PortalBTCLib/npubCash.ts

import {
  CashuMint,
  CashuWallet,
  MintQuoteState,
  type Proof,
} from "@cashu/cashu-ts";

import { privateKeyFromSeedWords as nostrPrivateKeyFromSeedWords } from "nostr-tools/nip06";
import { finalizeEvent, nip98 } from "nostr-tools";
import type { BodyInit } from "bun";

interface NpubCashQuote {
  createdAt: number;
  paidAt?: number;
  expiresAt: number;
  mintUrl: string;
  quoteId: string;
  request: string;
  amount: number;
  state: "PAID" | "ISSUED" | "INFLIGHT";
  locked: boolean;
}

interface NpubCashPaginationMetadata {
  total: number;
  limit: number;
}

export default class NpubCash {
  constructor(private mnemonic: string) {}

  private async fetchWithNip98<T>(
    { url, method, body }: {
      url: string;
      method: string;
      body?: BodyInit | null;
    },
  ): Promise<T> {
    const nostrPrivateKey = nostrPrivateKeyFromSeedWords(this.mnemonic);
    const urlWithoutQueryParams = url.split("?")[0] ?? "";
    const npubCashNip98 = await nip98.getToken(
      urlWithoutQueryParams,
      method,
      (event) => finalizeEvent(event, nostrPrivateKey),
    );
    return fetch(url, {
      method,
      headers: {
        "Authorization": `Nostr ${npubCashNip98}`,
      },
      body,
    }).then((data) => data.json() as Promise<T>);
  }

  private async getQuotes(since: number, limit: number, offset: number) {
    return this.fetchWithNip98<
      {
        error: false;
        data: { quotes: NpubCashQuote[] };
        metadata: NpubCashPaginationMetadata;
      } | {
        error: true;
        message: string;
      }
    >({
      url:
        `https://npubx.cash/api/v2/wallet/quotes?since=${since}&limit=${limit}&offset=${offset}`,
      method: "GET",
    });
  }

  private async getAllPaidQuotes(since: number) {
    const quotes: NpubCashQuote[] = [];
    let offset = 0;
    while (true) {
      const currentQuotes = await this.getQuotes(since, 50, offset);
      if (currentQuotes.error === false) {
        quotes.push(...currentQuotes.data.quotes);
        if (quotes.length >= currentQuotes.metadata.total) {
          break;
        }
      } else {
        throw new Error(currentQuotes.message ?? "Unknown error");
      }
      offset += 50;
    }
    return quotes.sort((a, b) => a.createdAt - b.createdAt).filter(
      (quote) => quote.state === "PAID",
    );
  }

  async *tryRedeemUnredeemedCashuQuotes(
    latestRedeemedCashuQuoteTimestamp: number,
  ) {
    const proofs: Proof[] = [];
    const quotes: NpubCashQuote[] = await this.getAllPaidQuotes(
      latestRedeemedCashuQuoteTimestamp,
    );
    for (const quote of quotes) {
      const mint = new CashuMint(quote.mintUrl);
      const wallet = new CashuWallet(mint);
      const req = await mint.checkMintQuote(quote.quoteId);
      if (
        req.state === MintQuoteState.PAID && typeof quote.paidAt === "number"
      ) {
        const newProofs = await wallet.mintProofs(
          quote.amount,
          quote.quoteId,
        );
        proofs.push(...newProofs);
        const amountReceived = newProofs.reduce(
          (sum, p) => sum + p.amount,
          0,
        );
        yield {
          quoteId: quote.quoteId,
          amountSat: amountReceived,
          timestamp: quote.paidAt,
        };
      }
    }
    return proofs;
  }
}