package handlers

import (
	"sync"
)

type Broker struct {
	mu   sync.Mutex
	subs map[string]map[chan struct{}]struct{} // key = path, val = set of channels
}

func NewBroker() *Broker {
	return &Broker{subs: make(map[string]map[chan struct{}]struct{})}
}

func (b *Broker) Subscribe(path string) chan struct{} {
	ch := make(chan struct{}, 1)
	b.mu.Lock()
	defer b.mu.Unlock()
	if b.subs[path] == nil {
		b.subs[path] = make(map[chan struct{}]struct{})
	}
	b.subs[path][ch] = struct{}{}
	return ch
}

func (b *Broker) Unsubscribe(path string, ch chan struct{}) {
	b.mu.Lock()
	defer b.mu.Unlock()
	if set, ok := b.subs[path]; ok {
		delete(set, ch)
		if len(set) == 0 {
			delete(b.subs, path)
		}
	}
	close(ch)
}

func (b *Broker) Publish(path string) {
	b.mu.Lock()
	defer b.mu.Unlock()
	for ch := range b.subs[path] {
		select {
		case ch <- struct{}{}:
		default:
		}
	}
}