tildewatch/main.go

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"os"
	"os/signal"
	"sync"
	"time"

	"github.com/charmbracelet/log"
	"github.com/go-chi/chi/middleware"
	"github.com/go-chi/chi/v5"
	"github.com/go-gandi/go-gandi"
	"github.com/go-gandi/go-gandi/config"
	"golang.org/x/exp/slices"
	"gopkg.in/yaml.v2"
)

func loadConfig(filename string) (*Config, error) {
	u := &Config{}
	yamlFile, err := os.ReadFile(filename)
	if err != nil {
		return nil, err
	}
	err = yaml.Unmarshal(yamlFile, u)
	if err != nil {
		return nil, err
	}
	return u, nil
}

func main() {
	ctx, endFn := context.WithCancel(context.Background())
	domain, ok := os.LookupEnv("WATCH_DOMAIN")
	if !ok {
		log.Fatal("no domain specified")
	}
	apikey, ok := os.LookupEnv("WATCH_API")
	if !ok {
		log.Fatal("no Gandi api key")
	}
	port, ok := os.LookupEnv("WATCH_PORT")
	if !ok {
		port = "6283"
	}
	file, ok := os.LookupEnv("WATCH_FILE")
	if !ok {
		file = "./config.yaml"
	}

	debug := os.Getenv("WATCH_DEBUG")
	watchusers, err := loadConfig(file)
	if err != nil {
		log.Fatal(err)
	}
	for _, v := range watchusers.Users {
		if v.Hostname == "" {
			log.Fatal("bad config", "user", v)
		}
	}

	conf := config.Config{
		APIKey: apikey,
	}

	a := &Watch{
		Tildes: make(map[string]Registration),
		debug:  debug != "",
		domain: domain,
		conf:   conf,
	}
	for _, v := range watchusers.Users {
		a.Tildes[v.Secret] = Registration{
			Domain: v.Hostname,
			Update: false,
			IPAddr: "",
		}
	}
	log.Info(a.Tildes)
	server := &http.Server{Addr: fmt.Sprintf("0.0.0.0:%v", port), Handler: a.server()}
	var wg sync.WaitGroup
	c := make(chan os.Signal, 1)
	signal.Notify(c, os.Interrupt)
	go func() {
		<-c
		log.Info("trying to shutdown cleanly")
		endFn()
		err := server.Shutdown(ctx)
		if err != nil {
			log.Warn("error shutting down tilde server", "error", err)
		}
	}()

	wg.Add(1)
	go func() {
		err := server.ListenAndServe()
		if err != nil {
			log.Warn("error shutting down web server", "error", err)
		}
		wg.Done()
		log.Info("watch web server shutdown")
	}()

	wg.Add(1)
	go func() {
		err := a.run(ctx)
		if err != nil {
			log.Warn("error shutting down update server", "error", err)
		}

		wg.Done()
		log.Info("watch updater shutdown")
	}()
	log.Info("watch running")
	wg.Wait()
	log.Info("shut down")
}

func (watch *Watch) server() http.Handler {
	r := chi.NewRouter()
	r.Use(middleware.Logger)
	r.Post("/submit", func(w http.ResponseWriter, r *http.Request) {
		var payload Request
		err := json.NewDecoder(r.Body).Decode(&payload)
		if err != nil {
			log.Warn("error parsing ip submission", "error", err)
			w.WriteHeader(http.StatusBadRequest)
			return
		}
		found := false
		for i, v := range watch.Tildes {
			if payload.Secret == i && v.IPAddr != payload.IPAddr {
				cur := watch.Tildes[i]
				watch.Tildes[i] = Registration{
					IPAddr: payload.IPAddr,
					Update: true,
					Domain: cur.Domain,
				}
				found = true
			}
		}
		if !found {
			w.WriteHeader(http.StatusUnauthorized)
		}
		w.WriteHeader(http.StatusOK)
	})
	return r
}

func (watch *Watch) run(ctx context.Context) error {
	ticker := time.NewTicker(5 * time.Second)
	for {
		select {
		case <-ticker.C:
			for i, v := range watch.Tildes {
				if v.Update {
					err := watch.runUpdate(i, v)
					if err != nil {
						log.Warn("error running update", "error", err)
					}
				}
			}

		case <-ctx.Done():
			ticker.Stop()
			return nil
		}
	}
}

func (watch *Watch) runUpdate(token string, reg Registration) error {
	if reg.Domain == "" || reg.IPAddr == "" {
		return fmt.Errorf("invalid registration for update %v: %v", reg.Domain, reg.IPAddr)
	}
	if watch.debug {
		log.Info("would run updates", "subdomain", reg.Domain)
		return nil
	}
	log.Info("updating registration", "subdomain", reg.Domain, "ip", reg.IPAddr)
	dnsclient := gandi.NewLiveDNSClient(watch.conf)
	log.Info("getting domain records", "domain", watch.domain, "subdomain", reg.Domain)
	curr, err := dnsclient.GetDomainRecordsByName(watch.domain, reg.Domain)
	if err != nil {
		return fmt.Errorf("error getting domain records: %w", err)
	}
	if len(curr) == 0 {
		log.Info("no records found for subdomain, not forcing creationg", "subdomain", reg.Domain)
	}
	for _, v := range curr {
		if v.RrsetType == "A" {
			if slices.Contains(v.RrsetValues, reg.IPAddr) {
				log.Info("not updating, already set", "host", reg.Domain, "ip", reg.IPAddr)
			} else {
				_, err := dnsclient.UpdateDomainRecordByNameAndType(watch.domain, reg.Domain, "A", 900, []string{reg.IPAddr})
				if err != nil {
					return fmt.Errorf("error updating record %w", err)
				}
				log.Info("updating domain succesfully", "subdomain", reg.Domain)
			}
			toUp := watch.Tildes[token]
			toUp.Update = false
			watch.Tildes[token] = toUp

		}
	}
	return nil
}