// Copyright 2013-2014 Fuzamei tech Ltd. All rights reserved.

package event

import (
	"math/rand"
	"sync"
	"time"
)

func init() {
	rand.Seed(time.Now().UnixNano())
}

type EventHandler func(v interface{}) error

type Event struct {
	sync.RWMutex
	handlers map[int64]EventHandler
}

func (e *Event) Attach(handler EventHandler) int64 {
	e.Lock()
	defer e.Unlock()
	for {
		n := rand.Int63()
		_, ok := e.handlers[n]
		if !ok {
			e.handlers[n] = handler
			return n
		}
	}
}

func (e *Event) Detach(handle int64) {
	e.Lock()
	delete(e.handlers, handle)
	e.Unlock()
}

func (e *Event) DetachAll() {
	e.Lock()
	e.handlers = nil
	e.Unlock()
}

func (e *Event) publish(v interface{}) {
	e.Lock()
	for k, h := range e.handlers {
		// if call e.Lock() in h(v), should deadlock,
		// so must Unlock, and then Lock
		e.Unlock()
		if h(v) != nil {
			e.Detach(k)
		}
		e.Lock()
	}
	e.Unlock()
}

type EventPublisher struct {
	event Event
}

func (p *EventPublisher) Event() *Event {
	if p.event.handlers == nil {
		p.event.handlers = make(map[int64]EventHandler)
	}
	return &p.event
}

func (p *EventPublisher) Publish(v interface{}) {
	p.event.publish(v)
}