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

package main

import (
	"flag"
	"fmt"
	"log"
	"math/rand"
	"net"
	"os"
	"regexp"
	"strings"
	"sync"
	"syscall"
	"time"

	"golang.org/x/sys/unix"
	"golang.zx2c4.com/irc/hbot"
)

func raiseFileLimit() error {
	var lim unix.Rlimit
	err := unix.Getrlimit(syscall.RLIMIT_NOFILE, &lim)
	if err != nil {
		return err
	}
	if lim.Cur == lim.Max {
		return nil
	}
	log.Printf("Raising file limit from %d to %d\n", lim.Cur, lim.Max)
	lim.Cur = lim.Max
	return unix.Setrlimit(syscall.RLIMIT_NOFILE, &lim)
}

func main() {
	accountIdArg := flag.String("account-id", "", "account ID number")
	srcChannelArg := flag.String("src-channel", "", "source channel")
	dstChannelArg := flag.String("dst-channel", "", "destination channel")
	srcServerArg := flag.String("src-server", "", "source server")
	dstServerArg := flag.String("dst-server", "", "destination server")
	flag.Parse()
	if matched, _ := regexp.MatchString(`^[0-9]+$`, *accountIdArg); !matched {
		fmt.Fprintln(os.Stderr, "Invalid account ID")
		flag.Usage()
		os.Exit(1)
	}
	if matched, _ := regexp.MatchString(`^#[a-zA-Z0-9_-]+$`, *srcChannelArg); !matched {
		fmt.Fprintln(os.Stderr, "Invalid source channel")
		flag.Usage()
		os.Exit(1)
	}
	if matched, _ := regexp.MatchString(`^#[a-zA-Z0-9_-]+$`, *dstChannelArg); !matched {
		fmt.Fprintln(os.Stderr, "Invalid destination channel")
		flag.Usage()
		os.Exit(1)
	}
	if _, _, err := net.SplitHostPort(*srcServerArg); err != nil {
		fmt.Fprintln(os.Stderr, "Invalid source server")
		flag.Usage()
		os.Exit(1)
	}
	if _, _, err := net.SplitHostPort(*dstServerArg); err != nil {
		fmt.Fprintln(os.Stderr, "Invalid destination server")
		flag.Usage()
		os.Exit(1)
	}

	privateKey, err := loadOrGeneratePrivateKey()
	if err != nil {
		log.Fatalln(err)
	}
	endpoints, err := getVpnEndpoints()
	if err != nil {
		log.Fatalln(err)
	}
	vpnConf, err := registerVpnConf(privateKey, *accountIdArg)
	if err != nil {
		log.Fatalln(err)
	}

	rand.Seed(time.Now().UnixNano())
	err = raiseFileLimit()
	if err != nil {
		log.Fatalln(err)
	}

	dialers, err := makeDialers(vpnConf, endpoints)
	if err != nil {
		log.Fatalln(err)
	}
	if len(dialers) < 2 {
		log.Fatalln("Not enough dialers returned")
	}
	writers := newIrcWriterGroup(*dstServerArg, *dstChannelArg)
	const writersPerIP = 10
	type nextDialer struct {
		sync.Mutex
		*dialer
	}
	dialNext := func(nd *nextDialer, v4 bool) {
		var last *dialer
		for {
			nd.Lock()
			if nd.dialer == last {
				nd.dialer = &dialers[rand.Intn(len(dialers))]
			}
			last = nd.dialer
			nd.Unlock()
			name := last.name
			dial := last.dial
			if v4 {
				name += "-v4"
				dial, _ = last.splitByAf()
			} else {
				name += "-v6"
				_, dial = last.splitByAf()
			}
			writers.runWriter(name, dial)
		}
	}
	for i := 0; i < vpnProviderMaxEndpointsInParallel/2; i++ {
		nd := new(nextDialer)
		for i := 0; i < writersPerIP; i++ {
			go dialNext(nd, true)
			go dialNext(nd, false)
		}
	}

	srcDial := dialers[rand.Intn(len(dialers))]
	logf := func(format string, args ...interface{}) {
		log.Printf("[SRC %s] "+format, append([]interface{}{srcDial.name}, args...)...)
	}
	bot := hbot.NewBot(&hbot.Config{
		Host:     *srcServerArg,
		Nick:     randomNick(),
		Channels: []string{*srcChannelArg},
		Dial:     srcDial.dial,
		Logger:   hbot.Logger{Verbosef: logf, Errorf: logf},
	})
	bot.AddTrigger(hbot.Trigger{
		Condition: func(b *hbot.Bot, m *hbot.Message) bool {
			return m.Param(0) == *srcChannelArg && m.Command == "PRIVMSG" &&
				!strings.HasPrefix(m.Prefix.User, hbot.CommonBotUserPrefix) &&
				!strings.HasPrefix(m.Prefix.User, "~"+hbot.CommonBotUserPrefix)
		},
		Action: func(b *hbot.Bot, m *hbot.Message) {
			writers.queueMessage(m.Prefix.Name, m.Trailing())
		},
	})
	for {
		bot.Run()
		time.Sleep(time.Second * 5)
	}
}