package web

import (
	"context"
	"crypto/tls"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strconv"
	"sync"
	"time"

	"github.com/go-chi/chi/v5"
	"github.com/go-chi/chi/v5/middleware"
	"github.com/google/uuid"
	"github.uio.no/torjus/apiary/config"
	"github.uio.no/torjus/apiary/honeypot"
	"github.uio.no/torjus/apiary/honeypot/store"
	"github.uio.no/torjus/apiary/models"
	"go.uber.org/zap"
	"golang.org/x/crypto/acme/autocert"
)

type Server struct {
	http.Server

	cfg config.FrontendConfig

	store store.LoginAttemptStore

	ServerLogger *zap.SugaredLogger
	AccessLogger *zap.SugaredLogger

	honeypotServer *honeypot.HoneypotServer

	attemptListenersLock sync.RWMutex
	attemptListeners     map[string]chan models.LoginAttempt

	streamContext      context.Context
	httpRedirectServer http.Server
}

func NewServer(cfg config.FrontendConfig, hs *honeypot.HoneypotServer, store store.LoginAttemptStore) *Server {
	s := &Server{
		ServerLogger: zap.NewNop().Sugar(),
		AccessLogger: zap.NewNop().Sugar(),
		store:        store,
		cfg:          cfg,
	}

	if cfg.Autocert.Enable {
		certManager := autocert.Manager{
			Prompt:     autocert.AcceptTOS,
			HostPolicy: autocert.HostWhitelist(cfg.Autocert.Domains...),
			Email:      cfg.Autocert.Email,
		}
		if cfg.Autocert.CacheDir != "" {
			certManager.Cache = autocert.DirCache(cfg.Autocert.CacheDir)
		}

		tlsConfig := certManager.TLSConfig()
		tlsConfig.MinVersion = tls.VersionTLS12
		s.TLSConfig = tlsConfig
		s.RegisterOnShutdown(func() {
			timeoutCtx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
			defer cancel()
			s.httpRedirectServer.Shutdown(timeoutCtx)
		})
		s.Addr = ":443"

		if cfg.Autocert.RedirectHTTP {
			s.httpRedirectServer.Addr = ":80"
			s.httpRedirectServer.Handler = certManager.HTTPHandler(nil)
		}
	} else {
		s.Addr = cfg.ListenAddr
	}

	r := chi.NewRouter()

	// Setup middleware
	r.Use(middleware.RealIP)
	r.Use(middleware.RequestID)
	r.Use(s.LoggingMiddleware)

	r.Route("/", func(r chi.Router) {
		r.Get("/*", s.IndexHandler("web/vue-frontend/dist"))
		r.Get("/stream", s.HandlerAttemptStream)
		r.Route("/api", func(r chi.Router) {
			r.Use(middleware.SetHeader("Content-Type", "application/json"))
			r.Get("/stats", s.HandlerStats)
			r.Get("/stream", s.HandlerAttemptStream)
		})
	})
	s.Handler = r
	s.honeypotServer = hs
	s.attemptListeners = make(map[string]chan models.LoginAttempt)
	streamCtx, streamCancel := context.WithCancel(context.Background())
	s.streamContext = streamCtx
	s.RegisterOnShutdown(func() {
		streamCancel()
	})

	hs.AddLoginCallback(func(l models.LoginAttempt) {
		s.attemptListenersLock.RLock()
		defer s.attemptListenersLock.RUnlock()
		for i := range s.attemptListeners {
			s.attemptListeners[i] <- l
		}
	})

	return s
}

func (s *Server) StartServe() error {
	if s.cfg.Autocert.Enable {
		if s.cfg.Autocert.RedirectHTTP {
			s.ServerLogger.Debug("Starting HTTP redirect server")
			go func() {
				if err := s.httpRedirectServer.ListenAndServe(); err != nil && err != http.ErrServerClosed {
					s.ServerLogger.Warnw("HTTP redirect server returned error", "error", err)
				}
			}()
		}
		return s.ListenAndServeTLS("", "")
	} else {
		return s.ListenAndServe()
	}
}

func (s *Server) addAttemptListener() (string, chan models.LoginAttempt) {
	ch := make(chan models.LoginAttempt)
	s.attemptListenersLock.Lock()
	defer s.attemptListenersLock.Unlock()
	id := uuid.Must(uuid.NewRandom())
	s.attemptListeners[id.String()] = ch
	return id.String(), ch
}

func (s *Server) closeAttemptListener(id string) {
	s.attemptListenersLock.Lock()
	defer s.attemptListenersLock.Unlock()
	ch := s.attemptListeners[id]
	close(ch)
	delete(s.attemptListeners, id)
}
func (s *Server) HandlerAttemptStream(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "text/event-stream")
	w.Header().Set("Cache-Control", "no-cache")
	w.Header().Set("Connection", "keep-alive")
	w.Header().Set("Access-Control-Allow-Origin", "*")
	id, ch := s.addAttemptListener()
	defer s.closeAttemptListener(id)

	flusher := w.(http.Flusher)
	ticker := time.NewTicker(30 * time.Second)
	defer ticker.Stop()

	for {
		select {
		case l := <-ch:
			data, err := json.Marshal(l)
			if err != nil {
				return
			}
			_, err = io.WriteString(w, fmt.Sprintf("data: %s\n\n", string(data)))
			if err != nil {
				s.ServerLogger.Warnw("Error writing event", "error", err)
			}
			flusher.Flush()
		case <-s.streamContext.Done():
			return
		case <-r.Context().Done():
			return
		case <-ticker.C:
			if _, err := io.WriteString(w, ": keep-alive\n\n"); err != nil {
				s.ServerLogger.Warnw("Error writing event", "error", err)
			}
			flusher.Flush()
		}
	}
}

func (s *Server) HandlerStats(w http.ResponseWriter, r *http.Request) {
	statType := store.LoginStats(r.URL.Query().Get("type"))
	if statType == store.LoginStatsUndefined {
		statType = store.LoginStatsPasswords
	}
	var limit int
	limitString := r.URL.Query().Get("limit")

	limit, err := strconv.Atoi(limitString)
	if err != nil {
		limit = 0
	}

	stats, err := s.store.Stats(statType, limit)
	if err != nil {
		s.ServerLogger.Warnw("Error fetching stats", "error", err)
		s.WriteAPIError(w, r, http.StatusInternalServerError, "Error fetching stats")
		return
	}

	encoder := json.NewEncoder(w)
	if err := encoder.Encode(stats); err != nil {
		s.ServerLogger.Debugf("Error encoding or writing response", "remote_ip", r.RemoteAddr, "error", err)
	}
}

type APIErrorResponse struct {
	Error string `json:"error"`
}

func (s *Server) WriteAPIError(w http.ResponseWriter, r *http.Request, status int, message string) {
	encoder := json.NewEncoder(w)
	apiErr := APIErrorResponse{Error: message}
	w.WriteHeader(status)
	if err := encoder.Encode(&apiErr); err != nil {
		s.ServerLogger.Debugf("Error encoding or writing error response", "remote_ip", r.RemoteAddr, "error", err)
	}
}