`ChainObserver` supports retrieving the Chain Point of the tip of the chain

[jpraynaud]

Why

We need to retrieve the block number of the tip of the Cardano chain with the Chain observer to use it to create new types of beacons.

What

Add a new function in the ChainObserver trait:

async fn get_current_chain_point(&self) -> Result<Option<ChainPoint>, ChainObserverError>;

And a new entity type:

struct ChainPoint {
    slot_number: u64,
    block_number: u64,
    block_hash: String //hex encoded bytes Vec<u8>
}

And implement this function for the:

• PallasChainObserver by using n2c mini-protocol to get access to it
• CardanoCLIChainObserver by using the query tip command (already used for implementing get_current_epoch)

See

• Cardano node code base: https://github.com/IntersectMBO/cardano-api/blob/14deccd3dd4e56bc4c1d8aaf4c2e87be4786af54/cardano-api/internal/Cardano/Api/Block.hs#L368
• Pallas code base: https://docs.rs/pallas-network/0.24.0/src/pallas_network/miniprotocols/common.rs.html#68
• Ouroboros abstract protocol: https://ouroboros-consensus.cardano.intersectmbo.org/docs/for-developers/AbstractProtocol

How

• [x] Adapt ChainObserver trait (@jpraynaud)
• [x] Implement trait function for FakeChainObserver (@jpraynaud)
• [x] Implement trait function for CardanoCliChainObserver (@jpraynaud)
• [ ] Implement trait function for PallasChainObserver (@falcucci )

[jpraynaud]

Hi @falcucci, the PR #1623 has been merged 👍 You can work on the implementation of the new function in the ChainObserver trait in the PallasChainObserver: https://github.com/input-output-hk/mithril/blob/f700c4692b26c4b78ed9c83515af8992461a3040/mithril-common/src/chain_observer/pallas_observer.rs#L387

[falcucci]

thank you! @jpraynaud