// Package cli provides utilities for writing command line utilities that
// interact with services.
package cli

import "os"
import "fmt"
import "flag"
import "os/user"
import "strings"
import "strconv"
import "path/filepath"

// Sayf is like Printf, but prints the program name before the message. This is
// used for printing messages and errors.
func Sayf (format string, values ...any) {
	Printf(os.Args[0] + ": " + format, values...)
}

// Printf prints to stderr.
func Printf (format string, values ...any) {
	fmt.Fprintf(flag.CommandLine.Output(), format, values...)
}

// ServiceUser returns the system user that corresponds to the given service
// name. This is not necissarily equivalent Hnakra user, although it is good
// practice to have a 1:1 correspondance between them.
func ServiceUser (service string) string {
	return "hn-" + strings.ToLower(service)
}

// DataDir returns the standard Hnakra data directory.
func DataDir () string {
	return "/var/hnakra"
}

// ServiceDir returns the standard data directory of a service.
func ServiceDir (service string) string {
	return filepath.Join(DataDir(), "services", ServiceUser(service))
}

// NeedRoot halts the program and displays an error if it is not being run as
// root. This should be called whenever an operation takes place that requires
// root privelages.
func NeedRoot() {
	uid := os.Getuid()
	if uid != 0 {
		Sayf("this utility must be run as root")
		os.Exit(1)
	}
}

// MkdirFor makes a directory makes the specified directory (if it doesnt
// already exist) and gives ownership of it to the specified uid and gid.
func MkdirFor (directory string, uid, gid int) error {
	err := os.MkdirAll(directory, 0755)
	if err != nil { return err }
	err = os.Chmod(directory, 0770)
	if err != nil { return err }
	err = os.Chown(directory, uid, gid)
	if err != nil { return err }

	return nil
}

// LookupUID returns the uid and gid of the given username, if it exists.
func LookupUID (name string) (uid, gid uint32, err error) {
	user, err := user.Lookup(name)
	if err != nil {
		return 0, 0, err
	}

	puid, err := strconv.Atoi(user.Uid)
	if err != nil {
		return 0, 0, err
	}
	pgid, err := strconv.Atoi(user.Gid)
	if err != nil {
		return 0, 0, err
	}
	return uint32(puid), uint32(pgid), nil
}