package reseed

import (
	"bytes"
	"context"
	"crypto/tls"
	"io"
	"io/ioutil"
	"log"
	"net"
	"net/http"
	"os"
	"strconv"
	"time"

	"github.com/cretz/bine/tor"
	"github.com/cretz/bine/torutil/ed25519"
	"github.com/throttled/throttled"
	"github.com/throttled/throttled/store"
	"github.com/gorilla/handlers"
	"github.com/justinas/alice"
)

const (
	i2pUserAgent = "Wget/1.11.4"
)

type Server struct {
	*http.Server
	Reseeder      Reseeder
	Blacklist     *Blacklist
	OnionListener *tor.OnionService
}

func NewServer(prefix string, trustProxy bool) *Server {
	config := &tls.Config{
//		MinVersion:               tls.VersionTLS10,
//		PreferServerCipherSuites: true,
//		CipherSuites: []uint16{
//			tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
//			tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
//			tls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
//			tls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
//			tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA,
//			tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA,
//			tls.TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,
//			tls.TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA,
//		},
		MinVersion:               tls.VersionTLS13,
		PreferServerCipherSuites: true,
		CipherSuites: []uint16{
			tls.TLS_AES_256_GCM_SHA384,
			tls.TLS_CHACHA20_POLY1305_SHA256,
		},
		CurvePreferences: []tls.CurveID{tls.CurveP384, tls.CurveP521}, // default CurveP256 removed
	}
	h := &http.Server{TLSConfig: config}
	server := Server{Server: h, Reseeder: nil}

	th := throttled.RateLimit(throttled.PerHour(4), &throttled.VaryBy{RemoteAddr: true}, store.NewMemStore(200000))

	middlewareChain := alice.New()
	if trustProxy {
		middlewareChain = middlewareChain.Append(proxiedMiddleware)
	}

	errorHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusNotFound)
		if _, err := w.Write(nil); nil != err {
			log.Println(err)
		}
	})

	mux := http.NewServeMux()
	mux.Handle("/", middlewareChain.Append(disableKeepAliveMiddleware, loggingMiddleware).Then(errorHandler))
	mux.Handle(prefix+"/i2pseeds.su3", middlewareChain.Append(disableKeepAliveMiddleware, loggingMiddleware, verifyMiddleware, th.Throttle).Then(http.HandlerFunc(server.reseedHandler)))
	server.Handler = mux

	return &server
}

func (srv *Server) ListenAndServe() error {
	addr := srv.Addr
	if addr == "" {
		addr = ":http"
	}
	ln, err := net.Listen("tcp", addr)
	if err != nil {
		return err
	}

	return srv.Serve(newBlacklistListener(ln, srv.Blacklist))
}

func (srv *Server) ListenAndServeTLS(certFile, keyFile string) error {
	addr := srv.Addr
	if addr == "" {
		addr = ":https"
	}

	if srv.TLSConfig == nil {
		srv.TLSConfig = &tls.Config{}
	}

	if srv.TLSConfig.NextProtos == nil {
		srv.TLSConfig.NextProtos = []string{"http/1.1"}
	}

	var err error
	srv.TLSConfig.Certificates = make([]tls.Certificate, 1)
	srv.TLSConfig.Certificates[0], err = tls.LoadX509KeyPair(certFile, keyFile)
	if err != nil {
		return err
	}

	ln, err := net.Listen("tcp", addr)
	if err != nil {
		return err
	}

	tlsListener := tls.NewListener(newBlacklistListener(ln, srv.Blacklist), srv.TLSConfig)
	return srv.Serve(tlsListener)
}

func (srv *Server) ListenAndServeOnion(startConf *tor.StartConf, listenConf *tor.ListenConf, onionKey string) error {
	log.Println("Starting and registering onion service, please wait a couple of minutes...")
	tor, err := tor.Start(nil, startConf)
	if err != nil {
		return err
	}
	defer tor.Close()

	listenCtx, listenCancel := context.WithTimeout(context.Background(), 3*time.Minute)
	defer listenCancel()
	srv.OnionListener, err = tor.Listen(listenCtx, listenConf)
	if err != nil {
		return err
	}
	err = ioutil.WriteFile(onionKey, []byte(srv.OnionListener.Key.(ed25519.KeyPair).PrivateKey()), 0644)
	if err != nil {
		return err
	}
	log.Printf("Onionv3 server started on http://%v.onion\n", srv.OnionListener.ID)
	return srv.Serve(srv.OnionListener)
}

func (srv *Server) reseedHandler(w http.ResponseWriter, r *http.Request) {
	var peer Peer
	if ip, _, err := net.SplitHostPort(r.RemoteAddr); err == nil {
		peer = Peer(ip)
	} else {
		peer = Peer(r.RemoteAddr)
	}

	su3Bytes, err := srv.Reseeder.PeerSu3Bytes(peer)
	if nil != err {
		http.Error(w, "500 Unable to serve su3", http.StatusInternalServerError)
		return
	}

	w.Header().Set("Content-Disposition", "attachment; filename=i2pseeds.su3")
	w.Header().Set("Content-Type", "application/octet-stream")
	w.Header().Set("Content-Length", strconv.FormatInt(int64(len(su3Bytes)), 10))

	io.Copy(w, bytes.NewReader(su3Bytes))
}

func disableKeepAliveMiddleware(next http.Handler) http.Handler {
	fn := func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Connection", "close")
		next.ServeHTTP(w, r)
	}
	return http.HandlerFunc(fn)
}

func loggingMiddleware(next http.Handler) http.Handler {
	return handlers.CombinedLoggingHandler(os.Stdout, next)
}

func verifyMiddleware(next http.Handler) http.Handler {
	fn := func(w http.ResponseWriter, r *http.Request) {
		if i2pUserAgent != r.UserAgent() {
			http.Error(w, "403 Forbidden", http.StatusForbidden)
			return
		}

		next.ServeHTTP(w, r)
	}
	return http.HandlerFunc(fn)
}

func proxiedMiddleware(next http.Handler) http.Handler {
	fn := func(w http.ResponseWriter, r *http.Request) {
		if prior, ok := r.Header["X-Forwarded-For"]; ok {
			r.RemoteAddr = prior[0]
		}

		next.ServeHTTP(w, r)
	}
	return http.HandlerFunc(fn)
}