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nats.go
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nats.go
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package event
import (
"bytes"
"encoding/gob"
"github.com/nats-io/go-nats"
"github.com/tinrab/meower/schema"
)
type NatsEventStore struct {
nc *nats.Conn
meowCreatedSubscription *nats.Subscription
meowCreatedChan chan MeowCreatedMessage
}
func NewNats(url string) (*NatsEventStore, error) {
nc, err := nats.Connect(url)
if err != nil {
return nil, err
}
return &NatsEventStore{nc: nc}, nil
}
func (e *NatsEventStore) SubscribeMeowCreated() (<-chan MeowCreatedMessage, error) {
m := MeowCreatedMessage{}
e.meowCreatedChan = make(chan MeowCreatedMessage, 64)
ch := make(chan *nats.Msg, 64)
var err error
e.meowCreatedSubscription, err = e.nc.ChanSubscribe(m.Key(), ch)
if err != nil {
return nil, err
}
// Decode message
go func() {
for {
select {
case msg := <-ch:
e.readMessage(msg.Data, &m)
e.meowCreatedChan <- m
}
}
}()
return (<-chan MeowCreatedMessage)(e.meowCreatedChan), nil
}
func (e *NatsEventStore) OnMeowCreated(f func(MeowCreatedMessage)) (err error) {
m := MeowCreatedMessage{}
e.meowCreatedSubscription, err = e.nc.Subscribe(m.Key(), func(msg *nats.Msg) {
e.readMessage(msg.Data, &m)
f(m)
})
return
}
func (e *NatsEventStore) Close() {
if e.nc != nil {
e.nc.Close()
}
if e.meowCreatedSubscription != nil {
e.meowCreatedSubscription.Unsubscribe()
}
close(e.meowCreatedChan)
}
func (e *NatsEventStore) PublishMeowCreated(meow schema.Meow) error {
m := MeowCreatedMessage{meow.ID, meow.Body, meow.CreatedAt}
data, err := e.writeMessage(&m)
if err != nil {
return err
}
return e.nc.Publish(m.Key(), data)
}
func (mq *NatsEventStore) writeMessage(m Message) ([]byte, error) {
b := bytes.Buffer{}
err := gob.NewEncoder(&b).Encode(m)
if err != nil {
return nil, err
}
return b.Bytes(), nil
}
func (mq *NatsEventStore) readMessage(data []byte, m interface{}) error {
b := bytes.Buffer{}
b.Write(data)
return gob.NewDecoder(&b).Decode(m)
}