Build exchange workspace and shared transaction services (#28)

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

@@ -0,0 +1,150 @@
+import 'dart:async';
+
+import 'package:flutter/foundation.dart';
+
+import 'package:sxchnge_analytics/sxchnge_analytics.dart';
+
+import '../models/wallet.dart';
+import '../services/contracts.dart';
+
+class WalletProvider extends ChangeNotifier {
+  WalletProvider(this.service, this.analytics);
+  final WalletService service;
+  final AnalyticsService analytics;
+  WalletSnapshot? data;
+  bool loading = false,
+      failed = false,
+      profileLoading = false,
+      profileFailed = false,
+      saving = false,
+      saveFailed = false;
+  String? preferredLocale;
+  bool _disposed = false;
+  int _revision = 0;
+  Timer? _poll;
+  final _settlements = <String, (JourneyRecorder, JourneyOperation)>{};
+  CurrencyAccount? account(String? id) {
+    for (final a in data?.accounts ?? <CurrencyAccount>[]) {
+      if (a.id == id) return a;
+    }
+    return null;
+  }
+
+  WalletOperation? operation(String id) {
+    for (final o in data?.operations ?? <WalletOperation>[]) {
+      if (o.id == id) return o;
+    }
+    return null;
+  }
+
+  bool get hasPending =>
+      data?.operations.any((o) => o.status == OperationStatus.pending) ?? false;
+  Future<void> refresh() async {
+    final rev = ++_revision;
+    loading = true;
+    failed = false;
+    notifyListeners();
+    try {
+      final result = await service.fetch();
+      if (_disposed || rev != _revision) return;
+      data = result;
+      for (final o in result.operations) {
+        if (o.status == OperationStatus.pending) continue;
+        final pair = _settlements.remove(o.id);
+        if (pair != null) {
+          pair.$1.finish(
+            pair.$2,
+            simulated: service.isSimulated,
+            failure: o.status == OperationStatus.failed
+                ? JourneyFailure.declined
+                : null,
+            terminal: true,
+          );
+          pair.$1.dispose();
+        }
+      }
+    } catch (_) {
+      if (_disposed || rev != _revision) return;
+      failed = true;
+    }
+    if (_disposed || rev != _revision) return;
+    loading = false;
+    _poll?.cancel();
+    if (hasPending) {
+      _poll = Timer(const Duration(seconds: 3), () {
+        if (!_disposed) refresh();
+      });
+    }
+    notifyListeners();
+  }
+
+  void track(
+    WalletOperation operation,
+    JourneyRecorder recorder,
+    JourneyKind kind,
+  ) {
+    final step = recorder.begin(
+      kind,
+      JourneyStep.settlement,
+      simulated: service.isSimulated,
+    );
+    _settlements[operation.id] = (recorder, step);
+    final snapshot = data;
+    if (snapshot != null) {
+      data = WalletSnapshot(
+        accounts: snapshot.accounts,
+        operations: [
+          operation,
+          ...snapshot.operations.where((o) => o.id != operation.id),
+        ],
+      );
+    }
+    unawaited(refresh());
+  }
+
+  Future<void> loadProfile() async {
+    if (profileLoading) return;
+    profileLoading = true;
+    profileFailed = false;
+    notifyListeners();
+    try {
+      final result = await service.profile();
+      if (_disposed) return;
+      preferredLocale = result.locale;
+    } catch (_) {
+      if (_disposed) return;
+      profileFailed = true;
+    }
+    profileLoading = false;
+    notifyListeners();
+  }
+
+  Future<bool> saveLocale(String locale) async {
+    if (saving) return false;
+    saving = true;
+    saveFailed = false;
+    notifyListeners();
+    try {
+      final result = await service.saveLocale(locale);
+      if (_disposed) return false;
+      preferredLocale = result.locale;
+    } catch (_) {
+      if (_disposed) return false;
+      saveFailed = true;
+    }
+    saving = false;
+    notifyListeners();
+    return !saveFailed;
+  }
+
+  @override
+  void dispose() {
+    _disposed = true;
+    _poll?.cancel();
+    for (final p in _settlements.values) {
+      p.$1.dispose(abandonActive: false);
+    }
+    _settlements.clear();
+    super.dispose();
+  }
+}