package westworldwithwoman

import (
	"math/rand"
	"sync"
)

// wifesGlobalState is Elsa's global state - its Execute runs on
// every single tick of her state machine, in addition to whatever
// her current state is doing (see StateMachine.Update). That's what
// makes it the right place for "does nature call right now" logic:
// the book says that can happen "during any state and at any time,"
// which is exactly what a global state is for.
type wifesGlobalState struct{}

var (
	wifesGlobalStateInstance *wifesGlobalState
	wifesGlobalStateOnce     sync.Once
)

// WifesGlobalState is the Go stand-in for
// "WifesGlobalState::Instance()".
func WifesGlobalState() *wifesGlobalState {
	wifesGlobalStateOnce.Do(func() {
		wifesGlobalStateInstance = &wifesGlobalState{}
	})
	return wifesGlobalStateInstance
}

var _ State[Elsa] = (*wifesGlobalState)(nil)

// Enter and Exit do nothing - a global state is set once, in
// NewElsa, and never changed, so these never actually get called.
// They only exist to satisfy the State[Elsa] interface.
func (s *wifesGlobalState) Enter(e *Elsa) {}
func (s *wifesGlobalState) Exit(e *Elsa)  {}

// bathroomCallChance is a 1-in-N chance, per the chapter's "1 in 10
// chance to change to VisitBathroom state."
const bathroomCallChance = 10

// Execute rolls the dice every tick. If it comes up, and Elsa isn't
// already in the bathroom (checked with IsInState, so this can't
// interrupt a bathroom trip that's already happening), she breaks
// off into VisitBathroom.
func (s *wifesGlobalState) Execute(e *Elsa) {
	if !e.FSM().IsInState(VisitBathroom()) && rand.Intn(bathroomCallChance) == 0 {
		e.ChangeState(VisitBathroom())
	}
}