wallet-core/packages/taler-wallet-webextension/src/wallet/ExchangeSelection/state.ts

/*
 This file is part of GNU Taler
 (C) 2022 Taler Systems S.A.

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

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

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

import { DenomOperationMap, FeeDescription } from "@gnu-taler/taler-util";
import {
  createPairTimeline,
  WalletApiOperation,
} from "@gnu-taler/taler-wallet-core";
import { useState } from "preact/hooks";
import { alertFromError, useAlertContext } from "../../context/alert.js";
import { useBackendContext } from "../../context/backend.js";
import { useTranslationContext } from "../../context/translation.js";
import { useAsyncAsHook } from "../../hooks/useAsyncAsHook.js";
import { Props, State } from "./index.js";

export function useComponentState({
  onCancel,
  onSelection,
  list: exchanges,
  initialValue,
}: Props): State {
  const api = useBackendContext();
  const { pushAlertOnError } = useAlertContext();
  const { i18n } = useTranslationContext();
  const initialValueIdx = exchanges.findIndex(
    (e) => e.exchangeBaseUrl === initialValue,
  );
  if (initialValueIdx === -1) {
    throw Error(
      `wrong usage of ExchangeSelection component, currentExchange '${initialValue}' is not in the list of exchanges`,
    );
  }
  const [value, setValue] = useState(String(initialValueIdx));

  const selectedIdx = parseInt(value, 10);
  const selectedExchange = exchanges[selectedIdx];

  const comparingExchanges = selectedIdx !== initialValueIdx;

  const initialExchange = comparingExchanges
    ? exchanges[initialValueIdx]
    : undefined;

  const hook = useAsyncAsHook(async () => {
    const selected = await api.wallet.call(
      WalletApiOperation.GetExchangeDetailedInfo,
      {
        exchangeBaseUrl: selectedExchange.exchangeBaseUrl,
      },
    );

    const original = !initialExchange
      ? undefined
      : await api.wallet.call(WalletApiOperation.GetExchangeDetailedInfo, {
          exchangeBaseUrl: initialExchange.exchangeBaseUrl,
        });

    return {
      exchanges,
      selected: selected.exchange,
      original: original?.exchange,
    };
  }, [selectedExchange, initialExchange]);

  const [showingTos, setShowingTos] = useState<string | undefined>(undefined);
  const [showingPrivacy, setShowingPrivacy] = useState<string | undefined>(
    undefined,
  );

  if (!hook) {
    return {
      status: "loading",
      error: undefined,
    };
  }
  if (hook.hasError) {
    return {
      status: "error",
      error: alertFromError(
        i18n.str`Could not load exchange details info`,
        hook,
      ),
    };
  }

  const { selected, original } = hook.response;

  const exchangeMap = exchanges.reduce(
    (prev, cur, idx) => ({ ...prev, [String(idx)]: cur.exchangeBaseUrl }),
    {} as Record<string, string>,
  );

  if (showingPrivacy) {
    return {
      status: "showing-privacy",
      error: undefined,
      onClose: {
        onClick: pushAlertOnError(async () => setShowingPrivacy(undefined)),
      },
      exchangeUrl: showingPrivacy,
    };
  }
  if (showingTos) {
    return {
      status: "showing-tos",
      error: undefined,
      onClose: {
        onClick: pushAlertOnError(async () => setShowingTos(undefined)),
      },
      exchangeUrl: showingTos,
    };
  }

  if (!comparingExchanges || !original) {
    // !original <=> selected == original
    return {
      status: "ready",
      exchanges: {
        list: exchangeMap,
        value: value,
        onChange: pushAlertOnError(async (v) => {
          setValue(v);
        }),
      },
      error: undefined,
      onClose: {
        onClick: pushAlertOnError(onCancel),
      },
      selected,
      onShowPrivacy: {
        onClick: pushAlertOnError(async () => {
          setShowingPrivacy(selected.exchangeBaseUrl);
        }),
      },
      onShowTerms: {
        onClick: pushAlertOnError(async () => {
          setShowingTos(selected.exchangeBaseUrl);
        }),
      },
    };
  }

  //this may be expensive, useMemo
  const coinOperationTimeline: DenomOperationMap<FeeDescription[]> = {
    deposit: createPairTimeline(
      selected.denomFees.deposit,
      original.denomFees.deposit,
    ),
    refresh: createPairTimeline(
      selected.denomFees.refresh,
      original.denomFees.refresh,
    ),
    refund: createPairTimeline(
      selected.denomFees.refund,
      original.denomFees.refund,
    ),
    withdraw: createPairTimeline(
      selected.denomFees.withdraw,
      original.denomFees.withdraw,
    ),
  };

  const globalFeeTimeline = createPairTimeline(
    selected.globalFees,
    original.globalFees,
  );

  const allWireType = Object.keys(selected.transferFees).concat(
    Object.keys(original.transferFees),
  );

  const wireFeeTimeline: Record<string, FeeDescription[]> = {};

  const missingWireTYpe: string[] = [];
  const newWireType: string[] = [];

  for (const wire of allWireType) {
    const selectedWire = selected.transferFees[wire];
    const originalWire = original.transferFees[wire];

    if (!selectedWire) {
      newWireType.push(wire);
      continue;
    }
    if (!originalWire) {
      missingWireTYpe.push(wire);
      continue;
    }

    wireFeeTimeline[wire] = createPairTimeline(selectedWire, originalWire);
  }

  return {
    status: "comparing",
    exchanges: {
      list: exchangeMap,
      value: value,
      onChange: pushAlertOnError(async (v) => {
        setValue(v);
      }),
    },
    error: undefined,
    onReset: {
      onClick: pushAlertOnError(async () => {
        setValue(String(initialValue));
      }),
    },
    onSelect: {
      onClick: pushAlertOnError(async () => {
        onSelection(selected.exchangeBaseUrl);
      }),
    },
    onShowPrivacy: {
      onClick: pushAlertOnError(async () => {
        setShowingPrivacy(selected.exchangeBaseUrl);
      }),
    },
    onShowTerms: {
      onClick: pushAlertOnError(async () => {
        setShowingTos(selected.exchangeBaseUrl);
      }),
    },
    selected,
    coinOperationTimeline,
    wireFeeTimeline,
    globalFeeTimeline,
    missingWireTYpe,
    newWireType,
  };
}