package event

import "sync"

// Dispatcher 是进程内轻量事件总线（内存版）。
// 对于 request/reply 事件，Publish 会同步调用订阅者，
// 因此调用方可直接从 Reply 通道等待结果。
type Dispatcher struct {
	mu   sync.RWMutex
	subs map[string][]func(Event)
}

func NewDispatcher() *Dispatcher {
	return &Dispatcher{
		subs: make(map[string][]func(Event)),
	}
}

func (d *Dispatcher) Subscribe(eventType string, handler func(Event)) {
	if eventType == "" || handler == nil {
		return
	}
	d.mu.Lock()
	defer d.mu.Unlock()
	d.subs[eventType] = append(d.subs[eventType], handler)
}

func (d *Dispatcher) Publish(e Event) {
	if e == nil {
		return
	}
	eventType := e.Type()

	d.mu.RLock()
	handlers := append([]func(Event){}, d.subs[eventType]...)
	d.mu.RUnlock()

	for _, h := range handlers {
		h(e)
	}
}