package route

import (
	"bytes"
	"encoding/json"
	"net"
	"net/http"
	"strings"
	"time"

	C "github.com/Dreamacro/clash/constant"
	"github.com/Dreamacro/clash/log"
	"github.com/Dreamacro/clash/tunnel/statistic"

	"github.com/go-chi/chi/v5"
	"github.com/go-chi/cors"
	"github.com/go-chi/render"
	"github.com/gorilla/websocket"
)

var (
	serverSecret = ""
	serverAddr   = ""

	uiPath = ""

	upgrader = websocket.Upgrader{
		CheckOrigin: func(r *http.Request) bool {
			return true
		},
	}
)

type Traffic struct {
	Up   int64 `json:"up"`
	Down int64 `json:"down"`
}

func SetUIPath(path string) {
	uiPath = C.Path.Resolve(path)
}

func Start(addr string, secret string) {
	if serverAddr != "" {
		return
	}

	serverAddr = addr
	serverSecret = secret

	r := chi.NewRouter()

	cors := cors.New(cors.Options{
		AllowedOrigins: []string{"*"},
		AllowedMethods: []string{"GET", "POST", "PUT", "PATCH", "DELETE"},
		AllowedHeaders: []string{"Content-Type", "Authorization"},
		MaxAge:         300,
	})

	r.Use(cors.Handler)
	r.Group(func(r chi.Router) {
		r.Use(authentication)

		r.Get("/", hello)
		r.Get("/logs", getLogs)
		r.Get("/traffic", traffic)
		r.Get("/version", version)
		r.Mount("/configs", configRouter())
		r.Mount("/proxies", proxyRouter())
		r.Mount("/rules", ruleRouter())
		r.Mount("/connections", connectionRouter())
		r.Mount("/providers/proxies", proxyProviderRouter())
		r.Mount("/providers/rules", ruleProviderRouter())
	})

	if uiPath != "" {
		r.Group(func(r chi.Router) {
			fs := http.StripPrefix("/ui", http.FileServer(http.Dir(uiPath)))
			r.Get("/ui", http.RedirectHandler("/ui/", http.StatusTemporaryRedirect).ServeHTTP)
			r.Get("/ui/*", func(w http.ResponseWriter, r *http.Request) {
				fs.ServeHTTP(w, r)
			})
		})
	}

	l, err := net.Listen("tcp", addr)
	if err != nil {
		log.Errorln("External controller listen error: %s", err)
		return
	}
	serverAddr = l.Addr().String()
	log.Infoln("RESTful API listening at: %s", serverAddr)
	if err = http.Serve(l, r); err != nil {
		log.Errorln("External controller serve error: %s", err)
	}
}

func authentication(next http.Handler) http.Handler {
	fn := func(w http.ResponseWriter, r *http.Request) {
		if serverSecret == "" {
			next.ServeHTTP(w, r)
			return
		}

		// Browser websocket not support custom header
		if websocket.IsWebSocketUpgrade(r) && r.URL.Query().Get("token") != "" {
			token := r.URL.Query().Get("token")
			if token != serverSecret {
				render.Status(r, http.StatusUnauthorized)
				render.JSON(w, r, ErrUnauthorized)
				return
			}
			next.ServeHTTP(w, r)
			return
		}

		header := r.Header.Get("Authorization")
		text := strings.SplitN(header, " ", 2)

		hasInvalidHeader := text[0] != "Bearer"
		hasInvalidSecret := len(text) != 2 || text[1] != serverSecret
		if hasInvalidHeader || hasInvalidSecret {
			render.Status(r, http.StatusUnauthorized)
			render.JSON(w, r, ErrUnauthorized)
			return
		}
		next.ServeHTTP(w, r)
	}
	return http.HandlerFunc(fn)
}

func hello(w http.ResponseWriter, r *http.Request) {
	render.JSON(w, r, render.M{"hello": "clash"})
}

func traffic(w http.ResponseWriter, r *http.Request) {
	var wsConn *websocket.Conn
	if websocket.IsWebSocketUpgrade(r) {
		var err error
		wsConn, err = upgrader.Upgrade(w, r, nil)
		if err != nil {
			return
		}
	}

	if wsConn == nil {
		w.Header().Set("Content-Type", "application/json")
		render.Status(r, http.StatusOK)
	}

	tick := time.NewTicker(time.Second)
	defer tick.Stop()
	t := statistic.DefaultManager
	buf := &bytes.Buffer{}
	var err error
	for range tick.C {
		buf.Reset()
		up, down := t.Now()
		if err := json.NewEncoder(buf).Encode(Traffic{
			Up:   up,
			Down: down,
		}); err != nil {
			break
		}

		if wsConn == nil {
			_, err = w.Write(buf.Bytes())
			w.(http.Flusher).Flush()
		} else {
			err = wsConn.WriteMessage(websocket.TextMessage, buf.Bytes())
		}

		if err != nil {
			break
		}
	}
}

type Log struct {
	Type    string `json:"type"`
	Payload string `json:"payload"`
}

func getLogs(w http.ResponseWriter, r *http.Request) {
	levelText := r.URL.Query().Get("level")
	if levelText == "" {
		levelText = "info"
	}

	level, ok := log.LogLevelMapping[levelText]
	if !ok {
		render.Status(r, http.StatusBadRequest)
		render.JSON(w, r, ErrBadRequest)
		return
	}

	var wsConn *websocket.Conn
	if websocket.IsWebSocketUpgrade(r) {
		var err error
		wsConn, err = upgrader.Upgrade(w, r, nil)
		if err != nil {
			return
		}
	}

	if wsConn == nil {
		w.Header().Set("Content-Type", "application/json")
		render.Status(r, http.StatusOK)
	}

	sub := log.Subscribe()
	defer log.UnSubscribe(sub)
	buf := &bytes.Buffer{}
	var err error
	for elm := range sub {
		buf.Reset()
		log := elm.(*log.Event)
		if log.LogLevel < level {
			continue
		}

		if err := json.NewEncoder(buf).Encode(Log{
			Type:    log.Type(),
			Payload: log.Payload,
		}); err != nil {
			break
		}

		if wsConn == nil {
			_, err = w.Write(buf.Bytes())
			w.(http.Flusher).Flush()
		} else {
			err = wsConn.WriteMessage(websocket.TextMessage, buf.Bytes())
		}

		if err != nil {
			break
		}
	}
}

func version(w http.ResponseWriter, r *http.Request) {
	render.JSON(w, r, render.M{"experimental": true, "version": C.Version})
}
