// Package env contains functions for dealing with environment variables
package env

import (
	"os"
	"os/user"

	homedir "github.com/mitchellh/go-homedir"
)

// ShellExpandHelp describes what ShellExpand does for inclusion into help
const ShellExpandHelp = "\n\nLeading `~` will be expanded in the file name as will environment variables such as `${RCLONE_CONFIG_DIR}`.\n"

// ShellExpand replaces a leading "~" with the home directory" and
// expands all environment variables afterwards.
func ShellExpand(s string) string {
	if s != "" {
		if s[0] == '~' {
			newS, err := homedir.Expand(s)
			if err == nil {
				s = newS
			}
		}
		s = os.ExpandEnv(s)
	}
	return s
}

// CurrentUser finds the current user name or "" if not found
func CurrentUser() (userName string) {
	userName = os.Getenv("USER")
	// If we are making docs just use $USER
	if userName == "$USER" {
		return userName
	}
	// Try reading using the OS
	usr, err := user.Current()
	if err == nil {
		return usr.Username
	}
	// Fall back to reading $USER then $LOGNAME
	if userName != "" {
		return userName
	}
	return os.Getenv("LOGNAME")
}