Code convention issue

[andreykutkov]

The codebase seems to have some points to improve code convention-wise. Two major improvements that can made are:

• Using Promise instead of Callback style communication between functions.
• Remove circular dependency and make function dependency graph more hierarchical.

Example call stack:

`src/network/receive.ts`:201 initGrpcSubscriptions() <<< note B
  `src/grpc/index.ts`:15 subscribeInvoices(parseKeysendInvoice) <<< note A
    `src/utils/lightning.ts`:46 loadLightning()
       (node_module grpc).load("rpc.proto")
    [success] `src/network/receive.ts`:248 parseKeysendInvoice <<< note A
    [failure] `src/gprc/index.ts`:120 reconnectToLND()
        `src/network/receive.ts`:201 initGrpcSubscriptions() <<< note B

note A: Callback style here. Can be replaced with Promise. note B: Circular dependency. *** The code lines might be different due to frequent code update. But left there for reference assuming the difference might be not so huge.

[Evanfeenstra]

Thanks for your comments.

The parseKeysendInvoice callback is called many times, as invoices payments are received from LND over the GRPC subscription. How would you propose handling that with a promise?

[andreykutkov]

As there's only one party listening for subscribeInvoices, current callback style will work fine. If there're more than one listeners, other coding paradigms can be considered.

Regarding node B: Another drawback of circular dependency is that the call stack can get deepen resulting in possible failure of system on constant failures. So I suggest the following style. The pseudocode is:

// src/network/receive.ts
export async function initGrpcSubscriptions() {
    await getInfo() // Just leaving this will rethrow error.
    let error = InitialError();
    // The loop that retries subscribeInvoices
    while (error) {
        try {
            await lndService.subscribeInvoices(parseKeysendInvoice)
        }
        catch (caught) {
            if (error is CriticalError) {
                throw caught
            }
            else {
                error = caught;
            }
        }
    }
}

// src/grpc/index.ts
export function subscribeInvoices(parseKeysendInvoice) {
    // On success:
    parseKeysendInvoice(response)
    resolve(status);
    // On failure that requires retry
    reject(SomeError());
    // On critical failure that doesn't require retry
    rejects(CriticalError());
}