Minor work on the transaction signing task

processor/signers/src/transaction/mod.rs

@@ -0,0 +1,70 @@
+use serai_db::{Get, DbTxn, Db};
+
+use primitives::task::ContinuallyRan;
+use scanner::ScannerFeed;
+use scheduler::TransactionsToSign;
+
+mod db;
+use db::IndexDb;
+
+// Fetches transactions to sign and signs them.
+pub(crate) struct TransactionTask<D: Db, S: ScannerFeed, Sch: Scheduler> {
+  db: D,
+  keys: ThresholdKeys<<Sch::SignableTransaction as SignableTransaction>::Ciphersuite>,
+  attempt_manager:
+    AttemptManager<D, <Sch::SignableTransaction as SignableTransaction>::PreprocessMachine>,
+}
+
+impl<D: Db, S: ScannerFeed> TransactionTask<D, S> {
+  pub(crate) async fn new(
+    db: D,
+    keys: ThresholdKeys<<Sch::SignableTransaction as SignableTransaction>::Ciphersuite>,
+  ) -> Self {
+    Self { db, keys, attempt_manager: AttemptManager::new() }
+  }
+}
+
+#[async_trait::async_trait]
+impl<D: Db, S: ScannerFeed> ContinuallyRan for TransactionTask<D, S> {
+  async fn run_iteration(&mut self) -> Result<bool, String> {
+    let mut iterated = false;
+
+    // Check for new transactions to sign
+    loop {
+      let mut txn = self.db.txn();
+      let Some(tx) = TransactionsToSign::try_recv(&mut txn, self.key) else { break };
+      iterated = true;
+
+      let mut machines = Vec::with_capacity(self.keys.len());
+      for keys in &self.keys {
+        machines.push(tx.clone().sign(keys.clone()));
+      }
+      let messages = self.attempt_manager.register(tx.id(), machines);
+      todo!("TODO");
+      txn.commit();
+    }
+
+    // Check for completed Eventualities (meaning we should no longer sign for these transactions)
+    loop {
+      let mut txn = self.db.txn();
+      let Some(tx) = CompletedEventualities::try_recv(&mut txn, self.key) else { break };
+      iterated = true;
+
+      self.attempt_manager.retire(tx);
+      txn.commit();
+    }
+
+    loop {
+      let mut txn = self.db.txn();
+      let Some(msg) = TransactionSignMessages::try_recv(&mut txn, self.key) else { break };
+      iterated = true;
+
+      match self.attempt_manager.handle(msg) {
+        Response::Messages(messages) => todo!("TODO"),
+        Response::Signature(signature) => todo!("TODO"),
+      }
+    }
+
+    Ok(iterated)
+  }
+}