feat: finalize with step 5

chapter-2-state-driven-agent-design/westworldwithmessaging/state_eat_stew.go

@@ -0,0 +1,62 @@
+package westworldwithmessaging
+
+import (
+	"fmt"
+	"sync"
+)
+
+// eatStew is the Go version of the (not yet pasted) singleton class
+// EatStew from the book. Same pattern as every other state:
+// unexported type, one shared instance, reached only through the
+// function below.
+type eatStew struct{}
+
+var (
+	eatStewInstance *eatStew
+	eatStewOnce     sync.Once
+)
+
+// EatStew is the Go stand-in for "EatStew::Instance()".
+func EatStew() *eatStew {
+	eatStewOnce.Do(func() {
+		eatStewInstance = &eatStew{}
+	})
+	return eatStewInstance
+}
+
+var _ State[Miner] = (*eatStew)(nil)
+
+// The book never pasted this state's actual source - it only ever
+// referenced EatStew::Instance() as a switch target. This whole
+// implementation is reverse-engineered from a sample run of the
+// finished program, which shows this exact sequence: Bob enters
+// (one line), eats (one line, then immediately heads back to
+// whatever he was doing - a single-tick state, same shape as
+// QuenchThirst), and leaving prints one more line before he's back
+// in GoHomeAndSleepTilRested.
+
+// Enter announces that dinner smells good.
+func (s *eatStew) Enter(m *Miner) {
+	fmt.Printf("\n%s: Smells reaaal goood, Elsa!", GetNameOfEntity(m.ID()))
+}
+
+// Execute is the entire meal: announce it, then head back to
+// whatever state he was in before dinner interrupted him. The sample
+// output never shows more than one "Tastes real good too!" line, so
+// - like QuenchThirst - this doesn't loop across multiple ticks.
+func (s *eatStew) Execute(m *Miner) {
+	fmt.Printf("\n%s: Tastes real good too!", GetNameOfEntity(m.ID()))
+	m.ChangeState(GoHomeAndSleepTilRested())
+}
+
+// Exit thanks Elsa for the meal on the way out.
+func (s *eatStew) Exit(m *Miner) {
+	fmt.Printf("\n%s: Thank ya li'l lady. Ah better get back to whatever ah wuz doin'", GetNameOfEntity(m.ID()))
+}
+
+// OnMessage is required now that State[T] includes it. The sample
+// output doesn't show Bob reacting to any message while eating, so
+// false ("not handled") is the correct default.
+func (s *eatStew) OnMessage(m *Miner, msg Telegram) bool {
+	return false
+}