package handlers

import (
	"encoding/json"
	"log/slog"
	"net/http"
	"sync"

	"github.com/gorilla/websocket"
	"golang.org/x/time/rate"

	"gogs.fxtmmsk.ru/foxtime/photoplaces/backend/internal/middleware"
)

type VisitorDot struct {
	UserID string  `json:"user_id,omitempty"`
	Lat    float64 `json:"lat"`
	Lng    float64 `json:"lng"`
}

type visitorsPayload struct {
	Visitors []VisitorDot `json:"visitors"`
}

const maxWSConnections = 1000

type WSHub struct {
	mu             sync.Mutex
	clients        map[*Client]bool
	register       chan *Client
	unregister     chan *Client
	broadcast      chan []byte
	allowedOrigins []string
	isProd         bool
	connLimiter    *rate.Limiter
}

func NewWSHub(allowedOrigins []string, isProd bool) *WSHub {
	return &WSHub{
		clients:        make(map[*Client]bool),
		register:       make(chan *Client),
		unregister:     make(chan *Client),
		broadcast:      make(chan []byte, 256),
		allowedOrigins: allowedOrigins,
		isProd:         isProd,
		connLimiter:    rate.NewLimiter(maxWSConnections, maxWSConnections),
	}
}

func (h *WSHub) Run() {
	for {
		select {
		case client := <-h.register:
			h.mu.Lock()
			if len(h.clients) >= maxWSConnections {
				h.mu.Unlock()
				slog.Warn("ws max connections reached, rejecting")
				client.conn.Close()
				continue
			}
			h.clients[client] = true
			h.mu.Unlock()
			h.broadcastVisitors()

		case client := <-h.unregister:
			h.mu.Lock()
			if _, ok := h.clients[client]; ok {
				delete(h.clients, client)
				h.mu.Unlock()
				close(client.send)
				h.broadcastVisitors()
			} else {
				h.mu.Unlock()
			}

		case message := <-h.broadcast:
			h.mu.Lock()
			for client := range h.clients {
				select {
				case client.send <- message:
				default:
					close(client.send)
					delete(h.clients, client)
				}
			}
			h.mu.Unlock()
		}
	}
}

func (h *WSHub) broadcastVisitors() {
	h.mu.Lock()
	visitors := make([]VisitorDot, 0, len(h.clients))
	clients := make([]*Client, 0, len(h.clients))
	for c := range h.clients {
		visitors = append(visitors, VisitorDot{
			UserID: c.userID,
			Lat:    c.lat,
			Lng:    c.lng,
		})
		clients = append(clients, c)
	}
	h.mu.Unlock()

	data, err := json.Marshal(visitorsPayload{Visitors: visitors})
	if err != nil {
		return
	}
	msg, err := json.Marshal(wsMessage{Type: "visitors", Data: data})
	if err != nil {
		return
	}

	for _, client := range clients {
		select {
		case client.send <- msg:
		default:
			h.mu.Lock()
			close(client.send)
			delete(h.clients, client)
			h.mu.Unlock()
		}
	}
}

func (h *WSHub) HandleWS(w http.ResponseWriter, r *http.Request) {
	upgrader := websocket.Upgrader{
		CheckOrigin: func(r *http.Request) bool {
			if len(h.allowedOrigins) == 0 {
				return !h.isProd
			}
			origin := r.Header.Get("Origin")
			for _, o := range h.allowedOrigins {
				if o == origin {
					return true
				}
			}
			return false
		},
	}

	conn, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		slog.Error("ws upgrade failed", "error", err)
		return
	}

	client := newClient(h, conn)

	userID := middleware.GetUserID(r.Context())
	if userID != "" {
		client.userID = userID
	}

	if !h.connLimiter.Allow() {
		slog.Warn("ws connection rate limit exceeded")
		conn.Close()
		return
	}

	h.register <- client

	go client.writePump()
	go client.readPump()
}