Build exchange workspace and shared transaction services (#28)

frontend/app/lib/workspace/summary.dart

@@ -0,0 +1,84 @@
+import 'package:flutter/material.dart';
+
+import 'package:intl/intl.dart';
+
+import 'package:provider/provider.dart';
+
+import 'package:sxchnge_wallet/sxchnge_wallet.dart';
+
+import 'copy.dart';
+
+import '../generated/i18n/app_localizations.dart';
+
+class TransferSummary extends StatelessWidget {
+  const TransferSummary({super.key, required this.quote});
+  final Quote quote;
+  @override
+  Widget build(BuildContext context) {
+    final p = context.read<WalletProvider>();
+    final l = AppLocalizations.of(context)!;
+    final q = quote;
+    final a = p.account(q.request.source);
+    final b = p.account(q.request.destination) ?? a;
+    if (a == null || b == null) return Text(l.wNotFound);
+    return Card(
+      child: Padding(
+        padding: const EdgeInsets.all(24),
+        child: Column(
+          crossAxisAlignment: CrossAxisAlignment.stretch,
+          children: [
+            _row(
+              context,
+              q.request.kind == TransferKind.topUp ? l.wYouPay : l.wTotalDebit,
+              money(context, a, q.debit),
+              large: true,
+            ),
+            const Divider(height: 32),
+            _row(context, l.wFee, money(context, a, q.fee)),
+            if (q.request.kind == TransferKind.exchange) ...[
+              const SizedBox(height: 16),
+              _row(
+                context,
+                l.wRate,
+                '1 ${a.currency} = ${NumberFormat('0.0000', Localizations.localeOf(context).toLanguageTag()).format(q.rateNumerator / q.rateDenominator)} ${b.currency}',
+              ),
+            ],
+            const SizedBox(height: 16),
+            _row(
+              context,
+              q.request.kind == TransferKind.payout
+                  ? l.wRecipientGets
+                  : l.wCredit,
+              money(context, b, q.credit),
+              large: true,
+            ),
+            if (q.request.kind == TransferKind.payout) ...[
+              const Divider(height: 32),
+              Text(l.wRecipient),
+              SelectableText(q.request.recipient),
+            ],
+          ],
+        ),
+      ),
+    );
+  }
+
+  Widget _row(
+    BuildContext context,
+    String label,
+    String value, {
+    bool large = false,
+  }) => Column(
+    crossAxisAlignment: CrossAxisAlignment.start,
+    children: [
+      Text(label),
+      const SizedBox(height: 4),
+      Text(
+        value,
+        style: large
+            ? Theme.of(context).textTheme.headlineSmall
+            : Theme.of(context).textTheme.titleMedium,
+      ),
+    ],
+  );
+}