Add tasks to publish data onto Serai

coordinator/substrate/src/publish_batch.rs

@@ -0,0 +1,66 @@
+use core::future::Future;
+use std::sync::Arc;
+
+use serai_db::{DbTxn, Db};
+
+use serai_client::{primitives::NetworkId, SeraiError, Serai};
+
+use serai_task::ContinuallyRan;
+
+use crate::SignedBatches;
+
+/// Publish `SignedBatch`s from `SignedBatches` onto Serai.
+pub struct PublishBatchTask<D: Db> {
+  db: D,
+  serai: Arc<Serai>,
+  network: NetworkId,
+}
+
+impl<D: Db> PublishBatchTask<D> {
+  /// Create a task to publish `SignedBatch`s onto Serai.
+  ///
+  /// Returns None if `network == NetworkId::Serai`.
+  // TODO: ExternalNetworkId
+  pub fn new(db: D, serai: Arc<Serai>, network: NetworkId) -> Option<Self> {
+    if network == NetworkId::Serai {
+      None?
+    };
+    Some(Self { db, serai, network })
+  }
+}
+
+impl<D: Db> ContinuallyRan for PublishBatchTask<D> {
+  type Error = SeraiError;
+
+  fn run_iteration(&mut self) -> impl Send + Future<Output = Result<bool, Self::Error>> {
+    async move {
+      let mut made_progress = false;
+
+      loop {
+        let mut txn = self.db.txn();
+        let Some(batch) = SignedBatches::try_recv(&mut txn, self.network) else {
+          // No batch to publish at this time
+          break;
+        };
+
+        // Publish this Batch if it hasn't already been published
+        let serai = self.serai.as_of_latest_finalized_block().await?;
+        let last_batch = serai.in_instructions().last_batch_for_network(self.network).await?;
+        if last_batch < Some(batch.batch.id) {
+          // This stream of Batches *should* be sequential within the larger context of the Serai
+          // coordinator. In this library, we use a more relaxed definition and don't assert
+          // sequence. This does risk hanging the task, if Batch #n+1 is sent before Batch #n, but
+          // that is a documented fault of the `SignedBatches` API.
+          self
+            .serai
+            .publish(&serai_client::in_instructions::SeraiInInstructions::execute_batch(batch))
+            .await?;
+        }
+
+        txn.commit();
+        made_progress = true;
+      }
+      Ok(made_progress)
+    }
+  }
+}