Implement working State Machine

1 files changed, 94 insertions, 0 deletions

diff --git a/src/state.go b/src/state.go
new file mode 100644
index 0000000..9c6ab66
--- /dev/null
+++ b/src/state.go
@@ -0,0 +1,94 @@
+// vim: shiftwidth=4 tabstop=4 noexpandtab
+
+package main
+
+import (
+	"log"
+	"time"
+)
+
+type Machine struct {
+	name string
+	initial string
+	current string
+	states StateMap
+	api chan string
+}
+
+type StateMap map[string]MachineState
+
+type MachineState struct {
+	on TransitionMap
+}
+
+type TransitionMap map[string]MachineTransition
+
+type MachineTransition struct {
+	to string
+}
+
+func (m Machine) GetState() string {
+	if m.current == "" {
+		return m.initial
+	}
+	return m.current
+}
+
+func (m *Machine) processEvent(event string) string {
+	current := m.GetState()
+	next := m.states[current].on[event].to
+	if next != "" {
+		log.Printf("State machine '%s' changes from '%s' to '%s'\n", m.name, current, next)
+		m.current = next
+		m.runHooks(current, next)
+		return next
+	}
+	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)
+	}
+}
+
+func (m *Machine) runHooks(last string, next string) {
+	if next == "single_picture" {
+		// TODO implement launch of python subprocess here
+		go func() {
+			time.Sleep(1 * time.Second)
+			m.SendEvent("single_picture_taken")
+		}()
+	}
+}
+
+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),
+	}
+}
+