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path: root/cmd/dolmetschctld/statemachine.go
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//
//  dolmetschctl
//
//
//  Copyright (C) 2019 Christian Pointner <equinox@spreadspace.org>
//
//  This file is part of dolmetschctl.
//
//  dolmetschctl is free software: you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  any later version.
//
//  dolmetschctl is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with dolmetschctl. If not, see <http://www.gnu.org/licenses/>.
//

package main

import (
	"errors"
	"log"

	"spreadspace.org/dolmetschctl/pkg/mixer"
)

type State int

const (
	StateNew = iota
	StateSettling
	StateSettled
)

func (s State) String() string {
	switch s {
	case StateNew:
		return "new"
	case StateSettling:
		return "settling"
	case StateSettled:
		return "settled"
	default:
		return "unknown"
	}
}

type Language string

type LanguageChannels struct {
	main  mixer.Channel
	voice mixer.Channel
}

type selectLangRequest struct {
	l        Language
	resultCh chan error
}

type StateMachine struct {
	mixer        *mixer.Mixer
	selectLangCh chan selectLangRequest
	quitCh       chan bool
	exitedCh     chan struct{}

	languages map[Language]LanguageChannels

	currentState State
	currentLang  Language
	targetLang   Language
}

func NewStateMachine(m *mixer.Mixer) (*StateMachine, error) {
	sm := &StateMachine{mixer: m}
	sm.selectLangCh = make(chan selectLangRequest, 10)
	sm.quitCh = make(chan bool, 1)
	sm.exitedCh = make(chan struct{})

	sm.languages = make(map[Language]LanguageChannels)
	sm.languages["en"] = LanguageChannels{0x20, 0x24}
	sm.languages["de"] = LanguageChannels{0x22, 0x25}

	sm.currentState = StateNew
	sm.currentLang = ""
	sm.targetLang = ""

	return sm, nil
}

func (sm *StateMachine) selectLang(l Language) error {
	if l != "" {
		if _, exists := sm.languages[l]; !exists {
			return errors.New("language '" + string(l) + "' does not exist")
		}
	}
	sm.targetLang = l
	log.Printf("new target language: '%s'", sm.targetLang)
	return nil
}

func (sm *StateMachine) reconcile() {
	if sm.targetLang == sm.currentLang {
		sm.currentState = StateSettled
		return
	}
	sm.currentState = StateSettling
}

func (sm *StateMachine) run() {
	defer close(sm.exitedCh)

	for {
		select {
		case req := <-sm.selectLangCh:
			req.resultCh <- sm.selectLang(req.l)
		case <-sm.quitCh:
			return
		}

		oldState := sm.currentState
		sm.reconcile()
		if oldState != sm.currentState {
			log.Printf("new state: %s", sm.currentState)
		}
	}
}

func (sm *StateMachine) Start() {
	go sm.run()
}

func (sm *StateMachine) SelectLanguage(l Language) error {
	resultCh := make(chan error)
	sm.selectLangCh <- selectLangRequest{l, resultCh}
	return <-resultCh
}

func (sm *StateMachine) Shutdown() {
	select {
	case sm.quitCh <- true:
	default:
	}
	<-sm.exitedCh
}