156 lines
2.8 KiB
Go
156 lines
2.8 KiB
Go
package gubgub
|
|
|
|
import (
|
|
"context"
|
|
"fmt"
|
|
"sync"
|
|
)
|
|
|
|
// AsyncTopic allows any message T to be broadcast to subscribers. Publishing as well as
|
|
// subscribing happens asynchronously. Due to the nature of async processes this cannot guarantee
|
|
// message delivery nor delivery order.
|
|
type AsyncTopic[T any] struct {
|
|
options AsyncTopicOptions
|
|
|
|
mu sync.RWMutex
|
|
closed bool
|
|
|
|
publishCh chan T
|
|
subscribeCh chan Subscriber[T]
|
|
}
|
|
|
|
// NewAsyncTopic creates an AsyncTopic that will be closed when the given context is cancelled.
|
|
func NewAsyncTopic[T any](ctx context.Context, opts ...AsyncTopicOption) *AsyncTopic[T] {
|
|
options := AsyncTopicOptions{
|
|
onClose: func() {},
|
|
onSubscribe: func(count int) {},
|
|
}
|
|
|
|
for _, opt := range opts {
|
|
opt(&options)
|
|
}
|
|
|
|
t := AsyncTopic[T]{
|
|
options: options,
|
|
publishCh: make(chan T, 1),
|
|
subscribeCh: make(chan Subscriber[T]),
|
|
}
|
|
|
|
go t.run(ctx)
|
|
|
|
return &t
|
|
}
|
|
|
|
func (t *AsyncTopic[T]) run(ctx context.Context) {
|
|
defer t.close()
|
|
|
|
var subscribers []Subscriber[T]
|
|
|
|
for {
|
|
select {
|
|
case <-ctx.Done():
|
|
return
|
|
|
|
case newCallback := <-t.subscribeCh:
|
|
subscribers = append(subscribers, newCallback)
|
|
t.options.onSubscribe(len(subscribers))
|
|
|
|
case msg := <-t.publishCh:
|
|
keepers := make([]Subscriber[T], 0, len(subscribers))
|
|
|
|
for _, callback := range subscribers {
|
|
keep := callback(msg)
|
|
if keep {
|
|
keepers = append(keepers, callback)
|
|
}
|
|
}
|
|
|
|
subscribers = keepers
|
|
}
|
|
}
|
|
}
|
|
|
|
// Publish broadcasts a msg to all subscribers.
|
|
func (t *AsyncTopic[T]) Publish(msg T) error {
|
|
t.mu.RLock()
|
|
|
|
if t.closed {
|
|
t.mu.RUnlock()
|
|
return fmt.Errorf("async topic publish: %w", ErrTopicClosed)
|
|
}
|
|
|
|
go func() {
|
|
t.publishCh <- msg
|
|
t.mu.RUnlock()
|
|
}()
|
|
|
|
return nil
|
|
}
|
|
|
|
// Subscribe adds a Subscriber func that will consume future published messages.
|
|
func (t *AsyncTopic[T]) Subscribe(fn Subscriber[T]) error {
|
|
t.mu.RLock()
|
|
|
|
if t.closed {
|
|
t.mu.RUnlock()
|
|
return fmt.Errorf("async topic subscribe: %w", ErrTopicClosed)
|
|
}
|
|
|
|
go func() {
|
|
t.subscribeCh <- fn
|
|
t.mu.RUnlock()
|
|
}()
|
|
|
|
return nil
|
|
}
|
|
|
|
func (t *AsyncTopic[T]) close() {
|
|
var wg sync.WaitGroup
|
|
|
|
wg.Add(2)
|
|
|
|
go func() {
|
|
defer wg.Done()
|
|
for range t.publishCh {
|
|
// drain publishCh to release all read locks
|
|
}
|
|
}()
|
|
|
|
go func() {
|
|
defer wg.Done()
|
|
for range t.subscribeCh {
|
|
// drain subscribeCh to release all read locks
|
|
}
|
|
}()
|
|
|
|
t.mu.Lock()
|
|
t.closed = true // no more subscribing or publishing
|
|
t.mu.Unlock()
|
|
|
|
close(t.publishCh)
|
|
close(t.subscribeCh)
|
|
|
|
wg.Wait()
|
|
|
|
t.options.onClose()
|
|
}
|
|
|
|
type AsyncTopicOptions struct {
|
|
onClose func()
|
|
onSubscribe func(count int)
|
|
}
|
|
|
|
type AsyncTopicOption func(*AsyncTopicOptions)
|
|
|
|
func WithOnClose(fn func()) AsyncTopicOption {
|
|
return func(opts *AsyncTopicOptions) {
|
|
opts.onClose = fn
|
|
}
|
|
}
|
|
|
|
func WithOnSubscribe(fn func(count int)) AsyncTopicOption {
|
|
return func(opts *AsyncTopicOptions) {
|
|
opts.onSubscribe = fn
|
|
}
|
|
}
|