feat: westworldwithwoman. add elsa

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

@@ -0,0 +1,48 @@
+package westworldwithwoman
+
+import (
+	"fmt"
+	"math/rand"
+	"sync"
+)
+
+// doHousework is Elsa's everyday default state - the singleton
+// pattern is the same one used throughout this package.
+type doHousework struct{}
+
+var (
+	doHouseworkInstance *doHousework
+	doHouseworkOnce     sync.Once
+)
+
+// DoHousework is the Go stand-in for "DoHousework::Instance()".
+func DoHousework() *doHousework {
+	doHouseworkOnce.Do(func() {
+		doHouseworkInstance = &doHousework{}
+	})
+	return doHouseworkInstance
+}
+
+var _ State[Elsa] = (*doHousework)(nil)
+
+// chores is our own small stand-in for the book's actual chore list
+// - it only ever showed two examples in its sample output ("Moppin'
+// the floor", "Makin' the bed"), so that's exactly what's reused
+// here. One gets picked at random each tick.
+var chores = []string{
+	"Moppin' the floor",
+	"Makin' the bed",
+}
+
+// Enter does nothing - the book's sample output never shows a
+// message when Elsa starts doing housework, only while she's doing
+// it (Execute) and when she leaves the bathroom back into it.
+func (s *doHousework) Enter(e *Elsa) {}
+
+// Execute announces one randomly chosen chore per tick.
+func (s *doHousework) Execute(e *Elsa) {
+	fmt.Printf("\n%s: %s", GetNameOfEntity(e.ID()), chores[rand.Intn(len(chores))])
+}
+
+// Exit does nothing, for the same reason as Enter.
+func (s *doHousework) Exit(e *Elsa) {}