// tunneld is a single-node, self-hosted OpenTunnel server: it speaks the
// wire protocol from docs/protocol.md, so the official opentunnel CLI and
// SDK work against it unchanged.
package main

import (
	"context"
	"crypto/tls"
	"flag"
	"log"
	"net"
	"net/http"
	"os"
	"os/signal"
	"path/filepath"
	"strconv"
	"syscall"
	"time"

	"gitea.tzgyn.dev/TZGyn/tunnel/internal/server"
)

// version is shown on the admin dashboard; override with
// -ldflags "-X main.version=<v>".
var version = "dev"

func envOr(key, fallback string) string {
	if value := os.Getenv(key); value != "" {
		return value
	}
	return fallback
}

func envInt(key string, fallback int) int {
	if value := os.Getenv(key); value != "" {
		if n, err := strconv.Atoi(value); err == nil {
			return n
		}
	}
	return fallback
}

func defaultDataDir() string {
	if xdg := os.Getenv("XDG_DATA_HOME"); xdg != "" {
		return filepath.Join(xdg, "tunneld")
	}
	if home, err := os.UserHomeDir(); err == nil {
		return filepath.Join(home, ".local", "share", "tunneld")
	}
	return ".local"
}

func main() {
	dataDefault := filepath.Join(defaultDataDir(), "data.json")

	domain := flag.String("domain", envOr("OPENTUNNEL_DOMAIN", "localhost"), "API domain; tunnels are <id>.<domain>")
	tlsListen := flag.String("tls-listen", envOr("TLS_LISTEN", "127.0.0.1:8443"), "public TLS listen address (SNI router)")
	httpListen := flag.String("http-listen", envOr("HTTP_LISTEN", "127.0.0.1:8080"), `HTTP listen address ("off" disables)`)
	httpMode := flag.String("http-mode", envOr("HTTP_MODE", "serve"), `"serve" runs the whole app on plain HTTP, "redirect" 301s to the domain`)
	dataPath := flag.String("data", envOr("TUNNELD_DATA", dataDefault), "tunnel store file (created 0600)")
	caFile := flag.String("ca-file", envOr("LOCAL_CA_FILE", ""), "write the local CA certificate here for clients to trust")
	adminToken := flag.String("admin-token", envOr("ADMIN_TOKEN", ""), "bearer token for the admin dashboard at / and /api/admin/overview; empty disables the admin API")
	acmeDirectory := flag.String("acme-directory", envOr("ACME_DIRECTORY_URL", "https://acme-v02.api.letsencrypt.org/directory"), "ACME directory URL")
	acmeEmail := flag.String("acme-email", envOr("ACME_EMAIL", ""), "contact email registered with the ACME account")
	acmeCABundle := flag.String("acme-ca-bundle", envOr("ACME_CA_BUNDLE", ""), "extra CA roots for the ACME server's TLS (Pebble)")
	acmePropagation := flag.Int("acme-propagation-seconds", envInt("ACME_PROPAGATION_TIMEOUT_SECONDS", 60), "wait this long for challenge TXT records to propagate; 0 skips the check")
	dnsProvider := flag.String("dns-provider", envOr("DNS_PROVIDER", ""), `challenge DNS: "porkbun" (default when its keys are set) or "challtestsrv" (Pebble)`)
	porkbunKey := flag.String("porkbun-api-key", envOr("PORKBUN_API_KEY", ""), "Porkbun API key for DNS-01 challenges")
	porkbunSecret := flag.String("porkbun-secret-api-key", envOr("PORKBUN_SECRET_API_KEY", ""), "Porkbun secret API key")
	dnsZone := flag.String("dns-zone", envOr("DNS_ZONE", ""), "zone hosting the challenge records (default: derived from the domain)")
	challtestsrvURL := flag.String("challtestsrv-url", envOr("CHALLTESTSRV_URL", ""), "pebble-challtestsrv management URL for DNS_PROVIDER=challtestsrv")
	flag.Parse()

	if *caFile == "" {
		*caFile = filepath.Join(filepath.Dir(*dataPath), "ca.pem")
	}

	store, err := server.OpenStore(*dataPath)
	if err != nil {
		log.Fatalf("open store: %v", err)
	}
	if err := os.MkdirAll(filepath.Dir(*caFile), 0o700); err != nil {
		log.Fatalf("ca file directory: %v", err)
	}
	if err := os.WriteFile(*caFile, []byte(store.CACertPEM()), 0o644); err != nil {
		log.Fatalf("write CA file: %v", err)
	}
	certPEM, keyPEM, err := store.ServerCertificate(*domain)
	if err != nil {
		log.Fatalf("server certificate: %v", err)
	}
	serverCert, err := tls.X509KeyPair(certPEM, keyPEM)
	if err != nil {
		log.Fatalf("parse server certificate: %v", err)
	}

	hub := server.NewHub(store)

	// Certificate issuance: ACME (DNS-01) when a challenge DNS provider is
	// configured, the built-in local CA otherwise.
	issuerName := "local"
	var issuer server.Issuer = server.NewLocalIssuer(store)
	var dns server.DNSProvider
	switch {
	case *dnsProvider == "challtestsrv":
		dns = &server.ChallengeTestSrvDNS{BaseURL: *challtestsrvURL}
	case *dnsProvider == "porkbun", *dnsProvider == "" && *porkbunKey != "" && *porkbunSecret != "":
		if *porkbunKey == "" || *porkbunSecret == "" {
			log.Fatal("DNS_PROVIDER=porkbun needs PORKBUN_API_KEY and PORKBUN_SECRET_API_KEY")
		}
		zone := *dnsZone
		if zone == "" {
			zone = server.DNSZone(*domain)
		}
		log.Printf("dns: Porkbun zone %s", zone)
		dns = &server.PorkbunDNS{APIKey: *porkbunKey, SecretKey: *porkbunSecret, Zone: zone}
	case *dnsProvider != "":
		log.Fatalf("unknown DNS_PROVIDER %q (want porkbun or challtestsrv)", *dnsProvider)
	}
	if dns != nil {
		acme, err := server.NewACMEIssuer(store, server.ACMEOptions{
			DirectoryURL:       *acmeDirectory,
			Email:              *acmeEmail,
			CABundleFile:       *acmeCABundle,
			DNS:                dns,
			PropagationTimeout: time.Duration(*acmePropagation) * time.Second,
		})
		if err != nil {
			log.Fatalf("acme issuer: %v", err)
		}
		issuer = acme
		issuerName = *acmeDirectory
		log.Printf("certificate issuer: ACME %s", *acmeDirectory)
	} else {
		log.Printf("certificate issuer: local CA (set PORKBUN_API_KEY and PORKBUN_SECRET_API_KEY to use ACME)")
	}

	api := &server.API{
		Store:      store,
		Hub:        hub,
		Domain:     *domain,
		AdminToken: *adminToken,
		StartedAt:  time.Now(),
		Version:    version,
		Issuer:     issuer,
		IssuerName: issuerName,
	}
	if *adminToken == "" {
		log.Printf("admin dashboard: disabled (set ADMIN_TOKEN to enable it at /)")
	} else {
		log.Printf("admin dashboard: enabled at /")
	}

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	api.StartRenewal(ctx)

	// Public TLS listener: SNI routing, with API terminations handed to the
	// shared HTTP server.
	ln, err := net.Listen("tcp", *tlsListen)
	if err != nil {
		log.Fatalf("tls listen: %v", err)
	}
	apiListener := server.NewChanListener(64, ln.Addr())
	relay := &server.Relay{
		Domain:   *domain,
		Store:    store,
		Hub:      hub,
		Server:   &serverCert,
		APIConns: apiListener.Conns(),
	}
	go relay.Serve(ln)
	go func() {
		if err := http.Serve(apiListener, api); err != nil {
			log.Printf("api over tls: %v", err)
		}
	}()
	log.Printf("tls: listening on %s (domain %s)", ln.Addr(), *domain)

	var httpLn net.Listener
	if *httpListen != "off" {
		httpLn, err = net.Listen("tcp", *httpListen)
		if err != nil {
			log.Fatalf("http listen: %v", err)
		}
		var handler http.Handler = api
		if *httpMode == "redirect" {
			handler = server.RedirectHandler(*domain)
		}
		go func() {
			if err := http.Serve(httpLn, handler); err != nil {
				log.Printf("http: %v", err)
			}
		}()
		log.Printf("http: listening on %s (mode %s)", httpLn.Addr(), *httpMode)
	}

	signals := make(chan os.Signal, 1)
	signal.Notify(signals, syscall.SIGINT, syscall.SIGTERM)
	sig := <-signals
	log.Printf("received %s; draining bridges", sig)
	cancel()
	hub.DrainAll()
	ln.Close()
	if httpLn != nil {
		httpLn.Close()
	}
	time.Sleep(500 * time.Millisecond)
	log.Printf("bye")
}