package main

import (
	"fmt"
	"net"
	"log"
	"bufio"
	"flag"
	"os/exec"
)

type Options struct {
	Addr string
}

func ParseOptions() Options {
	var opts Options

	flag.StringVar(&opts.Addr, "addr", "127.0.0.1:9001", "address to bind to recv blocks")
	flag.Parse()

	return opts
}

func handleConnection(conn net.Conn) {
	defer conn.Close()

	scan := bufio.NewScanner(conn)

	for scan.Scan() {
		addr, _, err := net.SplitHostPort(scan.Text())
		if err != nil {
			fmt.Println("Invalid host:port")
			continue
		}

		if addr == "127.0.0.1" {
			fmt.Println("IGNORE", addr)
			continue
		}

		fmt.Println("BLOCK: ", addr)

		cmd := exec.Command("nft",
			"add", "rule", "inet",
			"dentata", "input",
			"ip", "saddr",
			addr, "drop")

		err = cmd.Run()
		if err != nil {
			panic(err)
		}
	}
}

func listener(addr string) {
	server, err := net.Listen("tcp", addr)

	if err != nil { panic(err) }

	for {
		conn, err := server.Accept()

		if err != nil {	
			log.Println("ACCEPT ERROR", err)
		} else {
			go handleConnection(conn)
		}
	}
}

func main() {
	opts := ParseOptions()

	listener(opts.Addr)
}