Add optional KYC flow and service-backed account limits

frontend/packages/sxchnge_kyc/lib/src/providers/identity.dart

@@ -0,0 +1,235 @@
+import 'dart:math';
+
+import 'package:flutter/foundation.dart';
+
+import 'package:sxchnge_analytics/sxchnge_analytics.dart';
+
+import '../models/identity.dart';
+import '../services/contracts.dart';
+import '../services/dummy.dart';
+
+class IdentityProvider extends ChangeNotifier {
+  IdentityProvider(
+    this.service,
+    this.photos,
+    this.journeys, {
+    this.onStatusChanged,
+  });
+  final Future<void> Function()? onStatusChanged;
+  final IdentityService service;
+  final PhotoService photos;
+  final JourneyRecorder journeys;
+  Identity? record;
+  Photo? passport;
+  Photo? selfie;
+  KycError? error;
+  PhotoKind? photoError;
+  bool busy = false;
+  bool stale = false;
+  bool editing = false;
+  bool confirmed = false;
+  int step = 0;
+  bool _disposed = false;
+  String? _key;
+  bool get hasDraft => passport != null || selfie != null;
+  bool get canSubmit =>
+      !busy &&
+      !stale &&
+      confirmed &&
+      passport != null &&
+      selfie != null &&
+      (record?.canSubmit ?? false);
+  bool get isDemo => service.isSimulated;
+  void _notify() {
+    if (!_disposed) notifyListeners();
+  }
+
+  JourneyOperation _begin(JourneyStep step) =>
+      journeys.begin(JourneyKind.kyc, step, simulated: isDemo);
+  Future<void> refresh() async {
+    if (busy) return;
+    busy = true;
+    error = null;
+    photoError = null;
+    _notify();
+    final op = _begin(JourneyStep.kycStatus);
+    try {
+      final result = await service.fetch();
+      if (_disposed) return;
+      record = result;
+      stale = false;
+      await onStatusChanged?.call();
+      if (_disposed) return;
+      if (!result.canSubmit) {
+        _clear();
+        editing = false;
+      }
+      journeys.finish(op, simulated: isDemo, terminal: true);
+    } catch (e) {
+      if (_disposed) return;
+      stale = true;
+      error = _error(e);
+      journeys.finish(op, failure: JourneyFailure.unavailable, terminal: false);
+    }
+    busy = false;
+    _notify();
+  }
+
+  void start() {
+    if (busy || stale || !(record?.canSubmit ?? false)) return;
+    editing = true;
+    error = null;
+    if (!hasDraft) {
+      step = 0;
+      confirmed = false;
+    }
+    final op = _begin(JourneyStep.kycPreparation);
+    journeys.finish(op, simulated: isDemo);
+    _notify();
+  }
+
+  Future<void> pick(PhotoKind kind) async {
+    if (busy || !editing) return;
+    busy = true;
+    error = null;
+    photoError = null;
+    _notify();
+    final op = _begin(
+      kind == PhotoKind.passport
+          ? JourneyStep.kycPassport
+          : JourneyStep.kycSelfie,
+    );
+    try {
+      final photo = await photos.pick();
+      if (_disposed) return;
+      if (photo != null) {
+        if (kind == PhotoKind.passport) {
+          passport = photo;
+        } else {
+          selfie = photo;
+        }
+        confirmed = false;
+        _key = null;
+      }
+      journeys.finish(op, simulated: isDemo, cancelled: photo == null);
+    } catch (e) {
+      if (_disposed) return;
+      error = _error(e);
+      photoError = kind;
+      journeys.finish(op, failure: JourneyFailure.document);
+    }
+    busy = false;
+    _notify();
+  }
+
+  void remove(PhotoKind kind) {
+    if (busy) return;
+    if (kind == PhotoKind.passport) {
+      passport = null;
+    } else {
+      selfie = null;
+    }
+    confirmed = false;
+    _key = null;
+    _notify();
+  }
+
+  void back() {
+    if (!busy && step > 0) {
+      step--;
+      error = null;
+      _notify();
+    }
+  }
+
+  void next() {
+    if (busy ||
+        (step == 0 && passport == null) ||
+        (step == 1 && selfie == null))
+      return;
+    if (step < 2) step++;
+    error = null;
+    _notify();
+  }
+
+  void confirm(bool value) {
+    if (!busy) {
+      confirmed = value;
+      _notify();
+    }
+  }
+
+  Future<void> submit() async {
+    if (!canSubmit) return;
+    busy = true;
+    error = null;
+    photoError = null;
+    _notify();
+    _key ??= List.generate(
+      16,
+      (_) => Random.secure().nextInt(256).toRadixString(16).padLeft(2, '0'),
+    ).join();
+    final op = _begin(JourneyStep.kycSubmission);
+    try {
+      final result = await service.submit(
+        passport: passport!,
+        selfie: selfie!,
+        idempotencyKey: _key!,
+      );
+      if (_disposed) return;
+      if (result.canSubmit) throw const KycException(KycError.conflict);
+      record = result;
+      editing = false;
+      _clear();
+      await onStatusChanged?.call();
+      if (_disposed) return;
+      journeys.finish(op, simulated: isDemo, terminal: true);
+    } catch (e) {
+      if (_disposed) return;
+      error = _error(e);
+      if (error == KycError.conflict || error == KycError.sessionExpired)
+        stale = true;
+      journeys.finish(op, failure: JourneyFailure.unavailable);
+    }
+    busy = false;
+    _notify();
+  }
+
+  Future<void> demoReview(IdentityStatus status, {ReviewReason? reason}) async {
+    if (busy || service is! DummyIdentityService) return;
+    try {
+      (service as DummyIdentityService).review(status, reason: reason);
+    } on KycException catch (e) {
+      error = e.code;
+      _notify();
+      return;
+    }
+    await refresh();
+  }
+
+  void exit() {
+    if (busy) return;
+    journeys.abandon(JourneyExit.navigation);
+    _clear();
+    editing = false;
+    error = null;
+    _notify();
+  }
+
+  void _clear() {
+    passport = null;
+    selfie = null;
+    confirmed = false;
+    _key = null;
+    step = 0;
+  }
+
+  KycError _error(Object e) => e is KycException ? e.code : KycError.internal;
+  @override
+  void dispose() {
+    _disposed = true;
+    _clear();
+    journeys.dispose();
+    super.dispose();
+  }
+}