`MerkleDB` & `IMerkleDB` Solidity

Description

Create IMerkleDB interface and the implementation contract MerkleDB.

State

bytes32 merkleRoot: Root of the merkle tree. Used to generate proofs that certain rows are present in the database.
bytes32 merkleTreeIPFS : IPFS Hash pointing to Merkle Tree used to generate proofs
bytes32 databaseIPFS : IPFS Hash pointing to OrbitDB document store for a more indexable table formatted version of the data.

Events

DatabaseUpdate(bytes32 merkleRoot, bytes32 merkleTreeIPFS, bytes32 databaseIPFS): Event emitted whenever MerkleDB smart contract is updated.

Interface

Read

public view merkleProofData(bytes memory bytes, bytes32[] path) returns (bool) : Prove that some CBOR data is in the merkle tree. Use keccak256(bytes memory) to compute the leaf node’s hash and then recursively hash keccak(a+b) of sibling nodes to get the root hash. Return true if this is indeed the stored merkleRoot.

Write

public updateMerkleDB(bytes32 _merkleRoot, bytes32 _merkleTreeIPFS, bytes32 _databaseIPFS) onlyOwner : Update the MerkleDB data. Limited privileged access to contract owner. Emits a DatabaseUpdate event. Updated data comes from the following sources
- merkleRoot : db.rootHash()
  - Checkpoints: https://rocksdb.org/blog/2015/11/10/use-checkpoints-for-efficient-snapshots.html
- merkleTreeIPFS : Computed CID of state.db file data https://github.com/nomic-io/node-merk#usage after https://github.com/nomic-io/node-merk#dbflushsync
- databaseIPFS: Mostly static according to https://github.com/orbitdb/orbit-db/blob/main/GUIDE.md#manifest, can be updated if the OrbitDB is reset (eg. changed access control)