package config

import (
	"fmt"
	"strings"
	"unicode"
)

// ValidateName checks that a name follows shorewall naming conventions:
// starts with a letter, composed of letters, digits, and underscores.
func ValidateName(name, kind string) error {
	if len(name) == 0 {
		return fmt.Errorf("%s name is empty", kind)
	}
	if !unicode.IsLetter(rune(name[0])) {
		return fmt.Errorf("%s name %q must start with a letter", kind, name)
	}
	for _, r := range name {
		if !unicode.IsLetter(r) && !unicode.IsDigit(r) && r != '_' {
			return fmt.Errorf("%s name %q contains invalid character %q", kind, name, r)
		}
	}
	return nil
}

// ValidateInterfaceRef checks that an interface reference is valid.
// Strips any @suffix (e.g. "sit1@NONE" -> "sit1"), allows trailing + for wildcards.
func ValidateInterfaceRef(name string) string {
	if idx := strings.IndexByte(name, '@'); idx >= 0 {
		name = name[:idx]
	}
	return name
}

// IsWildcardInterface returns true if the interface name is a wildcard (ends with +).
func IsWildcardInterface(name string) bool {
	return strings.HasSuffix(name, "+")
}

// ValidateDNSName checks shorewall's DNS name rules: fully qualified,
// minimum two periods. Returns an error if the name looks like a DNS name
// but doesn't meet the requirements.
func ValidateDNSName(name string) error {
	if !strings.Contains(name, ".") {
		return nil
	}
	count := strings.Count(name, ".")
	if count < 2 {
		trimmed := strings.TrimSuffix(name, ".")
		if strings.Count(trimmed, ".") < 1 {
			return fmt.Errorf("DNS name %q must be fully qualified with at least two periods", name)
		}
	}
	return nil
}