package server

import (
	"context"
	"crypto/tls"
	"encoding/base64"
	"errors"
	"fmt"
	"io"
	"local/oauth2/oauth2client"
	"local/rproxy3/config"
	"local/rproxy3/storage"
	"local/rproxy3/storage/packable"
	"log"
	"net"
	"net/http"
	"net/url"
	"strings"
	"time"

	"golang.org/x/time/rate"
)

const nsRouting = "routing"
const nsBOAuthZ = "oauth"

type listenerScheme int

const (
	schemeHTTP  listenerScheme = iota
	schemeHTTPS listenerScheme = iota
	schemeTCP   listenerScheme = iota
)

func (ls listenerScheme) String() string {
	switch ls {
	case schemeHTTP:
		return "http"
	case schemeHTTPS:
		return "https"
	case schemeTCP:
		return "tcp"
	}
	return ""
}

type Server struct {
	db       storage.DB
	addr     string
	altaddr  string
	username string
	password string
	limiter  *rate.Limiter
}

func (s *Server) Route(src string, dst config.Proxy) error {
	hasOAuth := strings.HasPrefix(src, "+")
	src = strings.TrimPrefix(src, "+")
	log.Printf("Adding route %q -> %v...\n", src, dst)
	u, err := url.Parse(dst.To)
	if err != nil {
		return err
	}
	s.db.Set(nsBOAuthZ, src, packable.NewString(fmt.Sprint(hasOAuth)))
	return s.db.Set(nsRouting, src, packable.NewURL(u))
}

func (s *Server) Run() error {
	go s.alt()
	scheme := getScheme()
	log.Printf("Listening for %v on %v...\n", scheme, s.addr)
	switch scheme {
	case schemeHTTP:
		return http.ListenAndServe(s.addr, s)
	case schemeHTTPS:
		c, k, _ := config.GetSSL()
		httpsServer := &http.Server{
			Addr:    s.addr,
			Handler: s,
			TLSConfig: &tls.Config{
				MinVersion:               tls.VersionTLS12,
				CurvePreferences:         []tls.CurveID{tls.CurveP521, tls.CurveP384, tls.CurveP256},
				PreferServerCipherSuites: true,
				CipherSuites: []uint16{
					tls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
					tls.TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,
					tls.TLS_RSA_WITH_AES_256_GCM_SHA384,
					tls.TLS_RSA_WITH_AES_256_CBC_SHA,
				},
			},
			TLSNextProto: make(map[string]func(*http.Server, *tls.Conn, http.Handler), 0),
		}
		return httpsServer.ListenAndServeTLS(c, k)
	case schemeTCP:
		addr, _ := config.GetTCP()
		return s.ServeTCP(addr)
	}
	return errors.New("did not load server")
}

func (s *Server) doAuth(foo http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		rusr, rpwd, ok := config.GetAuth()
		if ok {
			usr, pwd, ok := r.BasicAuth()
			if !ok || rusr != usr || rpwd != pwd {
				w.WriteHeader(http.StatusUnauthorized)
				log.Printf("denying proxy basic auth")
				return
			}
		}
		key := mapKey(r.Host)
		ok, err := s.lookupBOAuthZ(key)
		if err != nil {
			w.WriteHeader(http.StatusInternalServerError)
			return
		}
		if url, exists := config.GetBOAuthZ(); ok && exists {
			err := oauth2client.Authenticate(url, key, w, r)
			if err != nil {
				return
			}
		}
		foo(w, r)
	}
}

func (s *Server) ServeTCP(addr string) error {
	listen, err := net.Listen("tcp", s.addr)
	if err != nil {
		return err
	}
	for {
		c, err := listen.Accept()
		if err != nil {
			return err
		}
		go func(c net.Conn) {
			d, err := net.Dial("tcp", addr)
			if err != nil {
				log.Println(err)
				return
			}
			go pipe(c, d)
			go pipe(d, c)
		}(c)
	}
}

func pipe(a, b net.Conn) {
	log.Println("open pipe")
	defer log.Println("close pipe")
	defer a.Close()
	defer b.Close()
	io.Copy(a, b)
}

func (s *Server) Pre(foo http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		ctx, can := context.WithTimeout(r.Context(), time.Duration(config.GetTimeout()))
		defer can()
		if err := s.limiter.Wait(ctx); err != nil {
			w.WriteHeader(http.StatusTooManyRequests)
			return
		}
		s.doAuth(foo)(w, r)
	}
}

func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	s.Pre(s.Proxy)(w, r)
}

func getProxyAuth(r *http.Request) (string, string) {
	proxyAuthHeader := r.Header.Get("Proxy-Authorization")
	proxyAuthB64 := strings.TrimPrefix(proxyAuthHeader, "Basic ")
	proxyAuthBytes, _ := base64.StdEncoding.DecodeString(proxyAuthB64)
	proxyAuth := string(proxyAuthBytes)
	if !strings.Contains(proxyAuth, ":") {
		return "", ""
	}
	proxyAuthSplit := strings.Split(proxyAuth, ":")
	return proxyAuthSplit[0], proxyAuthSplit[1]
}

func (s *Server) alt() {
	switch getScheme() {
	case schemeHTTP:
	case schemeHTTPS:
	default:
		return
	}
	foo := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		r.URL.Scheme = getScheme().String()
		if hostname := r.URL.Hostname(); hostname != "" {
			r.URL.Host = r.URL.Hostname() + s.addr
		} else if hostname := r.URL.Host; hostname != "" {
			r.URL.Host = r.URL.Host + s.addr
		} else {
			u := url.URL{Host: r.Host}
			r.URL.Host = u.Hostname() + s.addr
		}
		http.Redirect(w, r, r.URL.String(), http.StatusSeeOther)
	})
	log.Println("redirecting from", s.altaddr)
	if err := http.ListenAndServe(s.altaddr, foo); err != nil {
		panic(err)
	}
}

func getScheme() listenerScheme {
	scheme := schemeHTTP
	if _, _, ok := config.GetSSL(); ok {
		scheme = schemeHTTPS
	}
	if _, ok := config.GetTCP(); ok {
		scheme = schemeTCP
	}
	return scheme
}