feat(c-bindings): list pubsub topics

library/README.md

@@ -847,6 +847,24 @@ For example:
 }
 ```
 
+### `extern char* waku_relay_topics()`
+
+Get the list of subscribed pubsub topics in Waku Relay.
+
+**Returns**
+
+A [`JsonResponse`](#jsonresponse-type).
+If the execution is successful, the `result` field will contain an array of pubsub topics.
+
+For example:
+
+```json
+{
+  "result": ["pubsubTopic1", "pubsubTopic2"]
+}
+```
+
+
 **Events**
 
 When a message is received, a ``"message"` event` is emitted containing the message, pubsub topic, and node ID in which

library/api_relay.go

@@ -6,57 +6,72 @@ import (
 	mobile "github.com/waku-org/go-waku/mobile"
 )
 
-//export waku_relay_enough_peers
 // Determine if there are enough peers to publish a message on a topic. Use NULL
 // to verify the number of peers in the default pubsub topic
+//
+//export waku_relay_enough_peers
 func waku_relay_enough_peers(topic *C.char) *C.char {
 	response := mobile.RelayEnoughPeers(C.GoString(topic))
 	return C.CString(response)
 }
 
-//export waku_relay_publish
 // Publish a message using waku relay and returns the message ID. Use NULL for topic to use the default pubsub topic
 // If ms is greater than 0, the broadcast of the message must happen before the timeout
 // (in milliseconds) is reached, or an error will be returned.
+//
+//export waku_relay_publish
 func waku_relay_publish(messageJSON *C.char, topic *C.char, ms C.int) *C.char {
 	response := mobile.RelayPublish(C.GoString(messageJSON), C.GoString(topic), int(ms))
 	return C.CString(response)
 }
 
-//export waku_relay_publish_enc_asymmetric
 // Publish a message encrypted with a secp256k1 public key using waku relay  and returns the message ID. Use NULL for topic to use the default pubsub topic.
 // publicKey must be a hex string prefixed with "0x" containing a valid secp256k1 public key.
 // optionalSigningKey is an optional hex string prefixed with "0x" containing a valid secp256k1 private key for signing the message. Use NULL otherwise
 // If ms is greater than 0, the broadcast of the message must happen before the timeout
 // (in milliseconds) is reached, or an error will be returned.
+//
+//export waku_relay_publish_enc_asymmetric
 func waku_relay_publish_enc_asymmetric(messageJSON *C.char, topic *C.char, publicKey *C.char, optionalSigningKey *C.char, ms C.int) *C.char {
 	response := mobile.RelayPublishEncodeAsymmetric(C.GoString(messageJSON), C.GoString(topic), C.GoString(publicKey), C.GoString(optionalSigningKey), int(ms))
 	return C.CString(response)
 }
 
-//export waku_relay_publish_enc_symmetric
 // Publish a message encrypted with a 32 bytes symmetric key using waku relay  and returns the message ID. Use NULL for topic to use the default pubsub topic.
 // symmetricKey must be a hex string prefixed with "0x" containing a 32 bytes symmetric key
 // optionalSigningKey is an optional hex string prefixed with "0x" containing a valid secp256k1 private key for signing the message. Use NULL otherwise
 // If ms is greater than 0, the broadcast of the message must happen before the timeout
 // (in milliseconds) is reached, or an error will be returned.
+//
+//export waku_relay_publish_enc_symmetric
 func waku_relay_publish_enc_symmetric(messageJSON *C.char, topic *C.char, symmetricKey *C.char, optionalSigningKey *C.char, ms C.int) *C.char {
 	response := mobile.RelayPublishEncodeSymmetric(C.GoString(messageJSON), C.GoString(topic), C.GoString(symmetricKey), C.GoString(optionalSigningKey), int(ms))
 	return C.CString(response)
 }
 
-//export waku_relay_subscribe
 // Subscribe to a WakuRelay topic. Set the topic to NULL to subscribe
 // to the default topic. Returns a json response. When a message is received,
 // a "message" event is emitted containing the message and pubsub topic in which
 // the message was received
+//
+//export waku_relay_subscribe
 func waku_relay_subscribe(topic *C.char) *C.char {
 	response := mobile.RelaySubscribe(C.GoString(topic))
 	return C.CString(response)
 }
 
-//export waku_relay_unsubscribe
+// Returns a json response with the list of pubsub topics the node
+// is subscribed to in WakuRelay
+//
+//export waku_relay_topics
+func waku_relay_topics() *C.char {
+	response := mobile.RelayTopics()
+	return C.CString(response)
+}
+
 // Closes the pubsub subscription to a pubsub topic
+//
+//export waku_relay_unsubscribe
 func waku_relay_unsubscribe(topic *C.char) *C.char {
 	response := mobile.RelayUnsubscribe(C.GoString(topic))
 	return C.CString(response)

mobile/api_relay.go

@@ -114,6 +114,14 @@ func RelaySubscribe(topic string) string {
 	return MakeJSONResponse(relaySubscribe(topic))
 }
 
+func RelayTopics() string {
+	if wakuState.node == nil {
+		return MakeJSONResponse(errWakuNodeNotReady)
+	}
+
+	return PrepareJSONResponse(wakuState.node.Relay().Topics(), nil)
+}
+
 func RelayUnsubscribe(topic string) string {
 	if wakuState.node == nil {
 		return MakeJSONResponse(errWakuNodeNotReady)