Events sub

src/frame/balances.rs

@@ -114,10 +114,12 @@ mod tests {
             Error,
             RuntimeError,
         },
+        events::EventsDecoder,
         signer::{
             PairSigner,
             Signer,
         },
+        subscription::EventSubscription,
         system::AccountStoreExt,
         tests::{
             test_client,
@@ -201,4 +203,28 @@ mod tests {
             panic!("expected an error");
         }
     }
+
+    #[async_std::test]
+    async fn test_transfer_subscription() {
+        env_logger::try_init().ok();
+        let alice = PairSigner::new(AccountKeyring::Alice.pair());
+        let bob = AccountKeyring::Bob.to_account_id();
+        let (client, _) = test_client().await;
+        let sub = client.subscribe_events().await.unwrap();
+        let mut decoder = EventsDecoder::<TestRuntime>::new(client.metadata().clone());
+        decoder.with_balances();
+        let mut sub = EventSubscription::<TestRuntime>::new(sub, decoder);
+        sub.filter_event::<TransferEvent<_>>();
+        client.transfer(&alice, &bob, 10_000).await.unwrap();
+        let raw = sub.next().await.unwrap().unwrap();
+        let event = TransferEvent::<TestRuntime>::decode(&mut &raw.data[..]).unwrap();
+        assert_eq!(
+            event,
+            TransferEvent {
+                from: alice.account_id().clone(),
+                to: bob.clone(),
+                amount: 10_000,
+            }
+        );
+    }
 }

src/lib.rs

@@ -68,6 +68,7 @@ mod metadata;
 mod rpc;
 mod runtimes;
 mod signer;
+mod subscription;
 
 pub use crate::{
     error::Error,
@@ -87,6 +88,7 @@ pub use crate::{
     },
     runtimes::*,
     signer::*,
+    subscription::*,
     substrate_subxt_proc_macro::*,
 };
 use crate::{

src/rpc.rs

@@ -70,13 +70,12 @@ use crate::{
         RawEvent,
     },
     frame::{
-        system::{
-            Phase,
-            System,
-        },
+        system::System,
         Event,
     },
     metadata::Metadata,
+    runtimes::Runtime,
+    subscription::EventSubscription,
 };
 
 pub type ChainBlock<T> =
@@ -107,12 +106,12 @@ where
 }
 
 /// Client for substrate rpc interfaces
-pub struct Rpc<T: System> {
+pub struct Rpc<T: Runtime> {
     client: Client,
     marker: PhantomData<T>,
 }
 
-impl<T: System> Clone for Rpc<T> {
+impl<T: Runtime> Clone for Rpc<T> {
     fn clone(&self) -> Self {
         Self {
             client: self.client.clone(),
@@ -121,7 +120,7 @@ impl<T: System> Clone for Rpc<T> {
     }
 }
 
-impl<T: System> Rpc<T> {
+impl<T: Runtime> Rpc<T> {
     pub fn new(client: Client) -> Self {
         Self {
             client,
@@ -256,7 +255,7 @@ impl<T: System> Rpc<T> {
     /// Subscribe to substrate System Events
     pub async fn subscribe_events(
         &self,
-    ) -> Result<Subscription<StorageChangeSet<<T as System>::Hash>>, Error> {
+    ) -> Result<Subscription<StorageChangeSet<T::Hash>>, Error> {
         let mut storage_key = twox_128(b"System").to_vec();
         storage_key.extend(twox_128(b"Events").to_vec());
         log::debug!("Events storage key {:?}", hex::encode(&storage_key));
@@ -360,14 +359,24 @@ impl<T: System> Rpc<T> {
                                 block_hash,
                                 signed_block.block.extrinsics.len()
                             );
-                            wait_for_block_events(
-                                decoder,
-                                ext_hash,
-                                signed_block,
-                                block_hash,
-                                events_sub,
-                            )
-                            .await
+                            let ext_index = find_extrinsic::<T>(&signed_block, &ext_hash)
+                                .ok_or_else(|| {
+                                    Error::Other(format!(
+                                        "Failed to find Extrinsic with hash {:?}",
+                                        ext_hash,
+                                    ))
+                                })?;
+                            let mut sub = EventSubscription::new(events_sub, decoder);
+                            sub.filter_extrinsic(block_hash, ext_index);
+                            let mut events = vec![];
+                            while let Some(event) = sub.next().await {
+                                events.push(event?);
+                            }
+                            Ok(ExtrinsicSuccess {
+                                block: block_hash,
+                                extrinsic: ext_hash,
+                                events,
+                            })
                         }
                         None => {
                             Err(format!("Failed to find block {:?}", block_hash).into())
@@ -425,58 +434,13 @@ impl<T: System> ExtrinsicSuccess<T> {
     }
 }
 
-/// Waits for events for the block triggered by the extrinsic
-pub async fn wait_for_block_events<T: System>(
-    decoder: EventsDecoder<T>,
-    ext_hash: T::Hash,
-    signed_block: ChainBlock<T>,
-    block_hash: T::Hash,
-    events_subscription: Subscription<StorageChangeSet<T::Hash>>,
-) -> Result<ExtrinsicSuccess<T>, Error> {
-    let ext_index = signed_block
-        .block
-        .extrinsics
-        .iter()
-        .position(|ext| {
-            let hash = T::Hashing::hash_of(ext);
-            hash == ext_hash
-        })
-        .ok_or_else(|| {
-            Error::Other(format!("Failed to find Extrinsic with hash {:?}", ext_hash))
-        })?;
-
-    let mut subscription = events_subscription;
-    while let change_set = subscription.next().await {
-        // only interested in events for the given block
-        if change_set.block != block_hash {
-            continue
-        }
-        let mut events = Vec::new();
-        for (_key, data) in change_set.changes {
-            if let Some(data) = data {
-                match decoder.decode_events(&mut &data.0[..]) {
-                    Ok(raw_events) => {
-                        for (phase, event) in raw_events {
-                            if let Phase::ApplyExtrinsic(i) = phase {
-                                if i as usize == ext_index {
-                                    events.push(event)
-                                }
-                            }
-                        }
-                    }
-                    Err(err) => return Err(err),
-                }
-            }
-        }
-        return if !events.is_empty() {
-            Ok(ExtrinsicSuccess {
-                block: block_hash,
-                extrinsic: ext_hash,
-                events,
-            })
-        } else {
-            Err(format!("No events found for block {}", block_hash).into())
-        }
-    }
-    unreachable!()
+/// Returns the index of an extrinsic in a block.
+pub fn find_extrinsic<T: Runtime>(
+    signed_block: &ChainBlock<T>,
+    extrinsic: &T::Hash,
+) -> Option<usize> {
+    signed_block.block.extrinsics.iter().position(|ext| {
+        let hash = T::Hashing::hash_of(ext);
+        hash == *extrinsic
+    })
 }

src/subscription.rs

@@ -0,0 +1,121 @@
+// Copyright 2019-2020 Parity Technologies (UK) Ltd.
+// This file is part of substrate-subxt.
+//
+// subxt is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// subxt is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with substrate-subxt.  If not, see <http://www.gnu.org/licenses/>.
+
+use jsonrpsee::client::Subscription;
+use sp_core::storage::StorageChangeSet;
+use std::collections::VecDeque;
+
+use crate::{
+    error::Error,
+    events::{
+        EventsDecoder,
+        RawEvent,
+    },
+    frame::{
+        system::Phase,
+        Event,
+    },
+    runtimes::Runtime,
+};
+
+/// Event subscription simplifies filtering a storage change set stream for
+/// events of interest.
+pub struct EventSubscription<T: Runtime> {
+    subscription: Subscription<StorageChangeSet<T::Hash>>,
+    decoder: EventsDecoder<T>,
+    block: Option<T::Hash>,
+    extrinsic: Option<usize>,
+    event: Option<(&'static str, &'static str)>,
+    events: VecDeque<RawEvent>,
+    finished: bool,
+}
+
+impl<T: Runtime> EventSubscription<T> {
+    /// Creates a new event subscription.
+    pub fn new(
+        subscription: Subscription<StorageChangeSet<T::Hash>>,
+        decoder: EventsDecoder<T>,
+    ) -> Self {
+        Self {
+            subscription,
+            decoder,
+            block: None,
+            extrinsic: None,
+            event: None,
+            events: Default::default(),
+            finished: false,
+        }
+    }
+
+    /// Only returns events contained in the block with the given hash.
+    pub fn filter_block(&mut self, block: T::Hash) {
+        self.block = Some(block);
+    }
+
+    /// Only returns events from block emitted by extrinsic with index.
+    pub fn filter_extrinsic(&mut self, block: T::Hash, ext_index: usize) {
+        self.block = Some(block);
+        self.extrinsic = Some(ext_index);
+    }
+
+    /// Filters events by type.
+    pub fn filter_event<E: Event<T>>(&mut self) {
+        self.event = Some((E::MODULE, E::EVENT));
+    }
+
+    /// Gets the next event.
+    pub async fn next(&mut self) -> Option<Result<RawEvent, Error>> {
+        loop {
+            if let Some(event) = self.events.pop_front() {
+                return Some(Ok(event))
+            }
+            if self.finished {
+                return None
+            }
+            let change_set = self.subscription.next().await;
+            if let Some(hash) = self.block.as_ref() {
+                if &change_set.block == hash {
+                    self.finished = true;
+                } else {
+                    continue
+                }
+            }
+            for (_key, data) in change_set.changes {
+                if let Some(data) = data {
+                    let raw_events = match self.decoder.decode_events(&mut &data.0[..]) {
+                        Ok(events) => events,
+                        Err(error) => return Some(Err(error)),
+                    };
+                    for (phase, event) in raw_events {
+                        if let Phase::ApplyExtrinsic(i) = phase {
+                            if let Some(ext_index) = self.extrinsic {
+                                if i as usize != ext_index {
+                                    continue
+                                }
+                            }
+                            if let Some((module, variant)) = self.event {
+                                if event.module != module || event.variant != variant {
+                                    continue
+                                }
+                            }
+                            self.events.push_back(event);
+                        }
+                    }
+                }
+            }
+        }
+    }
+}