feat: westworldwithwoman. add elsa

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

@@ -0,0 +1,49 @@
+package westworldwithwoman
+
+// Elsa is the miner's wife, introduced in this section of the book.
+// She's built the exact same way Miner is: embed *BaseGameEntity for
+// her ID, own a *StateMachine[Elsa] and delegate all state
+// bookkeeping to it. This is the payoff of making State[T] and
+// StateMachine[T] generic earlier - Elsa reuses both unchanged,
+// just with the blank slot filled in as Elsa instead of Miner.
+type Elsa struct {
+	*BaseGameEntity
+
+	stateMachine *StateMachine[Elsa]
+}
+
+// NewElsa sets up Elsa's state machine: DoHousework is her ordinary,
+// everyday state, and WifesGlobalState is what checks - every single
+// tick, no matter what she's currently doing - whether nature is
+// calling. That's exactly why it has to be a global state rather
+// than logic inside DoHousework: the book says "Elsa may feel the
+// call of nature during any state and at any time," and a global
+// state's Execute runs regardless of the current state.
+func NewElsa(id int) *Elsa {
+	e := &Elsa{
+		BaseGameEntity: NewBaseGameEntity(id),
+	}
+
+	e.stateMachine = NewStateMachine(e)
+	e.stateMachine.SetCurrentState(DoHousework())
+	e.stateMachine.SetGlobalState(WifesGlobalState())
+
+	return e
+}
+
+// FSM returns Elsa's state machine.
+func (e *Elsa) FSM() *StateMachine[Elsa] {
+	return e.stateMachine
+}
+
+// Update satisfies the Entity interface (alongside the ID() method
+// borrowed from BaseGameEntity) and just delegates to the state
+// machine, same shape as Miner.Update.
+func (e *Elsa) Update() {
+	e.stateMachine.Update()
+}
+
+// ChangeState forwards to the state machine, same as Miner.ChangeState.
+func (e *Elsa) ChangeState(newState State[Elsa]) {
+	e.stateMachine.ChangeState(newState)
+}