wallet-core/packages/taler-wallet-core/src/util/coinSelection.test.ts

/*
 This file is part of GNU Taler
 (C) 2021 Taler Systems S.A.

 GNU Taler is free software; you can redistribute it and/or modify it under the
 terms of the GNU General Public License as published by the Free Software
 Foundation; either version 3, or (at your option) any later version.

 GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
 A PARTICULAR PURPOSE.  See the GNU General Public License for more details.

 You should have received a copy of the GNU General Public License along with
 GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
 */

/**
 * Imports.
 */
import test from "ava";
import { AmountJson, Amounts, DenomKeyType } from "@gnu-taler/taler-util";
import { AvailableCoinInfo, selectPayCoins } from "./coinSelection.js";

function a(x: string): AmountJson {
  const amt = Amounts.parse(x);
  if (!amt) {
    throw Error("invalid amount");
  }
  return amt;
}

function fakeAci(current: string, feeDeposit: string): AvailableCoinInfo {
  return {
    availableAmount: a(current),
    coinPub: "foobar",
    denomPub: {
      cipher: DenomKeyType.Rsa,
      rsa_public_key: "foobar",
    },
    feeDeposit: a(feeDeposit),
    exchangeBaseUrl: "https://example.com/",
  };
}

test("it should be able to pay if merchant takes the fees", (t) => {
  const acis: AvailableCoinInfo[] = [
    fakeAci("EUR:1.0", "EUR:0.1"),
    fakeAci("EUR:1.0", "EUR:0.0"),
  ];
  acis.forEach((x, i) => (x.coinPub = String(i)));

  const res = selectPayCoins({
    candidates: {
      candidateCoins: acis,
      wireFeesPerExchange: {},
    },
    contractTermsAmount: a("EUR:2.0"),
    depositFeeLimit: a("EUR:0.1"),
    wireFeeLimit: a("EUR:0"),
    wireFeeAmortization: 1,
  });

  if (!res) {
    t.fail();
    return;
  }
  t.deepEqual(res.coinPubs, ["1", "0"]);
  t.pass();
});

test("it should take the last two coins if it pays less fees", (t) => {
  const acis: AvailableCoinInfo[] = [
    fakeAci("EUR:1.0", "EUR:0.5"),
    fakeAci("EUR:1.0", "EUR:0.0"),
    // Merchant covers the fee, this one shouldn't be used
    fakeAci("EUR:1.0", "EUR:0.0"),
  ];
  acis.forEach((x, i) => (x.coinPub = String(i)));

  const res = selectPayCoins({
    candidates: {
      candidateCoins: acis,
      wireFeesPerExchange: {},
    },
    contractTermsAmount: a("EUR:2.0"),
    depositFeeLimit: a("EUR:0.5"),
    wireFeeLimit: a("EUR:0"),
    wireFeeAmortization: 1,
  });

  if (!res) {
    t.fail();
    return;
  }
  t.deepEqual(res.coinPubs, ["1", "2"]);
  t.pass();
});

test("it should take the last coins if the merchant doest not take all the fee", (t) => {
  const acis: AvailableCoinInfo[] = [
    fakeAci("EUR:1.0", "EUR:0.5"),
    fakeAci("EUR:1.0", "EUR:0.5"),
    // this coin should be selected instead of previous one with fee
    fakeAci("EUR:1.0", "EUR:0.0"),
  ];
  acis.forEach((x, i) => (x.coinPub = String(i)));

  const res = selectPayCoins({
    candidates: {
      candidateCoins: acis,
      wireFeesPerExchange: {},
    },
    contractTermsAmount: a("EUR:2.0"),
    depositFeeLimit: a("EUR:0.5"),
    wireFeeLimit: a("EUR:0"),
    wireFeeAmortization: 1,
  });

  if (!res) {
    t.fail();
    return;
  }
  t.deepEqual(res.coinPubs, ["2", "0"]);
  t.pass();
});

test("it should use 3 coins to cover fees and payment", (t) => {
  const acis: AvailableCoinInfo[] = [
    fakeAci("EUR:1.0", "EUR:0.5"), //contributed value 1 (fee by the merchant)
    fakeAci("EUR:1.0", "EUR:0.5"), //contributed value .5
    fakeAci("EUR:1.0", "EUR:0.5"), //contributed value .5
  ];

  const res = selectPayCoins({
    candidates: {
      candidateCoins: acis,
      wireFeesPerExchange: {},
    },
    contractTermsAmount: a("EUR:2.0"),
    depositFeeLimit: a("EUR:0.5"),
    wireFeeLimit: a("EUR:0"),
    wireFeeAmortization: 1,
  });

  if (!res) {
    t.fail();
    return;
  }
  t.true(res.coinPubs.length === 3);
  t.pass();
});

test("it should return undefined if there is not enough coins", (t) => {
  const acis: AvailableCoinInfo[] = [
    fakeAci("EUR:1.0", "EUR:0.5"),
    fakeAci("EUR:1.0", "EUR:0.5"),
    fakeAci("EUR:1.0", "EUR:0.5"),
  ];

  const res = selectPayCoins({
    candidates: {
      candidateCoins: acis,
      wireFeesPerExchange: {},
    },
    contractTermsAmount: a("EUR:4.0"),
    depositFeeLimit: a("EUR:0.2"),
    wireFeeLimit: a("EUR:0"),
    wireFeeAmortization: 1,
  });

  t.true(!res);
  t.pass();
});

test("it should return undefined if there is not enough coins (taking into account fees)", (t) => {
  const acis: AvailableCoinInfo[] = [
    fakeAci("EUR:1.0", "EUR:0.5"),
    fakeAci("EUR:1.0", "EUR:0.5"),
  ];
  const res = selectPayCoins({
    candidates: {
      candidateCoins: acis,
      wireFeesPerExchange: {},
    },
    contractTermsAmount: a("EUR:2.0"),
    depositFeeLimit: a("EUR:0.2"),
    wireFeeLimit: a("EUR:0"),
    wireFeeAmortization: 1,
  });
  t.true(!res);
  t.pass();
});

test("it should not count into customer fee if merchant can afford it", (t) => {
  const acis: AvailableCoinInfo[] = [
    fakeAci("EUR:1.0", "EUR:0.1"),
    fakeAci("EUR:1.0", "EUR:0.1"),
  ];
  const res = selectPayCoins({
    candidates: {
      candidateCoins: acis,
      wireFeesPerExchange: {},
    },
    contractTermsAmount: a("EUR:2.0"),
    depositFeeLimit: a("EUR:0.2"),
    wireFeeLimit: a("EUR:0"),
    wireFeeAmortization: 1,
  });
  t.truthy(res);
  t.true(Amounts.cmp(res!.customerDepositFees, "EUR:0.0") === 0);
  t.true(
    Amounts.cmp(Amounts.sum(res!.coinContributions).amount, "EUR:2.0") === 0,
  );
  t.pass();
});

test("it should use the coins that spent less relative fee", (t) => {
  const acis: AvailableCoinInfo[] = [
    fakeAci("EUR:1.0", "EUR:0.2"),
    fakeAci("EUR:0.1", "EUR:0.2"),
    fakeAci("EUR:0.05", "EUR:0.05"),
    fakeAci("EUR:0.05", "EUR:0.05"),
  ];
  acis.forEach((x, i) => (x.coinPub = String(i)));

  const res = selectPayCoins({
    candidates: {
      candidateCoins: acis,
      wireFeesPerExchange: {},
    },
    contractTermsAmount: a("EUR:1.1"),
    depositFeeLimit: a("EUR:0.4"),
    wireFeeLimit: a("EUR:0"),
    wireFeeAmortization: 1,
  });
  if (!res) {
    t.fail();
    return;
  }
  t.deepEqual(res.coinPubs, ["0", "2", "3"]);
  t.pass();
});

test("coin selection 9", (t) => {
  const acis: AvailableCoinInfo[] = [
    fakeAci("EUR:1.0", "EUR:0.2"),
    fakeAci("EUR:0.2", "EUR:0.2"),
  ];
  const res = selectPayCoins({
    candidates: {
      candidateCoins: acis,
      wireFeesPerExchange: {},
    },
    contractTermsAmount: a("EUR:1.2"),
    depositFeeLimit: a("EUR:0.4"),
    wireFeeLimit: a("EUR:0"),
    wireFeeAmortization: 1,
  });
  if (!res) {
    t.fail();
    return;
  }
  t.true(res.coinContributions.length === 2);
  t.true(
    Amounts.cmp(Amounts.sum(res.coinContributions).amount, "EUR:1.2") === 0,
  );
  t.pass();
});