feat: generic payment method

[asmogo]

Fixes: #401

I have tested this with a CDK feature branch and the stripe payment processor

Description

added functions for minting and melting quotes with generic payment methods

Changes

• new api functions for generic payment methods

PR Tasks

• Open PR
• run npm run test --> no failing unit tests
• run npm run lint --> no warnings or errors
• run npm run format
• run npm run api:check --> run npm run api:update for changes to the API

[Egge21M]

Thank you so much for experimenting with this! This is very similar to what I had in mind, however I think this might not be generic enough yet. Right now Wallet._mintProofsGeneric assumes the method to have the same config as what we see today (e.g. a key-pair). But payment methods in the future might have new parameters that are required by the mint. If we have a generic method we should make sure it is fully generic.

E.g.: The createMingQuoteGeneric method could not be used to generate a bolt12 quote, as it lacks a field for pubkey.

What if we replace all config parameters with factory functions or the config itself instead that are then called by cashu-ts to create things like MintQuotePayload?

E.g.:

	async createMintQuoteGeneric<T extends Record<string, unknown>>(
		method: string,
                payloadFactory: () => Record<string, unknown>
	): Promise<T & { quote: string; amount: number; unit: string; expiry: number }> {
		const payload = payloadFactory();
		return this.mint.createMintQuote<T>(method, payload);
	}

or in the case of mintProofsGeneric:

	 createMintQuoteGeneric<T extends Record<string, unknown>>(
		method: string,
                payloadFactory: (blindMessages) => Record<string, unknown>
	): Promise<T & { quote: string; amount: number; unit: string; expiry: number }>

[Egge21M]

Why is quote.quote asserted to be a string here if the params define it as unkown?

[robwoodgate]

This is a solid start, thank you for this! As Egge says, I also wonder if it can be more generic.

I was thinking something along the lines of:

// Mint class method
public async createMintQuote<
  TRes extends Record<string, unknown> = Record<string, unknown>
>(
  method: string,
  mintQuotePayload: MintQuoteBaseRequest & Record<string, unknown>,
  customRequest?: RequestFn
): Promise<MintQuoteBaseResponse & TRes> {
  // Validate method string and make request
  failIf(!this.isValidMethodString(method), `Invalid mint quote method: ${method}`, this._logger);
  return this.requestWithAuth<MintQuoteBaseResponse & TRes>(
    'POST',
    `/v1/mint/quote/${method}`,
    { requestBody: mintQuotePayload },
    customRequest
  );
}

// Example: custom bank transfer (as below, or  MintQuoteBaseRequest & { amount: number; } )
type BankTransferQuoteReq = {
  unit: string;
  amount: number;
};

type BankTransferQuoteRes = {
  expiry: number;     // unix seconds until which the instructions are valid
  reference: string;  // payer reference to include on the transfer
};

const bankQuote = await mint.createMintQuote<BankTransferQuoteRes>(
  'bank',
  { unit: 'sat', amount: 25000 }
);

// bankQuote is typed as:
/// {
///   quote: string;
///   request: string;
///   unit: string;
///   expiry: number;
///   reference: string;
/// }

// Example response shape:
/// {
///   "quote": "q_9b7f2c...",
///   "request": "Beneficiary: Cashu Mint Ltd; IBAN: DE89 3704 0044 0532 0130 00; BIC: COLSDE33; Amount: 25000 sat; Reference: REF-2Y6Q9N",
///   "unit": "sat",
///   "expiry": 1731369600,
///   "reference": "REF-2Y6Q9N"
/// }

[robwoodgate]

GM @asmogo - You'll be pleased to know that the SIG_ALL changes and type refactor PRs are now merged, so you should have a clear run at this now.

As part of SIG_ALL, I implemented a generic melt:
Mint side: https://github.com/cashubtc/cashu-ts/blob/development/src/mint/Mint.ts#L417
Wallet side: https://github.com/cashubtc/cashu-ts/blob/development/src/wallet/Wallet.ts#L1961

The Mint/Melt types have also been refactored to make them easier to use with generics:
NUT-04: https://github.com/cashubtc/cashu-ts/blob/development/src/model/types/NUT04.ts
NUT-05:https://github.com/cashubtc/cashu-ts/blob/development/src/model/types/NUT05.ts