79 lines
1.6 KiB
Go
79 lines
1.6 KiB
Go
package server
|
|
|
|
import (
|
|
"context"
|
|
"errors"
|
|
"log"
|
|
"math/rand"
|
|
"sync"
|
|
"time"
|
|
)
|
|
|
|
// topic represents a channel to which subscribers can subscribe, and publishers
|
|
// can publish a message
|
|
type topic struct {
|
|
id string
|
|
subscribers map[int]subscriber
|
|
messages int
|
|
last time.Time
|
|
ctx context.Context
|
|
cancel context.CancelFunc
|
|
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 {
|
|
ctx, cancel := context.WithCancel(context.Background())
|
|
return &topic{
|
|
id: id,
|
|
subscribers: make(map[int]subscriber),
|
|
last: time.Now(),
|
|
ctx: ctx,
|
|
cancel: cancel,
|
|
}
|
|
}
|
|
|
|
func (t *topic) Subscribe(s subscriber) int {
|
|
t.mu.Lock()
|
|
defer t.mu.Unlock()
|
|
subscriberID := rand.Int()
|
|
t.subscribers[subscriberID] = s
|
|
t.last = time.Now()
|
|
return subscriberID
|
|
}
|
|
|
|
func (t *topic) Unsubscribe(id int) int {
|
|
t.mu.Lock()
|
|
defer t.mu.Unlock()
|
|
delete(t.subscribers, id)
|
|
return len(t.subscribers)
|
|
}
|
|
|
|
func (t *topic) Publish(m *message) error {
|
|
t.mu.Lock()
|
|
defer t.mu.Unlock()
|
|
if len(t.subscribers) == 0 {
|
|
return errors.New("no subscribers")
|
|
}
|
|
t.last = time.Now()
|
|
t.messages++
|
|
for _, s := range t.subscribers {
|
|
if err := s(m); err != nil {
|
|
log.Printf("error publishing message to subscriber")
|
|
}
|
|
}
|
|
return nil
|
|
}
|
|
|
|
func (t *topic) Stats() (subscribers int, messages int) {
|
|
t.mu.Lock()
|
|
defer t.mu.Unlock()
|
|
return len(t.subscribers), t.messages
|
|
}
|
|
|
|
func (t *topic) Close() {
|
|
t.cancel()
|
|
}
|