// Binary radvd sends IPv6 router advertisments.
package main

import (
	"encoding/json"
	"flag"
	"io/ioutil"
	"log"
	"os"
	"os/signal"
	"syscall"

	"router7/internal/dhcp6"
	"router7/internal/radvd"
)

func logic() error {
	srv, err := radvd.NewServer()
	if err != nil {
		return err
	}
	readConfig := func() error {
		b, err := ioutil.ReadFile("/perm/dhcp6/wire/lease.json")
		if err != nil {
			return err
		}
		var cfg dhcp6.Config
		if err := json.Unmarshal(b, &cfg); err != nil {
			return err
		}
		srv.SetPrefixes(cfg.Prefixes)
		return nil
	}
	if err := readConfig(); err != nil {
		log.Printf("cannot announce IPv6 prefixes: %v", err)
	}
	ch := make(chan os.Signal, 1)
	signal.Notify(ch, syscall.SIGUSR1)
	go func() {
		for range ch {
			if err := readConfig(); err != nil {
				log.Printf("readConfig: %v", err)
			}
		}
	}()
	return srv.ListenAndServe("lan0")
}

func main() {
	// TODO: drop privileges, run as separate uid?
	flag.Parse()
	if err := logic(); err != nil {
		log.Fatal(err)
	}
}