package hub

import (
	"net/http"
	"sync"

	"github.com/gorilla/websocket"
	"websocket-relay/internal/logging"
	"websocket-relay/internal/metrics"
)

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

type Hub struct {
	clients    map[*websocket.Conn]bool
	broadcast  chan []byte
	register   chan *websocket.Conn
	unregister chan *websocket.Conn
	stop       chan struct{}
	mu         sync.RWMutex
	logger     *logging.Logger
}

func New(logger *logging.Logger) *Hub {
	return &Hub{
		clients:    make(map[*websocket.Conn]bool),
		broadcast:  make(chan []byte),
		register:   make(chan *websocket.Conn),
		unregister: make(chan *websocket.Conn),
		stop:       make(chan struct{}),
		logger:     logger,
	}
}

func (h *Hub) Run() {
	for {
		select {
		case <-h.stop:
			h.mu.Lock()
			for conn := range h.clients {
				conn.WriteMessage(websocket.CloseMessage,
					websocket.FormatCloseMessage(websocket.CloseGoingAway, "server shutting down"))
				conn.Close()
				delete(h.clients, conn)
			}
			h.mu.Unlock()
			metrics.ConnectedClients.Set(0)
			h.logger.Info("Hub stopped, all clients disconnected")
			return

		case conn := <-h.register:
			h.mu.Lock()
			h.clients[conn] = true
			h.mu.Unlock()
			metrics.ConnectedClients.Set(float64(len(h.clients)))
			metrics.ConnectionsTotal.Inc()
			h.logger.Infof("Client connected. Total: %d", len(h.clients))

		case conn := <-h.unregister:
			h.mu.Lock()
			if _, ok := h.clients[conn]; ok {
				delete(h.clients, conn)
				conn.Close()
			}
			h.mu.Unlock()
			metrics.ConnectedClients.Set(float64(len(h.clients)))
			metrics.DisconnectionsTotal.Inc()
			h.logger.Infof("Client disconnected. Total: %d", len(h.clients))

		case message := <-h.broadcast:
			metrics.MessagesTotal.Inc()
			h.mu.RLock()
			var failed []*websocket.Conn
			for conn := range h.clients {
				if err := conn.WriteMessage(websocket.TextMessage, message); err != nil {
					failed = append(failed, conn)
				}
			}
			h.mu.RUnlock()

			// Remove failed clients properly so metrics stay consistent
			for _, conn := range failed {
				h.mu.Lock()
				if _, ok := h.clients[conn]; ok {
					delete(h.clients, conn)
					conn.Close()
					metrics.ConnectedClients.Set(float64(len(h.clients)))
					metrics.DisconnectionsTotal.Inc()
					h.logger.Warnf("Client disconnected (write error). Total: %d", len(h.clients))
				}
				h.mu.Unlock()
			}
		}
	}
}

// Shutdown gracefully stops the hub, closing all client connections.
func (h *Hub) Shutdown() {
	close(h.stop)
}

func (h *Hub) HandleWebSocket(w http.ResponseWriter, r *http.Request) {
	conn, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		h.logger.Errorf("WebSocket upgrade error: %v", err)
		return
	}

	h.register <- conn

	go func() {
		defer func() {
			h.unregister <- conn
		}()

		for {
			_, message, err := conn.ReadMessage()
			if err != nil {
				break
			}
			h.broadcast <- message
		}
	}()
}

func (h *Hub) ClientCount() int {
	h.mu.RLock()
	defer h.mu.RUnlock()
	return len(h.clients)
}