Persist Merkle tree, valid roots and last sync block

[fryorcraken]

Summary

Merkle tree, valid roots and last sync blocks are necessary to generate and validate proof.
This information is retrieved from the blockchain.

Accessing the blockchain represent several challenges:

• Web3 wallet/ Web3 RPC Provider needs to be present, logged in and ready. Even if no "write" action is necessary it's unsure that read access is always available. Meaning user may have to log in.
• An extra query before the node can start sending or verifying messages

Proposed solution

Cache the information locally (local storage?). The information is publicly available on the blockchain and does not need to be protected.

Note

• Need to verify some assumptions. If using a wallet extension or wallet connect, can the Web3 Provider be used to read smart contract data without the user being logged in?
• Should we look into and provide alternative to the usual Web3 Provider in terms of reading abilities.
• There are probably some unknowns here (does sled-db run in wasm? should we create an specific persistance mechanism?).
• This may be a nice to have. We can review and descope later.

[fryorcraken]

@richard-ramos @rymnc except if sled-db magically store information in the local storage, and even so, it is most likely more efficient to pass on our persistence by storing data in json format in the browser's local storage.

[rymnc]

@richard-ramos @rymnc except if sled-db magically store information in the local storage, and even so, it is most likely more efficient to pass on our persistence by storing data in json format in the browser's local storage.

not too sure about where the sled db will be stored in wasm land, but what we can do is add 2 fns to the rln-wasm api, import and export, which accepts a json blob and returns one respectively. This way, on initialisation of the rln object, you can "import" the json blob into the new sled db instance, and before shutting down, "export" it to localStorage?