package realtime

import (
	"encoding/json"
	"sync"
)

type Event struct {
	Topic string          `json:"topic"`
	Data  json.RawMessage `json:"data"`
}

type Hub struct {
	mu   sync.RWMutex
	subs map[string]map[chan Event]struct{}
}

func New() *Hub { return &Hub{subs: make(map[string]map[chan Event]struct{})} }

func (h *Hub) Publish(topic string, value any) {
	data, err := json.Marshal(value)
	if err != nil {
		return
	}
	h.mu.RLock()
	defer h.mu.RUnlock()
	for _, key := range []string{"*", topic} {
		for ch := range h.subs[key] {
			select {
			case ch <- Event{Topic: topic, Data: data}:
			default:
			}
		}
	}
}

func (h *Hub) Subscribe(topic string) (<-chan Event, func()) {
	ch := make(chan Event, 16)
	h.mu.Lock()
	if h.subs[topic] == nil {
		h.subs[topic] = make(map[chan Event]struct{})
	}
	h.subs[topic][ch] = struct{}{}
	h.mu.Unlock()
	return ch, func() {
		h.mu.Lock()
		delete(h.subs[topic], ch)
		close(ch)
		h.mu.Unlock()
	}
}