feat: westworldwithmessaging. add entitymanager, telegram, messagehandlers, delayedmessages, expand baseentity

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

@@ -0,0 +1,40 @@
+package westworldwithmessaging
+
+import (
+	"sync"
+	"time"
+)
+
+// clockSingleton is our own stand-in for whatever timer/clock utility
+// class the book uses elsewhere (it only shows up here as
+// "Clock->GetCurrentTime()" - the book hasn't shown us that class's
+// actual source, likely a separate timer file). All DispatchMessage
+// and DispatchDelayedMessages actually need is a steadily increasing
+// number of seconds, so this just measures time elapsed since the
+// clock was first used.
+type clockSingleton struct {
+	start time.Time
+}
+
+var (
+	clockInstance *clockSingleton
+	clockOnce     sync.Once
+)
+
+func newClock() *clockSingleton {
+	clockOnce.Do(func() {
+		clockInstance = &clockSingleton{start: time.Now()}
+	})
+	return clockInstance
+}
+
+// Clock is a shorthand for the clock singleton, same "#define"-style
+// convenience pattern as EntityMgr and Dispatch.
+var Clock = newClock()
+
+// GetCurrentTime returns the number of seconds elapsed since the
+// clock started, matching the book's
+// "double CurrentTime = Clock->GetCurrentTime();".
+func (c *clockSingleton) GetCurrentTime() float64 {
+	return time.Since(c.start).Seconds()
+}