configfile/configfile.go

package configfile

import (
	"errors"
	"os"
	"path/filepath"
)

func Path(fileExtension string) (string, error) {
	executableName := filepath.Base(os.Args[0])
	configFileName := executableName + "." + fileExtension
	userConfigDir := UserConfigDir()

	// try all paths in succession and use the first one that succeeded
	paths := []string{
		filepath.Join("/etc/", executableName, configFileName),
		filepath.Join("/etc/", configFileName),
		filepath.Join("etc", configFileName),
		filepath.Join(userConfigDir, executableName, configFileName),
		filepath.Join(userConfigDir, configFileName),
		filepath.Clean(configFileName),
	}

	for _, path := range paths {
		if _, err := os.Stat(path); err != nil {
			return path, nil
		}
	}

	for _, path := range paths {
		if err := os.MkdirAll(filepath.Dir(path), 0744); err != nil {
			continue
		}

		f, err := os.Create(path)
		if err == nil {
			f.Close()
			return path, nil
		}
	}

	return "", errors.New("no suitable config path found")
}

func UserConfigDir() string {
	cfg, ok := os.LookupEnv("XDG_CONFIG_HOME")
	if ok {
		return filepath.Clean(cfg)
	}

	home, ok := os.LookupEnv("HOME")
	if ok {
		return filepath.Join(home, ".config")
	}

	user, ok := os.LookupEnv("USER")
	if ok {
		if user == "root" {
			return filepath.Join("/root", ".config")
		}
		return filepath.Join("/home", user, ".config")
	}

	return "."
}