Further work on transaction signing

processor/scanner/src/db.rs

@@ -520,3 +520,26 @@ impl SubstrateToEventualityDb {
     Burns::try_recv(txn, acknowledged_block)
   }
 }
+
+mod _completed_eventualities {
+  use serai_db::{Get, DbTxn, create_db, db_channel};
+
+  db_channel! {
+    ScannerPublic {
+      CompletedEventualities: (empty_key: ()) -> [u8; 32],
+    }
+  }
+}
+
+/// The IDs of completed Eventualities found on-chain, within a finalized block.
+pub struct CompletedEventualities<S: ScannerFeed>(PhantomData<S>);
+impl<S: ScannerFeed> CompletedEventualities<S> {
+  pub(crate) fn send(txn: &mut impl DbTxn, id: [u8; 32]) {
+    _completed_eventualities::CompletedEventualities::send(txn, (), &id);
+  }
+
+  /// Receive the ID of a completed Eventuality.
+  pub fn try_recv(txn: &mut impl DbTxn) -> Option<[u8; 32]> {
+    _completed_eventualities::CompletedEventualities::try_recv(txn, ())
+  }
+}

processor/scanner/src/eventuality/mod.rs

@@ -14,7 +14,7 @@ use crate::{
     ScanToEventualityDb,
   },
   BlockExt, ScannerFeed, KeyFor, AddressFor, OutputFor, EventualityFor, SchedulerUpdate, Scheduler,
-  sort_outputs,
+  CompletedEventualities, sort_outputs,
   scan::{next_to_scan_for_outputs_block, queue_output_until_block},
 };
 
@@ -292,8 +292,13 @@ impl<D: Db, S: ScannerFeed, Sch: Scheduler<S>> ContinuallyRan for EventualityTas
           completed_eventualities
         };
 
-        for tx in completed_eventualities.keys() {
-          log::info!("eventuality resolved by {}", hex::encode(tx.as_ref()));
+        for (tx, eventuality) in &completed_eventualities {
+          log::info!(
+            "eventuality {} resolved by {}",
+            hex::encode(eventuality.id()),
+            hex::encode(tx.as_ref())
+          );
+          CompletedEventualities::<S>::send(&mut txn, eventuality.id());
         }
 
         // Fetch all non-External outputs

processor/scanner/src/lib.rs

@@ -21,6 +21,7 @@ pub use lifetime::LifetimeStage;
 
 // Database schema definition and associated functions.
 mod db;
+pub use db::CompletedEventualities;
 // Task to index the blockchain, ensuring we don't reorganize finalized blocks.
 mod index;
 // Scans blocks for received coins.
@@ -170,6 +171,10 @@ pub type EventualityFor<S> = <<S as ScannerFeed>::Block as Block>::Eventuality;
 /// The block type for this ScannerFeed.
 pub type BlockFor<S> = <S as ScannerFeed>::Block;
 
+/// An object usable to publish a Batch.
+// This will presumably be the Batch signer defined in `serai-processor-signers` or a test shim.
+// It could also be some app-layer database for the purpose of verifying the Batches published to
+// Serai.
 #[async_trait::async_trait]
 pub trait BatchPublisher: 'static + Send + Sync {
   /// An error encountered when publishing the Batch.