import 'dart:async';
import 'dart:convert';

import 'package:flutter_test/flutter_test.dart';
import 'package:http/http.dart' as http;
import 'package:http/testing.dart';
import 'package:shared_preferences/shared_preferences.dart';

import 'package:miler/data/api_config.dart';
import 'package:miler/data/miler_api.dart';
import 'package:miler/data/mock_backend.dart';
import 'package:miler/data/mutation_guard.dart';

/// ─────────────────────────────────────────────────────────────────────────
/// ONE PRESS, ONE REQUEST
///
/// Every business-critical action here is a POST the backend is not idempotent
/// about. A rider presses them on a moving bike, with gloves, on a screen he
/// cannot look at for long — so a double tap is not an edge case. Two
/// `duty/start` calls are a server error; two `payment` calls are two payments;
/// two `accept` calls race each other to decide what the list shows.
/// ─────────────────────────────────────────────────────────────────────────
void main() {
  TestWidgetsFlutterBinding.ensureInitialized();

  late int calls;
  late Completer<void> release;

  /// A server that does not answer until the test lets it, so a second press
  /// genuinely lands while the first is still in flight.
  void stubSlow({int code = 200, Map<String, dynamic>? body}) {
    calls = 0;
    release = Completer<void>();
    MilerApi.client = MockClient((_) async {
      calls++;
      await release.future;
      return http.Response(
        json.encode(body ?? {'success': true}),
        code,
        headers: const {'content-type': 'application/json'},
      );
    });
  }

  setUp(() async {
    MockBackend.enabled = false;
    MutationGuard.reset();
    SharedPreferences.setMockInitialValues({'authtoken': 'test-token'});
    await ApiConfig.setToken('test-token');
  });

  tearDown(() {
    MilerApi.client = http.Client();
    MockBackend.enabled = kMockBackend;
    MutationGuard.reset();
    MilerApi.onUnauthorized = null;
  });

  test('a double tap on accept sends one request', () async {
    stubSlow();

    final first = MilerApi.acceptAssignment(1042);
    final second = MilerApi.acceptAssignment(1042);

    release.complete();
    final results = await Future.wait([first, second]);

    expect(calls, 1, reason: 'the second press must not reach the server');
    expect(results.where((r) => r.ok).length, 1);

    // ── The dropped press is a failure, not a silent null ──
    //
    // A caller that does not know about the guard still has to take its error
    // path rather than reading nothing as success.
    final dropped = results.firstWhere((r) => !r.ok);
    expect(dropped.message, contains('already going through'));
  });

  test('two different assignments are not blocked by each other', () async {
    stubSlow();

    final a = MilerApi.acceptAssignment(1);
    final b = MilerApi.acceptAssignment(2);
    release.complete();
    await Future.wait([a, b]);

    expect(calls, 2, reason: 'the guard is keyed by resource, not by verb');
  });

  test(
    'the key frees on completion, so a genuine retry goes through',
    () async {
      stubSlow();
      final first = MilerApi.acceptAssignment(7);
      release.complete();
      await first;

      stubSlow();
      final retry = MilerApi.acceptAssignment(7);
      release.complete();
      await retry;

      expect(calls, 1, reason: 'the second stub saw a fresh request');
    },
  );

  test('a failed mutation frees its key too', () async {
    // A guard that leaks on failure is worse than no guard: the rider's retry
    // would be dropped for the rest of the session.
    MilerApi.client = MockClient((_) async => throw const _Dead());
    await MilerApi.pickupComplete(55);
    expect(MutationGuard.isBusy('pickup-complete:55'), isFalse);
  });

  test('duty start and end share one key, in both directions', () async {
    stubSlow();
    final start = MilerApi.startDuty(lat: 11, lon: 76);
    final end = MilerApi.endDuty();
    release.complete();
    await Future.wait([start, end]);

    expect(
      calls,
      1,
      reason:
          'a rider tapping the switch again because the first tap "did '
          'nothing" is the commonest way to double-fire duty',
    );
  });

  group('every non-idempotent mutation is guarded', () {
    Future<void> expectGuarded(
      String label,
      Future<dynamic> Function() call,
    ) async {
      stubSlow();
      final a = call();
      final b = call();
      release.complete();
      await Future.wait([a, b]);
      expect(calls, 1, reason: '$label is not protected against a double tap');
    }

    test('the pickup flow', () async {
      await expectGuarded('reached', () => MilerApi.reached(9));
      await expectGuarded('parcel', () => MilerApi.submitParcels(9, const []));
      await expectGuarded(
        'payment',
        () => MilerApi.submitPayment(9, paymentMode: 'Cash', amount: 120),
      );
      await expectGuarded('pickup-complete', () => MilerApi.pickupComplete(9));
    });

    test('the delivery flow', () async {
      await expectGuarded(
        'deliver',
        () => MilerApi.deliver(3, deliveredToName: 'Joe'),
      );
      await expectGuarded(
        'skip',
        () => MilerApi.skipConsignment(3, reason: 'Nobody home'),
      );
    });

    test('availability and breaks', () async {
      await expectGuarded(
        'availability',
        () => MilerApi.setAvailability('Available'),
      );
      await expectGuarded('break', () => MilerApi.startBreak('Personal'));
    });

    test('reject and cancel', () async {
      await expectGuarded(
        'reject',
        () => MilerApi.rejectAssignment(4, reason: 'Too far'),
      );
      await expectGuarded(
        'cancel',
        () => MilerApi.cancelBooking(4, reason: 'Shop closed'),
      );
    });
  });

  group('a 401 ends the session, once, centrally', () {
    test('the dead token is dropped and the app is told', () async {
      var told = 0;
      MilerApi.onUnauthorized = () => told++;
      MilerApi.client = MockClient(
        (_) async => http.Response(
          json.encode({'success': false, 'message': 'token expired'}),
          401,
          headers: const {'content-type': 'application/json'},
        ),
      );

      final res = await MilerApi.getProfile();

      expect(res.ok, isFalse);
      expect(res.status, 401);
      expect(told, 1);
      expect(
        await ApiConfig.getToken(),
        isNull,
        reason: 'nothing may retry with a token the server has refused',
      );
    });

    test('a wrong PIN does not log anybody out', () async {
      var told = 0;
      MilerApi.onUnauthorized = () => told++;
      MilerApi.client = MockClient(
        (_) async => http.Response(
          json.encode({'success': false, 'message': 'incorrect PIN'}),
          401,
          headers: const {'content-type': 'application/json'},
        ),
      );

      await MilerApi.verifyPin(phone: '9787698259', pin: '0000');

      expect(
        told,
        0,
        reason:
            'a 401 on an auth route is about a credential, not an expired '
            'session — clearing state here is a logout in response to a typo',
      );
    });

    test('a 429 is a failure, not a session end', () async {
      var told = 0;
      MilerApi.onUnauthorized = () => told++;
      MilerApi.client = MockClient(
        (_) async => http.Response(
          json.encode({'success': false, 'message': 'rate limited'}),
          429,
          headers: const {'content-type': 'application/json'},
        ),
      );

      final res = await MilerApi.assignments();
      expect(res.ok, isFalse);
      expect(res.status, 429);
      expect(res.message, 'rate limited');
      expect(told, 0);
      expect(await ApiConfig.getToken(), isNotNull);
    });
  });
}

class _Dead implements Exception {
  const _Dead();
}