well-goknown/vendor/github.com/nbd-wtf/go-nostr/subscription.go

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package nostr
import (
"context"
"fmt"
"sync"
"sync/atomic"
)
type Subscription struct {
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counter int64
id string
Relay *Relay
Filters Filters
// for this to be treated as a COUNT and not a REQ this must be set
countResult chan int64
// the Events channel emits all EVENTs that come in a Subscription
// will be closed when the subscription ends
Events chan *Event
mu sync.Mutex
// the EndOfStoredEvents channel gets closed when an EOSE comes for that subscription
EndOfStoredEvents chan struct{}
// the ClosedReason channel emits the reason when a CLOSED message is received
ClosedReason chan string
// Context will be .Done() when the subscription ends
Context context.Context
match func(*Event) bool // this will be either Filters.Match or Filters.MatchIgnoringTimestampConstraints
live atomic.Bool
eosed atomic.Bool
closed atomic.Bool
cancel context.CancelFunc
// this keeps track of the events we've received before the EOSE that we must dispatch before
// closing the EndOfStoredEvents channel
storedwg sync.WaitGroup
}
type EventMessage struct {
Event Event
Relay string
}
// When instantiating relay connections, some options may be passed.
// SubscriptionOption is the type of the argument passed for that.
// Some examples are WithLabel.
type SubscriptionOption interface {
IsSubscriptionOption()
}
// WithLabel puts a label on the subscription (it is prepended to the automatic id) that is sent to relays.
type WithLabel string
func (_ WithLabel) IsSubscriptionOption() {}
var _ SubscriptionOption = (WithLabel)("")
func (sub *Subscription) start() {
<-sub.Context.Done()
// the subscription ends once the context is canceled (if not already)
sub.Unsub() // this will set sub.live to false
// do this so we don't have the possibility of closing the Events channel and then trying to send to it
sub.mu.Lock()
close(sub.Events)
sub.mu.Unlock()
}
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func (sub *Subscription) GetID() string { return sub.id }
func (sub *Subscription) dispatchEvent(evt *Event) {
added := false
if !sub.eosed.Load() {
sub.storedwg.Add(1)
added = true
}
go func() {
sub.mu.Lock()
defer sub.mu.Unlock()
if sub.live.Load() {
select {
case sub.Events <- evt:
case <-sub.Context.Done():
}
}
if added {
sub.storedwg.Done()
}
}()
}
func (sub *Subscription) dispatchEose() {
if sub.eosed.CompareAndSwap(false, true) {
sub.match = sub.Filters.MatchIgnoringTimestampConstraints
go func() {
sub.storedwg.Wait()
sub.EndOfStoredEvents <- struct{}{}
}()
}
}
func (sub *Subscription) dispatchClosed(reason string) {
if sub.closed.CompareAndSwap(false, true) {
go func() {
sub.ClosedReason <- reason
}()
}
}
// Unsub closes the subscription, sending "CLOSE" to relay as in NIP-01.
// Unsub() also closes the channel sub.Events and makes a new one.
func (sub *Subscription) Unsub() {
// cancel the context (if it's not canceled already)
sub.cancel()
// mark subscription as closed and send a CLOSE to the relay (naïve sync.Once implementation)
if sub.live.CompareAndSwap(true, false) {
sub.Close()
}
// remove subscription from our map
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sub.Relay.Subscriptions.Delete(sub.counter)
}
// Close just sends a CLOSE message. You probably want Unsub() instead.
func (sub *Subscription) Close() {
if sub.Relay.IsConnected() {
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closeMsg := CloseEnvelope(sub.id)
closeb, _ := (&closeMsg).MarshalJSON()
<-sub.Relay.Write(closeb)
}
}
// Sub sets sub.Filters and then calls sub.Fire(ctx).
// The subscription will be closed if the context expires.
func (sub *Subscription) Sub(_ context.Context, filters Filters) {
sub.Filters = filters
sub.Fire()
}
// Fire sends the "REQ" command to the relay.
func (sub *Subscription) Fire() error {
var reqb []byte
if sub.countResult == nil {
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reqb, _ = ReqEnvelope{sub.id, sub.Filters}.MarshalJSON()
} else {
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reqb, _ = CountEnvelope{sub.id, sub.Filters, nil}.MarshalJSON()
}
sub.live.Store(true)
if err := <-sub.Relay.Write(reqb); err != nil {
sub.cancel()
return fmt.Errorf("failed to write: %w", err)
}
return nil
}