Simple event observer in Golang

observer.go

// Copyright © 2017 Sebastian Döll <sebastian@katallaxie.me>
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

package observer

import "sync"
import "time"

// Observer holds channels to publish events to
type Observer struct {
	channels map[chan<- interface{}]struct{}
	sync.RWMutex
}

// New returns a new Observer
func New() *Observer {
	return &Observer{channels: make(map[chan<- interface{}]struct{})}
}

// Subscribe attaches a channel to an Observer
func (o *Observer) Subscribe(channel chan<- interface{}) {
	o.Lock()
	defer o.Unlock()

	o.channels[channel] = struct{}{}
}

// Unsubscribe dettaches a channel from an Observer
func (o *Observer) Unsubscribe(channel chan<- interface{}) error {
	o.Lock()
	defer o.Unlock()

	_, ok := o.channels[channel]
	if !ok {
		return &EventNotFound{}
	}

	delete(o.channels, channel)

	return nil
}

// Delete dettaches all the channels from the Observer
func (o *Observer) Delete(channel chan<- interface{}) error {
	o.Lock()
	defer o.Unlock()

	for channel := range o.channels {
		close(channel)
	}

	o.channels = make(map[chan<- interface{}]struct{})

	return nil
}

// Publish channels data to the attached channels
func (o *Observer) Publish(data interface{}) error {
	o.RLock()
	defer o.RUnlock()

	for channel := range o.channels {
		channel <- data
	}

	return nil
}

// PublishWithTimeout channels data to the attached channels with an timeout
func (o *Observer) PublishWithTimeout(data interface{}, timeout time.Duration) error {
	o.RLock()
	defer o.RUnlock()

	for channel := range o.channels {
		select {
		case channel <- data:
		case <-time.After(timeout):
		}
	}

	return nil
}