path: root/src/wallet.ts

/*
 This file is part of TALER
 (C) 2015 GNUnet e.V.

 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.

 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
 TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
 */

/**
 * High-level wallet operations that should be indepentent from the underlying
 * browser extension interface.
 */

/**
 * Imports.
 */
import { CryptoApi, CryptoWorkerFactory } from "./crypto/cryptoApi";
import {
  amountToPretty,
  canonicalJson,
  canonicalizeBaseUrl,
  getTalerStampSec,
  strcmp,
} from "./helpers";
import { HttpRequestLibrary, RequestException } from "./http";
import * as LibtoolVersion from "./libtoolVersion";
import {
  AbortTransaction,
  JoinLeftResult,
  JoinResult,
  QueryRoot,
} from "./query";
import { TimerGroup } from "./timer";

import { AmountJson } from "./amounts";
import * as Amounts from "./amounts";

import URI = require("urijs");

import {
  CoinRecord,
  CoinStatus,
  CoinsReturnRecord,
  CurrencyRecord,
  DenominationRecord,
  DenominationStatus,
  ExchangeRecord,
  PreCoinRecord,
  ProposalDownloadRecord,
  PurchaseRecord,
  RefreshPreCoinRecord,
  RefreshSessionRecord,
  ReserveRecord,
  Stores,
  TipRecord,
  WireFee,
} from "./dbTypes";
import {
  Auditor,
  ContractTerms,
  Denomination,
  ExchangeHandle,
  ExchangeWireJson,
  KeysJson,
  MerchantRefundPermission,
  MerchantRefundResponse,
  PayReq,
  PaybackConfirmation,
  Proposal,
  RefundRequest,
  ReserveStatus,
  TipPlanchetDetail,
  TipResponse,
  WithdrawOperationStatusResponse,
  TipPickupGetResponse,
} from "./talerTypes";
import {
  Badge,
  BenchmarkResult,
  CoinSelectionResult,
  CoinWithDenom,
  ConfirmPayResult,
  ConfirmReserveRequest,
  CreateReserveRequest,
  CreateReserveResponse,
  HistoryRecord,
  NextUrlResult,
  Notifier,
  PayCoinInfo,
  ReserveCreationInfo,
  ReturnCoinsRequest,
  SenderWireInfos,
  TipStatus,
  WalletBalance,
  WalletBalanceEntry,
  PreparePayResult,
  DownloadedWithdrawInfo,
  WithdrawDetails,
  AcceptWithdrawalResponse,
  PurchaseDetails,
} from "./walletTypes";
import { openPromise } from "./promiseUtils";
import {
  parsePayUri,
  parseWithdrawUri,
  parseTipUri,
  parseRefundUri,
} from "./taleruri";

interface SpeculativePayData {
  payCoinInfo: PayCoinInfo;
  exchangeUrl: string;
  proposalId: number;
  proposal: ProposalDownloadRecord;
}

/**
 * Wallet protocol version spoken with the exchange
 * and merchant.
 *
 * Uses libtool's current:revision:age versioning.
 */
export const WALLET_PROTOCOL_VERSION = "3:0:0";

const WALLET_CACHE_BREAKER_CLIENT_VERSION = "2";

const builtinCurrencies: CurrencyRecord[] = [
  {
    auditors: [
      {
        auditorPub: "BW9DC48PHQY4NH011SHHX36DZZ3Q22Y6X7FZ1VD1CMZ2PTFZ6PN0",
        baseUrl: "https://auditor.demo.taler.net/",
        expirationStamp: new Date(2027, 1).getTime(),
      },
    ],
    exchanges: [],
    fractionalDigits: 2,
    name: "KUDOS",
  },
];

function isWithdrawableDenom(d: DenominationRecord) {
  const nowSec = new Date().getTime() / 1000;
  const stampWithdrawSec = getTalerStampSec(d.stampExpireWithdraw);
  if (stampWithdrawSec === null) {
    return false;
  }
  const stampStartSec = getTalerStampSec(d.stampStart);
  if (stampStartSec === null) {
    return false;
  }
  // Withdraw if still possible to withdraw within a minute
  if (stampWithdrawSec + 60 > nowSec && nowSec >= stampStartSec) {
    return true;
  }
  return false;
}

interface SelectPayCoinsResult {
  cds: CoinWithDenom[];
  totalFees: AmountJson;
}

/**
 * Get the amount that we lose when refreshing a coin of the given denomination
 * with a certain amount left.
 *
 * If the amount left is zero, then the refresh cost
 * is also considered to be zero.  If a refresh isn't possible (e.g. due to lack of
 * the right denominations), then the cost is the full amount left.
 *
 * Considers refresh fees, withdrawal fees after refresh and amounts too small
 * to refresh.
 */
export function getTotalRefreshCost(
  denoms: DenominationRecord[],
  refreshedDenom: DenominationRecord,
  amountLeft: AmountJson,
): AmountJson {
  const withdrawAmount = Amounts.sub(amountLeft, refreshedDenom.feeRefresh)
    .amount;
  const withdrawDenoms = getWithdrawDenomList(withdrawAmount, denoms);
  const resultingAmount = Amounts.add(
    Amounts.getZero(withdrawAmount.currency),
    ...withdrawDenoms.map(d => d.value),
  ).amount;
  const totalCost = Amounts.sub(amountLeft, resultingAmount).amount;
  Wallet.enableTracing &&
    console.log(
      "total refresh cost for",
      amountToPretty(amountLeft),
      "is",
      amountToPretty(totalCost),
    );
  return totalCost;
}

/**
 * Select coins for a payment under the merchant's constraints.
 *
 * @param denoms all available denoms, used to compute refresh fees
 */
export function selectPayCoins(
  denoms: DenominationRecord[],
  cds: CoinWithDenom[],
  paymentAmount: AmountJson,
  depositFeeLimit: AmountJson,
): SelectPayCoinsResult | undefined {
  if (cds.length === 0) {
    return undefined;
  }
  // Sort by ascending deposit fee and denomPub if deposit fee is the same
  // (to guarantee deterministic results)
  cds.sort(
    (o1, o2) =>
      Amounts.cmp(o1.denom.feeDeposit, o2.denom.feeDeposit) ||
      strcmp(o1.denom.denomPub, o2.denom.denomPub),
  );
  const currency = cds[0].denom.value.currency;
  const cdsResult: CoinWithDenom[] = [];
  let accDepositFee: AmountJson = Amounts.getZero(currency);
  let accAmount: AmountJson = Amounts.getZero(currency);
  for (const { coin, denom } of cds) {
    if (coin.suspended) {
      continue;
    }
    if (coin.status !== CoinStatus.Fresh) {
      continue;
    }
    if (Amounts.cmp(denom.feeDeposit, coin.currentAmount) >= 0) {
      continue;
    }
    cdsResult.push({ coin, denom });
    accDepositFee = Amounts.add(denom.feeDeposit, accDepositFee).amount;
    let leftAmount = Amounts.sub(
      coin.currentAmount,
      Amounts.sub(paymentAmount, accAmount).amount,
    ).amount;
    accAmount = Amounts.add(coin.currentAmount, accAmount).amount;
    const coversAmount = Amounts.cmp(accAmount, paymentAmount) >= 0;
    const coversAmountWithFee =
      Amounts.cmp(
        accAmount,
        Amounts.add(paymentAmount, denom.feeDeposit).amount,
      ) >= 0;
    const isBelowFee = Amounts.cmp(accDepositFee, depositFeeLimit) <= 0;

    Wallet.enableTracing &&
      console.log("candidate coin selection", {
        coversAmount,
        isBelowFee,
        accDepositFee,
        accAmount,
        paymentAmount,
      });

    if ((coversAmount && isBelowFee) || coversAmountWithFee) {
      const depositFeeToCover = Amounts.sub(accDepositFee, depositFeeLimit)
        .amount;
      leftAmount = Amounts.sub(leftAmount, depositFeeToCover).amount;
      Wallet.enableTracing &&
        console.log("deposit fee to cover", amountToPretty(depositFeeToCover));

      let totalFees: AmountJson = Amounts.getZero(currency);
      if (coversAmountWithFee && !isBelowFee) {
        // these are the fees the customer has to pay
        // because the merchant doesn't cover them
        totalFees = Amounts.sub(depositFeeLimit, accDepositFee).amount;
      }
      totalFees = Amounts.add(
        totalFees,
        getTotalRefreshCost(denoms, denom, leftAmount),
      ).amount;
      return { cds: cdsResult, totalFees };
    }
  }
  return undefined;
}

/**
 * Get a list of denominations (with repetitions possible)
 * whose total value is as close as possible to the available
 * amount, but never larger.
 */
function getWithdrawDenomList(
  amountAvailable: AmountJson,
  denoms: DenominationRecord[],
): DenominationRecord[] {
  let remaining = Amounts.copy(amountAvailable);
  const ds: DenominationRecord[] = [];

  denoms = denoms.filter(isWithdrawableDenom);
  denoms.sort((d1, d2) => Amounts.cmp(d2.value, d1.value));

  // This is an arbitrary number of coins
  // we can withdraw in one go.  It's not clear if this limit
  // is useful ...
  for (let i = 0; i < 1000; i++) {
    let found = false;
    for (const d of denoms) {
      const cost = Amounts.add(d.value, d.feeWithdraw).amount;
      if (Amounts.cmp(remaining, cost) < 0) {
        continue;
      }
      found = true;
      remaining = Amounts.sub(remaining, cost).amount;
      ds.push(d);
      break;
    }
    if (!found) {
      break;
    }
  }
  return ds;
}

interface CoinsForPaymentArgs {
  allowedAuditors: Auditor[];
  allowedExchanges: ExchangeHandle[];
  depositFeeLimit: AmountJson;
  paymentAmount: AmountJson;
  wireFeeAmortization: number;
  wireFeeLimit: AmountJson;
  wireFeeTime: number;
  wireMethod: string;
}

/**
 * The platform-independent wallet implementation.
 */
export class Wallet {
  /**
   * IndexedDB database used by the wallet.
   */
  db: IDBDatabase;
  static enableTracing = false;
  private http: HttpRequestLibrary;
  private badge: Badge;
  private notifier: Notifier;
  private cryptoApi: CryptoApi;
  private processPreCoinConcurrent = 0;
  private processPreCoinThrottle: { [url: string]: number } = {};
  private timerGroup: TimerGroup;
  private speculativePayData: SpeculativePayData | undefined;
  private cachedNextUrl: { [fulfillmentUrl: string]: NextUrlResult } = {};
  private activeTipOperations: { [s: string]: Promise<void> } = {};
  private activeProcessReserveOperations: {
    [reservePub: string]: Promise<void>;
  } = {};
  private activeProcessPreCoinOperations: {
    [preCoinPub: string]: Promise<void>;
  } = {};
  private activeRefreshOperations: {
    [coinPub: string]: Promise<void>;
  } = {};

  /**
   * Set of identifiers for running operations.
   */
  private runningOperations: Set<string> = new Set();

  q(): QueryRoot {
    return new QueryRoot(this.db);
  }

  constructor(
    db: IDBDatabase,
    http: HttpRequestLibrary,
    badge: Badge,
    notifier: Notifier,
    cryptoWorkerFactory: CryptoWorkerFactory,
  ) {
    this.db = db;
    this.http = http;
    this.badge = badge;
    this.notifier = notifier;
    this.cryptoApi = new CryptoApi(cryptoWorkerFactory);
    this.timerGroup = new TimerGroup();

    const init = async () => {
      await this.fillDefaults().catch(e => console.log(e));
      await this.collectGarbage().catch(e => console.log(e));
      this.updateExchanges();
      this.resumePendingFromDb();
      this.timerGroup.every(1000 * 60 * 15, () => this.updateExchanges());
    };

    init();
  }

  private async fillDefaults() {
    const onTrue = (r: QueryRoot) => {};
    const onFalse = (r: QueryRoot) => {
      Wallet.enableTracing && console.log("applying defaults");
      r.put(Stores.config, { key: "currencyDefaultsApplied", value: true })
        .putAll(Stores.currencies, builtinCurrencies)
        .finish();
    };
    await this.q()
      .iter(Stores.config)
      .filter(x => x.key === "currencyDefaultsApplied")
      .first()
      .cond(x => x && x.value, onTrue, onFalse);
  }

  private startOperation(operationId: string) {
    this.runningOperations.add(operationId);
    this.badge.startBusy();
  }

  private stopOperation(operationId: string) {
    this.runningOperations.delete(operationId);
    if (this.runningOperations.size === 0) {
      this.badge.stopBusy();
    }
  }

  async updateExchanges(): Promise<void> {
    const exchangesUrls = await this.q()
      .iter(Stores.exchanges)
      .map(e => e.baseUrl)
      .toArray();

    for (const url of exchangesUrls) {
      this.updateExchangeFromUrl(url).catch(e => {
        console.error("updating exchange failed", e);
      });
    }
  }

  /**
   * Resume various pending operations that are pending
   * by looking at the database.
   */
  private resumePendingFromDb(): void {
    Wallet.enableTracing && console.log("resuming pending operations from db");

    this.q()
      .iter(Stores.reserves)
      .forEach(reserve => {
        Wallet.enableTracing &&
          console.log("resuming reserve", reserve.reserve_pub);
        this.processReserve(reserve.reserve_pub);
      });

    this.q()
      .iter(Stores.precoins)
      .forEach(preCoin => {
        Wallet.enableTracing && console.log("resuming precoin");
        this.processPreCoin(preCoin.coinPub);
      });

    this.q()
      .iter(Stores.refresh)
      .forEach((r: RefreshSessionRecord) => {
        this.continueRefreshSession(r);
      });

    this.q()
      .iter(Stores.coinsReturns)
      .forEach((r: CoinsReturnRecord) => {
        this.depositReturnedCoins(r);
      });

    // FIXME: optimize via index
    this.q()
      .iter(Stores.coins)
      .forEach((c: CoinRecord) => {
        if (c.status === CoinStatus.Dirty) {
          Wallet.enableTracing &&
            console.log("resuming pending refresh for coin", c);
          this.refresh(c.coinPub);
        }
      });
  }

  private async getCoinsForReturn(
    exchangeBaseUrl: string,
    amount: AmountJson,
  ): Promise<CoinWithDenom[] | undefined> {
    const exchange = await this.q().get(Stores.exchanges, exchangeBaseUrl);
    if (!exchange) {
      throw Error(`Exchange ${exchangeBaseUrl} not known to the wallet`);
    }

    const coins: CoinRecord[] = await this.q()
      .iterIndex(Stores.coins.exchangeBaseUrlIndex, exchange.baseUrl)
      .toArray();

    if (!coins || !coins.length) {
      return [];
    }

    const denoms = await this.q()
      .iterIndex(Stores.denominations.exchangeBaseUrlIndex, exchange.baseUrl)
      .toArray();

    // Denomination of the first coin, we assume that all other
    // coins have the same currency
    const firstDenom = await this.q().get(Stores.denominations, [
      exchange.baseUrl,
      coins[0].denomPub,
    ]);
    if (!firstDenom) {
      throw Error("db inconsistent");
    }
    const currency = firstDenom.value.currency;

    const cds: CoinWithDenom[] = [];
    for (const coin of coins) {
      const denom = await this.q().get(Stores.denominations, [
        exchange.baseUrl,
        coin.denomPub,
      ]);
      if (!denom) {
        throw Error("db inconsistent");
      }
      if (denom.value.currency !== currency) {
        console.warn(
          `same pubkey for different currencies at exchange ${exchange.baseUrl}`,
        );
        continue;
      }
      if (coin.suspended) {
        continue;
      }
      if (coin.status !== CoinStatus.Fresh) {
        continue;
      }
      cds.push({ coin, denom });
    }

    console.log("coin return:  selecting from possible coins", { cds, amount });

    const res = selectPayCoins(denoms, cds, amount, amount);
    if (res) {
      return res.cds;
    }
    return undefined;
  }

  /**
   * Get exchanges and associated coins that are still spendable, but only
   * if the sum the coins' remaining value covers the payment amount and fees.
   */
  private async getCoinsForPayment(
    args: CoinsForPaymentArgs,
  ): Promise<CoinSelectionResult | undefined> {
    const {
      allowedAuditors,
      allowedExchanges,
      depositFeeLimit,
      paymentAmount,
      wireFeeAmortization,
      wireFeeLimit,
      wireFeeTime,
      wireMethod,
    } = args;

    let remainingAmount = paymentAmount;

    const exchanges = await this.q()
      .iter(Stores.exchanges)
      .toArray();

    for (const exchange of exchanges) {
      let isOkay: boolean = false;

      // is the exchange explicitly allowed?
      for (const allowedExchange of allowedExchanges) {
        if (allowedExchange.master_pub === exchange.masterPublicKey) {
          isOkay = true;
          break;
        }
      }

      // is the exchange allowed because of one of its auditors?
      if (!isOkay) {
        for (const allowedAuditor of allowedAuditors) {
          for (const auditor of exchange.auditors) {
            if (auditor.auditor_pub === allowedAuditor.auditor_pub) {
              isOkay = true;
              break;
            }
          }
          if (isOkay) {
            break;
          }
        }
      }

      if (!isOkay) {
        continue;
      }

      const coins: CoinRecord[] = await this.q()
        .iterIndex(Stores.coins.exchangeBaseUrlIndex, exchange.baseUrl)
        .toArray();

      const denoms = await this.q()
        .iterIndex(Stores.denominations.exchangeBaseUrlIndex, exchange.baseUrl)
        .toArray();
      if (!coins || coins.length === 0) {
        continue;
      }

      // Denomination of the first coin, we assume that all other
      // coins have the same currency
      const firstDenom = await this.q().get(Stores.denominations, [
        exchange.baseUrl,
        coins[0].denomPub,
      ]);
      if (!firstDenom) {
        throw Error("db inconsistent");
      }
      const currency = firstDenom.value.currency;
      const cds: CoinWithDenom[] = [];
      for (const coin of coins) {
        const denom = await this.q().get(Stores.denominations, [
          exchange.baseUrl,
          coin.denomPub,
        ]);
        if (!denom) {
          throw Error("db inconsistent");
        }
        if (denom.value.currency !== currency) {
          console.warn(
            `same pubkey for different currencies at exchange ${exchange.baseUrl}`,
          );
          continue;
        }
        if (coin.suspended) {
          continue;
        }
        if (coin.status !== CoinStatus.Fresh) {
          continue;
        }
        cds.push({ coin, denom });
      }

      const fees = await this.q().get(
        Stores.exchangeWireFees,
        exchange.baseUrl,
      );
      if (!fees) {
        console.error("no fees found for exchange", exchange);
        continue;
      }

      let totalFees = Amounts.getZero(currency);
      let wireFee: AmountJson | undefined;
      for (const fee of fees.feesForType[wireMethod] || []) {
        if (fee.startStamp <= wireFeeTime && fee.endStamp >= wireFeeTime) {
          wireFee = fee.wireFee;
          break;
        }
      }

      if (wireFee) {
        const amortizedWireFee = Amounts.divide(wireFee, wireFeeAmortization);
        if (Amounts.cmp(wireFeeLimit, amortizedWireFee) < 0) {
          totalFees = Amounts.add(amortizedWireFee, totalFees).amount;
          remainingAmount = Amounts.add(amortizedWireFee, remainingAmount)
            .amount;
        }
      }

      const res = selectPayCoins(denoms, cds, remainingAmount, depositFeeLimit);

      if (res) {
        totalFees = Amounts.add(totalFees, res.totalFees).amount;
        return {
          cds: res.cds,
          exchangeUrl: exchange.baseUrl,
          totalAmount: remainingAmount,
          totalFees,
        };
      }
    }
    return undefined;
  }

  /**
   * Record all information that is necessary to
   * pay for a proposal in the wallet's database.
   */
  private async recordConfirmPay(
    proposal: ProposalDownloadRecord,
    payCoinInfo: PayCoinInfo,
    chosenExchange: string,
  ): Promise<PurchaseRecord> {
    const payReq: PayReq = {
      coins: payCoinInfo.sigs,
      merchant_pub: proposal.contractTerms.merchant_pub,
      mode: "pay",
      order_id: proposal.contractTerms.order_id,
    };
    const t: PurchaseRecord = {
      abortDone: false,
      abortRequested: false,
      contractTerms: proposal.contractTerms,
      contractTermsHash: proposal.contractTermsHash,
      finished: false,
      lastSessionId: undefined,
      merchantSig: proposal.merchantSig,
      payReq,
      refundsDone: {},
      refundsPending: {},
      timestamp: new Date().getTime(),
      timestamp_refund: 0,
    };

    await this.q()
      .put(Stores.purchases, t)
      .putAll(Stores.coins, payCoinInfo.updatedCoins)
      .finish();
    this.badge.showNotification();
    this.notifier.notify();
    return t;
  }

  getNextUrl(contractTerms: ContractTerms): string {
    const fu = new URI(contractTerms.fulfillment_url);
    fu.addSearch("order_id", contractTerms.order_id);
    return fu.href();
  }

  /**
   * Check if a payment for the given taler://pay/ URI is possible.
   *
   * If the payment is possible, the signature are already generated but not
   * yet send to the merchant.
   */
  async preparePay(talerPayUri: string): Promise<PreparePayResult> {
    const uriResult = parsePayUri(talerPayUri);

    if (!uriResult) {
      return {
        status: "error",
        error: "URI not supported",
      };
    }

    let proposalId: number;
    try {
      proposalId = await this.downloadProposal(
        uriResult.downloadUrl,
        uriResult.sessionId,
      );
    } catch (e) {
      return {
        status: "error",
        error: e.toString(),
      };
    }
    const proposal = await this.getProposal(proposalId);
    if (!proposal) {
      throw Error("could not get proposal");
    }

    console.log("proposal", proposal);

    const differentPurchase = await this.q().getIndexed(
      Stores.purchases.fulfillmentUrlIndex,
      proposal.contractTerms.fulfillment_url,
    );

    if (differentPurchase) {
      // We do this check to prevent merchant B to find out if we bought a
      // digital product with merchant A by abusing the existing payment
      // redirect feature.
      if (
        differentPurchase.contractTerms.merchant_pub !=
        proposal.contractTerms.merchant_pub
      ) {
        console.warn(
          "merchant with different public key offered contract with same fulfillment URL as an existing purchase",
        );
      } else {
        if (uriResult.sessionId) {
          await this.submitPay(
            differentPurchase.contractTermsHash,
            uriResult.sessionId,
          );
        }
        return {
          status: "paid",
          contractTerms: differentPurchase.contractTerms,
          nextUrl: this.getNextUrl(differentPurchase.contractTerms),
        };
      }
    }

    // First check if we already payed for it.
    const purchase = await this.q().get(
      Stores.purchases,
      proposal.contractTermsHash,
    );

    if (!purchase) {
      const paymentAmount = Amounts.parseOrThrow(proposal.contractTerms.amount);
      let wireFeeLimit;
      if (proposal.contractTerms.max_wire_fee) {
        wireFeeLimit = Amounts.parseOrThrow(
          proposal.contractTerms.max_wire_fee,
        );
      } else {
        wireFeeLimit = Amounts.getZero(paymentAmount.currency);
      }
      // If not already payed, check if we could pay for it.
      const res = await this.getCoinsForPayment({
        allowedAuditors: proposal.contractTerms.auditors,
        allowedExchanges: proposal.contractTerms.exchanges,
        depositFeeLimit: Amounts.parseOrThrow(proposal.contractTerms.max_fee),
        paymentAmount,
        wireFeeAmortization: proposal.contractTerms.wire_fee_amortization || 1,
        wireFeeLimit,
        wireFeeTime: getTalerStampSec(proposal.contractTerms.timestamp) || 0,
        wireMethod: proposal.contractTerms.wire_method,
      });

      if (!res) {
        console.log("not confirming payment, insufficient coins");
        return {
          status: "insufficient-balance",
          contractTerms: proposal.contractTerms,
          proposalId: proposal.id!,
        };
      }

      // Only create speculative signature if we don't already have one for this proposal
      if (
        !this.speculativePayData ||
        (this.speculativePayData &&
          this.speculativePayData.proposalId !== proposalId)
      ) {
        const { exchangeUrl, cds, totalAmount } = res;
        const payCoinInfo = await this.cryptoApi.signDeposit(
          proposal.contractTerms,
          cds,
          totalAmount,
        );
        this.speculativePayData = {
          exchangeUrl,
          payCoinInfo,
          proposal,
          proposalId,
        };
        Wallet.enableTracing &&
          console.log("created speculative pay data for payment");
      }

      return {
        status: "payment-possible",
        contractTerms: proposal.contractTerms,
        proposalId: proposal.id!,
        totalFees: res.totalFees,
      };
    }

    if (uriResult.sessionId) {
      await this.submitPay(purchase.contractTermsHash, uriResult.sessionId);
    }

    return {
      status: "paid",
      contractTerms: proposal.contractTerms,
      nextUrl: this.getNextUrl(purchase.contractTerms),
    };
  }

  /**
   * Download a proposal and store it in the database.
   * Returns an id for it to retrieve it later.
   *
   * @param sessionId Current session ID, if the proposal is being
   *  downloaded in the context of a session ID.
   */
  async downloadProposal(url: string, sessionId?: string): Promise<number> {
    const oldProposal = await this.q().getIndexed(
      Stores.proposals.urlIndex,
      url,
    );
    if (oldProposal) {
      return oldProposal.id!;
    }

    const { priv, pub } = await this.cryptoApi.createEddsaKeypair();
    const parsed_url = new URI(url);
    const urlWithNonce = parsed_url.setQuery({ nonce: pub }).href();
    console.log("downloading contract from '" + urlWithNonce + "'");
    let resp;
    try {
      resp = await this.http.get(urlWithNonce);
    } catch (e) {
      console.log("contract download failed", e);
      throw e;
    }

    const proposal = Proposal.checked(resp.responseJson);

    const contractTermsHash = await this.hashContract(proposal.contract_terms);

    const proposalRecord: ProposalDownloadRecord = {
      contractTerms: proposal.contract_terms,
      contractTermsHash,
      merchantSig: proposal.sig,
      noncePriv: priv,
      timestamp: new Date().getTime(),
      url,
      downloadSessionId: sessionId,
    };

    const id = await this.q().putWithResult(Stores.proposals, proposalRecord);
    this.notifier.notify();
    if (typeof id !== "number") {
      throw Error("db schema wrong");
    }
    return id;
  }

  async refundFailedPay(proposalId: number) {
    console.log(`refunding failed payment with proposal id ${proposalId}`);
    const proposal: ProposalDownloadRecord | undefined = await this.q().get(
      Stores.proposals,
      proposalId,
    );

    if (!proposal) {
      throw Error(`proposal with id ${proposalId} not found`);
    }

    const purchase = await this.q().get(
      Stores.purchases,
      proposal.contractTermsHash,
    );
    if (!purchase) {
      throw Error("purchase not found for proposal");
    }

    if (purchase.finished) {
      throw Error("can't auto-refund finished purchase");
    }
  }

  async submitPay(
    contractTermsHash: string,
    sessionId: string | undefined,
  ): Promise<ConfirmPayResult> {
    const purchase = await this.q().get(Stores.purchases, contractTermsHash);
    if (!purchase) {
      throw Error("Purchase not found: " + contractTermsHash);
    }
    if (purchase.abortRequested) {
      throw Error("not submitting payment for aborted purchase");
    }
    let resp;
    const payReq = { ...purchase.payReq, session_id: sessionId };

    const payUrl = new URI("pay").absoluteTo(purchase.contractTerms.merchant_base_url).href()

    try {
      resp = await this.http.postJson(payUrl, payReq);
    } catch (e) {
      // Gives the user the option to retry / abort and refresh
      console.log("payment failed", e);
      throw e;
    }
    const merchantResp = resp.responseJson;
    console.log("got success from pay URL");

    const merchantPub = purchase.contractTerms.merchant_pub;
    const valid: boolean = await this.cryptoApi.isValidPaymentSignature(
      merchantResp.sig,
      contractTermsHash,
      merchantPub,
    );
    if (!valid) {
      console.error("merchant payment signature invalid");
      // FIXME: properly display error
      throw Error("merchant payment signature invalid");
    }
    purchase.finished = true;
    const modifiedCoins: CoinRecord[] = [];
    for (const pc of purchase.payReq.coins) {
      const c = await this.q().get<CoinRecord>(Stores.coins, pc.coin_pub);
      if (!c) {
        console.error("coin not found");
        throw Error("coin used in payment not found");
      }
      c.status = CoinStatus.Dirty;
      modifiedCoins.push(c);
    }

    await this.q()
      .putAll(Stores.coins, modifiedCoins)
      .put(Stores.purchases, purchase)
      .finish();
    for (const c of purchase.payReq.coins) {
      this.refresh(c.coin_pub);
    }

    const nextUrl = this.getNextUrl(purchase.contractTerms);
    this.cachedNextUrl[purchase.contractTerms.fulfillment_url] = {
      nextUrl,
      lastSessionId: sessionId,
    };

    return { nextUrl };
  }

  /**
   * Refresh all dirty coins.
   * The returned promise resolves only after all refresh
   * operations have completed.
   */
  async refreshDirtyCoins(): Promise<{ numRefreshed: number }> {
    let n = 0;
    const coins = await this.q()
      .iter(Stores.coins)
      .toArray();
    for (let coin of coins) {
      if (coin.status == CoinStatus.Dirty) {
        try {
          await this.refresh(coin.coinPub);
        } catch (e) {
          console.log("error during refresh");
        }

        n += 1;
      }
    }
    return { numRefreshed: n };
  }

  /**
   * Add a contract to the wallet and sign coins, and send them.
   */
  async confirmPay(
    proposalId: number,
    sessionIdOverride: string | undefined,
  ): Promise<ConfirmPayResult> {
    Wallet.enableTracing &&
      console.log(
        `executing confirmPay with proposalId ${proposalId} and sessionIdOverride ${sessionIdOverride}`,
      );
    const proposal: ProposalDownloadRecord | undefined = await this.q().get(
      Stores.proposals,
      proposalId,
    );

    if (!proposal) {
      throw Error(`proposal with id ${proposalId} not found`);
    }

    const sessionId = sessionIdOverride || proposal.downloadSessionId;

    let purchase = await this.q().get(
      Stores.purchases,
      proposal.contractTermsHash,
    );

    if (purchase) {
      return this.submitPay(purchase.contractTermsHash, sessionId);
    }

    const contractAmount = Amounts.parseOrThrow(proposal.contractTerms.amount);

    let wireFeeLimit;
    if (!proposal.contractTerms.max_wire_fee) {
      wireFeeLimit = Amounts.getZero(contractAmount.currency);
    } else {
      wireFeeLimit = Amounts.parseOrThrow(proposal.contractTerms.max_wire_fee);
    }

    const res = await this.getCoinsForPayment({
      allowedAuditors: proposal.contractTerms.auditors,
      allowedExchanges: proposal.contractTerms.exchanges,
      depositFeeLimit: Amounts.parseOrThrow(proposal.contractTerms.max_fee),
      paymentAmount: Amounts.parseOrThrow(proposal.contractTerms.amount),
      wireFeeAmortization: proposal.contractTerms.wire_fee_amortization || 1,
      wireFeeLimit,
      wireFeeTime: getTalerStampSec(proposal.contractTerms.timestamp) || 0,
      wireMethod: proposal.contractTerms.wire_method,
    });

    Wallet.enableTracing && console.log("coin selection result", res);

    if (!res) {
      // Should not happen, since checkPay should be called first
      console.log("not confirming payment, insufficient coins");
      throw Error("insufficient balance");
    }

    const sd = await this.getSpeculativePayData(proposalId);
    if (!sd) {
      const { exchangeUrl, cds, totalAmount } = res;
      const payCoinInfo = await this.cryptoApi.signDeposit(
        proposal.contractTerms,
        cds,
        totalAmount,
      );
      purchase = await this.recordConfirmPay(
        proposal,
        payCoinInfo,
        exchangeUrl,
      );
    } else {
      purchase = await this.recordConfirmPay(
        sd.proposal,
        sd.payCoinInfo,
        sd.exchangeUrl,
      );
    }

    return this.submitPay(purchase.contractTermsHash, sessionId);
  }

  /**
   * Get the speculative pay data, but only if coins have not changed in between.
   */
  async getSpeculativePayData(
    proposalId: number,
  ): Promise<SpeculativePayData | undefined> {
    const sp = this.speculativePayData;
    if (!sp) {
      return;
    }
    if (sp.proposalId !== proposalId) {
      return;
    }
    const coinKeys = sp.payCoinInfo.updatedCoins.map(x => x.coinPub);
    const coins = await this.q().getMany(Stores.coins, coinKeys);
    for (let i = 0; i < coins.length; i++) {
      const specCoin = sp.payCoinInfo.originalCoins[i];
      const currentCoin = coins[i];

      // Coin does not exist anymore!
      if (!currentCoin) {
        return;
      }
      if (
        Amounts.cmp(specCoin.currentAmount, currentCoin.currentAmount) !== 0
      ) {
        return;
      }
    }
    return sp;
  }

  private async sendReserveInfoToBank(reservePub: string) {
    const reserve = await this.q().get<ReserveRecord>(
      Stores.reserves,
      reservePub,
    );
    if (!reserve) {
      throw Error("reserve not in db");
    }

    const bankStatusUrl = reserve.bankWithdrawStatusUrl;
    if (!bankStatusUrl) {
      throw Error("reserve not confirmed yet, and no status URL available.");
    }

    const now = new Date().getTime();
    let status;
    try {
      const statusResp = await this.http.get(bankStatusUrl);
      status = WithdrawOperationStatusResponse.checked(statusResp.responseJson);
    } catch (e) {
      console.log("bank error response", e);
      throw e;
    }

    if (status.transfer_done) {
      await this.q().mutate(Stores.reserves, reservePub, r => {
        r.timestamp_confirmed = now;
        return r;
      });
    } else if (reserve.timestamp_reserve_info_posted === 0) {
      try {
        if (!status.selection_done) {
          const bankResp = await this.http.postJson(bankStatusUrl, {
            reserve_pub: reservePub,
            selected_exchange: reserve.exchangeWire,
          });
        }
      } catch (e) {
        console.log("bank error response", e);
        throw e;
      }
      await this.q().mutate(Stores.reserves, reservePub, r => {
        r.timestamp_reserve_info_posted = now;
        return r;
      });
    }
  }

  /**
   * First fetch information requred to withdraw from the reserve,
   * then deplete the reserve, withdrawing coins until it is empty.
   */
  async processReserve(reservePub: string): Promise<void> {
    const activeOperation = this.activeProcessReserveOperations[reservePub];

    if (activeOperation) {
      return activeOperation;
    }

    const opId = "reserve-" + reservePub;
    this.startOperation(opId);

    // This opened promise gets resolved only once the
    // reserve withdraw operation succeeds, even after retries.
    const op = openPromise<void>();

    const processReserveInternal = async (retryDelayMs: number = 250) => {
      let isHardError = false;
      // By default, do random, exponential backoff truncated at 3 minutes.
      // Sometimes though, we want to try again faster.
      let maxTimeout = 3000 * 60;
      try {
        const reserve = await this.q().get<ReserveRecord>(
          Stores.reserves,
          reservePub,
        );
        if (!reserve) {
          isHardError = true;
          throw Error("reserve not in db");
        }

        if (reserve.timestamp_confirmed === 0) {
          const bankStatusUrl = reserve.bankWithdrawStatusUrl;
          if (!bankStatusUrl) {
            isHardError = true;
            throw Error(
              "reserve not confirmed yet, and no status URL available.",
            );
          }
          maxTimeout = 2000;
          /* This path is only taken if the wallet crashed after a withdraw was accepted,
           * and before the information could be sent to the bank. */
          await this.sendReserveInfoToBank(reservePub);
          throw Error("waiting for reserve to be confirmed");
        }

        const updatedReserve = await this.updateReserve(reservePub);
        await this.depleteReserve(updatedReserve);
        op.resolve();
      } catch (e) {
        if (isHardError) {
          op.reject(e);
        }
        const nextDelay = Math.min(
          2 * retryDelayMs + retryDelayMs * Math.random(),
          maxTimeout,
        );

        this.timerGroup.after(retryDelayMs, () =>
          processReserveInternal(nextDelay),
        );
      }
    };

    try {
      processReserveInternal();
      this.activeProcessReserveOperations[reservePub] = op.promise;
      await op.promise;
    } finally {
      this.stopOperation(opId);
      delete this.activeProcessReserveOperations[reservePub];
    }
  }

  /**
   * Given a planchet, withdraw a coin from the exchange.
   */
  private async processPreCoin(preCoinPub: string): Promise<void> {
    const activeOperation = this.activeProcessPreCoinOperations[preCoinPub];
    if (activeOperation) {
      return activeOperation;
    }

    const op = openPromise<void>();

    const processPreCoinInternal = async (retryDelayMs: number = 200) => {
      const preCoin = await this.q().get(Stores.precoins, preCoinPub);
      if (!preCoin) {
        console.log("processPreCoin: preCoinPub not found");
        return;
      }
      // Throttle concurrent executions of this function,
      // so we don't withdraw too many coins at once.
      if (
        this.processPreCoinConcurrent >= 4 ||
        this.processPreCoinThrottle[preCoin.exchangeBaseUrl]
      ) {
        const timeout = Math.min(retryDelayMs * 2, 5 * 60 * 1000);
        Wallet.enableTracing &&
          console.log(
            `throttling processPreCoin of ${preCoinPub} for ${timeout}ms`,
          );
        this.timerGroup.after(retryDelayMs, () => processPreCoinInternal());
        return op.promise;
      }

      this.processPreCoinConcurrent++;

      try {
        const exchange = await this.q().get(
          Stores.exchanges,
          preCoin.exchangeBaseUrl,
        );
        if (!exchange) {
          console.error("db inconsistent: exchange for precoin not found");
          return;
        }
        const denom = await this.q().get(Stores.denominations, [
          preCoin.exchangeBaseUrl,
          preCoin.denomPub,
        ]);
        if (!denom) {
          console.error("db inconsistent: denom for precoin not found");
          return;
        }

        const coin = await this.withdrawExecute(preCoin);

        const mutateReserve = (r: ReserveRecord) => {
          const x = Amounts.sub(
            r.precoin_amount,
            preCoin.coinValue,
            denom.feeWithdraw,
          );
          if (x.saturated) {
            console.error("database inconsistent");
            throw AbortTransaction;
          }
          r.precoin_amount = x.amount;
          return r;
        };

        await this.q()
          .mutate(Stores.reserves, preCoin.reservePub, mutateReserve)
          .delete(Stores.precoins, coin.coinPub)
          .add(Stores.coins, coin)
          .finish();

        this.badge.showNotification();

        this.notifier.notify();
        op.resolve();
      } catch (e) {
        console.error(
          "Failed to withdraw coin from precoin, retrying in",
          retryDelayMs,
          "ms",
          e,
        );
        // exponential backoff truncated at one minute
        const nextRetryDelayMs = Math.min(retryDelayMs * 2, 5 * 60 * 1000);
        this.timerGroup.after(retryDelayMs, () =>
          processPreCoinInternal(nextRetryDelayMs),
        );

        const currentThrottle =
          this.processPreCoinThrottle[preCoin.exchangeBaseUrl] || 0;
        this.processPreCoinThrottle[preCoin.exchangeBaseUrl] =
          currentThrottle + 1;
        this.timerGroup.after(retryDelayMs, () => {
          this.processPreCoinThrottle[preCoin.exchangeBaseUrl]--;
        });
      } finally {
        this.processPreCoinConcurrent--;
      }
    };

    try {
      this.activeProcessPreCoinOperations[preCoinPub] = op.promise;
      await processPreCoinInternal();
      return op.promise;
    } finally {
      delete this.activeProcessPreCoinOperations[preCoinPub];
    }
  }

  /**
   * Update the timestamp of when an exchange was used.
   */
  async updateExchangeUsedTime(exchangeBaseUrl: string): Promise<void> {
    const now = new Date().getTime();
    const update = (r: ExchangeRecord) => {
      r.lastUsedTime = now;
      return r;
    };
    await this.q()
      .mutate(Stores.exchanges, exchangeBaseUrl, update)
      .finish();
  }

  /**
   * Create a reserve, but do not flag it as confirmed yet.
   *
   * Adds the corresponding exchange as a trusted exchange if it is neither
   * audited nor trusted already.
   */
  async createReserve(
    req: CreateReserveRequest,
  ): Promise<CreateReserveResponse> {
    const keypair = await this.cryptoApi.createEddsaKeypair();
    const now = new Date().getTime();
    const canonExchange = canonicalizeBaseUrl(req.exchange);

    const reserveRecord: ReserveRecord = {
      created: now,
      current_amount: null,
      exchange_base_url: canonExchange,
      hasPayback: false,
      precoin_amount: Amounts.getZero(req.amount.currency),
      requested_amount: req.amount,
      reserve_priv: keypair.priv,
      reserve_pub: keypair.pub,
      senderWire: req.senderWire,
      timestamp_confirmed: 0,
      timestamp_reserve_info_posted: 0,
      timestamp_depleted: 0,
      bankWithdrawStatusUrl: req.bankWithdrawStatusUrl,
      exchangeWire: req.exchangeWire,
    };

    const senderWire = req.senderWire;
    if (senderWire) {
      const rec = {
        paytoUri: senderWire,
      };
      await this.q()
        .put(Stores.senderWires, rec)
        .finish();
    }

    await this.updateExchangeUsedTime(req.exchange);
    const exchangeInfo = await this.updateExchangeFromUrl(req.exchange);
    const { isAudited, isTrusted } = await this.getExchangeTrust(exchangeInfo);
    let currencyRecord = await this.q().get(
      Stores.currencies,
      exchangeInfo.currency,
    );
    if (!currencyRecord) {
      currencyRecord = {
        auditors: [],
        exchanges: [],
        fractionalDigits: 2,
        name: exchangeInfo.currency,
      };
    }

    if (!isAudited && !isTrusted) {
      currencyRecord.exchanges.push({
        baseUrl: req.exchange,
        exchangePub: exchangeInfo.masterPublicKey,
      });
    }

    await this.q()
      .put(Stores.currencies, currencyRecord)
      .put(Stores.reserves, reserveRecord)
      .finish();

    if (req.bankWithdrawStatusUrl) {
      this.processReserve(keypair.pub);
    }

    const r: CreateReserveResponse = {
      exchange: canonExchange,
      reservePub: keypair.pub,
    };
    return r;
  }

  /**
   * Mark an existing reserve as confirmed.  The wallet will start trying
   * to withdraw from that reserve.  This may not immediately succeed,
   * since the exchange might not know about the reserve yet, even though the
   * bank confirmed its creation.
   *
   * A confirmed reserve should be shown to the user in the UI, while
   * an unconfirmed reserve should be hidden.
   */
  async confirmReserve(req: ConfirmReserveRequest): Promise<void> {
    const now = new Date().getTime();
    const reserve: ReserveRecord | undefined = await this.q().get<
      ReserveRecord
    >(Stores.reserves, req.reservePub);
    if (!reserve) {
      console.error("Unable to confirm reserve, not found in DB");
      return;
    }
    reserve.timestamp_confirmed = now;
    await this.q()
      .put(Stores.reserves, reserve)
      .finish();
    this.notifier.notify();

    this.processReserve(reserve.reserve_pub);
  }

  private async withdrawExecute(pc: PreCoinRecord): Promise<CoinRecord> {
    const wd: any = {};
    wd.denom_pub_hash = pc.denomPubHash;
    wd.reserve_pub = pc.reservePub;
    wd.reserve_sig = pc.withdrawSig;
    wd.coin_ev = pc.coinEv;
    const reqUrl = new URI("reserve/withdraw").absoluteTo(pc.exchangeBaseUrl);
    const resp = await this.http.postJson(reqUrl.href(), wd);

    if (resp.status !== 200) {
      throw new RequestException({
        hint: "Withdrawal failed",
        status: resp.status,
      });
    }
    const r = resp.responseJson;
    const denomSig = await this.cryptoApi.rsaUnblind(
      r.ev_sig,
      pc.blindingKey,
      pc.denomPub,
    );
    const coin: CoinRecord = {
      blindingKey: pc.blindingKey,
      coinPriv: pc.coinPriv,
      coinPub: pc.coinPub,
      currentAmount: pc.coinValue,
      denomPub: pc.denomPub,
      denomPubHash: pc.denomPubHash,
      denomSig,
      exchangeBaseUrl: pc.exchangeBaseUrl,
      reservePub: pc.reservePub,
      status: CoinStatus.Fresh,
    };
    return coin;
  }

  /**
   * Withdraw coins from a reserve until it is empty.
   *
   * When finished, marks the reserve as depleted by setting
   * the depleted timestamp.
   */
  private async depleteReserve(reserve: ReserveRecord): Promise<void> {
    Wallet.enableTracing && console.log("depleting reserve");
    if (!reserve.current_amount) {
      throw Error("can't withdraw when amount is unknown");
    }
    const withdrawAmount = reserve.current_amount;
    if (!withdrawAmount) {
      throw Error("can't withdraw when amount is unknown");
    }
    const denomsForWithdraw = await this.getVerifiedWithdrawDenomList(
      reserve.exchange_base_url,
      withdrawAmount,
    );
    const smallestAmount = await this.getVerifiedSmallestWithdrawAmount(
      reserve.exchange_base_url,
    );

    console.log(`withdrawing ${denomsForWithdraw.length} coins`);

    const ps = denomsForWithdraw.map(async denom => {
      function mutateReserve(r: ReserveRecord): ReserveRecord {
        const currentAmount = r.current_amount;
        if (!currentAmount) {
          throw Error("can't withdraw when amount is unknown");
        }
        r.precoin_amount = Amounts.add(
          r.precoin_amount,
          denom.value,
          denom.feeWithdraw,
        ).amount;
        const result = Amounts.sub(
          currentAmount,
          denom.value,
          denom.feeWithdraw,
        );
        if (result.saturated) {
          console.error("can't create precoin, saturated");
          throw AbortTransaction;
        }
        r.current_amount = result.amount;

        // Reserve is depleted if the amount left is too small to withdraw
        if (Amounts.cmp(r.current_amount, smallestAmount) < 0) {
          r.timestamp_depleted = new Date().getTime();
        }

        return r;
      }

      const preCoin = await this.cryptoApi.createPreCoin(denom, reserve);

      // This will fail and throw an exception if the remaining amount in the
      // reserve is too low to create a pre-coin.
      try {
        await this.q()
          .put(Stores.precoins, preCoin)
          .mutate(Stores.reserves, reserve.reserve_pub, mutateReserve)
          .finish();
        console.log("created precoin", preCoin.coinPub);
      } catch (e) {
        console.log("can't create pre-coin:", e.name, e.message);
        return;
      }
      await this.processPreCoin(preCoin.coinPub);
    });

    await Promise.all(ps);
  }

  /**
   * Update the information about a reserve that is stored in the wallet
   * by quering the reserve's exchange.
   */
  private async updateReserve(reservePub: string): Promise<ReserveRecord> {
    const reserve = await this.q().get<ReserveRecord>(
      Stores.reserves,
      reservePub,
    );
    if (!reserve) {
      throw Error("reserve not in db");
    }

    if (reserve.timestamp_confirmed === 0) {
      throw Error("");
    }

    const reqUrl = new URI("reserve/status").absoluteTo(
      reserve.exchange_base_url,
    );
    reqUrl.query({ reserve_pub: reservePub });
    const resp = await this.http.get(reqUrl.href());
    if (resp.status !== 200) {
      Wallet.enableTracing &&
        console.warn(`reserve/status returned ${resp.status}`);
      throw Error();
    }
    const reserveInfo = ReserveStatus.checked(resp.responseJson);
    if (!reserveInfo) {
      throw Error();
    }
    reserve.current_amount = Amounts.parseOrThrow(reserveInfo.balance);
    await this.q()
      .put(Stores.reserves, reserve)
      .finish();
    this.notifier.notify();
    return reserve;
  }

  /**
   * Get the wire information for the exchange with the given base URL.
   */
  async getWireInfo(exchangeBaseUrl: string): Promise<ExchangeWireJson> {
    exchangeBaseUrl = canonicalizeBaseUrl(exchangeBaseUrl);
    const reqUrl = new URI("wire")
      .absoluteTo(exchangeBaseUrl)
      .addQuery("cacheBreaker", WALLET_CACHE_BREAKER_CLIENT_VERSION);
    const resp = await this.http.get(reqUrl.href());

    if (resp.status !== 200) {
      throw Error("/wire request failed");
    }

    const wiJson = resp.responseJson;
    if (!wiJson) {
      throw Error("/wire response malformed");
    }

    return ExchangeWireJson.checked(wiJson);
  }

  async getPossibleDenoms(exchangeBaseUrl: string) {
    return this.q()
      .iterIndex(Stores.denominations.exchangeBaseUrlIndex, exchangeBaseUrl)
      .filter(
        d =>
          d.status === DenominationStatus.Unverified ||
          d.status === DenominationStatus.VerifiedGood,
      )
      .toArray();
  }

  /**
   * Compute the smallest withdrawable amount possible, based on verified denominations.
   *
   * Writes to the DB in order to record the result from verifying
   * denominations.
   */
  async getVerifiedSmallestWithdrawAmount(
    exchangeBaseUrl: string,
  ): Promise<AmountJson> {
    const exchange = await this.q().get(Stores.exchanges, exchangeBaseUrl);
    if (!exchange) {
      throw Error(`exchange ${exchangeBaseUrl} not found`);
    }

    const possibleDenoms = await this.q()
      .iterIndex(Stores.denominations.exchangeBaseUrlIndex, exchange.baseUrl)
      .filter(
        d =>
          d.status === DenominationStatus.Unverified ||
          d.status === DenominationStatus.VerifiedGood,
      )
      .toArray();
    possibleDenoms.sort((d1, d2) => {
      const a1 = Amounts.add(d1.feeWithdraw, d1.value).amount;
      const a2 = Amounts.add(d2.feeWithdraw, d2.value).amount;
      return Amounts.cmp(a1, a2);
    });

    for (const denom of possibleDenoms) {
      if (denom.status === DenominationStatus.VerifiedGood) {
        return Amounts.add(denom.feeWithdraw, denom.value).amount;
      }
      const valid = await this.cryptoApi.isValidDenom(
        denom,
        exchange.masterPublicKey,
      );
      if (!valid) {
        denom.status = DenominationStatus.VerifiedBad;
      } else {
        denom.status = DenominationStatus.VerifiedGood;
      }
      await this.q()
        .put(Stores.denominations, denom)
        .finish();
      if (valid) {
        return Amounts.add(denom.feeWithdraw, denom.value).amount;
      }
    }
    return Amounts.getZero(exchange.currency);
  }

  /**
   * Get a list of denominations to withdraw from the given exchange for the
   * given amount, making sure that all denominations' signatures are verified.
   *
   * Writes to the DB in order to record the result from verifying
   * denominations.
   */
  async getVerifiedWithdrawDenomList(
    exchangeBaseUrl: string,
    amount: AmountJson,
  ): Promise<DenominationRecord[]> {
    const exchange = await this.q().get(Stores.exchanges, exchangeBaseUrl);
    if (!exchange) {
      throw Error(`exchange ${exchangeBaseUrl} not found`);
    }

    const possibleDenoms = await this.q()
      .iterIndex(Stores.denominations.exchangeBaseUrlIndex, exchange.baseUrl)
      .filter(
        d =>
          d.status === DenominationStatus.Unverified ||
          d.status === DenominationStatus.VerifiedGood,
      )
      .toArray();

    let allValid = false;

    let selectedDenoms: DenominationRecord[];

    do {
      allValid = true;
      const nextPossibleDenoms = [];
      selectedDenoms = getWithdrawDenomList(amount, possibleDenoms);
      for (const denom of selectedDenoms || []) {
        if (denom.status === DenominationStatus.Unverified) {
          const valid = await this.cryptoApi.isValidDenom(
            denom,
            exchange.masterPublicKey,
          );
          if (!valid) {
            denom.status = DenominationStatus.VerifiedBad;
            allValid = false;
          } else {
            denom.status = DenominationStatus.VerifiedGood;
            nextPossibleDenoms.push(denom);
          }
          await this.q()
            .put(Stores.denominations, denom)
            .finish();
        } else {
          nextPossibleDenoms.push(denom);
        }
      }
    } while (selectedDenoms.length > 0 && !allValid);

    return selectedDenoms;
  }

  /**
   * Check if and how an exchange is trusted and/or audited.
   */
  async getExchangeTrust(
    exchangeInfo: ExchangeRecord,
  ): Promise<{ isTrusted: boolean; isAudited: boolean }> {
    let isTrusted = false;
    let isAudited = false;
    const currencyRecord = await this.q().get(
      Stores.currencies,
      exchangeInfo.currency,
    );
    if (currencyRecord) {
      for (const trustedExchange of currencyRecord.exchanges) {
        if (trustedExchange.exchangePub === exchangeInfo.masterPublicKey) {
          isTrusted = true;
          break;
        }
      }
      for (const trustedAuditor of currencyRecord.auditors) {
        for (const exchangeAuditor of exchangeInfo.auditors) {
          if (trustedAuditor.auditorPub === exchangeAuditor.auditor_pub) {
            isAudited = true;
            break;
          }
        }
      }
    }
    return { isTrusted, isAudited };
  }

  async getWithdrawDetailsForUri(
    talerWithdrawUri: string,
    maybeSelectedExchange?: string,
  ): Promise<WithdrawDetails> {
    const info = await this.getWithdrawalInfo(talerWithdrawUri);
    let rci: ReserveCreationInfo | undefined = undefined;
    if (maybeSelectedExchange) {
      rci = await this.getWithdrawDetailsForAmount(
        maybeSelectedExchange,
        info.amount,
      );
    }
    return {
      withdrawInfo: info,
      reserveCreationInfo: rci,
    };
  }

  async getWithdrawDetailsForAmount(
    baseUrl: string,
    amount: AmountJson,
  ): Promise<ReserveCreationInfo> {
    const exchangeInfo = await this.updateExchangeFromUrl(baseUrl);

    const selectedDenoms = await this.getVerifiedWithdrawDenomList(
      baseUrl,
      amount,
    );
    let acc = Amounts.getZero(amount.currency);
    for (const d of selectedDenoms) {
      acc = Amounts.add(acc, d.feeWithdraw).amount;
    }
    const actualCoinCost = selectedDenoms
      .map(
        (d: DenominationRecord) => Amounts.add(d.value, d.feeWithdraw).amount,
      )
      .reduce((a, b) => Amounts.add(a, b).amount);

    const wireInfo = await this.getWireInfo(baseUrl);

    const wireFees = await this.q().get(Stores.exchangeWireFees, baseUrl);
    if (!wireFees) {
      // should never happen unless DB is inconsistent
      throw Error(`no wire fees found for exchange ${baseUrl}`);
    }

    const exchangeWireAccounts: string[] = [];
    for (let account of wireInfo.accounts) {
      exchangeWireAccounts.push(account.url);
    }

    const { isTrusted, isAudited } = await this.getExchangeTrust(exchangeInfo);

    let earliestDepositExpiration = Infinity;
    for (const denom of selectedDenoms) {
      const expireDeposit = getTalerStampSec(denom.stampExpireDeposit)!;
      if (expireDeposit < earliestDepositExpiration) {
        earliestDepositExpiration = expireDeposit;
      }
    }

    const possibleDenoms =
      (await this.q()
        .iterIndex(Stores.denominations.exchangeBaseUrlIndex, baseUrl)
        .filter(d => d.isOffered)
        .toArray()) || [];

    const trustedAuditorPubs = [];
    const currencyRecord = await this.q().get<CurrencyRecord>(
      Stores.currencies,
      amount.currency,
    );
    if (currencyRecord) {
      trustedAuditorPubs.push(
        ...currencyRecord.auditors.map(a => a.auditorPub),
      );
    }

    let versionMatch;
    if (exchangeInfo.protocolVersion) {
      versionMatch = LibtoolVersion.compare(
        WALLET_PROTOCOL_VERSION,
        exchangeInfo.protocolVersion,
      );

      if (
        versionMatch &&
        !versionMatch.compatible &&
        versionMatch.currentCmp === -1
      ) {
        console.log("wallet version might be outdated, checking for updates");
        chrome.runtime.requestUpdateCheck((status, details) => {
          console.log("update check status:", status);
        });
      }
    }

    const ret: ReserveCreationInfo = {
      earliestDepositExpiration,
      exchangeInfo,
      exchangeWireAccounts,
      exchangeVersion: exchangeInfo.protocolVersion || "unknown",
      isAudited,
      isTrusted,
      numOfferedDenoms: possibleDenoms.length,
      overhead: Amounts.sub(amount, actualCoinCost).amount,
      selectedDenoms,
      trustedAuditorPubs,
      versionMatch,
      walletVersion: WALLET_PROTOCOL_VERSION,
      wireFees,
      withdrawFee: acc,
    };
    return ret;
  }

  async getExchangePaytoUri(
    exchangeBaseUrl: string,
    supportedTargetTypes: string[],
  ): Promise<string> {
    const wireInfo = await this.getWireInfo(exchangeBaseUrl);
    for (let account of wireInfo.accounts) {
      const paytoUri = new URI(account.url);
      if (supportedTargetTypes.includes(paytoUri.authority())) {
        return account.url;
      }
    }
    throw Error("no matching exchange account found");
  }

  /**
   * Update or add exchange DB entry by fetching the /keys information.
   * Optionally link the reserve entry to the new or existing
   * exchange entry in then DB.
   */
  async updateExchangeFromUrl(baseUrl: string): Promise<ExchangeRecord> {
    baseUrl = canonicalizeBaseUrl(baseUrl);
    const keysUrl = new URI("keys")
      .absoluteTo(baseUrl)
      .addQuery("cacheBreaker", WALLET_CACHE_BREAKER_CLIENT_VERSION);
    const keysResp = await this.http.get(keysUrl.href());
    if (keysResp.status !== 200) {
      throw Error("/keys request failed");
    }
    const exchangeKeysJson = KeysJson.checked(keysResp.responseJson);
    const exchangeWire = await this.getWireInfo(baseUrl);
    return this.updateExchangeFromJson(baseUrl, exchangeKeysJson, exchangeWire);
  }

  private async suspendCoins(exchangeInfo: ExchangeRecord): Promise<void> {
    const resultSuspendedCoins = await this.q()
      .iterIndex(Stores.coins.exchangeBaseUrlIndex, exchangeInfo.baseUrl)
      .indexJoinLeft(
        Stores.denominations.exchangeBaseUrlIndex,
        e => e.exchangeBaseUrl,
      )
      .fold(
        (
          cd: JoinLeftResult<CoinRecord, DenominationRecord>,
          suspendedCoins: CoinRecord[],
        ) => {
          if (!cd.right || !cd.right.isOffered) {
            return Array.prototype.concat(suspendedCoins, [cd.left]);
          }
          return Array.prototype.concat(suspendedCoins);
        },
        [],
      );

    const q = this.q();
    resultSuspendedCoins.map((c: CoinRecord) => {
      Wallet.enableTracing && console.log("suspending coin", c);
      c.suspended = true;
      q.put(Stores.coins, c);
      this.badge.showNotification();
      this.notifier.notify();
    });
    await q.finish();
  }

  private async updateExchangeFromJson(
    baseUrl: string,
    exchangeKeysJson: KeysJson,
    wireMethodDetails: ExchangeWireJson,
  ): Promise<ExchangeRecord> {
    // FIXME: all this should probably be commited atomically
    const updateTimeSec = getTalerStampSec(exchangeKeysJson.list_issue_date);
    if (updateTimeSec === null) {
      throw Error("invalid update time");
    }

    if (exchangeKeysJson.denoms.length === 0) {
      throw Error("exchange doesn't offer any denominations");
    }

    const r = await this.q().get<ExchangeRecord>(Stores.exchanges, baseUrl);

    let exchangeInfo: ExchangeRecord;

    if (!r) {
      exchangeInfo = {
        auditors: exchangeKeysJson.auditors,
        baseUrl,
        currency: Amounts.parseOrThrow(exchangeKeysJson.denoms[0].value)
          .currency,
        lastUpdateTime: updateTimeSec,
        lastUsedTime: 0,
        masterPublicKey: exchangeKeysJson.master_public_key,
      };
      Wallet.enableTracing && console.log("making fresh exchange");
    } else {
      if (updateTimeSec < r.lastUpdateTime) {
        Wallet.enableTracing && console.log("outdated /keys, not updating");
        return r;
      }
      exchangeInfo = r;
      exchangeInfo.lastUpdateTime = updateTimeSec;
      Wallet.enableTracing && console.log("updating old exchange");
    }

    const updatedExchangeInfo = await this.updateExchangeInfo(
      exchangeInfo,
      exchangeKeysJson,
    );
    await this.suspendCoins(updatedExchangeInfo);
    updatedExchangeInfo.protocolVersion = exchangeKeysJson.version;

    await this.q()
      .put(Stores.exchanges, updatedExchangeInfo)
      .finish();

    let oldWireFees = await this.q().get(Stores.exchangeWireFees, baseUrl);
    if (!oldWireFees) {
      oldWireFees = {
        exchangeBaseUrl: baseUrl,
        feesForType: {},
      };
    }

    for (const paytoTargetType in wireMethodDetails.fees) {
      let latestFeeStamp = 0;
      const newFeeDetails = wireMethodDetails.fees[paytoTargetType];
      const oldFeeDetails = oldWireFees.feesForType[paytoTargetType] || [];
      oldWireFees.feesForType[paytoTargetType] = oldFeeDetails;
      for (const oldFee of oldFeeDetails) {
        if (oldFee.endStamp > latestFeeStamp) {
          latestFeeStamp = oldFee.endStamp;
        }
      }
      for (const fee of newFeeDetails) {
        const start = getTalerStampSec(fee.start_date);
        if (start === null) {
          console.error("invalid start stamp in fee", fee);
          continue;
        }
        if (start < latestFeeStamp) {
          continue;
        }
        const end = getTalerStampSec(fee.end_date);
        if (end === null) {
          console.error("invalid end stamp in fee", fee);
          continue;
        }
        const wf: WireFee = {
          closingFee: Amounts.parseOrThrow(fee.closing_fee),
          endStamp: end,
          sig: fee.sig,
          startStamp: start,
          wireFee: Amounts.parseOrThrow(fee.wire_fee),
        };
        const valid: boolean = await this.cryptoApi.isValidWireFee(
          paytoTargetType,
          wf,
          exchangeInfo.masterPublicKey,
        );
        if (!valid) {
          console.error("fee signature invalid", fee);
          throw Error("fee signature invalid");
        }
        oldFeeDetails.push(wf);
      }
    }

    await this.q().put(Stores.exchangeWireFees, oldWireFees);

    if (exchangeKeysJson.payback) {
      for (const payback of exchangeKeysJson.payback) {
        const denom = await this.q().getIndexed(
          Stores.denominations.denomPubHashIndex,
          payback.h_denom_pub,
        );
        if (!denom) {
          continue;
        }
        Wallet.enableTracing && console.log(`cashing back denom`, denom);
        const coins = await this.q()
          .iterIndex(Stores.coins.denomPubIndex, denom.denomPub)
          .toArray();
        for (const coin of coins) {
          this.payback(coin.coinPub);
        }
      }
    }

    return updatedExchangeInfo;
  }

  private async updateExchangeInfo(
    exchangeInfo: ExchangeRecord,
    newKeys: KeysJson,
  ): Promise<ExchangeRecord> {
    if (exchangeInfo.masterPublicKey !== newKeys.master_public_key) {
      throw Error("public keys do not match");
    }

    const existingDenoms: {
      [denomPub: string]: DenominationRecord;
    } = await this.q()
      .iterIndex(
        Stores.denominations.exchangeBaseUrlIndex,
        exchangeInfo.baseUrl,
      )
      .fold(
        (x: DenominationRecord, acc: typeof existingDenoms) => (
          (acc[x.denomPub] = x), acc
        ),
        {},
      );

    const newDenoms: typeof existingDenoms = {};
    const newAndUnseenDenoms: typeof existingDenoms = {};

    for (const d of newKeys.denoms) {
      const dr = await this.denominationRecordFromKeys(exchangeInfo.baseUrl, d);
      if (!(d.denom_pub in existingDenoms)) {
        newAndUnseenDenoms[dr.denomPub] = dr;
      }
      newDenoms[dr.denomPub] = dr;
    }

    for (const oldDenomPub in existingDenoms) {
      if (!(oldDenomPub in newDenoms)) {
        const d = existingDenoms[oldDenomPub];
        d.isOffered = false;
      }
    }

    await this.q()
      .putAll(
        Stores.denominations,
        Object.keys(newAndUnseenDenoms).map(d => newAndUnseenDenoms[d]),
      )
      .putAll(
        Stores.denominations,
        Object.keys(existingDenoms).map(d => existingDenoms[d]),
      )
      .finish();
    return exchangeInfo;
  }

  /**
   * Get detailed balance information, sliced by exchange and by currency.
   */
  async getBalances(): Promise<WalletBalance> {
    /**
     * Add amount to a balance field, both for
     * the slicing by exchange and currency.
     */
    function addTo(
      balance: WalletBalance,
      field: keyof WalletBalanceEntry,
      amount: AmountJson,
      exchange: string,
    ): void {
      const z = Amounts.getZero(amount.currency);
      const balanceIdentity = {
        available: z,
        paybackAmount: z,
        pendingIncoming: z,
        pendingPayment: z,
      };
      let entryCurr = balance.byCurrency[amount.currency];
      if (!entryCurr) {
        balance.byCurrency[amount.currency] = entryCurr = {
          ...balanceIdentity,
        };
      }
      let entryEx = balance.byExchange[exchange];
      if (!entryEx) {
        balance.byExchange[exchange] = entryEx = { ...balanceIdentity };
      }
      entryCurr[field] = Amounts.add(entryCurr[field], amount).amount;
      entryEx[field] = Amounts.add(entryEx[field], amount).amount;
    }

    function collectBalances(c: CoinRecord, balance: WalletBalance) {
      if (c.suspended) {
        return balance;
      }
      if (c.status === CoinStatus.Fresh) {
        addTo(balance, "available", c.currentAmount, c.exchangeBaseUrl);
        return balance;
      }
      if (c.status === CoinStatus.Dirty) {
        addTo(balance, "pendingIncoming", c.currentAmount, c.exchangeBaseUrl);
        return balance;
      }
      return balance;
    }

    function collectPendingWithdraw(r: ReserveRecord, balance: WalletBalance) {
      if (!r.timestamp_confirmed) {
        return balance;
      }
      let amount = Amounts.getZero(r.requested_amount.currency);
      /*
      let amount = r.current_amount;
      if (!amount) {
        amount = r.requested_amount;
      }
      */
      amount = Amounts.add(amount, r.precoin_amount).amount;
      if (Amounts.cmp(smallestWithdraw[r.exchange_base_url], amount) < 0) {
        addTo(balance, "pendingIncoming", amount, r.exchange_base_url);
      }
      return balance;
    }

    function collectPaybacks(r: ReserveRecord, balance: WalletBalance) {
      if (!r.hasPayback) {
        return balance;
      }
      if (
        Amounts.cmp(smallestWithdraw[r.exchange_base_url], r.current_amount!) <
        0
      ) {
        addTo(balance, "paybackAmount", r.current_amount!, r.exchange_base_url);
      }
      return balance;
    }

    function collectPendingRefresh(
      r: RefreshSessionRecord,
      balance: WalletBalance,
    ) {
      // Don't count finished refreshes, since the refresh already resulted
      // in coins being added to the wallet.
      if (r.finished) {
        return balance;
      }
      addTo(balance, "pendingIncoming", r.valueOutput, r.exchangeBaseUrl);

      return balance;
    }

    function collectPayments(t: PurchaseRecord, balance: WalletBalance) {
      if (t.finished) {
        return balance;
      }
      for (const c of t.payReq.coins) {
        addTo(
          balance,
          "pendingPayment",
          Amounts.parseOrThrow(c.contribution),
          c.exchange_url,
        );
      }
      return balance;
    }

    function collectSmallestWithdraw(
      e: JoinResult<ExchangeRecord, DenominationRecord>,
      sw: any,
    ) {
      let min = sw[e.left.baseUrl];
      const v = Amounts.add(e.right.value, e.right.feeWithdraw).amount;
      if (!min) {
        min = v;
      } else if (Amounts.cmp(v, min) < 0) {
        min = v;
      }
      sw[e.left.baseUrl] = min;
      return sw;
    }

    const balanceStore = {
      byCurrency: {},
      byExchange: {},
    };
    // Mapping from exchange pub to smallest
    // possible amount we can withdraw
    let smallestWithdraw: { [baseUrl: string]: AmountJson } = {};

    smallestWithdraw = await this.q()
      .iter(Stores.exchanges)
      .indexJoin(Stores.denominations.exchangeBaseUrlIndex, x => x.baseUrl)
      .fold(collectSmallestWithdraw, {});

    const tx = this.q();
    tx.iter(Stores.coins).fold(collectBalances, balanceStore);
    tx.iter(Stores.refresh).fold(collectPendingRefresh, balanceStore);
    tx.iter(Stores.reserves).fold(collectPendingWithdraw, balanceStore);
    tx.iter(Stores.reserves).fold(collectPaybacks, balanceStore);
    tx.iter(Stores.purchases).fold(collectPayments, balanceStore);
    await tx.finish();
    return balanceStore;
  }

  async createRefreshSession(
    oldCoinPub: string,
  ): Promise<RefreshSessionRecord | undefined> {
    const coin = await this.q().get<CoinRecord>(Stores.coins, oldCoinPub);

    if (!coin) {
      throw Error("coin not found");
    }

    if (coin.currentAmount.value === 0 && coin.currentAmount.fraction === 0) {
      return undefined;
    }

    const exchange = await this.updateExchangeFromUrl(coin.exchangeBaseUrl);

    if (!exchange) {
      throw Error("db inconsistent");
    }

    const oldDenom = await this.q().get(Stores.denominations, [
      exchange.baseUrl,
      coin.denomPub,
    ]);

    if (!oldDenom) {
      throw Error("db inconsistent");
    }

    const availableDenoms: DenominationRecord[] = await this.q()
      .iterIndex(Stores.denominations.exchangeBaseUrlIndex, exchange.baseUrl)
      .toArray();

    const availableAmount = Amounts.sub(coin.currentAmount, oldDenom.feeRefresh)
      .amount;

    const newCoinDenoms = getWithdrawDenomList(
      availableAmount,
      availableDenoms,
    );

    Wallet.enableTracing && console.log("refreshing coin", coin);
    Wallet.enableTracing && console.log("refreshing into", newCoinDenoms);

    if (newCoinDenoms.length === 0) {
      Wallet.enableTracing &&
        console.log(
          `not refreshing, available amount ${amountToPretty(
            availableAmount,
          )} too small`,
        );
      coin.status = CoinStatus.Useless;
      await this.q().put(Stores.coins, coin);
      this.notifier.notify();
      return undefined;
    }

    const refreshSession: RefreshSessionRecord = await this.cryptoApi.createRefreshSession(
      exchange.baseUrl,
      3,
      coin,
      newCoinDenoms,
      oldDenom.feeRefresh,
    );

    function mutateCoin(c: CoinRecord): CoinRecord {
      const r = Amounts.sub(c.currentAmount, refreshSession.valueWithFee);
      if (r.saturated) {
        // Something else must have written the coin value
        throw AbortTransaction;
      }
      c.currentAmount = r.amount;
      c.status = CoinStatus.Refreshed;
      return c;
    }

    // Store refresh session and subtract refreshed amount from
    // coin in the same transaction.
    const query = this.q();
    query
      .put(Stores.refresh, refreshSession, "refreshKey")
      .mutate(Stores.coins, coin.coinPub, mutateCoin);
    await query.finish();
    this.notifier.notify();

    const key = query.key("refreshKey");
    if (!key || typeof key !== "number") {
      throw Error("insert failed");
    }

    refreshSession.id = key;

    return refreshSession;
  }

  async refresh(oldCoinPub: string): Promise<void> {
    const refreshImpl = async () => {
      const oldRefreshSessions = await this.q()
        .iter(Stores.refresh)
        .toArray();
      for (const session of oldRefreshSessions) {
        Wallet.enableTracing &&
          console.log("got old refresh session for", oldCoinPub, session);
        return this.continueRefreshSession(session);
      }
      const coin = await this.q().get(Stores.coins, oldCoinPub);
      if (!coin) {
        console.warn("can't refresh, coin not in database");
        return;
      }
      if (
        coin.status === CoinStatus.Useless ||
        coin.status === CoinStatus.Fresh
      ) {
        return;
      }
      const refreshSession = await this.createRefreshSession(oldCoinPub);
      if (!refreshSession) {
        // refreshing not necessary
        Wallet.enableTracing && console.log("not refreshing", oldCoinPub);
        return;
      }
      return this.continueRefreshSession(refreshSession);
    };

    const activeRefreshOp = this.activeRefreshOperations[oldCoinPub];

    if (activeRefreshOp) {
      return activeRefreshOp;
    }

    try {
      const newOp = refreshImpl();
      this.activeRefreshOperations[oldCoinPub] = newOp;
      const res = await newOp;
      return res;
    } finally {
      delete this.activeRefreshOperations[oldCoinPub];
    }
  }

  async continueRefreshSession(refreshSession: RefreshSessionRecord) {
    if (refreshSession.finished) {
      return;
    }
    if (typeof refreshSession.norevealIndex !== "number") {
      await this.refreshMelt(refreshSession);
      const r = await this.q().get<RefreshSessionRecord>(
        Stores.refresh,
        refreshSession.id,
      );
      if (!r) {
        throw Error("refresh session does not exist anymore");
      }
      refreshSession = r;
    }

    await this.refreshReveal(refreshSession);
  }

  async refreshMelt(refreshSession: RefreshSessionRecord): Promise<void> {
    if (refreshSession.norevealIndex !== undefined) {
      console.error("won't melt again");
      return;
    }

    const coin = await this.q().get<CoinRecord>(
      Stores.coins,
      refreshSession.meltCoinPub,
    );
    if (!coin) {
      console.error("can't melt coin, it does not exist");
      return;
    }

    const reqUrl = new URI("refresh/melt").absoluteTo(
      refreshSession.exchangeBaseUrl,
    );
    const meltReq = {
      coin_pub: coin.coinPub,
      confirm_sig: refreshSession.confirmSig,
      denom_pub_hash: coin.denomPubHash,
      denom_sig: coin.denomSig,
      rc: refreshSession.hash,
      value_with_fee: refreshSession.valueWithFee,
    };
    Wallet.enableTracing && console.log("melt request:", meltReq);
    const resp = await this.http.postJson(reqUrl.href(), meltReq);

    Wallet.enableTracing && console.log("melt response:", resp.responseJson);

    if (resp.status !== 200) {
      console.error(resp.responseJson);
      throw Error("refresh failed");
    }

    const respJson = resp.responseJson;

    const norevealIndex = respJson.noreveal_index;

    if (typeof norevealIndex !== "number") {
      throw Error("invalid response");
    }

    refreshSession.norevealIndex = norevealIndex;

    await this.q()
      .put(Stores.refresh, refreshSession)
      .finish();
    this.notifier.notify();
  }

  async refreshReveal(refreshSession: RefreshSessionRecord): Promise<void> {
    const norevealIndex = refreshSession.norevealIndex;
    if (norevealIndex === undefined) {
      throw Error("can't reveal without melting first");
    }
    const privs = Array.from(refreshSession.transferPrivs);
    privs.splice(norevealIndex, 1);

    const preCoins = refreshSession.preCoinsForGammas[norevealIndex];
    if (!preCoins) {
      throw Error("refresh index error");
    }

    const meltCoinRecord = await this.q().get(
      Stores.coins,
      refreshSession.meltCoinPub,
    );
    if (!meltCoinRecord) {
      throw Error("inconsistent database");
    }

    const evs = preCoins.map((x: RefreshPreCoinRecord) => x.coinEv);

    const linkSigs: string[] = [];
    for (let i = 0; i < refreshSession.newDenoms.length; i++) {
      const linkSig = await this.cryptoApi.signCoinLink(
        meltCoinRecord.coinPriv,
        refreshSession.newDenomHashes[i],
        refreshSession.meltCoinPub,
        refreshSession.transferPubs[norevealIndex],
        preCoins[i].coinEv,
      );
      linkSigs.push(linkSig);
    }

    const req = {
      coin_evs: evs,
      new_denoms_h: refreshSession.newDenomHashes,
      rc: refreshSession.hash,
      transfer_privs: privs,
      transfer_pub: refreshSession.transferPubs[norevealIndex],
      link_sigs: linkSigs,
    };

    const reqUrl = new URI("refresh/reveal").absoluteTo(
      refreshSession.exchangeBaseUrl,
    );
    Wallet.enableTracing && console.log("reveal request:", req);

    let resp;
    try {
      resp = await this.http.postJson(reqUrl.href(), req);
    } catch (e) {
      console.error("got error during /refresh/reveal request");
      return;
    }

    Wallet.enableTracing && console.log("session:", refreshSession);
    Wallet.enableTracing && console.log("reveal response:", resp);

    if (resp.status !== 200) {
      console.error("error: /refresh/reveal returned status " + resp.status);
      return;
    }

    const respJson = resp.responseJson;

    if (!respJson.ev_sigs || !Array.isArray(respJson.ev_sigs)) {
      console.error("/refresh/reveal did not contain ev_sigs");
      return;
    }

    const exchange = await this.q().get<ExchangeRecord>(
      Stores.exchanges,
      refreshSession.exchangeBaseUrl,
    );
    if (!exchange) {
      console.error(`exchange ${refreshSession.exchangeBaseUrl} not found`);
      return;
    }

    const coins: CoinRecord[] = [];

    for (let i = 0; i < respJson.ev_sigs.length; i++) {
      const denom = await this.q().get(Stores.denominations, [
        refreshSession.exchangeBaseUrl,
        refreshSession.newDenoms[i],
      ]);
      if (!denom) {
        console.error("denom not found");
        continue;
      }
      const pc =
        refreshSession.preCoinsForGammas[refreshSession.norevealIndex!][i];
      const denomSig = await this.cryptoApi.rsaUnblind(
        respJson.ev_sigs[i].ev_sig,
        pc.blindingKey,
        denom.denomPub,
      );
      const coin: CoinRecord = {
        blindingKey: pc.blindingKey,
        coinPriv: pc.privateKey,
        coinPub: pc.publicKey,
        currentAmount: denom.value,
        denomPub: denom.denomPub,
        denomPubHash: denom.denomPubHash,
        denomSig,
        exchangeBaseUrl: refreshSession.exchangeBaseUrl,
        reservePub: undefined,
        status: CoinStatus.Fresh,
      };

      coins.push(coin);
    }

    refreshSession.finished = true;

    await this.q()
      .putAll(Stores.coins, coins)
      .put(Stores.refresh, refreshSession)
      .finish();
    this.notifier.notify();
  }

  /**
   * Retrive the full event history for this wallet.
   */
  async getHistory(): Promise<{ history: HistoryRecord[] }> {
    const history: HistoryRecord[] = [];

    // FIXME: do pagination instead of generating the full history

    // We uniquely identify history rows via their timestamp.
    // This works as timestamps are guaranteed to be monotonically
    // increasing even

    const proposals = await this.q()
      .iter<ProposalDownloadRecord>(Stores.proposals)
      .toArray();
    for (const p of proposals) {
      history.push({
        detail: {
          contractTermsHash: p.contractTermsHash,
          merchantName: p.contractTerms.merchant.name,
        },
        timestamp: p.timestamp,
        type: "offer-contract",
      });
    }

    const purchases = await this.q()
      .iter<PurchaseRecord>(Stores.purchases)
      .toArray();
    for (const p of purchases) {
      history.push({
        detail: {
          amount: p.contractTerms.amount,
          contractTermsHash: p.contractTermsHash,
          fulfillmentUrl: p.contractTerms.fulfillment_url,
          merchantName: p.contractTerms.merchant.name,
        },
        timestamp: p.timestamp,
        type: "pay",
      });
      if (p.timestamp_refund) {
        const contractAmount = Amounts.parseOrThrow(p.contractTerms.amount);
        const amountsPending = Object.keys(p.refundsPending).map(x =>
          Amounts.parseOrThrow(p.refundsPending[x].refund_amount),
        );
        const amountsDone = Object.keys(p.refundsDone).map(x =>
          Amounts.parseOrThrow(p.refundsDone[x].refund_amount),
        );
        const amounts: AmountJson[] = amountsPending.concat(amountsDone);
        const amount = Amounts.add(
          Amounts.getZero(contractAmount.currency),
          ...amounts,
        ).amount;

        history.push({
          detail: {
            contractTermsHash: p.contractTermsHash,
            fulfillmentUrl: p.contractTerms.fulfillment_url,
            merchantName: p.contractTerms.merchant.name,
            refundAmount: amount,
          },
          timestamp: p.timestamp_refund,
          type: "refund",
        });
      }
    }

    const reserves: ReserveRecord[] = await this.q()
      .iter<ReserveRecord>(Stores.reserves)
      .toArray();
    for (const r of reserves) {
      history.push({
        detail: {
          exchangeBaseUrl: r.exchange_base_url,
          requestedAmount: r.requested_amount,
          reservePub: r.reserve_pub,
        },
        timestamp: r.created,
        type: "create-reserve",
      });
      if (r.timestamp_depleted) {
        history.push({
          detail: {
            exchangeBaseUrl: r.exchange_base_url,
            requestedAmount: r.requested_amount,
            reservePub: r.reserve_pub,
          },
          timestamp: r.timestamp_depleted,
          type: "depleted-reserve",
        });
      }
    }

    const tips: TipRecord[] = await this.q()
      .iter<TipRecord>(Stores.tips)
      .toArray();
    for (const tip of tips) {
      history.push({
        detail: {
          accepted: tip.accepted,
          amount: tip.amount,
          merchantDomain: tip.merchantDomain,
          tipId: tip.tipId,
        },
        timestamp: tip.timestamp,
        type: "tip",
      });
    }

    history.sort((h1, h2) => Math.sign(h1.timestamp - h2.timestamp));

    return { history };
  }

  async getDenoms(exchangeUrl: string): Promise<DenominationRecord[]> {
    const denoms = await this.q()
      .iterIndex(Stores.denominations.exchangeBaseUrlIndex, exchangeUrl)
      .toArray();
    return denoms;
  }

  async getProposal(
    proposalId: number,
  ): Promise<ProposalDownloadRecord | undefined> {
    const proposal = await this.q().get(Stores.proposals, proposalId);
    return proposal;
  }

  async getExchanges(): Promise<ExchangeRecord[]> {
    return this.q()
      .iter<ExchangeRecord>(Stores.exchanges)
      .toArray();
  }

  async getCurrencies(): Promise<CurrencyRecord[]> {
    return this.q()
      .iter<CurrencyRecord>(Stores.currencies)
      .toArray();
  }

  async updateCurrency(currencyRecord: CurrencyRecord): Promise<void> {
    Wallet.enableTracing && console.log("updating currency to", currencyRecord);
    await this.q()
      .put(Stores.currencies, currencyRecord)
      .finish();
    this.notifier.notify();
  }

  async getReserves(exchangeBaseUrl: string): Promise<ReserveRecord[]> {
    return this.q()
      .iter<ReserveRecord>(Stores.reserves)
      .filter((r: ReserveRecord) => r.exchange_base_url === exchangeBaseUrl)
      .toArray();
  }

  async getCoins(exchangeBaseUrl: string): Promise<CoinRecord[]> {
    return this.q()
      .iter<CoinRecord>(Stores.coins)
      .filter((c: CoinRecord) => c.exchangeBaseUrl === exchangeBaseUrl)
      .toArray();
  }

  async getPreCoins(exchangeBaseUrl: string): Promise<PreCoinRecord[]> {
    return this.q()
      .iter<PreCoinRecord>(Stores.precoins)
      .filter((c: PreCoinRecord) => c.exchangeBaseUrl === exchangeBaseUrl)
      .toArray();
  }

  async hashContract(contract: ContractTerms): Promise<string> {
    return this.cryptoApi.hashString(canonicalJson(contract));
  }

  async getCurrencyRecord(
    currency: string,
  ): Promise<CurrencyRecord | undefined> {
    return this.q().get(Stores.currencies, currency);
  }

  async payback(coinPub: string): Promise<void> {
    let coin = await this.q().get(Stores.coins, coinPub);
    if (!coin) {
      throw Error(`Coin ${coinPub} not found, can't request payback`);
    }
    const reservePub = coin.reservePub;
    if (!reservePub) {
      throw Error(`Can't request payback for a refreshed coin`);
    }
    const reserve = await this.q().get(Stores.reserves, reservePub);
    if (!reserve) {
      throw Error(`Reserve of coin ${coinPub} not found`);
    }
    switch (coin.status) {
      case CoinStatus.Refreshed:
        throw Error(
          `Can't do payback for coin ${coinPub} since it's refreshed`,
        );
      case CoinStatus.PaybackDone:
        console.log(`Coin ${coinPub} already payed back`);
        return;
    }
    coin.status = CoinStatus.PaybackPending;
    // Even if we didn't get the payback yet, we suspend withdrawal, since
    // technically we might update reserve status before we get the response
    // from the reserve for the payback request.
    reserve.hasPayback = true;
    await this.q()
      .put(Stores.coins, coin)
      .put(Stores.reserves, reserve);
    this.notifier.notify();

    const paybackRequest = await this.cryptoApi.createPaybackRequest(coin);
    const reqUrl = new URI("payback").absoluteTo(coin.exchangeBaseUrl);
    const resp = await this.http.postJson(reqUrl.href(), paybackRequest);
    if (resp.status !== 200) {
      throw Error();
    }
    const paybackConfirmation = PaybackConfirmation.checked(resp.responseJson);
    if (paybackConfirmation.reserve_pub !== coin.reservePub) {
      throw Error(`Coin's reserve doesn't match reserve on payback`);
    }
    coin = await this.q().get(Stores.coins, coinPub);
    if (!coin) {
      throw Error(`Coin ${coinPub} not found, can't confirm payback`);
    }
    coin.status = CoinStatus.PaybackDone;
    await this.q().put(Stores.coins, coin);
    this.notifier.notify();
    await this.updateReserve(reservePub!);
  }

  async denominationRecordFromKeys(
    exchangeBaseUrl: string,
    denomIn: Denomination,
  ): Promise<DenominationRecord> {
    const denomPubHash = await this.cryptoApi.hashDenomPub(denomIn.denom_pub);
    const d: DenominationRecord = {
      denomPub: denomIn.denom_pub,
      denomPubHash,
      exchangeBaseUrl,
      feeDeposit: Amounts.parseOrThrow(denomIn.fee_deposit),
      feeRefresh: Amounts.parseOrThrow(denomIn.fee_refresh),
      feeRefund: Amounts.parseOrThrow(denomIn.fee_refund),
      feeWithdraw: Amounts.parseOrThrow(denomIn.fee_withdraw),
      isOffered: true,
      masterSig: denomIn.master_sig,
      stampExpireDeposit: denomIn.stamp_expire_deposit,
      stampExpireLegal: denomIn.stamp_expire_legal,
      stampExpireWithdraw: denomIn.stamp_expire_withdraw,
      stampStart: denomIn.stamp_start,
      status: DenominationStatus.Unverified,
      value: Amounts.parseOrThrow(denomIn.value),
    };
    return d;
  }

  async withdrawPaybackReserve(reservePub: string): Promise<void> {
    const reserve = await this.q().get(Stores.reserves, reservePub);
    if (!reserve) {
      throw Error(`Reserve ${reservePub} does not exist`);
    }
    reserve.hasPayback = false;
    await this.q().put(Stores.reserves, reserve);
    this.depleteReserve(reserve);
  }

  async getPaybackReserves(): Promise<ReserveRecord[]> {
    return await this.q()
      .iter(Stores.reserves)
      .filter(r => r.hasPayback)
      .toArray();
  }

  /**
   * Stop ongoing processing.
   */
  stop() {
    this.timerGroup.stopCurrentAndFutureTimers();
    this.cryptoApi.stop();
  }

  async getSenderWireInfos(): Promise<SenderWireInfos> {
    const m: { [url: string]: Set<string> } = {};
    await this.q()
      .iter(Stores.exchangeWireFees)
      .map(x => {
        const s = (m[x.exchangeBaseUrl] = m[x.exchangeBaseUrl] || new Set());
        Object.keys(x.feesForType).map(k => s.add(k));
      })
      .run();
    Wallet.enableTracing && console.log(m);
    const exchangeWireTypes: { [url: string]: string[] } = {};
    Object.keys(m).map(e => {
      exchangeWireTypes[e] = Array.from(m[e]);
    });

    const senderWiresSet: Set<string> = new Set();
    await this.q()
      .iter(Stores.senderWires)
      .map(x => {
        senderWiresSet.add(x.paytoUri);
      })
      .run();
    const senderWires: string[] = Array.from(senderWiresSet);

    return {
      exchangeWireTypes,
      senderWires,
    };
  }

  /**
   * Trigger paying coins back into the user's account.
   */
  async returnCoins(req: ReturnCoinsRequest): Promise<void> {
    Wallet.enableTracing && console.log("got returnCoins request", req);
    const wireType = (req.senderWire as any).type;
    Wallet.enableTracing && console.log("wireType", wireType);
    if (!wireType || typeof wireType !== "string") {
      console.error(`wire type must be a non-empty string, not ${wireType}`);
      return;
    }
    const stampSecNow = Math.floor(new Date().getTime() / 1000);
    const exchange = await this.q().get(Stores.exchanges, req.exchange);
    if (!exchange) {
      console.error(`Exchange ${req.exchange} not known to the wallet`);
      return;
    }
    Wallet.enableTracing && console.log("selecting coins for return:", req);
    const cds = await this.getCoinsForReturn(req.exchange, req.amount);
    Wallet.enableTracing && console.log(cds);

    if (!cds) {
      throw Error("coin return impossible, can't select coins");
    }

    const { priv, pub } = await this.cryptoApi.createEddsaKeypair();

    const wireHash = await this.cryptoApi.hashString(
      canonicalJson(req.senderWire),
    );

    const contractTerms: ContractTerms = {
      H_wire: wireHash,
      amount: Amounts.toString(req.amount),
      auditors: [],
      exchanges: [
        { master_pub: exchange.masterPublicKey, url: exchange.baseUrl },
      ],
      extra: {},
      fulfillment_url: "",
      locations: [],
      max_fee: Amounts.toString(req.amount),
      merchant: {},
      merchant_pub: pub,
      order_id: "none",
      pay_deadline: `/Date(${stampSecNow + 60 * 5})/`,
      merchant_base_url: "taler://return-to-account",
      products: [],
      refund_deadline: `/Date(${stampSecNow + 60 * 5})/`,
      timestamp: `/Date(${stampSecNow})/`,
      wire_method: wireType,
    };

    const contractTermsHash = await this.cryptoApi.hashString(
      canonicalJson(contractTerms),
    );

    const payCoinInfo = await this.cryptoApi.signDeposit(
      contractTerms,
      cds,
      Amounts.parseOrThrow(contractTerms.amount),
    );

    Wallet.enableTracing && console.log("pci", payCoinInfo);

    const coins = payCoinInfo.sigs.map(s => ({ coinPaySig: s }));

    const coinsReturnRecord: CoinsReturnRecord = {
      coins,
      contractTerms,
      contractTermsHash,
      exchange: exchange.baseUrl,
      merchantPriv: priv,
      wire: req.senderWire,
    };

    await this.q()
      .put(Stores.coinsReturns, coinsReturnRecord)
      .putAll(Stores.coins, payCoinInfo.updatedCoins)
      .finish();
    this.badge.showNotification();
    this.notifier.notify();

    this.depositReturnedCoins(coinsReturnRecord);
  }

  async depositReturnedCoins(
    coinsReturnRecord: CoinsReturnRecord,
  ): Promise<void> {
    for (const c of coinsReturnRecord.coins) {
      if (c.depositedSig) {
        continue;
      }
      const req = {
        H_wire: coinsReturnRecord.contractTerms.H_wire,
        coin_pub: c.coinPaySig.coin_pub,
        coin_sig: c.coinPaySig.coin_sig,
        contribution: c.coinPaySig.contribution,
        denom_pub: c.coinPaySig.denom_pub,
        h_contract_terms: coinsReturnRecord.contractTermsHash,
        merchant_pub: coinsReturnRecord.contractTerms.merchant_pub,
        pay_deadline: coinsReturnRecord.contractTerms.pay_deadline,
        refund_deadline: coinsReturnRecord.contractTerms.refund_deadline,
        timestamp: coinsReturnRecord.contractTerms.timestamp,
        ub_sig: c.coinPaySig.ub_sig,
        wire: coinsReturnRecord.wire,
        wire_transfer_deadline: coinsReturnRecord.contractTerms.pay_deadline,
      };
      Wallet.enableTracing && console.log("req", req);
      const reqUrl = new URI("deposit").absoluteTo(coinsReturnRecord.exchange);
      const resp = await this.http.postJson(reqUrl.href(), req);
      if (resp.status !== 200) {
        console.error("deposit failed due to status code", resp);
        continue;
      }
      const respJson = resp.responseJson;
      if (respJson.status !== "DEPOSIT_OK") {
        console.error("deposit failed", resp);
        continue;
      }

      if (!respJson.sig) {
        console.error("invalid 'sig' field", resp);
        continue;
      }

      // FIXME: verify signature

      // For every successful deposit, we replace the old record with an updated one
      const currentCrr = await this.q().get(
        Stores.coinsReturns,
        coinsReturnRecord.contractTermsHash,
      );
      if (!currentCrr) {
        console.error("database inconsistent");
        continue;
      }
      for (const nc of currentCrr.coins) {
        if (nc.coinPaySig.coin_pub === c.coinPaySig.coin_pub) {
          nc.depositedSig = respJson.sig;
        }
      }
      await this.q().put(Stores.coinsReturns, currentCrr);
      this.notifier.notify();
    }
  }

  private async acceptRefundResponse(
    refundResponse: MerchantRefundResponse,
  ): Promise<string> {
    const refundPermissions = refundResponse.refund_permissions;

    if (!refundPermissions.length) {
      console.warn("got empty refund list");
      throw Error("empty refund");
    }

    /**
     * Add refund to purchase if not already added.
     */
    function f(t: PurchaseRecord | undefined): PurchaseRecord | undefined {
      if (!t) {
        console.error("purchase not found, not adding refunds");
        return;
      }

      t.timestamp_refund = new Date().getTime();

      for (const perm of refundPermissions) {
        if (
          !t.refundsPending[perm.merchant_sig] &&
          !t.refundsDone[perm.merchant_sig]
        ) {
          t.refundsPending[perm.merchant_sig] = perm;
        }
      }
      return t;
    }

    const hc = refundResponse.h_contract_terms;

    // Add the refund permissions to the purchase within a DB transaction
    await this.q()
      .mutate(Stores.purchases, hc, f)
      .finish();
    this.notifier.notify();

    await this.submitRefunds(hc);

    return hc;
  }

  /**
   * Accept a refund, return the contract hash for the contract
   * that was involved in the refund.
   */
  async applyRefund(talerRefundUri: string): Promise<string> {
    const parseResult = parseRefundUri(talerRefundUri);

    if (!parseResult) {
      throw Error("invalid refund URI");
    }

    const refundUrl = parseResult.refundUrl;

    Wallet.enableTracing && console.log("processing refund");
    let resp;
    try {
      resp = await this.http.get(refundUrl);
    } catch (e) {
      console.error("error downloading refund permission", e);
      throw e;
    }

    const refundResponse = MerchantRefundResponse.checked(resp.responseJson);
    return this.acceptRefundResponse(refundResponse);
  }

  private async submitRefunds(contractTermsHash: string): Promise<void> {
    const purchase = await this.q().get(Stores.purchases, contractTermsHash);
    if (!purchase) {
      console.error(
        "not submitting refunds, contract terms not found:",
        contractTermsHash,
      );
      return;
    }
    const pendingKeys = Object.keys(purchase.refundsPending);
    if (pendingKeys.length === 0) {
      return;
    }
    for (const pk of pendingKeys) {
      const perm = purchase.refundsPending[pk];
      const req: RefundRequest = {
        coin_pub: perm.coin_pub,
        h_contract_terms: purchase.contractTermsHash,
        merchant_pub: purchase.contractTerms.merchant_pub,
        merchant_sig: perm.merchant_sig,
        refund_amount: perm.refund_amount,
        refund_fee: perm.refund_fee,
        rtransaction_id: perm.rtransaction_id,
      };
      console.log("sending refund permission", perm);
      // FIXME: not correct once we support multiple exchanges per payment
      const exchangeUrl = purchase.payReq.coins[0].exchange_url;
      const reqUrl = new URI("refund").absoluteTo(exchangeUrl);
      const resp = await this.http.postJson(reqUrl.href(), req);
      if (resp.status !== 200) {
        console.error("refund failed", resp);
        continue;
      }

      // Transactionally mark successful refunds as done
      const transformPurchase = (
        t: PurchaseRecord | undefined,
      ): PurchaseRecord | undefined => {
        if (!t) {
          console.warn("purchase not found, not updating refund");
          return;
        }
        if (t.refundsPending[pk]) {
          t.refundsDone[pk] = t.refundsPending[pk];
          delete t.refundsPending[pk];
        }
        return t;
      };
      const transformCoin = (
        c: CoinRecord | undefined,
      ): CoinRecord | undefined => {
        if (!c) {
          console.warn("coin not found, can't apply refund");
          return;
        }
        const refundAmount = Amounts.parseOrThrow(perm.refund_amount);
        const refundFee = Amounts.parseOrThrow(perm.refund_fee);
        c.status = CoinStatus.Dirty;
        c.currentAmount = Amounts.add(c.currentAmount, refundAmount).amount;
        c.currentAmount = Amounts.sub(c.currentAmount, refundFee).amount;

        return c;
      };

      await this.q()
        .mutate(Stores.purchases, contractTermsHash, transformPurchase)
        .mutate(Stores.coins, perm.coin_pub, transformCoin)
        .finish();
      this.refresh(perm.coin_pub);
    }

    this.badge.showNotification();
    this.notifier.notify();
  }

  async getPurchase(
    contractTermsHash: string,
  ): Promise<PurchaseRecord | undefined> {
    return this.q().get(Stores.purchases, contractTermsHash);
  }

  async getFullRefundFees(
    refundPermissions: MerchantRefundPermission[],
  ): Promise<AmountJson> {
    if (refundPermissions.length === 0) {
      throw Error("no refunds given");
    }
    const coin0 = await this.q().get(
      Stores.coins,
      refundPermissions[0].coin_pub,
    );
    if (!coin0) {
      throw Error("coin not found");
    }
    let feeAcc = Amounts.getZero(
      Amounts.parseOrThrow(refundPermissions[0].refund_amount).currency,
    );

    const denoms = await this.q()
      .iterIndex(
        Stores.denominations.exchangeBaseUrlIndex,
        coin0.exchangeBaseUrl,
      )
      .toArray();
    for (const rp of refundPermissions) {
      const coin = await this.q().get(Stores.coins, rp.coin_pub);
      if (!coin) {
        throw Error("coin not found");
      }
      const denom = await this.q().get(Stores.denominations, [
        coin0.exchangeBaseUrl,
        coin.denomPub,
      ]);
      if (!denom) {
        throw Error(`denom not found (${coin.denomPub})`);
      }
      // FIXME:  this assumes that the refund already happened.
      // When it hasn't, the refresh cost is inaccurate.  To fix this,
      // we need introduce a flag to tell if a coin was refunded or
      // refreshed normally (and what about incremental refunds?)
      const refundAmount = Amounts.parseOrThrow(rp.refund_amount);
      const refundFee = Amounts.parseOrThrow(rp.refund_fee);
      const refreshCost = getTotalRefreshCost(
        denoms,
        denom,
        Amounts.sub(refundAmount, refundFee).amount,
      );
      feeAcc = Amounts.add(feeAcc, refreshCost, refundFee).amount;
    }
    return feeAcc;
  }

  async acceptTip(talerTipUri: string): Promise<void> {
    const { tipId, merchantOrigin } = await this.getTipStatus(talerTipUri);
    const key = `${tipId}${merchantOrigin}`;
    if (this.activeTipOperations[key]) {
      return this.activeTipOperations[key];
    }
    const p = this.acceptTipImpl(tipId, merchantOrigin);
    this.activeTipOperations[key] = p;
    try {
      return await p;
    } finally {
      delete this.activeTipOperations[key];
    }
  }

  private async acceptTipImpl(
    tipId: string,
    merchantOrigin: string,
  ): Promise<void> {
    let tipRecord = await this.q().get(Stores.tips, [tipId, merchantOrigin]);
    if (!tipRecord) {
      throw Error("tip not in database");
    }

    tipRecord.accepted = true;

    // Create one transactional query, within this transaction
    // both the tip will be marked as accepted and coins
    // already withdrawn will be untainted.
    await this.q()
      .put(Stores.tips, tipRecord)
      .finish();

    if (tipRecord.pickedUp) {
      console.log("tip already picked up");
      return;
    }
    await this.updateExchangeFromUrl(tipRecord.exchangeUrl);
    const denomsForWithdraw = await this.getVerifiedWithdrawDenomList(
      tipRecord.exchangeUrl,
      tipRecord.amount,
    );

    if (!tipRecord.planchets) {
      const planchets = await Promise.all(
        denomsForWithdraw.map(d => this.cryptoApi.createTipPlanchet(d)),
      );
      const coinPubs: string[] = planchets.map(x => x.coinPub);

      await this.q().mutate(Stores.tips, [tipId, merchantOrigin], r => {
        if (!r.planchets) {
          r.planchets = planchets;
          r.coinPubs = coinPubs;
        }
        return r;
      });

      this.notifier.notify();
    }

    tipRecord = await this.q().get(Stores.tips, [tipId, merchantOrigin]);
    if (!tipRecord) {
      throw Error("tip not in database");
    }

    if (!tipRecord.planchets) {
      throw Error("invariant violated");
    }

    console.log("got planchets for tip!");

    // Planchets in the form that the merchant expects
    const planchetsDetail: TipPlanchetDetail[] = tipRecord.planchets.map(p => ({
      coin_ev: p.coinEv,
      denom_pub_hash: p.denomPubHash,
    }));

    let merchantResp;

    try {
      const req = { planchets: planchetsDetail, tip_id: tipId };
      merchantResp = await this.http.postJson(tipRecord.pickupUrl, req);
      console.log("got merchant resp:", merchantResp);
    } catch (e) {
      console.log("tipping failed", e);
      throw e;
    }

    const response = TipResponse.checked(merchantResp.responseJson);

    if (response.reserve_sigs.length !== tipRecord.planchets.length) {
      throw Error("number of tip responses does not match requested planchets");
    }

    for (let i = 0; i < tipRecord.planchets.length; i++) {
      const planchet = tipRecord.planchets[i];
      const preCoin = {
        blindingKey: planchet.blindingKey,
        coinEv: planchet.coinEv,
        coinPriv: planchet.coinPriv,
        coinPub: planchet.coinPub,
        coinValue: planchet.coinValue,
        denomPub: planchet.denomPub,
        denomPubHash: planchet.denomPubHash,
        exchangeBaseUrl: tipRecord.exchangeUrl,
        isFromTip: true,
        reservePub: response.reserve_pub,
        withdrawSig: response.reserve_sigs[i].reserve_sig,
      };
      await this.q().put(Stores.precoins, preCoin);
      await this.processPreCoin(preCoin.coinPub);
    }

    tipRecord.pickedUp = true;

    await this.q()
      .put(Stores.tips, tipRecord)
      .finish();
    this.notifier.notify();
    this.badge.showNotification();
    return;
  }

  async getTipStatus(talerTipUri: string): Promise<TipStatus> {
    const res = parseTipUri(talerTipUri);
    if (!res) {
      throw Error("invalid taler://tip URI");
    }

    const tipStatusUrl = new URI(res.tipPickupUrl).href();
    console.log("checking tip status from", tipStatusUrl);
    const merchantResp = await this.http.get(tipStatusUrl);
    console.log("resp:", merchantResp.responseJson);
    const tipPickupStatus = TipPickupGetResponse.checked(
      merchantResp.responseJson,
    );

    console.log("status", tipPickupStatus);

    let amount = Amounts.parseOrThrow(tipPickupStatus.amount);

    let tipRecord = await this.q().get(Stores.tips, [
      res.tipId,
      res.merchantOrigin,
    ]);
    if (!tipRecord) {
      const withdrawDetails = await this.getWithdrawDetailsForAmount(
        tipPickupStatus.exchange_url,
        amount,
      );

      tipRecord = {
        accepted: false,
        amount,
        coinPubs: [],
        deadline: getTalerStampSec(tipPickupStatus.stamp_expire)!,
        exchangeUrl: tipPickupStatus.exchange_url,
        merchantDomain: res.merchantOrigin,
        nextUrl: undefined,
        pickedUp: false,
        planchets: undefined,
        response: undefined,
        timestamp: new Date().getTime(),
        tipId: res.tipId,
        pickupUrl: res.tipPickupUrl,
        totalFees: Amounts.add(
          withdrawDetails.overhead,
          withdrawDetails.withdrawFee,
        ).amount,
      };
      await this.q().put(Stores.tips, tipRecord);
    }

    const tipStatus: TipStatus = {
      accepted: !!tipRecord && tipRecord.accepted,
      amount: Amounts.parseOrThrow(tipPickupStatus.amount),
      amountLeft: Amounts.parseOrThrow(tipPickupStatus.amount_left),
      exchangeUrl: tipPickupStatus.exchange_url,
      nextUrl: tipPickupStatus.extra.next_url,
      merchantOrigin: res.merchantOrigin,
      tipId: res.tipId,
      expirationTimestamp: getTalerStampSec(tipPickupStatus.stamp_expire)!,
      timestamp: getTalerStampSec(tipPickupStatus.stamp_created)!,
      totalFees: tipRecord.totalFees,
    };

    return tipStatus;
  }

  async abortFailedPayment(contractTermsHash: string): Promise<void> {
    const purchase = await this.q().get(Stores.purchases, contractTermsHash);
    if (!purchase) {
      throw Error("Purchase not found, unable to abort with refund");
    }
    if (purchase.finished) {
      throw Error("Purchase already finished, not aborting");
    }
    if (purchase.abortDone) {
      console.warn("abort requested on already aborted purchase");
      return;
    }

    purchase.abortRequested = true;

    // From now on, we can't retry payment anymore,
    // so mark this in the DB in case the /pay abort
    // does not complete on the first try.
    await this.q().put(Stores.purchases, purchase);

    let resp;

    const abortReq = { ...purchase.payReq, mode: "abort-refund" };

    const payUrl = new URI("pay").absoluteTo(purchase.contractTerms.merchant_base_url).href()

    try {
      resp = await this.http.postJson(payUrl, abortReq);
    } catch (e) {
      // Gives the user the option to retry / abort and refresh
      console.log("aborting payment failed", e);
      throw e;
    }

    const refundResponse = MerchantRefundResponse.checked(resp.responseJson);
    await this.acceptRefundResponse(refundResponse);

    const markAbortDone = (p: PurchaseRecord) => {
      p.abortDone = true;
      return p;
    };
    await this.q().mutate(
      Stores.purchases,
      purchase.contractTermsHash,
      markAbortDone,
    );
  }

  /**
   * Remove unreferenced / expired data from the wallet's database
   * based on the current system time.
   */
  async collectGarbage() {
    // FIXME(#5845)
    // We currently do not garbage-collect the wallet database.  This might change
    // after the feature has been properly re-designed, and we have come up with a
    // strategy to test it.
  }

  async getWithdrawalInfo(
    talerWithdrawUri: string,
  ): Promise<DownloadedWithdrawInfo> {
    const uriResult = parseWithdrawUri(talerWithdrawUri);
    if (!uriResult) {
      throw Error("can't parse URL");
    }
    const resp = await this.http.get(uriResult.statusUrl);
    console.log("resp:", resp.responseJson);
    const status = WithdrawOperationStatusResponse.checked(resp.responseJson);
    return {
      amount: Amounts.parseOrThrow(status.amount),
      confirmTransferUrl: status.confirm_transfer_url,
      extractedStatusUrl: uriResult.statusUrl,
      selectionDone: status.selection_done,
      senderWire: status.sender_wire,
      suggestedExchange: status.suggested_exchange,
      transferDone: status.transfer_done,
      wireTypes: status.wire_types,
    };
  }

  async acceptWithdrawal(
    talerWithdrawUri: string,
    selectedExchange: string,
  ): Promise<AcceptWithdrawalResponse> {
    const withdrawInfo = await this.getWithdrawalInfo(talerWithdrawUri);
    const exchangeWire = await this.getExchangePaytoUri(
      selectedExchange,
      withdrawInfo.wireTypes,
    );
    const reserve = await this.createReserve({
      amount: withdrawInfo.amount,
      bankWithdrawStatusUrl: withdrawInfo.extractedStatusUrl,
      exchange: selectedExchange,
      senderWire: withdrawInfo.senderWire,
      exchangeWire: exchangeWire,
    });
    await this.sendReserveInfoToBank(reserve.reservePub);
    return {
      reservePub: reserve.reservePub,
      confirmTransferUrl: withdrawInfo.confirmTransferUrl,
    };
  }

  async getPurchaseDetails(hc: string): Promise<PurchaseDetails> {
    const purchase = await this.q().get(Stores.purchases, hc);
    if (!purchase) {
      throw Error("unknown purchase");
    }
    const refundsDoneAmounts = Object.values(purchase.refundsDone).map(x =>
      Amounts.parseOrThrow(x.refund_amount),
    );
    const refundsPendingAmounts = Object.values(purchase.refundsPending).map(
      x => Amounts.parseOrThrow(x.refund_amount),
    );
    const totalRefundAmount = Amounts.sum([
      ...refundsDoneAmounts,
      ...refundsPendingAmounts,
    ]).amount;
    const refundsDoneFees = Object.values(purchase.refundsDone).map(x =>
      Amounts.parseOrThrow(x.refund_amount),
    );
    const refundsPendingFees = Object.values(purchase.refundsPending).map(x =>
      Amounts.parseOrThrow(x.refund_amount),
    );
    const totalRefundFees = Amounts.sum([
      ...refundsDoneFees,
      ...refundsPendingFees,
    ]).amount;
    const totalFees = totalRefundFees;
    return {
      contractTerms: purchase.contractTerms,
      hasRefund: purchase.timestamp_refund !== 0,
      totalRefundAmount: totalRefundAmount,
      totalRefundAndRefreshFees: totalFees,
    };
  }

  /**
   * Reset the retry timeouts for ongoing operations.
   */
  resetRetryTimeouts(): void {
    // FIXME: implement
  }

  clearNotification(): void {
    this.badge.clearNotification();
  }

  benchmarkCrypto(repetitions: number): Promise<BenchmarkResult> {
    return this.cryptoApi.benchmark(repetitions);
  }
}