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|
package nostr
import (
"context"
"fmt"
"sync"
"github.com/coder/websocket"
)
// Relay represents a connection to a Nostr relay.
type Relay struct {
URL string
conn *websocket.Conn
mu sync.Mutex
subscriptions map[string]*Subscription
subscriptionsMu sync.RWMutex
}
// Connect establishes a WebSocket connection to the relay.
func Connect(ctx context.Context, url string) (*Relay, error) {
conn, _, err := websocket.Dial(ctx, url, nil)
if err != nil {
return nil, fmt.Errorf("failed to connect to relay: %w", err)
}
return &Relay{
URL: url,
conn: conn,
subscriptions: make(map[string]*Subscription),
}, nil
}
// Close closes the WebSocket connection.
func (r *Relay) Close() error {
r.mu.Lock()
defer r.mu.Unlock()
if r.conn == nil {
return nil
}
err := r.conn.Close(websocket.StatusNormalClosure, "")
r.conn = nil
return err
}
// Send sends an envelope to the relay.
func (r *Relay) Send(ctx context.Context, env Envelope) error {
data, err := env.MarshalJSON()
if err != nil {
return fmt.Errorf("failed to marshal envelope: %w", err)
}
r.mu.Lock()
defer r.mu.Unlock()
if r.conn == nil {
return fmt.Errorf("connection closed")
}
return r.conn.Write(ctx, websocket.MessageText, data)
}
// Receive reads the next envelope from the relay.
func (r *Relay) Receive(ctx context.Context) (Envelope, error) {
r.mu.Lock()
conn := r.conn
r.mu.Unlock()
if conn == nil {
return nil, fmt.Errorf("connection closed")
}
_, data, err := conn.Read(ctx)
if err != nil {
return nil, fmt.Errorf("failed to read message: %w", err)
}
return ParseEnvelope(data)
}
// Publish sends an event to the relay and waits for the OK response.
func (r *Relay) Publish(ctx context.Context, event *Event) error {
env := EventEnvelope{Event: event}
if err := r.Send(ctx, env); err != nil {
return fmt.Errorf("failed to send event: %w", err)
}
// Wait for OK response
for {
resp, err := r.Receive(ctx)
if err != nil {
return fmt.Errorf("failed to receive response: %w", err)
}
if ok, isOK := resp.(*OKEnvelope); isOK {
if ok.EventID == event.ID {
if !ok.OK {
return fmt.Errorf("event rejected: %s", ok.Message)
}
return nil
}
}
// Dispatch other messages to subscriptions
r.dispatchEnvelope(resp)
}
}
// Subscribe creates a subscription with the given filters.
func (r *Relay) Subscribe(ctx context.Context, id string, filters ...Filter) (*Subscription, error) {
sub := &Subscription{
ID: id,
relay: r,
Filters: filters,
Events: make(chan *Event, 100),
EOSE: make(chan struct{}, 1),
closed: make(chan struct{}),
}
r.subscriptionsMu.Lock()
r.subscriptions[id] = sub
r.subscriptionsMu.Unlock()
env := ReqEnvelope{
SubscriptionID: id,
Filters: filters,
}
if err := r.Send(ctx, env); err != nil {
r.subscriptionsMu.Lock()
delete(r.subscriptions, id)
r.subscriptionsMu.Unlock()
return nil, fmt.Errorf("failed to send subscription request: %w", err)
}
return sub, nil
}
// dispatchEnvelope routes incoming messages to the appropriate subscription.
func (r *Relay) dispatchEnvelope(env Envelope) {
switch e := env.(type) {
case *EventEnvelope:
r.subscriptionsMu.RLock()
sub, ok := r.subscriptions[e.SubscriptionID]
r.subscriptionsMu.RUnlock()
if ok {
select {
case sub.Events <- e.Event:
default:
// Channel full, drop event
}
}
case *EOSEEnvelope:
r.subscriptionsMu.RLock()
sub, ok := r.subscriptions[e.SubscriptionID]
r.subscriptionsMu.RUnlock()
if ok {
select {
case sub.EOSE <- struct{}{}:
default:
}
}
case *ClosedEnvelope:
r.subscriptionsMu.Lock()
if sub, ok := r.subscriptions[e.SubscriptionID]; ok {
close(sub.closed)
delete(r.subscriptions, e.SubscriptionID)
}
r.subscriptionsMu.Unlock()
}
}
// Listen reads messages from the relay and dispatches them to subscriptions.
// This should be called in a goroutine when using multiple subscriptions.
func (r *Relay) Listen(ctx context.Context) error {
for {
select {
case <-ctx.Done():
return ctx.Err()
default:
}
env, err := r.Receive(ctx)
if err != nil {
return err
}
r.dispatchEnvelope(env)
}
}
// Subscription represents an active subscription to a relay.
type Subscription struct {
ID string
relay *Relay
Filters []Filter
Events chan *Event
EOSE chan struct{}
closed chan struct{}
}
// Close unsubscribes from the relay.
func (s *Subscription) Close(ctx context.Context) error {
s.relay.subscriptionsMu.Lock()
delete(s.relay.subscriptions, s.ID)
s.relay.subscriptionsMu.Unlock()
env := CloseEnvelope{SubscriptionID: s.ID}
return s.relay.Send(ctx, env)
}
// Closed returns a channel that's closed when the subscription is terminated.
func (s *Subscription) Closed() <-chan struct{} {
return s.closed
}
|
