sdk: actually no, let's store all relay urls together in the same kvdb key.

sdk/event_relays.go

@@ -0,0 +1,115 @@
+package sdk
+
+import (
+	"encoding/binary"
+	"encoding/hex"
+	"fmt"
+)
+
+const eventRelayPrefix = byte('r')
+
+func makeEventRelayKey(eventID []byte) []byte {
+	// format: 'r' + first 8 bytes of event ID
+	key := make([]byte, 9)
+	key[0] = eventRelayPrefix
+	copy(key[1:], eventID[:8])
+	return key
+}
+
+func encodeRelayList(relays []string) []byte {
+	totalSize := 0
+	for _, relay := range relays {
+		totalSize += 2 + len(relay) // 2 bytes for length prefix
+	}
+
+	buf := make([]byte, totalSize)
+	offset := 0
+
+	for _, relay := range relays {
+		binary.LittleEndian.PutUint16(buf[offset:], uint16(len(relay)))
+		offset += 2
+		copy(buf[offset:], relay)
+		offset += len(relay)
+	}
+
+	return buf
+}
+
+func decodeRelayList(data []byte) []string {
+	relays := make([]string, 0)
+	offset := 0
+
+	for offset < len(data) {
+		if offset+2 > len(data) {
+			return nil // malformed
+		}
+
+		length := int(binary.LittleEndian.Uint16(data[offset:]))
+		offset += 2
+
+		if offset+length > len(data) {
+			return nil // malformed
+		}
+
+		relay := string(data[offset : offset+length])
+		relays = append(relays, relay)
+		offset += length
+	}
+
+	return relays
+}
+
+func (sys *System) trackEventRelayCommon(eventID string, relay string) {
+	// decode the event ID hex into bytes
+	idBytes, err := hex.DecodeString(eventID)
+	if err != nil || len(idBytes) < 8 {
+		return
+	}
+
+	// get the key for this event
+	key := makeEventRelayKey(idBytes)
+
+	// update the relay list atomically
+	sys.KVStore.Update(key, func(data []byte) ([]byte, error) {
+		var relays []string
+		if data != nil {
+			relays = decodeRelayList(data)
+		} else {
+			relays = make([]string, 0, 1)
+		}
+
+		// check if relay is already in list
+		for _, r := range relays {
+			if r == relay {
+				return data, nil // no change needed
+			}
+		}
+
+		// append new relay
+		relays = append(relays, relay)
+		return encodeRelayList(relays), nil
+	})
+}
+
+// GetEventRelays returns all known relay URLs that have been seen to carry the given event.
+func (sys *System) GetEventRelays(eventID string) ([]string, error) {
+	// decode the event ID hex into bytes
+	idBytes, err := hex.DecodeString(eventID)
+	if err != nil || len(idBytes) < 8 {
+		return nil, fmt.Errorf("invalid event id")
+	}
+
+	// get the key for this event
+	key := makeEventRelayKey(idBytes)
+
+	// get stored relay list
+	data, err := sys.KVStore.Get(key)
+	if err != nil {
+		return nil, err
+	}
+	if data == nil {
+		return nil, nil
+	}
+
+	return decodeRelayList(data), nil
+}