nip77: FetchIDsOnly()

nip77/idsonly.go

@@ -0,0 +1,70 @@
+package nip77
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/nbd-wtf/go-nostr"
+	"github.com/nbd-wtf/go-nostr/nip77/negentropy"
+	"github.com/nbd-wtf/go-nostr/nip77/negentropy/storage/empty"
+)
+
+func FetchIDsOnly(
+	ctx context.Context,
+	url string,
+	filter nostr.Filter,
+) (<-chan string, error) {
+	id := "go-nostr-tmp" // for now we can't have more than one subscription in the same connection
+
+	neg := negentropy.New(empty.Empty{}, 1024*1024)
+	result := make(chan error)
+
+	var r *nostr.Relay
+	r, err := nostr.RelayConnect(ctx, url, nostr.WithCustomHandler(func(data []byte) {
+		envelope := ParseNegMessage(data)
+		if envelope == nil {
+			return
+		}
+		switch env := envelope.(type) {
+		case *OpenEnvelope, *CloseEnvelope:
+			result <- fmt.Errorf("unexpected %s received from relay", env.Label())
+			return
+		case *ErrorEnvelope:
+			result <- fmt.Errorf("relay returned a %s: %s", env.Label(), env.Reason)
+			return
+		case *MessageEnvelope:
+			nextmsg, err := neg.Reconcile(env.Message)
+			if err != nil {
+				result <- fmt.Errorf("failed to reconcile: %w", err)
+				return
+			}
+
+			if nextmsg != "" {
+				msgb, _ := MessageEnvelope{id, nextmsg}.MarshalJSON()
+				r.Write(msgb)
+			}
+		}
+	}))
+	if err != nil {
+		return nil, err
+	}
+
+	msg := neg.Start()
+	open, _ := OpenEnvelope{id, filter, msg}.MarshalJSON()
+	err = <-r.Write(open)
+	if err != nil {
+		return nil, fmt.Errorf("failed to write to relay: %w", err)
+	}
+
+	ch := make(chan string)
+	go func() {
+		for id := range neg.HaveNots {
+			ch <- id
+		}
+		clse, _ := CloseEnvelope{id}.MarshalJSON()
+		r.Write(clse)
+		close(ch)
+	}()
+
+	return ch, nil
+}