseCommand\n(TeamCommand)" as Base
participant "SubCommand\n(TeamJoinSub)" as Sub
participant "TeamService" as Service
participant "TeamRepository" as Repo
participant "Team" as Team

Player -> Base : /team join <name>
activate Base

Base -> Base : route args[0]="join" → TeamJoinSub
Base -> Sub : execute(ctx)
activate Sub

Sub -> Service : getTeamByName(name)
activate Service
Service -> Repo : findByName(name)
activate Repo
Repo --> Service : Optional<Team>
deactivate Repo
Service --> Sub : Optional<Team>
deactivate Service

alt team not found
  Sub --> Base : CommandResult.failure("Team not found")
else team found
  Sub -> Service : joinTeam(team.id, playerId)
  activate Service

  Service -> Service : validateJoinable(team, playerId)
  alt team is PRIVATE
    Service --> Sub : throw TeamAccessException
    Sub --> Base : CommandResult.failure(ex.message)
  else player already in a team
    Service --> Sub : throw TeamAccessException
    Sub --> Base : CommandResult.failure(ex.message)
  else allowed
    Service -> Team : addMember(playerId)
    activate Team
    Team --> Service : member
    deactivate Team
    Service -> Repo : save(team)
    activate Repo
    Repo --> Service : team
    deactivate Repo
    Service -> Service : onMemberAdded(team, member)
    Service -> Service : onPlayerJoined(team, member)
    Service --> Sub : true
    Sub --> Base : CommandResult.success("Joined " + team.name)
  end
  deactivate Service
end

deactivate Sub
Base -> Base : handleResult → sender.sendMessage
Base --> Player : reply
deactivate Base

@enduml