package ser

import (
	"errors"
	"os/exec"
)

var ErrUnknownManager = errors.New("unknown service manager")
var ErrNoCandidateInstalled = errors.New("no package-manager candidate installed")

// available service managers
// var available = []string{"systemd", "init"}
var available = []string{"systemd"}

func Load(_manager string) (ServiceManager, error) {

	// 1. fail if unknown manager
	known := false
	for _, mgr := range available {
		if _manager == mgr {
			known = true
			break
		}
	}
	if !known {
		return nil, ErrUnknownManager
	}

	// 2. Create manager accordingly
	var manager ServiceManager
	switch _manager {
	case "systemd":
		manager = new(Systemd)
	default:
		return nil, ErrUnknownManager
	}

	// 2. fail if not installed
	if exec.Command("which", manager.Name()).Run() == nil {
		return nil, ErrNoCandidateInstalled
	}

	return manager, nil

}