Add OutputSweeper and persistence utils

We add an `OutputSweeper` object that will keep track of sweepable
outputs. To this end, we start by adding the general structures and the
required utilities to persist the `SpendableOutputStatus` to our
`KVStore`.

src/event.rs

@@ -611,12 +611,7 @@ where
 				);
 
 				match res {
-					Ok(Some(spending_tx)) => {
-						self.tx_broadcaster.broadcast_transactions(&[&spending_tx])
-					}
-					Ok(None) => {
-						log_debug!(self.logger, "Omitted spending static outputs: {:?}", outputs);
-					}
+					Ok(spending_tx) => self.tx_broadcaster.broadcast_transactions(&[&spending_tx]),
 					Err(err) => {
 						log_error!(self.logger, "Error spending outputs: {:?}", err);
 					}

src/io/mod.rs

@@ -21,6 +21,10 @@ pub(crate) const PEER_INFO_PERSISTENCE_KEY: &str = "peers";
 pub(crate) const PAYMENT_INFO_PERSISTENCE_PRIMARY_NAMESPACE: &str = "payments";
 pub(crate) const PAYMENT_INFO_PERSISTENCE_SECONDARY_NAMESPACE: &str = "";
 
+/// The spendable output information will be persisted under this prefix.
+pub(crate) const SPENDABLE_OUTPUT_INFO_PERSISTENCE_PRIMARY_NAMESPACE: &str = "spendable_outputs";
+pub(crate) const SPENDABLE_OUTPUT_INFO_PERSISTENCE_SECONDARY_NAMESPACE: &str = "";
+
 /// RapidGossipSync's `latest_sync_timestamp` will be persisted under this key.
 pub(crate) const LATEST_RGS_SYNC_TIMESTAMP_PRIMARY_NAMESPACE: &str = "";
 pub(crate) const LATEST_RGS_SYNC_TIMESTAMP_SECONDARY_NAMESPACE: &str = "";

src/io/utils.rs

@@ -3,6 +3,7 @@ use crate::WALLET_KEYS_SEED_LEN;
 
 use crate::logger::log_error;
 use crate::peer_store::PeerStore;
+use crate::sweep::SpendableOutputInfo;
 use crate::{Error, EventQueue, PaymentDetails};
 
 use lightning::routing::gossip::NetworkGraph;
@@ -199,6 +200,36 @@ where
 	Ok(res)
 }
 
+/// Read previously persisted spendable output information from the store.
+pub(crate) fn read_spendable_outputs<K: KVStore + Sync + Send, L: Deref>(
+	kv_store: Arc<K>, logger: L,
+) -> Result<Vec<SpendableOutputInfo>, std::io::Error>
+where
+	L::Target: Logger,
+{
+	let mut res = Vec::new();
+
+	for stored_key in kv_store.list(
+		SPENDABLE_OUTPUT_INFO_PERSISTENCE_PRIMARY_NAMESPACE,
+		SPENDABLE_OUTPUT_INFO_PERSISTENCE_SECONDARY_NAMESPACE,
+	)? {
+		let mut reader = Cursor::new(kv_store.read(
+			SPENDABLE_OUTPUT_INFO_PERSISTENCE_PRIMARY_NAMESPACE,
+			SPENDABLE_OUTPUT_INFO_PERSISTENCE_SECONDARY_NAMESPACE,
+			&stored_key,
+		)?);
+		let output = SpendableOutputInfo::read(&mut reader).map_err(|e| {
+			log_error!(logger, "Failed to deserialize SpendableOutputInfo: {}", e);
+			std::io::Error::new(
+				std::io::ErrorKind::InvalidData,
+				"Failed to deserialize SpendableOutputInfo",
+			)
+		})?;
+		res.push(output);
+	}
+	Ok(res)
+}
+
 pub(crate) fn read_latest_rgs_sync_timestamp<K: KVStore + Sync + Send, L: Deref>(
 	kv_store: Arc<K>, logger: L,
 ) -> Result<u32, std::io::Error>

src/lib.rs

@@ -85,6 +85,7 @@ pub mod io;
 mod logger;
 mod payment_store;
 mod peer_store;
+mod sweep;
 #[cfg(test)]
 mod test;
 mod tx_broadcaster;