/* SPDX-License-Identifier: GPL-2.0
 *
 * Copyright (C) 2021 Jason A. Donenfeld. All Rights Reserved.
 */

package main

import (
	"encoding/hex"
	"fmt"
	"log"
	"net"

	"golang.zx2c4.com/wireguard/conn"
	"golang.zx2c4.com/wireguard/device"
	"golang.zx2c4.com/wireguard/tun/netstack"
)

func makeNet(conf *vpnConf, endpoint vpnEndpoint) (*device.Device, *netstack.Net, error) {
	var localAddresses, dnsServers []net.IP
	for _, ip := range conf.ips {
		localAddresses = append(localAddresses, ip.IPAddr().IP)
	}
	for _, ip := range conf.dnses {
		dnsServers = append(dnsServers, ip.IPAddr().IP)
	}
	tun, stack, err := netstack.CreateNetTUN(localAddresses, dnsServers, 1420)
	if err != nil {
		return nil, nil, err
	}
	logf := func(format string, args ...interface{}) {
		log.Printf("[NET %s] "+format, append([]interface{}{endpoint.name}, args...)...)
	}
	dev := device.NewDevice(tun, conn.NewStdNetBind(), &device.Logger{logf, logf})
	err = dev.IpcSet(fmt.Sprintf("private_key=%s\npublic_key=%s\nendpoint=%s\nallowed_ip=0.0.0.0/0\nallowed_ip=::/0\n",
		hex.EncodeToString(conf.privateKey), hex.EncodeToString(endpoint.publicKey), endpoint.endpoint.String()))
	if err != nil {
		return nil, nil, err
	}
	err = dev.Up()
	if err != nil {
		return nil, nil, err
	}
	return dev, stack, nil
}

type dialer struct {
	name string
	dial func(network, address string) (net.Conn, error)
}

func makeDialers(conf *vpnConf, endpoints []vpnEndpoint) (dialers []dialer, err error) {
	var devs []*device.Device
	defer func() {
		if err != nil {
			for _, dev := range devs {
				dev.Close()
			}
		}
	}()
	for _, endpoint := range endpoints {
		dev, stack, err := makeNet(conf, endpoint)
		if err != nil {
			return nil, err
		}
		devs = append(devs, dev)
		dialers = append(dialers, dialer{endpoint.name, stack.Dial})
	}
	return dialers, nil
}

func (d *dialer) splitByAf() (v4, v6 func(network, address string) (net.Conn, error)) {
	return func(network, address string) (net.Conn, error) {
			if len(network) == 3 {
				network += "4"
			}
			return d.dial(network, address)
		}, func(network, address string) (net.Conn, error) {
			if len(network) == 3 {
				network += "6"
			}
			return d.dial(network, address)
		}
}