package serverevents

import (
	"encoding/json"
	"fmt"
	di "git.apihub24.de/admin/generic-di"
	"github.com/gorilla/websocket"
	"net/http"
)

func init() {
	di.Injectable(newServerEventsMiddleware)
}

type MiddlewareOptions struct {
	Path string
}

type IServerEventsMiddleware interface {
	Use(MiddlewareOptions, *http.ServeMux)
}

type serverEventsMiddleware struct {
	upgrader          websocket.Upgrader
	streamSubscribers map[string]bool
}

func newServerEventsMiddleware() IServerEventsMiddleware {
	return &serverEventsMiddleware{
		upgrader: websocket.Upgrader{
			CheckOrigin: func(r *http.Request) bool {
				return true
			},
		},
		streamSubscribers: make(map[string]bool),
	}
}

func (middleware *serverEventsMiddleware) Use(options MiddlewareOptions, muxer *http.ServeMux) {
	middleware.selectMethod(options.Path, func(w http.ResponseWriter, r *http.Request) {
		middleware.handleEventStream(w, r)
	}, muxer)
}

func (middleware *serverEventsMiddleware) handleEventStream(w http.ResponseWriter, r *http.Request) {
	emitter := di.Inject[IEventEmitter]()
	conn, err := middleware.upgrader.Upgrade(w, r, nil)
	if err != nil {
		fmt.Println("Error upgrading:", err)
		return
	}
	defer func() {
		// do not handle Error
		_ = conn.Close()
	}()
	id := r.URL.Query().Get("id")

	if _, ok := middleware.streamSubscribers[id]; !ok {
		subscription := emitter.OnAll(func(event Event) {
			if !event.IsBackendOnly {
				jsonData, jsonErr := json.Marshal(event)
				if jsonErr != nil {
					fmt.Println("Error make json string", jsonErr)
					return
				}
				_ = conn.WriteMessage(websocket.TextMessage, jsonData)
			}
		})
		defer func() {
			subscription.Unsubscribe()
			delete(middleware.streamSubscribers, id)
		}()
		middleware.streamSubscribers[id] = true
	}

	ctx := r.Context()
	for {
		_, _, err := conn.ReadMessage()
		if err != nil {
			return
		}
		select {
		case <-ctx.Done():
			return
		}
	}
}

func (middleware *serverEventsMiddleware) selectMethod(path string, todo http.HandlerFunc, muxer *http.ServeMux) {
	if muxer == nil {
		http.HandleFunc(path, todo)
	} else {
		muxer.HandleFunc(path, todo)
	}
}