@startuml uc-05-train-stat
autonumber
title UC-05 Train Stat (design sequence)
actor Player
participant "GymBoundary\n«/api/characters/{id}/gym»" as boundary <<boundary>>
participant "TrainingService\nsb-core::services::train_stat" as control <<control>>
participant "ResourceRegenerator\napply_regen" as regen <<entity>>
participant "TrainingGrounds\nTRAINING_GROUNDS + training_cost" as entity <<entity>>

== Train ==
Player -> boundary : POST stat name
boundary -> regen : apply_regen(character)
regen --> boundary : character (regenerated)
boundary -> control : train_stat(character, stat)
control -> entity : cost = training_cost (x1.3 per 10 points)
alt not enough energy
  control --> boundary : 422 (DomainError)
else not enough gold
  control --> boundary : 422 (DomainError)
else unknown stat
  control --> boundary : 400 (DomainError)
else ok
  control -> entity : stat +1 (energy -1, gold -cost)
  control -> entity : constitution: recompute max HP (clamp current)
  control --> boundary : {success, message, character}
  boundary --> Player : {success, message, character}
end
@enduml