package handlers

import (
	"errors"
	"regexp"
	"strconv"
)

const (
	// appNameMinLength is the minimum allowed length for an app name.
	appNameMinLength = 2
	// appNameMaxLength is the maximum allowed length for an app name.
	appNameMaxLength = 63
)

// validAppNameRe matches names containing only lowercase alphanumeric characters and
// hyphens, starting and ending with an alphanumeric character.
var validAppNameRe = regexp.MustCompile(`^[a-z0-9][a-z0-9-]*[a-z0-9]$`)

// validateAppName checks that the given app name is safe for use in Docker
// container names, image tags, and file system paths.
var (
	errAppNameLength = errors.New(
		"app name must be between " +
			strconv.Itoa(appNameMinLength) + " and " +
			strconv.Itoa(appNameMaxLength) + " characters",
	)
	errAppNamePattern = errors.New(
		"app name must contain only lowercase letters, numbers, " +
			"and hyphens, and must start and end with a letter or number",
	)
)

func validateAppName(name string) error {
	if len(name) < appNameMinLength || len(name) > appNameMaxLength {
		return errAppNameLength
	}

	if !validAppNameRe.MatchString(name) {
		return errAppNamePattern
	}

	return nil
}