// 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),
	}
}