diff --git a/crates/chain/src/chain_data.rs b/crates/chain/src/chain_data.rs
index 537f0bf7e9..20c8ebff8e 100644
--- a/crates/chain/src/chain_data.rs
+++ b/crates/chain/src/chain_data.rs
@@ -147,6 +147,8 @@ impl From<(&u32, &BlockHash)> for BlockId {
/// An [`Anchor`] implementation that also records the exact confirmation height of the transaction.
///
+/// Note that the confirmation block and the anchor block can be different here.
+///
/// Refer to [`Anchor`] for more details.
#[derive(Debug, Default, Clone, PartialEq, Eq, Copy, PartialOrd, Ord, core::hash::Hash)]
#[cfg_attr(
@@ -186,6 +188,8 @@ impl AnchorFromBlockPosition for ConfirmationHeightAnchor {
/// An [`Anchor`] implementation that also records the exact confirmation time and height of the
/// transaction.
///
+/// Note that the confirmation block and the anchor block can be different here.
+///
/// Refer to [`Anchor`] for more details.
#[derive(Debug, Default, Clone, PartialEq, Eq, Copy, PartialOrd, Ord, core::hash::Hash)]
#[cfg_attr(
diff --git a/crates/chain/src/chain_oracle.rs b/crates/chain/src/chain_oracle.rs
index e736be0354..cb5155724e 100644
--- a/crates/chain/src/chain_oracle.rs
+++ b/crates/chain/src/chain_oracle.rs
@@ -3,7 +3,7 @@ use crate::BlockId;
/// Represents a service that tracks the blockchain.
///
/// The main method is [`is_block_in_chain`] which determines whether a given block of [`BlockId`]
-/// is an ancestor of another "static block".
+/// is an ancestor of the `chain_tip`.
///
/// [`is_block_in_chain`]: Self::is_block_in_chain
pub trait ChainOracle {
diff --git a/crates/chain/src/indexed_tx_graph.rs b/crates/chain/src/indexed_tx_graph.rs
index 0e2620e0d1..504ce3cf28 100644
--- a/crates/chain/src/indexed_tx_graph.rs
+++ b/crates/chain/src/indexed_tx_graph.rs
@@ -1,7 +1,5 @@
-//! Contains the [`IndexedTxGraph`] structure and associated types.
-//!
-//! This is essentially a [`TxGraph`] combined with an indexer.
-
+//! Contains the [`IndexedTxGraph`] structure and associated types. Refer to the
+//! [`IndexedTxGraph`] documentation for more.
use alloc::vec::Vec;
use bitcoin::{Block, OutPoint, Transaction, TxOut, Txid};
diff --git a/crates/chain/src/lib.rs b/crates/chain/src/lib.rs
index ed167ebf6c..04ca62c4c6 100644
--- a/crates/chain/src/lib.rs
+++ b/crates/chain/src/lib.rs
@@ -12,9 +12,8 @@
//! you do it synchronously or asynchronously. If you know a fact about the blockchain, you can just
//! tell `bdk_chain`'s APIs about it, and that information will be integrated, if it can be done
//! consistently.
-//! 2. Error-free APIs.
-//! 3. Data persistence agnostic -- `bdk_chain` does not care where you cache on-chain data, what you
-//! cache or how you fetch it.
+//! 2. Data persistence agnostic -- `bdk_chain` does not care where you cache on-chain data, what you
+//! cache or how you retrieve it from persistent storage.
//!
//! [Bitcoin Dev Kit]: https://bitcoindevkit.org/
diff --git a/crates/chain/src/tx_data_traits.rs b/crates/chain/src/tx_data_traits.rs
index c957a3e57e..31935c475c 100644
--- a/crates/chain/src/tx_data_traits.rs
+++ b/crates/chain/src/tx_data_traits.rs
@@ -5,13 +5,17 @@ use alloc::vec::Vec;
/// Trait that "anchors" blockchain data to a specific block of height and hash.
///
-/// [`Anchor`] implementations must be [`Ord`] by the anchor block's [`BlockId`] first.
-///
-/// I.e. If transaction A is anchored in block B, then if block B is in the best chain, we can
+/// If transaction A is anchored in block B, and block B is in the best chain, we can
/// assume that transaction A is also confirmed in the best chain. This does not necessarily mean
/// that transaction A is confirmed in block B. It could also mean transaction A is confirmed in a
/// parent block of B.
///
+/// Every [`Anchor`] implementation must contain a [`BlockId`] parameter, and must implement
+/// [`Ord`]. When implementing [`Ord`], the anchors' [`BlockId`]s should take precedence
+/// over other elements inside the [`Anchor`]s for comparison purposes, i.e., you should first
+/// compare the anchors' [`BlockId`]s and then care about the rest.
+/// [`BlockId`]s.
+///
/// ```
/// # use bdk_chain::local_chain::LocalChain;
/// # use bdk_chain::tx_graph::TxGraph;
@@ -19,7 +23,6 @@ use alloc::vec::Vec;
/// # use bdk_chain::ConfirmationHeightAnchor;
/// # use bdk_chain::example_utils::*;
/// # use bitcoin::hashes::Hash;
-///
/// // Initialize the local chain with two blocks.
/// let chain = LocalChain::from_blocks(
/// [
diff --git a/crates/chain/src/tx_graph.rs b/crates/chain/src/tx_graph.rs
index 1f7bcdb122..5440c143c7 100644
--- a/crates/chain/src/tx_graph.rs
+++ b/crates/chain/src/tx_graph.rs
@@ -1,12 +1,30 @@
//! Module for structures that store and traverse transactions.
//!
-//! [`TxGraph`] is a monotone structure that inserts transactions and indexes the spends. The
-//! [`ChangeSet`] structure reports changes of [`TxGraph`] but can also be applied to a
-//! [`TxGraph`] as well. Lastly, [`TxDescendants`] is an [`Iterator`] that traverses descendants of
-//! a given transaction.
+//! [`TxGraph`] contains transactions and indexes them so you can easily traverse the graph of those transactions.
+//! `TxGraph` is *monotone* in that you can always insert a transaction -- it doesn't care whether that
+//! transaction is in the current best chain or whether it conflicts with any of the
+//! existing transactions or what order you insert the transactions.
+//! Furthermore, there is currently no way to delete a transaction.
+//!
+//! Transactions can be either whole or partial (i.e., transactions for which we only
+//! know some outputs, which we usually call "floating outputs").
+//!
+//! The graph contains transactions in the form of [`TxNode`]s. Each node contains the
+//! txid, the transaction (whole or partial), the blocks it's anchored in (see the [`Anchor`]
+//! documentation for more details), and the timestamp of the last time we saw
+//! the transaction as unconfirmed.
//!
//! Conflicting transactions are allowed to coexist within a [`TxGraph`]. This is useful for
-//! identifying and traversing conflicts and descendants of a given transaction.
+//! identifying and traversing conflicts and descendants of a given transaction. Some [`TxGraph`]
+//! methods only consider "canonical" (i.e., in the best chain or in mempool) transactions,
+//! we decide which transactions are canonical based on anchors `last_seen_unconfirmed`;
+//! see the [`try_get_chain_position`] documentation for more details.
+//!
+//! The [`ChangeSet`] reports changes made to a [`TxGraph`]; it can be used to either save to
+//! persistent storage, or to be applied to another [`TxGraph`].
+//!
+//! Lastly, you can use [`TxAncestors`]/[`TxDescendants`] to traverse ancestors and descendants of
+//! a given transaction, respectively.
//!
//! # Applying changes
//!
@@ -49,6 +67,7 @@
//! let changeset = graph.apply_update(update);
//! assert!(changeset.is_empty());
//! ```
+//! [`try_get_chain_position`]: TxGraph::try_get_chain_position
use crate::{
collections::*, keychain::Balance, local_chain::LocalChain, Anchor, Append, BlockId,
@@ -90,7 +109,7 @@ impl Default for TxGraph {
}
}
-/// An outward-facing view of a (transaction) node in the [`TxGraph`].
+/// A transaction node in the [`TxGraph`].
#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
pub struct TxNode<'a, T, A> {
/// Txid of the transaction.
@@ -127,7 +146,7 @@ impl Default for TxNodeInternal {
}
}
-/// An outwards-facing view of a transaction that is part of the *best chain*'s history.
+/// A transaction that is included in a certain chain.
#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
pub struct CanonicalTx<'a, T, A> {
/// How the transaction is observed as (confirmed or unconfirmed).
@@ -454,7 +473,7 @@ impl TxGraph {
/// Batch insert unconfirmed transactions.
///
/// Items of `txs` are tuples containing the transaction and a *last seen* timestamp. The
- /// *last seen* communicates when the transaction is last seen in the mempool which is used for
+ /// *last seen* communicates when the transaction is last seen in mempool which is used for
/// conflict-resolution (refer to [`TxGraph::insert_seen_at`] for details).
pub fn batch_insert_unconfirmed(
&mut self,
@@ -687,8 +706,21 @@ impl TxGraph {
/// Get the position of the transaction in `chain` with tip `chain_tip`.
///
- /// If the given transaction of `txid` does not exist in the chain of `chain_tip`, `None` is
- /// returned.
+ /// If the given `txid` does not exist in the chain of `chain_tip`, and
+ /// we believe that the transaction is not in mempool anymore, `None` is returned.
+ ///
+ /// There are two factors that we use to approximate whether an unconfirmed
+ /// transaction currently exists in mempool:
+ /// 1. Conflicts with confirmed txs. If the transaction `tx` or any of its unconfirmed
+ /// ancestors conflict with a confirmed transaction, then `tx` can't be in mempool.
+ /// 2. The `last_seen_unconfirmed` parameter. Given two conflicting transactions, we say
+ /// that the one with a higher `last_seen_unconfirmed` (i.e., we saw it later) has a higher
+ /// chance of still being in mempool. When trying to figure out if `tx`
+ /// is still in mempool, we first of all calculate `tx`'s `max_last_seen_unconfirmed`,
+ /// which is the max `last_seen_unconfirmed` between `tx` and all its descendants.
+ /// We then look at all the conflicts of `tx`, and if for all of them
+ /// `last_seen_unconfirmed` < `max_last_seen_unconfirmed` holds,
+ /// then we consider `tx` to be still in mempool.
///
/// # Error
///
@@ -714,7 +746,7 @@ impl TxGraph {
}
}
- // The tx is not anchored to a block which is in the best chain, which means that it
+ // The tx is not anchored to a block in the best chain, which means that it
// might be in mempool, or it might have been dropped already.
// Let's check conflicts to find out!
let tx = match tx_node {
@@ -911,7 +943,8 @@ impl TxGraph {
/// (`OI`) for convenience. If `OI` is not necessary, the caller can use `()`, or
/// [`Iterator::enumerate`] over a list of [`OutPoint`]s.
///
- /// Floating outputs are ignored.
+ /// Floating outputs (i.e., outputs for which we don't have the full transaction in the graph)
+ /// are ignored.
///
/// # Error
///