BTCPayServer Multi-Store Support and Native GraphQL Client

[1337bytes]

Project Summary

Implement multi-store support for the plugin and replace the RPC layer with a GraphQL backend using Zkool directly.

Project Description

Rearchitect the plugin to use the Zkool GraphQL API directly instead of the legacy RPC API, together with full multi-store support, removing the need to configure the wallet from an administrator account. This should reduce the long-term maintenance cost of the plugin given that redundant logic will be dropped.

Implement integration and cheatmode testing to allow for faster testing and development. Better support for using agentic workflows. A merchant wiki will be created to help merchants decide on what solution best fits their needs including guidance for repurposing existing Bitcoin/Monero RPC integrations to support Zcash (i.e. using zecd/zcash-wallet-rpc).

Proposed Problem

zcash-walletd is no longer actively maintained.

BTCPayServer merchants using third-party hosting are unable to use the plugin. This limits adoption.

Proposed Solution

Moving fully to the Zkool GraphQL API in the plugin instead of reimplementing the zcash-walletd RPC API using the Zkool crate will make the plugin more stable and easier to maintain going forward, dropping the legacy API.

More details at:

Grant Application - BTCPayServer Multi-Store GraphQL Client

[1337bytes]

For context:

@hanh

But moving forward, this plugin is getting messier. For context, @vaspholdings, when the plugin was originally written, there was no light wallet server (we only had zcashd). I wrote a small lightwallet server (zcash-walletd) and adapted the Monero plugin (which is single-store). Then BTCPayServer dev decided to kick out all altcoins from the main codebase into plugins. They defined an API (single & multistore). Now we have a few lightwallet options: Zkool/GraphQL, zecd (zcashd). Regardless of which one is used, there is no good reason for zcash-walletd anymore. IMO, we should leverage the multistore API and make the Zcash plugin directly multistore, 0conf and talk to either zkool or zecd. Instead, we are keeping the obsolete plugin design and trying to unravel it in an external server.

This application aims to address these concerns re the current state of the plugin by integrating the Zkool GraphQL API directly into the C# plugin and switching fully to the multi-store API.

Progress so far on GitHub: Multi-Store and GraphQL Client by macintoshhelper · Pull Request #13 · btcpay-zcash/btcpayserver-zcash-plugin · GitHub

This expands on the 0conf support from the previously funded grant. Around half the work is already completed for the GraphQL port: multi-store account creation, invoice creation, address generation, 0conf and payment confirmation are working locally. A wallet agnostic backend makes adding zecd support relatively straight forward also.

I am currently working on the integrated testing architecture.

I would not like the work on zcash-wallet-rpc to go unused/wasted and the idea of the Zcash Merchant Wiki is to document how a merchant using the Monero RPC can add drop-in support for Zcash with zcash-wallet-rpc.

Example of the wallet backend agnostic C# interface:

// `zecd`/`zcash-wallet-rpc` RPC interface (WIP)
public async Task<WalletAddress> CreateAddressAsync(long accountIndex, string label, CancellationToken cancellationToken = default)
        {
            var response = await _walletRpcClient.SendCommandAsync<CreateAddressRequest, CreateAddressResponse>(
                "create_address",
                new CreateAddressRequest
                {
                    AccountIndex = accountIndex,
                    Label = label
                },
                cancellationToken);

            return new WalletAddress
            {
                Address = response.Address,
                AddressIndex = response.AddressIndex,
                UnifiedAddress = response.Address
            };
        }

// GraphQL interface
public async Task<WalletAddress> CreateAddressAsync(long accountIndex, string label, CancellationToken cancellationToken = default)
{
    var accountId = await ResolveGraphQlAccountIdAsync(accountIndex, cancellationToken);
    return await CreateOrGetAddressAsync(accountId, cancellationToken);
}

// Different class:
ReserveAddress = s => walletBackend.CreateAddressAsync(accountIndex, $"btcpay invoice #{s}"),

LLM disclaimer:

• I am making manual use of Sonnet 5 prompts to aid with certain tasks.
• GitHub Copilot agent with Sonnet 5 was used for creating an initial non-working prototype of the refactor
• I am responsible for every line of code merged and thoroughly check and understand all code generated by LLMs.

[ZCG]

@1337bytes at the most recent meeting, ZCG voted to approve this proposal. Congratulations!

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