package nebula

import (
	"errors"
	"regexp"
)

var hostNameRegexp = regexp.MustCompile(`^[a-z][a-z0-9\-]*$`)

// HostName is the name of a host in a network. HostNames may only have
// lowercase letters, numbers, and hyphens, and must start with a letter.
type HostName string

// UnmarshalText parses and validates a HostName from a text string.
func (h *HostName) UnmarshalText(b []byte) error {
	if !hostNameRegexp.Match(b) {
		return errors.New("a host's name must start with a letter and only contain letters, numbers, and dashes")
	}

	*h = HostName(b)
	return nil
}