* Remove `chain_oracle::CacheBackend` for now as it is not used.
* `SparseChain` does not need to implement `ChainOracle`.
* Remove filter predicate for `list..` methods of `TxGraph` and
`IndexedTxGraph` as this is premature optimisation.
* `Append` can be implemented for all `BTreeMap`s and `BTreeSet`s,
instead of only `local_chain::ChangeSet`.
The `HashSet` was used for iterating without duplicate items. However,
since `anchors` is a `BTreeSet`, heights are in order. So a single
variable tracking last height will be sufficient.
Previously, I have misunderstood the definition of anchor. If a tx is
anchored in a block, it does not necessarily mean it is confirmed in
that block. The tx can be confirmed in an ancestor block of the anchor
block.
With this new definition, we need a new trait `ConfirmationHeight` that
has one method `confirmation_height`. This trait can be used to extend
`Anchor` for those implementations that can give us the exact
conirmation height of a tx (which is useful in most cases).
Another change is to add another variant to the `ObservedAs` enum;
`ObservedAs::ConfirmedImplicit(A)`. If a tx does not have an anchor, but
another tx that spends it has an anchor that in in the best chain, we
can assume that tx is also in the best chain. The logic of
`TxGraph::try_get_chain_position` is also changed to reflect this.
Some methods from `IndexedTxGraph` have been moved to `TxGraph` as they
do not require the `Indexer`. Some `TxGraph` methods have been renamed
for clarity and consistency.
Also more docs are added.
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.
