getaddressbalance JSON-RPC method

[teor2345]

Motivation

lightwalletd uses the getaddressbalance JSON-RPC method.

Required Fields

The method is documented here: https://zcash.github.io/rpc/getaddressbalance.html

lightwalletd always uses the multi-address argument format: https://github.com/zcash/lightwalletd/blob/master/frontend/service.go#L341

Request:

{
  "addresses:"
    [
      "address"  (string) The base58check encoded address
      ,...
    ]
}

And only these fields are used by lightwalletd: https://github.com/zcash/lightwalletd/blob/master/common/common.go#L124

Response:

{
  "balance"  (string) The current balance in zatoshis
}

Tasks

Implementation:

• Implement the new ReadRequest for ReadState
  Use the non-finalized and finalized indexes if they are ready (or an empty list if these tickets are still open):
  • Add balance_by_transparent_addr index to the finalized state #3950 - FinalizedState::address_balance()
  • feat(state): add transparent address indexes to the non-finalized state #4022 - ?
• Implement the RPC method

Testing:

• Add RPC unit tests
• Test that the RPC method works with lightwalletd

[ftm1000]

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[teor2345]

The state parts of this ticket aren't merged yet (#3963, #4022), but you could add a state request/response that returns a zero balance.