events.go

package webx

import (
	"sync"
)

var Events *EventsInstance = NewEvents()

func NewEvents() *EventsInstance {
	return &EventsInstance{
		listeners: make(map[string][]func(interface{}, func(bool))),
		lock:      new(sync.RWMutex),
	}
}

//并发执行事件
func GoEvent(eventName string, session interface{}, next func(bool)) {
	Events.GoExecute(eventName, session, next)
}

//顺序执行事件
func Event(eventName string, session interface{}, next func(bool)) {
	Events.Execute(eventName, session, next)
}

//删除事件
func DelEvent(eventName string) {
	Events.Delete(eventName)
}

//添加事件
func AddEvent(eventName string, handler func(interface{}, func(bool))) {
	Events.Register(eventName, handler)
}

type EventsInstance struct {
	listeners map[string][]func(interface{}, func(bool))
	lock      *sync.RWMutex
}

/*
注册事件
[Examle:]
Events.Register("AfterResponse", func(session interface{}, next func(bool)) {
	log.Println("Got AfterResponse event!")
	isSuccess := true
	next(isSuccess) //这里的next函数无论什么情况下必须执行。
})

采用不同的方式执行事件时，此处的next函数的作用也是不同的：
1、在并发执行事件的时候，next函数的作用是通知程序我已经执行完了(不理会这一步是否执行成功)；
2、在顺序执行事件的时候，next函数的作用是通知程序是否继续执行下一步，next(true)是继续执行下一步，next(false)是终止执行下一步
*/
func (e *EventsInstance) Register(eventName string, handler func(interface{}, func(bool))) {
	e.lock.Lock()
	defer e.lock.Unlock()
	if e.listeners == nil {
		e.listeners = make(map[string][]func(interface{}, func(bool)))
	}
	_, ok := e.listeners[eventName]
	if !ok {
		e.listeners[eventName] = make([]func(interface{}, func(bool)), 0)
	}
	e.listeners[eventName] = append(e.listeners[eventName], handler)
}

func (e *EventsInstance) Delete(eventName string) {
	e.lock.Lock()
	defer e.lock.Unlock()
	if e.listeners == nil {
		return
	}
	_, ok := e.listeners[eventName]
	if ok {
		delete(e.listeners, eventName)
	}
}

/*
并发执行事件
[Examle 1:]
Events.GoExecute("AfterHandler", session, func(_ bool) {//此匿名函数在本事件的最后执行
	session.Response.Send()
	session.Response.Close()
})

[Examle 2:]
Events.Execute("AfterResponse", session, func(_ bool) {})
*/
func (e *EventsInstance) GoExecute(eventName string, session interface{}, next func(bool)) {
	if e.listeners == nil {
		next(true)
		return
	}
	c := make(chan int)
	n := 0
	e.lock.RLock()
	defer e.lock.RUnlock()
	if l, ok := e.listeners[eventName]; ok {
		if len(l) > 0 {
			for _, h := range l {
				n++
				//h 的原型为 func(interface{}, func(bool))
				go h(session, func(_ bool) {
					c <- 1
				})
			}
		}
	}
	for n > 0 {
		i := <-c
		if i == 1 {
			n--
		}
	}
	next(true)
}

/**
 * 顺序执行事件
 */
func (e *EventsInstance) Execute(eventName string, session interface{}, next func(bool)) {
	if e.listeners == nil {
		next(true)
		return
	}
	e.lock.RLock()
	defer e.lock.RUnlock()
	var nextStep bool = false
	if l, ok := e.listeners[eventName]; ok {
		if len(l) > 0 {
			for _, h := range l {
				h(session, func(ok bool) {
					nextStep = ok
				})
				//一旦传入false，后面的全部忽略执行
				if !nextStep {
					break
				}
			}
		} else {
			nextStep = true
		}
	} else {
		nextStep = true
	}
	next(nextStep)
}