package util

import "strings"

// IsIPv4 checks if a string is a valid IPv4 address.
func IsIPv4(value string) bool {
	parts := strings.Split(value, ".")
	if len(parts) != 4 {
		return false
	}
	for _, part := range parts {
		if len(part) == 0 || len(part) > 3 {
			return false
		}
		for _, c := range part {
			if c < '0' || c > '9' {
				return false
			}
		}
		var n int
		for _, c := range part {
			n = n*10 + int(c-'0')
		}
		if n > 255 {
			return false
		}
	}
	return true
}

// IsIPv6 checks if a string is a valid IPv6 address (simplified).
func IsIPv6(value string) bool {
	if !strings.Contains(value, ":") {
		return false
	}
	for _, c := range value {
		if !((c >= '0' && c <= '9') || (c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F') || c == ':') {
			return false
		}
	}
	return true
}

// IsIPAddress checks if a string is any IP address.
func IsIPAddress(value string) bool {
	return IsIPv4(value) || IsIPv6(value)
}

// ShouldResolveServer returns true if the server value is a hostname that should be DNS-resolved.
func ShouldResolveServer(server string) bool {
	s := strings.TrimSpace(server)
	if s == "" || IsIPAddress(s) {
		return false
	}
	for _, c := range s {
		if !((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9') || c == '.' || c == '-') {
			return false
		}
	}
	return strings.Contains(s, ".")
}