Refactoring: Camera has Statemachine and not is Statemachine

4 files changed, 67 insertions, 48 deletions

diff --git a/src/camera.go b/src/camera.go
new file mode 100644
index 0000000..12a9d54
--- /dev/null
+++ b/src/camera.go
@@ -0,0 +1,38 @@
+// vim: shiftwidth=4 tabstop=4 noexpandtab
+
+package main
+
+type Camera struct {
+	statemachine Machine
+}
+
+func NewCamera() Camera {
+	return Camera{
+		statemachine: Machine{
+			name: "camera",
+			initial: "idle",
+			states: StateMap{
+				"idle": MachineState{
+					on: TransitionMap{
+						"take_single_picture": MachineTransition{
+							to: "single_picture",
+						},
+					},
+				},
+				"single_picture": MachineState{
+					on: TransitionMap{
+						"single_picture_taken": MachineTransition{
+							to: "idle",
+						},
+					},
+				},
+			},
+			api: make(chan string),
+			state_listeners: make([]*(chan string), 0),
+		},
+	}
+}
+
+func (cam *Camera) run() {
+	cam.statemachine.Run()
+}
diff --git a/src/main.go b/src/main.go
index af82e8f..768920a 100644
--- a/src/main.go
+++ b/src/main.go
@@ -11,7 +11,7 @@ import (
 )
 
 var (
-	camera Machine
+	camera Camera
 )
 
 type config struct {
@@ -31,7 +31,7 @@ func main() {
 	cfg := readConfig(configPath)
 
 	// setup camera state machine
-	camera = newCamStateMachine()
+	camera = NewCamera()
 
 	// start goroutines
 	server := NewWebServer(&cfg.WebConfig)
diff --git a/src/state.go b/src/state.go
index 9a08738..5970ba8 100644
--- a/src/state.go
+++ b/src/state.go
@@ -7,6 +7,7 @@ import (
 	"time"
 )
 
+// This struct represents the statemachine.
 type Machine struct {
 	name string
 	initial string
@@ -28,6 +29,16 @@ type MachineTransition struct {
 	to string
 }
 
+// This will run the statemachine (blocking).
+func (m *Machine) Run() {
+	var event string
+	for {
+		event = <-m.api  // read api (blocking)
+		m.processEvent(event)
+	}
+}
+
+// A simple Getter to retrieve the current state.
 func (m Machine) GetState() string {
 	if m.current == "" {
 		return m.initial
@@ -35,10 +46,14 @@ func (m Machine) GetState() string {
 	return m.current
 }
 
+// This function blocks until the current state differs
+// from the 'known' state. It then returns the current
+// state.
 func (m *Machine) GetStateOnChange(known string) string {
 	listener := make(chan string)
 	var current string
-	m.RegisterListener(&listener)
+	m.registerListener(&listener)
+	defer m.deregisterListener(&listener)
 	for {
 		if m.GetState() != known {
 			current = m.GetState()
@@ -49,15 +64,19 @@ func (m *Machine) GetStateOnChange(known string) string {
 			break
 		}
 	}
-	m.DeregisterListener(&listener)
 	return current
 }
 
-func (m *Machine) RegisterListener(listener *(chan string)) {
+// Use this function to send an event to the statemachine.
+func (m *Machine) SendEvent(event string) {
+	m.api <- event  // blocks until m.run() goroutine handles this event
+}
+
+func (m *Machine) registerListener(listener *(chan string)) {
 	m.state_listeners = append(m.state_listeners, listener)
 }
 
-func (m *Machine) DeregisterListener(listener *(chan string)) {
+func (m *Machine) deregisterListener(listener *(chan string)) {
 	wasRemoved := false
 	if len(m.state_listeners) == 0 {
 		log.Println("Not able to unregister listener from empty state_listener slice")
@@ -90,25 +109,13 @@ func (m *Machine) processEvent(event string) string {
 	return current
 }
 
-func (m *Machine) SendEvent(event string) {
-	m.api <- event  // blocks until m.run() goroutine handles this event
-}
-
-func (m *Machine) run() {
-	var event string
-	for {
-		event = <-m.api  // read api (blocking)
-		m.processEvent(event)
-	}
-}
-
+// In this function one can implement callback functions
+// which will be triggered on certain transitions.
 func (m *Machine) runHooks(last string, next string) {
 
-	log.Println("Send state to listeners ...")
 	for _,listener := range(m.state_listeners) {
 		*listener <- next
 	}
-	log.Println("State sent to listeners")
 
 	if last == "idle" && next == "single_picture" {
 		// TODO implement launch of python subprocess here
@@ -118,29 +125,3 @@ func (m *Machine) runHooks(last string, next string) {
 		}()
 	}
 }
-
-func newCamStateMachine() Machine {
-	return Machine{
-		name: "camera",
-		initial: "idle",
-		states: StateMap{
-			"idle": MachineState{
-				on: TransitionMap{
-					"take_single_picture": MachineTransition{
-						to: "single_picture",
-					},
-				},
-			},
-			"single_picture": MachineState{
-				on: TransitionMap{
-					"single_picture_taken": MachineTransition{
-						to: "idle",
-					},
-				},
-			},
-		},
-		api: make(chan string),
-		state_listeners: make([]*(chan string), 0),
-	}
-}
-
diff --git a/src/web.go b/src/web.go
index 206681d..53f8c0a 100644
--- a/src/web.go
+++ b/src/web.go
@@ -58,11 +58,11 @@ func jsHandler(w http.ResponseWriter, r *http.Request) {
 
 func stateHandler(w http.ResponseWriter, r *http.Request) {
 	known_state := r.FormValue("known_state")
-	w.Write([]byte(fmt.Sprintf("%s", camera.GetStateOnChange(known_state))))
+	w.Write([]byte(fmt.Sprintf("%s", camera.statemachine.GetStateOnChange(known_state))))
 }
 
 func singlePictureHandler(w http.ResponseWriter, r *http.Request) {
-	camera.SendEvent("take_single_picture")
+	camera.statemachine.SendEvent("take_single_picture")
 	fmt.Fprintf(w, http.StatusText(http.StatusOK))
 }