// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'dart:async';
import 'dart:io' as io;

import 'package:flutter_migrate/src/base/io.dart';
import 'package:flutter_migrate/src/base/signals.dart';
import 'package:test/fake.dart';

import '../src/common.dart';

void main() {
  group('Signals', () {
    late Signals signals;
    late FakeProcessSignal fakeSignal;
    late ProcessSignal signalUnderTest;

    setUp(() {
      signals = Signals.test();
      fakeSignal = FakeProcessSignal();
      signalUnderTest = ProcessSignal(fakeSignal);
    });

    testWithoutContext('signal handler runs', () async {
      final Completer<void> completer = Completer<void>();
      signals.addHandler(signalUnderTest, (ProcessSignal s) {
        expect(s, signalUnderTest);
        completer.complete();
      });

      fakeSignal.controller.add(fakeSignal);
      await completer.future;
    });

    testWithoutContext('signal handlers run in order', () async {
      final Completer<void> completer = Completer<void>();

      bool first = false;

      signals.addHandler(signalUnderTest, (ProcessSignal s) {
        expect(s, signalUnderTest);
        first = true;
      });

      signals.addHandler(signalUnderTest, (ProcessSignal s) {
        expect(s, signalUnderTest);
        expect(first, isTrue);
        completer.complete();
      });

      fakeSignal.controller.add(fakeSignal);
      await completer.future;
    });

    testWithoutContext(
        'signal handlers do not cause concurrent modification errors when removing handlers in a signal callback',
        () async {
      final Completer<void> completer = Completer<void>();
      late Object token;
      Future<void> handle(ProcessSignal s) async {
        expect(s, signalUnderTest);
        expect(await signals.removeHandler(signalUnderTest, token), true);
        completer.complete();
      }

      token = signals.addHandler(signalUnderTest, handle);

      fakeSignal.controller.add(fakeSignal);
      await completer.future;
    });

    testWithoutContext('signal handler error goes on error stream', () async {
      final Exception exn = Exception('Error');
      signals.addHandler(signalUnderTest, (ProcessSignal s) async {
        throw exn;
      });

      final Completer<void> completer = Completer<void>();
      final List<Object> errList = <Object>[];
      final StreamSubscription<Object> errSub = signals.errors.listen(
        (Object err) {
          errList.add(err);
          completer.complete();
        },
      );

      fakeSignal.controller.add(fakeSignal);
      await completer.future;
      await errSub.cancel();
      expect(errList, contains(exn));
    });

    testWithoutContext('removed signal handler does not run', () async {
      final Object token = signals.addHandler(
        signalUnderTest,
        (ProcessSignal s) async {
          fail('Signal handler should have been removed.');
        },
      );

      await signals.removeHandler(signalUnderTest, token);

      final List<Object> errList = <Object>[];
      final StreamSubscription<Object> errSub = signals.errors.listen(
        (Object err) {
          errList.add(err);
        },
      );

      fakeSignal.controller.add(fakeSignal);

      await errSub.cancel();
      expect(errList, isEmpty);
    });

    testWithoutContext('non-removed signal handler still runs', () async {
      final Completer<void> completer = Completer<void>();
      signals.addHandler(signalUnderTest, (ProcessSignal s) {
        expect(s, signalUnderTest);
        completer.complete();
      });

      final Object token = signals.addHandler(
        signalUnderTest,
        (ProcessSignal s) async {
          fail('Signal handler should have been removed.');
        },
      );
      await signals.removeHandler(signalUnderTest, token);

      final List<Object> errList = <Object>[];
      final StreamSubscription<Object> errSub = signals.errors.listen(
        (Object err) {
          errList.add(err);
        },
      );

      fakeSignal.controller.add(fakeSignal);
      await completer.future;
      await errSub.cancel();
      expect(errList, isEmpty);
    });

    testWithoutContext('only handlers for the correct signal run', () async {
      final FakeProcessSignal mockSignal2 = FakeProcessSignal();
      final ProcessSignal otherSignal = ProcessSignal(mockSignal2);

      final Completer<void> completer = Completer<void>();
      signals.addHandler(signalUnderTest, (ProcessSignal s) {
        expect(s, signalUnderTest);
        completer.complete();
      });

      signals.addHandler(otherSignal, (ProcessSignal s) async {
        fail('Wrong signal!.');
      });

      final List<Object> errList = <Object>[];
      final StreamSubscription<Object> errSub = signals.errors.listen(
        (Object err) {
          errList.add(err);
        },
      );

      fakeSignal.controller.add(fakeSignal);
      await completer.future;
      await errSub.cancel();
      expect(errList, isEmpty);
    });
  });
}

class FakeProcessSignal extends Fake implements io.ProcessSignal {
  final StreamController<io.ProcessSignal> controller =
      StreamController<io.ProcessSignal>();

  @override
  Stream<io.ProcessSignal> watch() => controller.stream;
}