package gateway

import (
	"encoding/json"
	"log/slog"
	"sync"
)

// Hub maintains the set of active clients and broadcasts messages to them.
type Hub struct {
	mu         sync.RWMutex
	clients    map[*Client]struct{}
	register   chan *Client
	unregister chan *Client
	broadcast  chan []byte
	logger     *slog.Logger
}

// NewHub creates a new Hub.
func NewHub(logger *slog.Logger) *Hub {
	return &Hub{
		clients:    make(map[*Client]struct{}),
		register:   make(chan *Client),
		unregister: make(chan *Client),
		broadcast:  make(chan []byte, 256),
		logger:     logger,
	}
}

// Run starts the hub's main event loop. Call this in a goroutine.
func (h *Hub) Run() {
	for {
		select {
		case client := <-h.register:
			h.mu.Lock()
			h.clients[client] = struct{}{}
			h.mu.Unlock()
			h.logger.Info("client connected", "user_id", client.UserID)

		case client := <-h.unregister:
			h.mu.Lock()
			if _, ok := h.clients[client]; ok {
				delete(h.clients, client)
				close(client.send)
			}
			h.mu.Unlock()
			h.logger.Info("client disconnected", "user_id", client.UserID)

		case message := <-h.broadcast:
			h.mu.RLock()
			for client := range h.clients {
				select {
				case client.send <- message:
				default:
					go func(c *Client) {
						h.unregister <- c
					}(client)
				}
			}
			h.mu.RUnlock()
		}
	}
}

// Register queues a client for registration with the hub.
func (h *Hub) Register(client *Client) {
	h.register <- client
}

// Unregister queues a client for removal from the hub.
func (h *Hub) Unregister(client *Client) {
	h.unregister <- client
}

// BroadcastEvent serializes an Event and broadcasts it to all connected clients.
func (h *Hub) BroadcastEvent(event Event) {
	data, err := json.Marshal(event)
	if err != nil {
		h.logger.Error("failed to marshal event", "type", event.Type, "error", err)
		return
	}
	h.broadcast <- data
}

// ClientCount returns the number of connected clients.
func (h *Hub) ClientCount() int {
	h.mu.RLock()
	defer h.mu.RUnlock()
	return len(h.clients)
}