1 files changed, 141 insertions, 0 deletions
diff --git a/packages/taler-wallet-webextension/src/hooks/useSelectedExchange.ts b/packages/taler-wallet-webextension/src/hooks/useSelectedExchange.ts
new file mode 100644
index 000000000..6907a247d
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+++ b/packages/taler-wallet-webextension/src/hooks/useSelectedExchange.ts
@@ -0,0 +1,141 @@
+/*
+ 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 { ExchangeListItem } from "@gnu-taler/taler-util";
+import { useState } from "preact/hooks";
+import { useAlertContext } from "../context/alert.js";
+import { ButtonHandler } from "../mui/handlers.js";
+
+type State = State.Ready | State.NoExchangeFound | State.Selecting;
+
+export namespace State {
+  export interface NoExchangeFound {
+    status: "no-exchange-found";
+    error: undefined;
+    currency: string;
+    defaultExchange: string | undefined;
+  }
+  export interface Ready {
+    status: "ready";
+    doSelect: ButtonHandler;
+    selected: ExchangeListItem;
+  }
+  export interface Selecting {
+    status: "selecting-exchange";
+    error: undefined;
+    onSelection: (url: string) => Promise<void>;
+    onCancel: () => Promise<void>;
+    list: ExchangeListItem[];
+    currency: string;
+    initialValue: string;
+  }
+}
+
+interface Props {
+  currency: string;
+  //there is a preference for the default at the initial state
+  defaultExchange?: string;
+  //list of exchanges
+  list: ExchangeListItem[];
+}
+
+export function useSelectedExchange({
+  currency,
+  defaultExchange,
+  list,
+}: Props): State {
+  const [isSelecting, setIsSelecting] = useState(false);
+  const [selectedExchange, setSelectedExchange] = useState<string | undefined>(
+    undefined,
+  );
+  const { pushAlertOnError } = useAlertContext();
+
+  if (!list.length) {
+    return {
+      status: "no-exchange-found",
+      error: undefined,
+      currency,
+      defaultExchange,
+    };
+  }
+
+  const exchangesWithThisCurrency = list.filter((e) => e.currency === currency);
+  if (!exchangesWithThisCurrency.length) {
+    // there should be at least one exchange for this currency
+    return {
+      status: "no-exchange-found",
+      error: undefined,
+      currency,
+      defaultExchange,
+    };
+  }
+
+  if (isSelecting) {
+    const currentExchange =
+      selectedExchange ??
+      defaultExchange ??
+      exchangesWithThisCurrency[0].exchangeBaseUrl;
+    return {
+      status: "selecting-exchange",
+      error: undefined,
+      list: exchangesWithThisCurrency,
+      currency,
+      initialValue: currentExchange,
+      onSelection: async (exchangeBaseUrl: string) => {
+        setIsSelecting(false);
+        setSelectedExchange(exchangeBaseUrl);
+      },
+      onCancel: async () => {
+        setIsSelecting(false);
+      },
+    };
+  }
+
+  {
+    const found = !selectedExchange
+      ? undefined
+      : list.find((e) => e.exchangeBaseUrl === selectedExchange);
+    if (found)
+      return {
+        status: "ready",
+        doSelect: {
+          onClick: pushAlertOnError(async () => setIsSelecting(true)),
+        },
+        selected: found,
+      };
+  }
+  {
+    const found = !defaultExchange
+      ? undefined
+      : list.find((e) => e.exchangeBaseUrl === defaultExchange);
+    if (found)
+      return {
+        status: "ready",
+        doSelect: {
+          onClick: pushAlertOnError(async () => setIsSelecting(true)),
+        },
+        selected: found,
+      };
+  }
+
+  return {
+    status: "ready",
+    doSelect: {
+      onClick: pushAlertOnError(async () => setIsSelecting(true)),
+    },
+    selected: exchangesWithThisCurrency[0],
+  };
+}