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ntfy/server/topic.go
2021-12-08 22:57:31 -05:00

63 lines
1.3 KiB
Go

package server
import (
"log"
"math/rand"
"sync"
)
// topic represents a channel to which subscribers can subscribe, and publishers
// can publish a message
type topic struct {
ID string
subscribers map[int]subscriber
mu sync.Mutex
}
// subscriber is a function that is called for every new message on a topic
type subscriber func(msg *message) error
// newTopic creates a new topic
func newTopic(id string) *topic {
return &topic{
ID: id,
subscribers: make(map[int]subscriber),
}
}
// Subscribe subscribes to this topic
func (t *topic) Subscribe(s subscriber) int {
t.mu.Lock()
defer t.mu.Unlock()
subscriberID := rand.Int()
t.subscribers[subscriberID] = s
return subscriberID
}
// Unsubscribe removes the subscription from the list of subscribers
func (t *topic) Unsubscribe(id int) {
t.mu.Lock()
defer t.mu.Unlock()
delete(t.subscribers, id)
}
// Publish asynchronously publishes to all subscribers
func (t *topic) Publish(m *message) error {
go func() {
t.mu.Lock()
defer t.mu.Unlock()
for _, s := range t.subscribers {
if err := s(m); err != nil {
log.Printf("error publishing message to subscriber")
}
}
}()
return nil
}
// Subscribers returns the number of subscribers to this topic
func (t *topic) Subscribers() int {
t.mu.Lock()
defer t.mu.Unlock()
return len(t.subscribers)
}