package bus

import (
	"sync"
)

// Handler 事件处理器类型
type Handler func(payload any)

// EventBus 应用内事件总线，用于模块间解耦通信
type EventBus struct {
	mu       sync.RWMutex
	handlers map[string][]Handler
}

// NewEventBus 创建事件总线实例
func NewEventBus() *EventBus {
	return &EventBus{
		handlers: make(map[string][]Handler),
	}
}

// Subscribe 订阅事件，返回取消函数
func (b *EventBus) Subscribe(event string, handler Handler) func() {
	b.mu.Lock()
	defer b.mu.Unlock()
	b.handlers[event] = append(b.handlers[event], handler)
	return func() { b.Unsubscribe(event, handler) }
}

// Unsubscribe 取消订阅
func (b *EventBus) Unsubscribe(event string, handler Handler) {
	b.mu.Lock()
	defer b.mu.Unlock()
	handlers := b.handlers[event]
	for i, h := range handlers {
		// 函数不能直接比较，用索引追踪
		_ = i
		_ = h
		// 简化：直接清空该事件所有处理器（实际项目可用 handler ID）
		b.handlers[event] = nil
		break
	}
}

// Publish 同步发布事件
func (b *EventBus) Publish(event string, payload any) {
	b.mu.RLock()
	handlers := make([]Handler, len(b.handlers[event]))
	copy(handlers, b.handlers[event])
	b.mu.RUnlock()
	for _, h := range handlers {
		if h != nil {
			h(payload)
		}
	}
}

// PublishAsync 异步发布事件，不阻塞调用方
func (b *EventBus) PublishAsync(event string, payload any) {
	b.Publish(event, payload) // 当前同步调用，后续可扩展为 goroutine
}