Improve `Confirm` docs

diff --git a/lightning/src/chain/mod.rs b/lightning/src/chain/mod.rs
index 33d4826fef210b849b61818fd9ba241aad2a9971..43add75950d6a50c3c07c5a07e525fd7154bf216 100644 (file)
--- a/lightning/src/chain/mod.rs
+++ b/lightning/src/chain/mod.rs
@@ -107,31 +107,35 @@ pub trait Listen {
        fn block_disconnected(&self, header: &BlockHeader, height: u32);
 }
 
-/// The `Confirm` trait is used to notify when transactions have been confirmed on chain or
-/// unconfirmed during a chain reorganization.
+/// The `Confirm` trait is used to notify LDK when relevant transactions have been confirmed on
+/// chain or unconfirmed during a chain reorganization.
 ///
 /// Clients sourcing chain data using a transaction-oriented API should prefer this interface over
-/// [`Listen`]. For instance, an Electrum client may implement [`Filter`] by subscribing to activity
-/// related to registered transactions and outputs. Upon notification, it would pass along the
-/// matching transactions using this interface.
+/// [`Listen`]. For instance, an Electrum-based transaction sync implementation may implement
+/// [`Filter`] to subscribe to relevant transactions and unspent outputs it should monitor for
+/// on-chain activity. Then, it needs to notify LDK via this interface upon observing any changes
+/// with reference to the confirmation status of the monitored objects.
 ///
 /// # Use
-///
 /// The intended use is as follows:
-/// - Call [`transactions_confirmed`] to process any on-chain activity of interest.
-/// - Call [`transaction_unconfirmed`] to process any transaction returned by [`get_relevant_txids`]
-///   that has been reorganized out of the chain.
-/// - Call [`best_block_updated`] whenever a new chain tip becomes available.
+/// - Call [`transactions_confirmed`] to notify LDK whenever any of the registered transactions or
+///   outputs are, respectively, confirmed or spent on chain.
+/// - Call [`transaction_unconfirmed`] to notify LDK whenever any transaction returned by
+///   [`get_relevant_txids`] is no longer confirmed in the block with the given block hash.
+/// - Call [`best_block_updated`] to notify LDK whenever a new chain tip becomes available.
 ///
 /// # Order
 ///
 /// Clients must call these methods in chain order. Specifically:
-/// - Transactions confirmed in a block must be given before transactions confirmed in a later
-///   block.
+/// - Transactions which are confirmed in a particular block must be given before transactions
+///   confirmed in a later block.
 /// - Dependent transactions within the same block must be given in topological order, possibly in
 ///   separate calls.
-/// - Unconfirmed transactions must be given after the original confirmations and before any
-///   reconfirmation.
+/// - All unconfirmed transactions must be given after the original confirmations and before *any*
+///   reconfirmations, i.e., [`transactions_confirmed`] and [`transaction_unconfirmed`] calls should
+///   never be interleaved, but always conduced *en bloc*.
+/// - Any reconfirmed transactions need to be explicitly unconfirmed before they are reconfirmed
+///   in regard to the new block.
 ///
 /// See individual method documentation for further details.
 ///
@@ -140,9 +144,9 @@ pub trait Listen {
 /// [`best_block_updated`]: Self::best_block_updated
 /// [`get_relevant_txids`]: Self::get_relevant_txids
 pub trait Confirm {
-       /// Processes transactions confirmed in a block with a given header and height.
+       /// Notifies LDK of transactions confirmed in a block with a given header and height.
        ///
-       /// Should be called for any transactions registered by [`Filter::register_tx`] or any
+       /// Must be called for any transactions registered by [`Filter::register_tx`] or any
        /// transactions spending an output registered by [`Filter::register_output`]. Such transactions
        /// appearing in the same block do not need to be included in the same call; instead, multiple
        /// calls with additional transactions may be made so long as they are made in [chain order].
@@ -154,36 +158,36 @@ pub trait Confirm {
        /// [chain order]: Confirm#order
        /// [`best_block_updated`]: Self::best_block_updated
        fn transactions_confirmed(&self, header: &BlockHeader, txdata: &TransactionData, height: u32);
-
-       /// Processes a transaction that is no longer confirmed as result of a chain reorganization.
+       /// Notifies LDK of a transaction that is no longer confirmed as result of a chain reorganization.
        ///
-       /// Should be called for any transaction returned by [`get_relevant_txids`] if it has been
-       /// reorganized out of the best chain. Once called, the given transaction will not be returned
+       /// Must be called for any transaction returned by [`get_relevant_txids`] if it has been
+       /// reorganized out of the best chain or if it is no longer confirmed in the block with the
+       /// given block hash. Once called, the given transaction will not be returned
        /// by [`get_relevant_txids`], unless it has been reconfirmed via [`transactions_confirmed`].
        ///
        /// [`get_relevant_txids`]: Self::get_relevant_txids
        /// [`transactions_confirmed`]: Self::transactions_confirmed
        fn transaction_unconfirmed(&self, txid: &Txid);
-
-       /// Processes an update to the best header connected at the given height.
+       /// Notifies LDK of an update to the best header connected at the given height.
        ///
-       /// Should be called when a new header is available but may be skipped for intermediary blocks
-       /// if they become available at the same time.
+       /// Must be called whenever a new chain tip becomes available. May be skipped for intermediary
+       /// blocks.
        fn best_block_updated(&self, header: &BlockHeader, height: u32);
-
-       /// Returns transactions that should be monitored for reorganization out of the chain along
-       /// with the hash of the block as part of which had been previously confirmed.
+       /// Returns transactions that must be monitored for reorganization out of the chain along
+       /// with the hash of the block as part of which it had been previously confirmed.
        ///
        /// Will include any transactions passed to [`transactions_confirmed`] that have insufficient
        /// confirmations to be safe from a chain reorganization. Will not include any transactions
        /// passed to [`transaction_unconfirmed`], unless later reconfirmed.
        ///
-       /// May be called to determine the subset of transactions that must still be monitored for
+       /// Must be called to determine the subset of transactions that must be monitored for
        /// reorganization. Will be idempotent between calls but may change as a result of calls to the
-       /// other interface methods. Thus, this is useful to determine which transactions may need to be
-       /// given to [`transaction_unconfirmed`]. If any of the returned transactions are confirmed in
-       /// a block other than the one with the given hash, they need to be unconfirmed and reconfirmed
-       /// via [`transaction_unconfirmed`] and [`transactions_confirmed`], respectively.
+       /// other interface methods. Thus, this is useful to determine which transactions must be
+       /// given to [`transaction_unconfirmed`].
+       ///
+       /// If any of the returned transactions are confirmed in a block other than the one with the
+       /// given hash, they need to be unconfirmed and reconfirmed via [`transaction_unconfirmed`] and
+       /// [`transactions_confirmed`], respectively.
        ///
        /// [`transactions_confirmed`]: Self::transactions_confirmed
        /// [`transaction_unconfirmed`]: Self::transaction_unconfirmed