Connect customer quotations and payment execution to Sendico (#50)

frontend/packages/sxchnge_wallet/lib/src/transport/backend.dart

@@ -0,0 +1,78 @@
+import 'dart:convert';
+
+import 'wallet.dart';
+
+/// Local BFF transport only; provider and widgets never parse response maps.
+class BackendDTO {
+  BackendDTO.decode(String body) {
+    final envelope = jsonDecode(body) as Map<String, dynamic>;
+    accepted = envelope['status'] == 'success';
+    data = envelope['data'];
+  }
+  late final bool accepted;
+  late final dynamic data;
+  String get error =>
+      (data as Map<String, dynamic>?)?['error'] as String? ?? 'unavailable';
+  String get locale => (data as Map<String, dynamic>)['locale'] as String;
+  String get key => (data as Map<String, dynamic>)['idempotencyKey'] as String;
+  List<AccountDTO> get accounts =>
+      ((data as Map<String, dynamic>)['accounts'] as List).map((v) {
+        final d = v as Map<String, dynamic>;
+        return AccountDTO(
+          d['id'] as String,
+          d['currency'] as String,
+          d['precision'] as int,
+          d['available'] as int,
+          payoutMethod: d['payoutMethod'] as String,
+          payoutLabel: d['payoutLabel'] as String,
+          canFund: d['canFund'] as bool,
+        );
+      }).toList();
+  List<OperationDTO> get operations =>
+      ((data as Map<String, dynamic>)['operations'] as List)
+          .map((v) => operation(v as Map<String, dynamic>))
+          .toList();
+  QuoteDTO get quoteValue => quote(data as Map<String, dynamic>);
+  OperationDTO? get operationValue =>
+      data == null ? null : operation(data as Map<String, dynamic>);
+  static QuoteDTO quote(Map<String, dynamic> d) {
+    final r = d['request'] as Map<String, dynamic>;
+    return QuoteDTO(
+      d['id'] as String,
+      RequestDTO(
+        r['kind'] as String,
+        r['source'] as String,
+        (r['destination'] as String?)?.isEmpty == true
+            ? null
+            : r['destination'] as String?,
+        r['amount'] as int,
+        r['recipient'] as String? ?? '',
+      ),
+      d['fee'] as int,
+      d['debit'] as int,
+      d['credit'] as int,
+      DateTime.parse(d['expiresAt'] as String),
+      d['rateNumerator'] as int,
+      d['rateDenominator'] as int,
+    );
+  }
+
+  static OperationDTO operation(Map<String, dynamic> d) => OperationDTO(
+    d['id'] as String,
+    quote(d['quote'] as Map<String, dynamic>),
+    DateTime.parse(d['createdAt'] as String),
+    DateTime.parse(d['createdAt'] as String),
+    status: d['status'] as String,
+  );
+  ChallengeDTO get challenge => ChallengeDTO(data as Map<String, dynamic>);
+}
+
+class ChallengeDTO {
+  ChallengeDTO(Map<String, dynamic> d)
+    : id = d['challengeId'] as String,
+      target = d['target'] as String,
+      expires = DateTime.parse(d['expiresAt'] as String),
+      resend = DateTime.parse(d['resendAt'] as String);
+  final String id, target;
+  final DateTime expires, resend;
+}