package main

import (
	"context"
	"sync"

	"github.com/coder/websocket"
)

type hub struct {
	mu    sync.Mutex
	conns map[string]map[*websocket.Conn]struct{}
}

func newHub() *hub {
	return &hub{conns: make(map[string]map[*websocket.Conn]struct{})}
}

func (h *hub) add(listID string, c *websocket.Conn) {
	h.mu.Lock()
	defer h.mu.Unlock()
	if h.conns[listID] == nil {
		h.conns[listID] = make(map[*websocket.Conn]struct{})
	}
	h.conns[listID][c] = struct{}{}
}

func (h *hub) remove(listID string, c *websocket.Conn) {
	h.mu.Lock()
	defer h.mu.Unlock()
	delete(h.conns[listID], c)
	if len(h.conns[listID]) == 0 {
		delete(h.conns, listID)
	}
}

func (h *hub) broadcast(listID string) {
	h.mu.Lock()
	conns := make([]*websocket.Conn, 0, len(h.conns[listID]))
	for c := range h.conns[listID] {
		conns = append(conns, c)
	}
	h.mu.Unlock()

	for _, c := range conns {
		go c.Write(context.Background(), websocket.MessageText, []byte("changed"))
	}
}