Add next_events_from_metadata and rename next_event (#545)

* remove obsolete comment

* make pub things pub

examples/examples/event_callback.rs

@@ -39,7 +39,7 @@ async fn main() {
 
 	// Wait for event callbacks from the node, which are received via subscription.
 	for _ in 0..5 {
-		let event_records = subscription.next_event::<RuntimeEvent, Hash>().unwrap().unwrap();
+		let event_records = subscription.next_events::<RuntimeEvent, Hash>().unwrap().unwrap();
 		for event_record in &event_records {
 			println!("decoded: {:?} {:?}", event_record.phase, event_record.event);
 			match &event_record.event {

node-api/src/events.rs

@@ -24,9 +24,6 @@ use sp_core::H256;
 
 /// A collection of events obtained from a block, bundled with the necessary
 /// information needed to decode and iterate over them.
-//
-// In subxt, this was generic over a `Config` type, but it's sole usage was to derive the
-// hash type. We omitted this here and use the `ac_primitives::Hash` instead.
 #[derive(Clone, Debug)]
 pub struct Events<Hash> {
 	metadata: Metadata,

src/api/rpc_api/events.rs

@@ -17,7 +17,7 @@ use crate::{
 	GetChainInfo, GetStorage,
 };
 use ac_compose_macros::rpc_params;
-use ac_node_api::{EventDetails, EventRecord, Events, Phase};
+use ac_node_api::{metadata::Metadata, EventDetails, EventRecord, Events, Phase};
 use ac_primitives::{ExtrinsicParams, FrameSystemConfig, StorageChangeSet};
 use alloc::{vec, vec::Vec};
 use codec::{Decode, Encode};
@@ -83,22 +83,30 @@ where
 /// Simplifies the event retrieval from the subscription.
 pub struct EventSubscription<Subscription, Hash> {
 	pub subscription: Subscription,
+	pub metadata: Metadata,
 	_phantom: PhantomData<Hash>,
 }
 
+impl<Subscription, Hash> EventSubscription<Subscription, Hash> {
+	/// Create a new wrapper around the subscription.
+	pub fn new(subscription: Subscription, metadata: Metadata) -> Self {
+		Self { subscription, metadata, _phantom: Default::default() }
+	}
+
+	/// Update the metadata.
+	pub fn update_metadata(&mut self, metadata: Metadata) {
+		self.metadata = metadata
+	}
+}
+
 impl<Subscription, Hash> EventSubscription<Subscription, Hash>
 where
-	Hash: DeserializeOwned,
+	Hash: DeserializeOwned + Copy,
 	Subscription: HandleSubscription<StorageChangeSet<Hash>>,
 {
-	/// Create a new wrapper around the subscription.
-	pub fn new(subscription: Subscription) -> Self {
-		Self { subscription, _phantom: Default::default() }
-	}
-
 	/// Wait for the next value from the internal subscription.
 	/// Upon encounter, it retrieves and decodes the expected `EventRecord`.
-	pub fn next_event<RuntimeEvent: Decode, Topic: Decode>(
+	pub fn next_events<RuntimeEvent: Decode, Topic: Decode>(
 		&mut self,
 	) -> Option<Result<Vec<EventRecord<RuntimeEvent, Topic>>>> {
 		let change_set = match self.subscription.next()? {
@@ -109,8 +117,29 @@ where
 		// changes in the set. Also, we don't care about the key but only the data, so take
 		// the second value in the tuple of two.
 		let storage_data = change_set.changes[0].1.as_ref()?;
-		let events = Decode::decode(&mut storage_data.0.as_slice()).map_err(Error::Codec);
-		Some(events)
+		let event_records = Decode::decode(&mut storage_data.0.as_slice()).map_err(Error::Codec);
+		Some(event_records)
+	}
+
+	/// Wait for the next value from the internal subscription.
+	/// Upon encounter, it retrieves and decodes the expected `EventDetails`.
+	//
+	// On the contrary to `next_events` this function only needs up-to-date metadata
+	// and is therefore updateable during runtime.
+	pub fn next_events_from_metadata(&mut self) -> Option<Result<Events<Hash>>> {
+		let change_set = match self.subscription.next()? {
+			Ok(set) => set,
+			Err(e) => return Some(Err(Error::RpcClient(e))),
+		};
+		let block_hash = change_set.block;
+		// Since we subscribed to only the events key, we can simply take the first value of the
+		// changes in the set. Also, we don't care about the key but only the data, so take
+		// the second value in the tuple of two.
+		let storage_data = change_set.changes[0].1.as_ref()?;
+		let event_bytes = storage_data.0.clone();
+
+		let events = Events::<Hash>::new(self.metadata.clone(), block_hash, event_bytes);
+		Some(Ok(events))
 	}
 
 	/// Unsubscribe from the internal subscription.
@@ -119,16 +148,6 @@ where
 	}
 }
 
-impl<Subscription, Hash> From<Subscription> for EventSubscription<Subscription, Hash>
-where
-	Hash: DeserializeOwned,
-	Subscription: HandleSubscription<StorageChangeSet<Hash>>,
-{
-	fn from(subscription: Subscription) -> Self {
-		EventSubscription::new(subscription)
-	}
-}
-
 pub trait SubscribeEvents {
 	type Client: Subscribe;
 	type Hash: DeserializeOwned;
@@ -151,7 +170,7 @@ where
 		let subscription = self
 			.client()
 			.subscribe("state_subscribeStorage", rpc_params![vec![key]], "state_unsubscribeStorage")
-			.map(|sub| sub.into())?;
+			.map(|sub| EventSubscription::new(sub, self.metadata().clone()))?;
 		Ok(subscription)
 	}
 }

testing/examples/events_tests.rs

@@ -70,7 +70,7 @@ async fn main() {
 	// Wait for event callbacks from the node, which are received via subscription.
 	for _ in 0..5 {
 		let event_records = event_subscription
-			.next_event::<RuntimeEvent, <Runtime as FrameSystemConfig>::Hash>()
+			.next_events::<RuntimeEvent, <Runtime as FrameSystemConfig>::Hash>()
 			.unwrap()
 			.unwrap();
 		for event_record in &event_records {
@@ -81,6 +81,20 @@ async fn main() {
 			}
 		}
 	}
+
+	// Wait for event callbacks from the node, which are received via subscription, in case no RuntimeEvents are accessible.
+	for _ in 0..5 {
+		let events = event_subscription.next_events_from_metadata().unwrap().unwrap();
+		for event in events.iter() {
+			let event = event.unwrap();
+			println!("got event: {:?} {:?}", event.pallet_name(), event.variant_name());
+			if let Ok(Some(_extrinisic_success)) = event.as_event::<ExtrinsicSuccess>() {
+				println!("Got System event, all good");
+			} else {
+				panic!("Unexpected event");
+			}
+		}
+	}
 }
 
 fn assert_assosciated_events_match_expected(events: Vec<EventDetails>) {