Build exchange workspace and shared transaction services (#28)

frontend/packages/sxchnge_wallet/lib/src/models/wallet.dart

@@ -0,0 +1,113 @@
+enum TransferKind { topUp, exchange, payout }
+
+enum OperationStatus { pending, completed, failed }
+
+enum WalletError {
+  unavailable,
+  invalidAmount,
+  insufficientFunds,
+  limitExceeded,
+  expiredQuote,
+  invalidRecipient,
+  unsupported,
+  notFound,
+  uncertain,
+}
+
+class WalletException implements Exception {
+  const WalletException(this.code);
+  final WalletError code;
+}
+
+class CurrencyAccount {
+  const CurrencyAccount({
+    required this.id,
+    required this.currency,
+    required this.precision,
+    required this.available,
+  });
+  final String id, currency;
+  final int precision, available;
+
+  /// Locale-aware decimal input, integer money. Grouping/exponents are rejected.
+  int? parse(String input) {
+    final value = input.trim().replaceAll(',', '.');
+    if (!RegExp(r'^\d+(\.\d+)?$').hasMatch(value)) return null;
+    final parts = value.split('.');
+    if (parts.length > 1 && parts[1].length > precision) return null;
+    final major = int.tryParse(parts[0]);
+    if (major == null || major > 100000000) return null;
+    final fraction = parts.length > 1
+        ? int.parse(parts[1].padRight(precision, '0'))
+        : 0;
+    return major * scale + fraction;
+  }
+
+  int get scale {
+    var v = 1;
+    for (var i = 0; i < precision; i++) {
+      v *= 10;
+    }
+    return v;
+  }
+}
+
+class TransferRequest {
+  const TransferRequest({
+    required this.kind,
+    required this.source,
+    required this.amount,
+    this.destination,
+    this.recipient = '',
+  });
+  final TransferKind kind;
+  final String source;
+  final int amount;
+  final String? destination;
+  final String recipient;
+}
+
+class Quote {
+  const Quote({
+    required this.id,
+    required this.request,
+    required this.fee,
+    required this.debit,
+    required this.credit,
+    required this.expiresAt,
+    required this.rateNumerator,
+    required this.rateDenominator,
+  });
+  final String id;
+  final TransferRequest request;
+  final int fee, debit, credit, rateNumerator, rateDenominator;
+  final DateTime expiresAt;
+}
+
+class WalletOperation {
+  const WalletOperation({
+    required this.id,
+    required this.quote,
+    required this.status,
+    required this.createdAt,
+  });
+  final String id;
+  final Quote quote;
+  final OperationStatus status;
+  final DateTime createdAt;
+}
+
+class WalletSnapshot {
+  WalletSnapshot({
+    required List<CurrencyAccount> accounts,
+    required List<WalletOperation> operations,
+  }) : accounts = List.unmodifiable(accounts),
+       operations = List.unmodifiable(operations);
+  final List<CurrencyAccount> accounts;
+  final List<WalletOperation> operations;
+}
+
+class AccountProfile {
+  const AccountProfile(this.locale);
+  final String locale;
+}