package internal

import (
	"fmt"
	"sync"

	"github.com/gorilla/websocket"
)

// Client represents a connected user WebSocket connection.
type Client struct {
	UID  string
	Conn *websocket.Conn
}

// Hub manages connected clients and their WebSocket connections.
type Hub struct {
	mu      sync.RWMutex
	clients map[string]*Client // uid -> client
}

// NewHub creates a new Hub.
func NewHub() *Hub {
	return &Hub{clients: make(map[string]*Client)}
}

// Register adds a client connection.
func (h *Hub) Register(uid string, conn *websocket.Conn) {
	h.mu.Lock()
	defer h.mu.Unlock()
	// Close existing connection if any
	if old, ok := h.clients[uid]; ok {
		old.Conn.Close()
	}
	h.clients[uid] = &Client{UID: uid, Conn: conn}
}

// Unregister removes a client connection.
func (h *Hub) Unregister(uid string) {
	h.mu.Lock()
	defer h.mu.Unlock()
	delete(h.clients, uid)
}

// GetClient returns a client by uid.
func (h *Hub) GetClient(uid string) *Client {
	h.mu.RLock()
	defer h.mu.RUnlock()
	return h.clients[uid]
}

// PushToClient sends a JSON message to a specific client.
// Returns an error if the client is not connected.
func (h *Hub) PushToClient(uid string, msg []byte) error {
	client := h.GetClient(uid)
	if client == nil {
		return fmt.Errorf("client %s not connected", uid)
	}
	return client.Conn.WriteMessage(websocket.TextMessage, msg)
}