wallet-core: towards faster coin selection

7 files changed, 239 insertions, 49 deletions

diff --git a/packages/taler-util/src/walletTypes.ts b/packages/taler-util/src/walletTypes.ts
index 7fcb752b1..c3e5c6ed0 100644
--- a/packages/taler-util/src/walletTypes.ts
+++ b/packages/taler-util/src/walletTypes.ts
@@ -694,6 +694,7 @@ const codecForDenominationInfo = (): Codec<DenominationInfo> =>
     .property("stampExpireWithdraw", codecForTimestamp)
     .property("stampExpireLegal", codecForTimestamp)
     .property("stampExpireDeposit", codecForTimestamp)
+    .property("exchangeBaseUrl", codecForString())
     .build("codecForDenominationInfo");
 
 export interface DenominationInfo {
@@ -747,6 +748,8 @@ export interface DenominationInfo {
    * Data after which coins of this denomination can't be deposited anymore.
    */
   stampExpireDeposit: TalerProtocolTimestamp;
+
+  exchangeBaseUrl: string;
 }
 
 export type Operation = "deposit" | "withdraw" | "refresh" | "refund";
diff --git a/packages/taler-wallet-core/src/db.ts b/packages/taler-wallet-core/src/db.ts
index 2c4d55820..760234941 100644
--- a/packages/taler-wallet-core/src/db.ts
+++ b/packages/taler-wallet-core/src/db.ts
@@ -348,6 +348,7 @@ export namespace DenominationRecord {
       stampExpireWithdraw: d.stampExpireWithdraw,
       stampStart: d.stampStart,
       value: DenominationRecord.getValue(d),
+      exchangeBaseUrl: d.exchangeBaseUrl,
     };
   }
 }
@@ -1778,6 +1779,10 @@ export const WalletStoresV1 = {
     {
       byBaseUrl: describeIndex("byBaseUrl", "exchangeBaseUrl"),
       byDenomPubHash: describeIndex("byDenomPubHash", "denomPubHash"),
+      byDenomPubHashAndStatus: describeIndex("byDenomPubHashAndStatus", [
+        "denomPubHash",
+        "status",
+      ]),
       byCoinEvHash: describeIndex("byCoinEvHash", "coinEvHash"),
     },
   ),
diff --git a/packages/taler-wallet-core/src/operations/deposits.ts b/packages/taler-wallet-core/src/operations/deposits.ts
index e6f1591ee..9747f21a3 100644
--- a/packages/taler-wallet-core/src/operations/deposits.ts
+++ b/packages/taler-wallet-core/src/operations/deposits.ts
@@ -51,7 +51,7 @@ import {
   OperationStatus,
 } from "../db.js";
 import { InternalWalletState } from "../internal-wallet-state.js";
-import { selectPayCoins } from "../util/coinSelection.js";
+import { selectPayCoinsLegacy } from "../util/coinSelection.js";
 import { readSuccessResponseJsonOrThrow } from "../util/http.js";
 import { spendCoins } from "../wallet.js";
 import { getExchangeDetails } from "./exchanges.js";
@@ -271,7 +271,7 @@ export async function getFeeForDeposit(
 
   const candidates = await getCandidatePayCoins(ws, csr);
 
-  const payCoinSel = selectPayCoins({
+  const payCoinSel = selectPayCoinsLegacy({
     candidates,
     contractTermsAmount: csr.amount,
     depositFeeLimit: csr.maxDepositFee,
@@ -367,7 +367,7 @@ export async function prepareDepositGroup(
     wireMethod: contractData.wireMethod,
   });
 
-  const payCoinSel = selectPayCoins({
+  const payCoinSel = selectPayCoinsLegacy({
     candidates,
     contractTermsAmount: contractData.amount,
     depositFeeLimit: contractData.maxDepositFee,
@@ -470,7 +470,7 @@ export async function createDepositGroup(
     wireMethod: contractData.wireMethod,
   });
 
-  const payCoinSel = selectPayCoins({
+  const payCoinSel = selectPayCoinsLegacy({
     candidates,
     contractTermsAmount: contractData.amount,
     depositFeeLimit: contractData.maxDepositFee,
diff --git a/packages/taler-wallet-core/src/operations/pay.ts b/packages/taler-wallet-core/src/operations/pay.ts
index 5e3c3dd15..fb3b2b991 100644
--- a/packages/taler-wallet-core/src/operations/pay.ts
+++ b/packages/taler-wallet-core/src/operations/pay.ts
@@ -26,6 +26,7 @@
  */
 import {
   AbsoluteTime,
+  AgeRestriction,
   AmountJson,
   Amounts,
   codecForContractTerms,
@@ -36,6 +37,8 @@ import {
   ConfirmPayResultType,
   ContractTerms,
   ContractTermsUtil,
+  DenominationInfo,
+  DenominationPubKey,
   Duration,
   encodeCrock,
   ForcedCoinSel,
@@ -50,6 +53,7 @@ import {
   PreparePayResult,
   PreparePayResultType,
   RefreshReason,
+  strcmp,
   TalerErrorCode,
   TalerErrorDetail,
   TalerProtocolTimestamp,
@@ -86,9 +90,11 @@ import { assertUnreachable } from "../util/assertUnreachable.js";
 import {
   AvailableCoinInfo,
   CoinCandidateSelection,
+  CoinSelectionTally,
   PreviousPayCoins,
   selectForcedPayCoins,
-  selectPayCoins,
+  selectPayCoinsLegacy,
+  tallyFees,
 } from "../util/coinSelection.js";
 import {
   getHttpResponseErrorDetails,
@@ -962,7 +968,7 @@ async function handleInsufficientFunds(
       }
     });
 
-  const res = selectPayCoins({
+  const res = selectPayCoinsLegacy({
     candidates,
     contractTermsAmount: contractData.amount,
     depositFeeLimit: contractData.maxDepositFee,
@@ -1019,6 +1025,205 @@ async function unblockBackup(
     });
 }
 
+export interface SelectPayCoinRequestNg {
+  exchanges: string[];
+  auditors: string[];
+  wireMethod: string;
+  contractTermsAmount: AmountJson;
+  depositFeeLimit: AmountJson;
+  wireFeeLimit: AmountJson;
+  wireFeeAmortization: number;
+  prevPayCoins?: PreviousPayCoins;
+  requiredMinimumAge?: number;
+}
+
+export type AvailableDenom = DenominationInfo & {
+  numAvailable: number;
+};
+
+/**
+ * Given a list of candidate coins, select coins to spend under the merchant's
+ * constraints.
+ *
+ * The prevPayCoins can be specified to "repair" a coin selection
+ * by adding additional coins, after a broken (e.g. double-spent) coin
+ * has been removed from the selection.
+ *
+ * This function is only exported for the sake of unit tests.
+ */
+export async function selectPayCoinsNew(
+  ws: InternalWalletState,
+  req: SelectPayCoinRequestNg,
+): Promise<PayCoinSelection | undefined> {
+  const {
+    contractTermsAmount,
+    depositFeeLimit,
+    wireFeeLimit,
+    wireFeeAmortization,
+  } = req;
+
+  const [candidateDenoms, wireFeesPerExchange] = await ws.db
+    .mktx((x) => [x.exchanges, x.exchangeDetails, x.denominations])
+    .runReadOnly(async (tx) => {
+      const denoms: AvailableDenom[] = [];
+      const exchanges = await tx.exchanges.iter().toArray();
+      const wfPerExchange: Record<string, AmountJson> = {};
+      for (const exchange of exchanges) {
+        const exchangeDetails = await getExchangeDetails(tx, exchange.baseUrl);
+        if (exchangeDetails?.currency !== contractTermsAmount.currency) {
+          continue;
+        }
+        let accepted = false;
+        if (req.exchanges.includes(exchange.baseUrl)) {
+          accepted = true;
+        } else {
+          for (const auditor of exchangeDetails.auditors) {
+            if (req.auditors.includes(auditor.auditor_url)) {
+              accepted = true;
+            }
+          }
+        }
+        if (!accepted) {
+          continue;
+        }
+        // FIXME: Do this query more efficiently via indexing
+        const exchangeDenoms = await tx.denominations.indexes.byExchangeBaseUrl
+          .iter(exchangeDetails.exchangeBaseUrl)
+          .filter((x) => x.freshCoinCount != null && x.freshCoinCount > 0);
+        // FIXME: Should we exclude denominations that are
+        // not spendable anymore?
+        for (const denom of exchangeDenoms) {
+          denoms.push({
+            ...DenominationRecord.toDenomInfo(denom),
+            numAvailable: denom.freshCoinCount ?? 0,
+          });
+        }
+      }
+      return [denoms, wfPerExchange];
+    });
+
+  const coinPubs: string[] = [];
+  const coinContributions: AmountJson[] = [];
+  const currency = contractTermsAmount.currency;
+
+  let tally: CoinSelectionTally = {
+    amountPayRemaining: contractTermsAmount,
+    amountWireFeeLimitRemaining: wireFeeLimit,
+    amountDepositFeeLimitRemaining: depositFeeLimit,
+    customerDepositFees: Amounts.getZero(currency),
+    customerWireFees: Amounts.getZero(currency),
+    wireFeeCoveredForExchange: new Set(),
+  };
+
+  const prevPayCoins = req.prevPayCoins ?? [];
+
+  // Look at existing pay coin selection and tally up
+  for (const prev of prevPayCoins) {
+    tally = tallyFees(
+      tally,
+      wireFeesPerExchange,
+      wireFeeAmortization,
+      prev.exchangeBaseUrl,
+      prev.feeDeposit,
+    );
+    tally.amountPayRemaining = Amounts.sub(
+      tally.amountPayRemaining,
+      prev.contribution,
+    ).amount;
+
+    coinPubs.push(prev.coinPub);
+    coinContributions.push(prev.contribution);
+  }
+
+  // Sort by available amount (descending),  deposit fee (ascending) and
+  // denomPub (ascending) if deposit fee is the same
+  // (to guarantee deterministic results)
+  candidateDenoms.sort(
+    (o1, o2) =>
+      -Amounts.cmp(o1.value, o2.value) ||
+      Amounts.cmp(o1.feeDeposit, o2.feeDeposit) ||
+      strcmp(o1.denomPubHash, o2.denomPubHash),
+  );
+
+  // FIXME:  Here, we should select coins in a smarter way.
+  // Instead of always spending the next-largest coin,
+  // we should try to find the smallest coin that covers the
+  // amount.
+
+  const selectedDenom: {
+    [dph: string]: AmountJson[];
+  } = {};
+
+  for (const aci of candidateDenoms) {
+    const contributions: AmountJson[] = [];
+    for (let i = 0; i < aci.numAvailable; i++) {
+      // Don't use this coin if depositing it is more expensive than
+      // the amount it would give the merchant.
+      if (Amounts.cmp(aci.feeDeposit, aci.value) > 0) {
+        continue;
+      }
+
+      if (Amounts.isZero(tally.amountPayRemaining)) {
+        // We have spent enough!
+        break;
+      }
+
+      tally = tallyFees(
+        tally,
+        wireFeesPerExchange,
+        wireFeeAmortization,
+        aci.exchangeBaseUrl,
+        aci.feeDeposit,
+      );
+
+      let coinSpend = Amounts.max(
+        Amounts.min(tally.amountPayRemaining, aci.value),
+        aci.feeDeposit,
+      );
+
+      tally.amountPayRemaining = Amounts.sub(
+        tally.amountPayRemaining,
+        coinSpend,
+      ).amount;
+      contributions.push(coinSpend);
+    }
+
+    if (contributions.length) {
+      selectedDenom[aci.denomPubHash] = contributions;
+    }
+
+    if (Amounts.isZero(tally.amountPayRemaining)) {
+      await ws.db
+        .mktx((x) => [x.coins, x.denominations])
+        .runReadOnly(async (tx) => {
+          for (const dph of Object.keys(selectedDenom)) {
+            const contributions = selectedDenom[dph];
+            const coins = await tx.coins.indexes.byDenomPubHashAndStatus.getAll(
+              [dph, CoinStatus.Fresh],
+              contributions.length,
+            );
+            if (coins.length != contributions.length) {
+              throw Error(
+                `coin selection failed (not available anymore, got only ${coins.length}/${contributions.length})`,
+              );
+            }
+            coinPubs.push(...coins.map((x) => x.coinPub));
+            coinContributions.push(...contributions);
+          }
+        });
+
+      return {
+        paymentAmount: contractTermsAmount,
+        coinContributions,
+        coinPubs,
+        customerDepositFees: tally.customerDepositFees,
+        customerWireFees: tally.customerWireFees,
+      };
+    }
+  }
+  return undefined;
+}
+
 export async function checkPaymentByProposalId(
   ws: InternalWalletState,
   proposalId: string,
@@ -1079,7 +1284,7 @@ export async function checkPaymentByProposalId(
       wireFeeAmortization: contractData.wireFeeAmortization,
       wireMethod: contractData.wireMethod,
     });
-    const res = selectPayCoins({
+    const res = selectPayCoinsLegacy({
       candidates,
       contractTermsAmount: contractData.amount,
       depositFeeLimit: contractData.maxDepositFee,
@@ -1408,7 +1613,7 @@ export async function confirmPay(
       requiredMinimumAge: contractData.minimumAge,
     });
   } else {
-    res = selectPayCoins({
+    res = selectPayCoinsLegacy({
       candidates,
       contractTermsAmount: contractData.amount,
       depositFeeLimit: contractData.maxDepositFee,
diff --git a/packages/taler-wallet-core/src/util/coinSelection.test.ts b/packages/taler-wallet-core/src/util/coinSelection.test.ts
index 55c007bbc..3c6ad0d82 100644
--- a/packages/taler-wallet-core/src/util/coinSelection.test.ts
+++ b/packages/taler-wallet-core/src/util/coinSelection.test.ts
@@ -19,7 +19,7 @@
  */
 import test from "ava";
 import { AmountJson, Amounts, DenomKeyType } from "@gnu-taler/taler-util";
-import { AvailableCoinInfo, selectPayCoins } from "./coinSelection.js";
+import { AvailableCoinInfo, selectPayCoinsLegacy } from "./coinSelection.js";
 
 function a(x: string): AmountJson {
   const amt = Amounts.parse(x);
@@ -66,7 +66,7 @@ test("it should be able to pay if merchant takes the fees", (t) => {
   ];
   acis.forEach((x, i) => (x.coinPub = String(i)));
 
-  const res = selectPayCoins({
+  const res = selectPayCoinsLegacy({
     candidates: {
       candidateCoins: acis,
       wireFeesPerExchange: {},
@@ -94,7 +94,7 @@ test("it should take the last two coins if it pays less fees", (t) => {
   ];
   acis.forEach((x, i) => (x.coinPub = String(i)));
 
-  const res = selectPayCoins({
+  const res = selectPayCoinsLegacy({
     candidates: {
       candidateCoins: acis,
       wireFeesPerExchange: {},
@@ -122,7 +122,7 @@ test("it should take the last coins if the merchant doest not take all the fee",
   ];
   acis.forEach((x, i) => (x.coinPub = String(i)));
 
-  const res = selectPayCoins({
+  const res = selectPayCoinsLegacy({
     candidates: {
       candidateCoins: acis,
       wireFeesPerExchange: {},
@@ -148,7 +148,7 @@ test("it should use 3 coins to cover fees and payment", (t) => {
     fakeAci("EUR:1.0", "EUR:0.5"), //contributed value .5
   ];
 
-  const res = selectPayCoins({
+  const res = selectPayCoinsLegacy({
     candidates: {
       candidateCoins: acis,
       wireFeesPerExchange: {},
@@ -174,7 +174,7 @@ test("it should return undefined if there is not enough coins", (t) => {
     fakeAci("EUR:1.0", "EUR:0.5"),
   ];
 
-  const res = selectPayCoins({
+  const res = selectPayCoinsLegacy({
     candidates: {
       candidateCoins: acis,
       wireFeesPerExchange: {},
@@ -194,7 +194,7 @@ test("it should return undefined if there is not enough coins (taking into accou
     fakeAci("EUR:1.0", "EUR:0.5"),
     fakeAci("EUR:1.0", "EUR:0.5"),
   ];
-  const res = selectPayCoins({
+  const res = selectPayCoinsLegacy({
     candidates: {
       candidateCoins: acis,
       wireFeesPerExchange: {},
@@ -213,7 +213,7 @@ test("it should not count into customer fee if merchant can afford it", (t) => {
     fakeAci("EUR:1.0", "EUR:0.1"),
     fakeAci("EUR:1.0", "EUR:0.1"),
   ];
-  const res = selectPayCoins({
+  const res = selectPayCoinsLegacy({
     candidates: {
       candidateCoins: acis,
       wireFeesPerExchange: {},
@@ -240,7 +240,7 @@ test("it should use the coins that spent less relative fee", (t) => {
   ];
   acis.forEach((x, i) => (x.coinPub = String(i)));
 
-  const res = selectPayCoins({
+  const res = selectPayCoinsLegacy({
     candidates: {
       candidateCoins: acis,
       wireFeesPerExchange: {},
@@ -263,7 +263,7 @@ test("coin selection 9", (t) => {
     fakeAci("EUR:1.0", "EUR:0.2"),
     fakeAci("EUR:0.2", "EUR:0.2"),
   ];
-  const res = selectPayCoins({
+  const res = selectPayCoinsLegacy({
     candidates: {
       candidateCoins: acis,
       wireFeesPerExchange: {},
@@ -290,7 +290,7 @@ test("it should be able to use unrestricted coins for age restricted contract",
     fakeAciWithAgeRestriction("EUR:1.0", "EUR:0.2"),
     fakeAciWithAgeRestriction("EUR:0.2", "EUR:0.2"),
   ];
-  const res = selectPayCoins({
+  const res = selectPayCoinsLegacy({
     candidates: {
       candidateCoins: acis,
       wireFeesPerExchange: {},
diff --git a/packages/taler-wallet-core/src/util/coinSelection.ts b/packages/taler-wallet-core/src/util/coinSelection.ts
index 97e25abd3..9622b3a76 100644
--- a/packages/taler-wallet-core/src/util/coinSelection.ts
+++ b/packages/taler-wallet-core/src/util/coinSelection.ts
@@ -97,7 +97,7 @@ export interface SelectPayCoinRequest {
   requiredMinimumAge?: number;
 }
 
-interface CoinSelectionTally {
+export interface CoinSelectionTally {
   /**
    * Amount that still needs to be paid.
    * May increase during the computation when fees need to be covered.
@@ -125,7 +125,7 @@ interface CoinSelectionTally {
 /**
  * Account for the fees of spending a coin.
  */
-function tallyFees(
+export function tallyFees(
   tally: CoinSelectionTally,
   wireFeesPerExchange: Record<string, AmountJson>,
   wireFeeAmortization: number,
@@ -204,7 +204,7 @@ function tallyFees(
  *
  * This function is only exported for the sake of unit tests.
  */
-export function selectPayCoins(
+export function selectPayCoinsLegacy(
   req: SelectPayCoinRequest,
 ): PayCoinSelection | undefined {
   const {
diff --git a/packages/taler-wallet-core/src/wallet.ts b/packages/taler-wallet-core/src/wallet.ts
index 49c7f77cf..4751f7976 100644
--- a/packages/taler-wallet-core/src/wallet.ts
+++ b/packages/taler-wallet-core/src/wallet.ts
@@ -743,19 +743,9 @@ async function getExchangeDetailedInfo(
         return;
       }
 
-      const denominations: DenomInfo[] = denominationRecords.map((x) => ({
-        denomPub: x.denomPub,
-        denomPubHash: x.denomPubHash,
-        feeDeposit: x.fees.feeDeposit,
-        feeRefresh: x.fees.feeRefresh,
-        feeRefund: x.fees.feeRefund,
-        feeWithdraw: x.fees.feeWithdraw,
-        stampExpireDeposit: x.stampExpireDeposit,
-        stampExpireLegal: x.stampExpireLegal,
-        stampExpireWithdraw: x.stampExpireWithdraw,
-        stampStart: x.stampStart,
-        value: DenominationRecord.getValue(x),
-      }));
+      const denominations: DenomInfo[] = denominationRecords.map((x) =>
+        DenominationRecord.toDenomInfo(x),
+      );
 
       return {
         info: {
@@ -1591,20 +1581,7 @@ class InternalWalletStateImpl implements InternalWalletState {
     }
     const d = await tx.denominations.get([exchangeBaseUrl, denomPubHash]);
     if (d) {
-      const denomInfo = {
-        denomPub: d.denomPub,
-        denomPubHash: d.denomPubHash,
-        feeDeposit: d.fees.feeDeposit,
-        feeRefresh: d.fees.feeRefresh,
-        feeRefund: d.fees.feeRefund,
-        feeWithdraw: d.fees.feeWithdraw,
-        stampExpireDeposit: d.stampExpireDeposit,
-        stampExpireLegal: d.stampExpireLegal,
-        stampExpireWithdraw: d.stampExpireWithdraw,
-        stampStart: d.stampStart,
-        value: DenominationRecord.getValue(d),
-      };
-      return denomInfo;
+      return DenominationRecord.toDenomInfo(d);
     }
     return undefined;
   }