The problem with the previous `ChainOracle` interface is that it had no
guarantee for consistency. For example, a block deemed to be part of the
"best chain" can be reorged out. So when `ChainOracle` is called
multiple times for an operation (such as getting the UTXO set), the
returned result may be inconsistent.
This PR changes `ChainOracle::is_block_in_chain` to take in another
input `static_block`, ensuring `block` is an ancestor of `static_block`.
Thus, if `static_block` is consistent across the operation, the result
will be consistent also.
`is_block_in_chain` now returns `Option<bool>`. The `None` case means
that the oracle implementation cannot determine whether block is an
ancestor of static block. `IndexedTxGraph::list_chain_txouts` handles
this case by checking child spends that are in chain, and if so, the
parent tx must be in chain too.
* Instead of implementing `ChainPosition` for `ObservedIn<BlockId>` to
use `FullTxOut` methods (`is_spendable_at` and `is_mature`), we create
alternative versions of those methods that require bounds with `Anchor`.
This removes all `ObservedIn<A>: ChainPosition` bounds for methods of
`IndexedTxGraph`.
* Various improvements to comments and names.
Introduce `chain_oracle::Cache` which is a cache for requests to the
chain oracle. `ChainOracle` has also been moved to the `chain_oracle`
module.
Introduce `get_tip_in_best_chain` method to the `ChainOracle` trait.
This allows for guaranteeing that chain state can be consistent across
operations with `IndexedTxGraph`.
Methods of old structures that return transaction(s) no longer return
`TxNode`, but `Transaction` as done previously.
`TxInGraph` is renamed to `TxNode`, while the internal `TxNode` is
renamed to `TxNodeInternal`.
Methods that list chain data have try and non-try versions. Both of
these versions now return an `Iterator`.
* Try versions return `Iterator<Item = Result>`.
* Non-try versions require the `ChainOracle` implementation to be
`ChainOracle<Error = Infallible>`.
The chain oracle keeps track of the best chain, while the transaction
index indexes transaction data in relation to script pubkeys.
This commit also includes initial work on `IndexedTxGraph`.
* Introduce `GraphedTx` struct to access transaction data of graphed
transactions.
* Ability to insert/access anchors and "seen at" values for graphed
transactions.
* `Additions` now records changes to anchors and last_seen_at.
Fixes include:
* Allow `bdk_esplora` to use async with tls
* Reorganize `bdk_esplora` crate to have separate files for
async vs blocking
* Use optional dependencies for `bdk_esplora` async
Creates a separate async EsploraAsyncExt trait for the
async client using async-trait crate. It has thesame
methods as the EsploraExt trait for the blocking client.
This trait is implemented on the AsyncClient of the
rust-esplora-client crate.
As mentioned by @LLFourn:
1. We have a "sparse chain" from which there is a subset of txids M that are missing from graph.
2. There is also another subset C that are in the graph but their positions have changed.
3. We used the Cow to avoid copying/duplicating in memory transactions in subset C and M
Instead in inflate_update we could remove transactions in subset M and just clone data in subset C (which is usually tiny).
