package main

import (
	"fmt"
	"strings"
	"errors"
	"flag"
	"os"
)

//go:generate stringer -type=Movement
type Movement int

const (
	Unknown Movement = iota
	Forward
	Backward
	Left
	Right
)

func newMovement(movement string) (Movement) {
	switch strings.ToLower(movement) {
	case "forward":
		return Forward
	case "backward":
		return Backward
	case "left":
		return Left
	case "right":
		return Right
	default:
		return Unknown
	}
}

func main() {
	direction := flag.String("direction", "", "The direction to move.")
	flag.Parse()

	if err := run(*direction); err != nil {
		fmt.Printf("Error: %v.\n", err)
		os.Exit(1)
	}
}

func run(direction string) error {
	if len(direction) == 0 {
		return errors.New("direction is not set")
	}

	move := newMovement(direction)
	if move == Unknown {
		return errors.New("unknown direction")
	}

	fmt.Printf("I moved %s.\n", move)

	return nil
}