package utils

import (
	"net/netip"

	"github.com/qdm12/gluetun/internal/configuration/settings"
	"github.com/qdm12/gluetun/internal/models"
	"github.com/qdm12/gluetun/internal/wireguard"
)

func BuildWireguardSettings(connection models.Connection,
	userSettings settings.Wireguard, ipv6Supported bool,
) (settings wireguard.Settings) {
	settings.PrivateKey = *userSettings.PrivateKey
	settings.PublicKey = connection.PubKey
	settings.PreSharedKey = *userSettings.PreSharedKey
	settings.InterfaceName = userSettings.Interface
	settings.Implementation = userSettings.Implementation
	settings.AmneziaWG = buildAmneziaWgSettings(userSettings.AmneziaWG)
	if *userSettings.MTU > 0 {
		settings.MTU = *userSettings.MTU
	} else {
		// The default is 1320 which is NOT the wireguard-go default
		// of 1420 because this impacts bandwidth a lot on some
		// VPN providers, see https://github.com/qdm12/gluetun/issues/1650.
		// It has been lowered to 1320 following quite a bit of
		// investigation in the issue: https://github.com/qdm12/gluetun/issues/2533.
		const defaultMTU = 1320
		settings.MTU = defaultMTU
	}
	settings.IPv6 = &ipv6Supported

	const rulePriority = 101 // 100 is to receive external connections
	settings.RulePriority = rulePriority

	settings.Endpoint = netip.AddrPortFrom(connection.IP, connection.Port)

	settings.Addresses = make([]netip.Prefix, 0, len(userSettings.Addresses))
	for _, address := range userSettings.Addresses {
		if !ipv6Supported && address.Addr().Is6() {
			continue
		}
		addressCopy := netip.PrefixFrom(address.Addr(), address.Bits())
		settings.Addresses = append(settings.Addresses, addressCopy)
	}

	settings.AllowedIPs = make([]netip.Prefix, 0, len(userSettings.AllowedIPs))
	for _, allowedIP := range userSettings.AllowedIPs {
		if !ipv6Supported && allowedIP.Addr().Is6() {
			continue
		}
		settings.AllowedIPs = append(settings.AllowedIPs, allowedIP)
	}

	settings.PersistentKeepaliveInterval = *userSettings.PersistentKeepaliveInterval

	return settings
}

func buildAmneziaWgSettings(s settings.AmneziaWg) wireguard.AmneziaSettings {
	return wireguard.AmneziaSettings{
		JunkPacketCount: *s.JunkPacketCount,
		JunkPacketMin:   *s.JunkPacketMin,
		JunkPacketMax:   *s.JunkPacketMax,
		PaddingS1:       *s.PaddingS1,
		PaddingS2:       *s.PaddingS2,
		PaddingS3:       *s.PaddingS3,
		PaddingS4:       *s.PaddingS4,
		HeaderH1:        *s.HeaderH1,
		HeaderH2:        *s.HeaderH2,
		HeaderH3:        *s.HeaderH3,
		HeaderH4:        *s.HeaderH4,
		InitPacketI1:    *s.InitPacketI1,
		InitPacketI2:    *s.InitPacketI2,
		InitPacketI3:    *s.InitPacketI3,
		InitPacketI4:    *s.InitPacketI4,
		InitPacketI5:    *s.InitPacketI5,
	}
}