package main

import (
	"bufio"
	"errors"
	"flag"
	"fmt"
	"log"
	"log/syslog"
	"os"
	"os/signal"
	"os/user"
	"path"
	"strconv"
	"strings"
	"syscall"
	"tunnel/pkg/config"
	"tunnel/pkg/server"
)

var (
	debugFlag  = flag.Bool("d", false, "debug: print time and source info")
	forceFlag = flag.Bool("f", false, "try start with force")
	syslogFlag = flag.Bool("s", false, "write log to syslog instead of stdout")
	configFlag = flag.String("c", "", "path to configuration file")
)

func initLog() {
	var logFlags int

	if *debugFlag {
		logFlags |= log.Ldate | log.Ltime | log.Lshortfile
	}

	log.SetFlags(logFlags)

	if *syslogFlag {
		sysLog, err := syslog.New(syslog.LOG_INFO, "tunneld")
		if err != nil {
			log.Fatal(err)
		}

		log.SetOutput(sysLog)
	}
}

func sighandler(c chan os.Signal, s *server.Server) {
	var try bool

	for sig := range c {
		if try {
			log.Fatal("force exit")
		}

		log.Printf("catch signal: %s", sig)
		try = true
		s.Stop()
	}
}

func initSignals(s *server.Server) {
	var c = make(chan os.Signal)

	signal.Notify(c, syscall.SIGINT, syscall.SIGTERM)

	go sighandler(c, s)
}

func getSocketPath() string {
	s := config.GetSocketPath()

	if err := os.Mkdir(path.Dir(s), 0700); err != nil {
		if !errors.Is(err, syscall.EEXIST) {
			log.Fatal(err)
		}
	}

	return s
}

func openConfig() (*os.File, error) {
	var c string

	if len(*configFlag) > 0 {
		c = *configFlag
	} else {
		c = config.GetConfigPath()
	}

	if c == "" {
		return nil, nil
	}

	fp, err := os.Open(c)
	if err != nil {
		if *configFlag == "" && errors.Is(err, syscall.ENOENT) {
			return nil, nil
		}

		return nil, err
	}

	return fp, nil
}

func readConfig(s *server.Server) error {
	fp, err := openConfig()
	if fp == nil || err != nil {
		return err
	}

	defer fp.Close()

	scanner := bufio.NewScanner(fp)
	scanner.Split(bufio.ScanLines)

	for nline := 1; scanner.Scan(); nline++ {
		args := strings.SplitN(scanner.Text(), "#", 2)
		cmd := strings.TrimSpace(args[0])

		if cmd == "" {
			continue
		}

		if err := s.Command(cmd); err != nil {
			return fmt.Errorf("%s:%d: %s: %w", fp.Name(), nline, cmd, err)
		}
	}

	return nil
}

func updateSocketGroup(s *server.Server, group string) error {
	var gid int

	if g, err := user.LookupGroup(group); err != nil {
		return err
	} else {
		var err error

		if gid, err = strconv.Atoi(g.Gid); err != nil {
			return fmt.Errorf("bad group id %s: %w", g.Gid, err)
		}
	}

	f := s.Socket()
	d := path.Dir(f)

	if err := os.Chown(d, -1, gid); err != nil {
		return err
	}

	if err := os.Chmod(d, 0750); err != nil {
		return err
	}

	if err := os.Chown(f, -1, gid); err != nil {
		return err
	}

	if err := os.Chmod(f, 0770); err != nil {
		return err
	}

	return nil
}

func configure(s *server.Server) error {
	if err := readConfig(s); err != nil {
		return err
	}

	if group, ok := s.Env().Find("server.socket.group"); ok {
		if err := updateSocketGroup(s, group); err != nil {
			return err
		}
	}

	return nil
}

func main() {
	flag.Parse()
	initLog()

	socket := getSocketPath()
	if *forceFlag {
		if err := os.Remove(socket); err != nil {
			if !errors.Is(err, syscall.ENOENT) {
				log.Fatal(err)
			}
		}
	}

	s, err := server.New(socket)
	if err != nil {
		log.Fatal(err)
	}

	if err := configure(s); err != nil {
		s.Stop()
		log.Fatal(err)
	}

	initSignals(s)

	log.Print("ready")

	s.Run()

	log.Print("exit")
}