// Copyright Safing ICS Technologies GmbH. Use of this source code is governed by the AGPL license that can be found in the LICENSE file.

package modules

import (
	"errors"
	"sync"

	"github.com/tevino/abool"
)

var (
	modulesLock  sync.Mutex
	modules      = make(map[string]*Module)
	modulesOrder []*Module

	// ErrCleanExit is returned by Start() when the program is interrupted before starting. This can happen for example, when using the "--help" flag.
	ErrCleanExit = errors.New("clean exit requested")
)

// Module represents a module.
type Module struct {
	Name         string
	Active       *abool.AtomicBool
	inTransition *abool.AtomicBool

	prep  func() error
	start func() error
	stop  func() error

	dependencies []string
}

func dummyAction() error {
	return nil
}

// Register registers a new module.
func Register(name string, prep, start, stop func() error, dependencies ...string) *Module {
	newModule := &Module{
		Name:         name,
		Active:       abool.NewBool(false),
		inTransition: abool.NewBool(false),
		prep:         prep,
		start:        start,
		stop:         stop,
		dependencies: dependencies,
	}

	// replace nil arguments with dummy action
	if newModule.prep == nil {
		newModule.prep = dummyAction
	}
	if newModule.start == nil {
		newModule.start = dummyAction
	}
	if newModule.stop == nil {
		newModule.stop = dummyAction
	}

	modulesLock.Lock()
	defer modulesLock.Unlock()
	modulesOrder = append(modulesOrder, newModule)
	modules[name] = newModule
	return newModule
}