Add a next block notification system to Tributary

Also adds a loop missing from the prior commit.

coordinator/tributary/src/blockchain.rs

@@ -1,4 +1,4 @@
-use std::collections::HashMap;
+use std::collections::{VecDeque, HashMap};
 
 use ciphersuite::{group::GroupEncoding, Ciphersuite, Ristretto};
 
@@ -13,7 +13,7 @@ use crate::{
   transaction::{Signed, TransactionKind, Transaction as TransactionTrait},
 };
 
-#[derive(Clone, PartialEq, Eq, Debug)]
+#[derive(Debug)]
 pub(crate) struct Blockchain<D: Db, T: TransactionTrait> {
   db: Option<D>,
   genesis: [u8; 32],
@@ -24,6 +24,8 @@ pub(crate) struct Blockchain<D: Db, T: TransactionTrait> {
 
   provided: ProvidedTransactions<D, T>,
   mempool: Mempool<D, T>,
+
+  pub(crate) next_block_notifications: VecDeque<tokio::sync::oneshot::Sender<()>>,
 }
 
 impl<D: Db, T: TransactionTrait> Blockchain<D, T> {
@@ -76,6 +78,8 @@ impl<D: Db, T: TransactionTrait> Blockchain<D, T> {
 
       provided: ProvidedTransactions::new(db.clone(), genesis),
       mempool: Mempool::new(db, genesis),
+
+      next_block_notifications: VecDeque::new(),
     };
 
     if let Some((block_number, tip)) = {
@@ -274,6 +278,10 @@ impl<D: Db, T: TransactionTrait> Blockchain<D, T> {
     txn.commit();
     self.db = Some(db);
 
+    for tx in self.next_block_notifications.drain(..) {
+      let _ = tx.send(());
+    }
+
     Ok(())
   }
 }

coordinator/tributary/src/lib.rs

@@ -336,6 +336,15 @@ impl<D: Db, T: TransactionTrait, P: P2p> Tributary<D, T, P> {
       _ => false,
     }
   }
+
+  /// Get a Future which will resolve once the next block has been added.
+  pub async fn next_block_notification(
+    &self,
+  ) -> impl Send + Sync + core::future::Future<Output = Result<(), impl Send + Sync>> {
+    let (tx, rx) = tokio::sync::oneshot::channel();
+    self.network.blockchain.write().await.next_block_notifications.push_back(tx);
+    rx
+  }
 }
 
 #[derive(Clone)]

coordinator/tributary/src/tests/blockchain.rs

@@ -104,7 +104,7 @@ fn invalid_block() {
 
   {
     // Add a valid transaction
-    let mut blockchain = blockchain.clone();
+    let (_, mut blockchain) = new_blockchain(genesis, &[tx.1.signer]);
     assert!(blockchain.add_transaction::<N>(
       true,
       Transaction::Application(tx.clone()),
@@ -129,7 +129,7 @@ fn invalid_block() {
 
   {
     // Invalid signature
-    let mut blockchain = blockchain.clone();
+    let (_, mut blockchain) = new_blockchain(genesis, &[tx.1.signer]);
     assert!(blockchain.add_transaction::<N>(
       true,
       Transaction::Application(tx),