// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
// for details. 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:math';

import 'package:async/async.dart' hide Result;
import 'package:collection/collection.dart';
import 'package:pedantic/pedantic.dart';
import 'package:pool/pool.dart';
import 'package:test_api/src/backend/group.dart'; // ignore: implementation_imports
import 'package:test_api/src/backend/invoker.dart'; // ignore: implementation_imports
import 'package:test_api/src/backend/live_test.dart'; // ignore: implementation_imports
import 'package:test_api/src/backend/live_test_controller.dart'; // ignore: implementation_imports
import 'package:test_api/src/backend/message.dart'; // ignore: implementation_imports
import 'package:test_api/src/backend/state.dart'; // ignore: implementation_imports
import 'package:test_api/src/backend/test.dart'; // ignore: implementation_imports

import 'coverage_stub.dart' if (dart.library.io) 'coverage.dart';
import 'live_suite.dart';
import 'live_suite_controller.dart';
import 'load_suite.dart';
import 'runner_suite.dart';
import 'util/iterable_set.dart';

/// An [Engine] manages a run that encompasses multiple test suites.
///
/// Test suites are provided by passing them into [suiteSink]. Once all suites
/// have been provided, the user should close [suiteSink] to indicate this.
/// [run] won't terminate until [suiteSink] is closed. Suites will be run in the
/// order they're provided to [suiteSink]. Tests within those suites will
/// likewise be run in the order they're declared.
///
/// The current status of every test is visible via [liveTests]. [onTestStarted]
/// can also be used to be notified when a test is about to be run.
///
/// The engine has some special logic for [LoadSuite]s and the tests they
/// contain, referred to as "load tests". Load tests exist to provide visibility
/// into the process of loading test files, but as long as that process is
/// proceeding normally users usually don't care about it, so the engine only
/// surfaces running load tests (that is, includes them in [liveTests] and other
/// collections) under specific circumstances.
///
/// If only load tests are running, exactly one load test will be in [active]
/// and [liveTests]. If this test passes, it will be removed from both [active]
/// and [liveTests] and *will not* be added to [passed]. If at any point a load
/// test fails, it will be added to [failed] and [liveTests].
///
/// The test suite loaded by a load suite will be automatically be run by the
/// engine; it doesn't need to be added to [suiteSink] manually.
///
/// Load tests will always be emitted through [onTestStarted] so users can watch
/// their event streams once they start running.
class Engine {
  /// Whether [run] has been called yet.
  var _runCalled = false;

  /// Whether [close] has been called.
  var _closed = false;

  /// Whether [close] was called before all the tests finished running.
  ///
  /// This is `null` if close hasn't been called and the tests are still
  /// running, `true` if close was called before the tests finished running, and
  /// `false` if the tests finished running before close was called.
  bool? _closedBeforeDone;

  /// The coverage output directory.
  String? _coverage;

  /// A pool that limits the number of test suites running concurrently.
  final Pool _runPool;

  /// A completer that will complete when this engine is unpaused.
  ///
  /// `null` if this engine is not paused.
  Completer? _pauseCompleter;

  /// A future that completes once this is unpaused.
  ///
  /// If this engine isn't paused, this future completes immediately.
  Future get _onUnpaused =>
      _pauseCompleter == null ? Future.value() : _pauseCompleter!.future;

  /// Whether all tests passed or were skipped.
  ///
  /// This fires once all tests have completed and [suiteSink] has been closed.
  /// This will be `null` if [close] was called before all the tests finished
  /// running.
  Future<bool?> get success async {
    await Future.wait(<Future>[_group.future, _runPool.done], eagerError: true);
    if (_closedBeforeDone!) return null;
    return liveTests.every((liveTest) =>
        liveTest.state.result.isPassing &&
        liveTest.state.status == Status.complete);
  }

  /// A group of futures for each test suite.
  final _group = FutureGroup();

  /// All of the engine's stream subscriptions.
  final _subscriptions = <StreamSubscription>{};

  /// A sink used to pass [RunnerSuite]s in to the engine to run.
  ///
  /// Suites may be added as quickly as they're available; the Engine will only
  /// run as many as necessary at a time based on its concurrency settings.
  ///
  /// Suites added to the sink will be closed by the engine based on its
  /// internal logic.
  Sink<RunnerSuite> get suiteSink => DelegatingSink(_suiteController.sink);
  final _suiteController = StreamController<RunnerSuite>();

  /// All the [RunnerSuite]s added to [suiteSink] so far.
  ///
  /// Note that if a [LoadSuite] is added, this will only contain that suite,
  /// not the suite it loads.
  Set<RunnerSuite> get addedSuites => UnmodifiableSetView(_addedSuites);
  final _addedSuites = <RunnerSuite>{};

  /// A broadcast stream that emits each [RunnerSuite] as it's added to the
  /// engine via [suiteSink].
  ///
  /// Note that if a [LoadSuite] is added, this will only return that suite, not
  /// the suite it loads.
  ///
  /// This is guaranteed to fire after the suite is added to [addedSuites].
  Stream<RunnerSuite> get onSuiteAdded => _onSuiteAddedController.stream;
  final _onSuiteAddedController = StreamController<RunnerSuite>.broadcast();

  /// All the currently-known suites that have run or are running.
  ///
  /// These are [LiveSuite]s, representing the in-progress state of each suite
  /// as its component tests are being run.
  ///
  /// Note that unlike [addedSuites], for suites that are loaded using
  /// [LoadSuite]s, both the [LoadSuite] and the suite it loads will eventually
  /// be in this set.
  Set<LiveSuite> get liveSuites => UnmodifiableSetView(_liveSuites);
  final _liveSuites = <LiveSuite>{};

  /// A broadcast stream that emits each [LiveSuite] as it's loaded.
  ///
  /// Note that unlike [onSuiteAdded], for suites that are loaded using
  /// [LoadSuite]s, both the [LoadSuite] and the suite it loads will eventually
  /// be emitted by this stream.
  Stream<LiveSuite> get onSuiteStarted => _onSuiteStartedController.stream;
  final _onSuiteStartedController = StreamController<LiveSuite>.broadcast();

  /// All the currently-known tests that have run or are running.
  ///
  /// These are [LiveTest]s, representing the in-progress state of each test.
  /// Tests that have not yet begun running are marked [Status.pending]; tests
  /// that have finished are marked [Status.complete].
  ///
  /// This is guaranteed to contain the same tests as the union of [passed],
  /// [skipped], [failed], and [active].
  ///
  /// [LiveTest.run] must not be called on these tests.
  Set<LiveTest> get liveTests =>
      UnionSet.from([passed, skipped, failed, IterableSet(active)],
          disjoint: true);

  /// A stream that emits each [LiveTest] as it's about to start running.
  ///
  /// This is guaranteed to fire before [LiveTest.onStateChange] first fires.
  Stream<LiveTest> get onTestStarted => _onTestStartedGroup.stream;
  final _onTestStartedGroup = StreamGroup<LiveTest>.broadcast();

  /// The set of tests that have completed and been marked as passing.
  Set<LiveTest> get passed => _passedGroup.set;
  final _passedGroup = UnionSetController<LiveTest>(disjoint: true);

  /// The set of tests that have completed and been marked as skipped.
  Set<LiveTest> get skipped => _skippedGroup.set;
  final _skippedGroup = UnionSetController<LiveTest>(disjoint: true);

  /// The set of tests that have completed and been marked as failing or error.
  Set<LiveTest> get failed => _failedGroup.set;
  final _failedGroup = UnionSetController<LiveTest>(disjoint: true);

  /// The tests that are still running, in the order they begain running.
  List<LiveTest> get active => UnmodifiableListView(_active);
  final _active = QueueList<LiveTest>();

  /// The set of tests that have been marked for restarting.
  ///
  /// This is always a subset of [active]. Once a test in here has finished
  /// running, it's run again.
  final _restarted = <LiveTest>{};

  /// The tests from [LoadSuite]s that are still running, in the order they
  /// began running.
  ///
  /// This is separate from [active] because load tests aren't always surfaced.
  final _activeLoadTests = <LiveTest>{};

  /// Whether this engine is idle—that is, not currently executing a test.
  bool get isIdle => _group.isIdle;

  /// A broadcast stream that fires an event whenever [isIdle] switches from
  /// `false` to `true`.
  Stream get onIdle => _group.onIdle;

  // TODO(nweiz): Use interface libraries to take a Configuration even when
  // dart:io is unavailable.
  /// Creates an [Engine] that will run all tests provided via [suiteSink].
  ///
  /// [concurrency] controls how many suites are loaded and ran at once, and
  /// defaults to 1.
  Engine({int? concurrency, String? coverage})
      : _runPool = Pool(concurrency ?? 1),
        _coverage = coverage {
    _group.future.then((_) {
      _onTestStartedGroup.close();
      _onSuiteStartedController.close();
      _closedBeforeDone ??= false;
    }).onError((_, __) {
      // Don't top-level errors. They'll be thrown via [success] anyway.
    });
  }

  /// Creates an [Engine] that will run all tests in [suites].
  ///
  /// An engine constructed this way will automatically close its [suiteSink],
  /// meaning that no further suites may be provided.
  ///
  /// [concurrency] controls how many suites are run at once. If [runSkipped] is
  /// `true`, skipped tests will be run as though they weren't skipped.
  factory Engine.withSuites(List<RunnerSuite> suites,
      {int? concurrency, String? coverage}) {
    var engine = Engine(concurrency: concurrency, coverage: coverage);
    for (var suite in suites) {
      engine.suiteSink.add(suite);
    }
    engine.suiteSink.close();
    return engine;
  }

  /// Runs all tests in all suites defined by this engine.
  ///
  /// This returns `true` if all tests succeed, and `false` otherwise. It will
  /// only return once all tests have finished running and [suiteSink] has been
  /// closed.
  ///
  /// If [success] completes with `null` this will complete with `null`.
  Future<bool?> run() {
    if (_runCalled) {
      throw StateError('Engine.run() may not be called more than once.');
    }
    _runCalled = true;

    late StreamSubscription subscription;
    subscription = _suiteController.stream.listen((suite) {
      _addedSuites.add(suite);
      _onSuiteAddedController.add(suite);

      _group.add(() async {
        var resource = await _runPool.request();
        LiveSuiteController? controller;
        try {
          if (suite is LoadSuite) {
            await _onUnpaused;
            controller = await _addLoadSuite(suite);
            if (controller == null) return;
          } else {
            controller = LiveSuiteController(suite);
          }

          _addLiveSuite(controller.liveSuite);

          if (_closed) return;
          await _runGroup(controller, controller.liveSuite.suite.group, []);
          controller.noMoreLiveTests();
          if (_coverage != null) await writeCoverage(_coverage!, controller);
        } finally {
          resource.allowRelease(() => controller?.close());
        }
      }());
    }, onDone: () {
      _subscriptions.remove(subscription);
      _onSuiteAddedController.close();
      _group.close();
      _runPool.close();
    });
    _subscriptions.add(subscription);

    return success;
  }

  /// Runs all the entries in [group] in sequence.
  ///
  /// [suiteController] is the controller fo the suite that contains [group].
  /// [parents] is a list of groups that contain [group]. It may be modified,
  /// but it's guaranteed to be in its original state once this function has
  /// finished.
  Future _runGroup(LiveSuiteController suiteController, Group group,
      List<Group> parents) async {
    parents.add(group);
    try {
      var suiteConfig = suiteController.liveSuite.suite.config;
      var skipGroup = !suiteConfig.runSkipped && group.metadata.skip;
      var setUpAllSucceeded = true;
      if (!skipGroup && group.setUpAll != null) {
        var liveTest = group.setUpAll!
            .load(suiteController.liveSuite.suite, groups: parents);
        await _runLiveTest(suiteController, liveTest, countSuccess: false);
        setUpAllSucceeded = liveTest.state.result.isPassing;
      }

      if (!_closed && setUpAllSucceeded) {
        // shuffle the group entries
        var entries = group.entries.toList();
        if (suiteConfig.testRandomizeOrderingSeed != null &&
            suiteConfig.testRandomizeOrderingSeed! > 0) {
          entries.shuffle(Random(suiteConfig.testRandomizeOrderingSeed));
        }

        for (var entry in entries) {
          if (_closed) return;

          if (entry is Group) {
            await _runGroup(suiteController, entry, parents);
          } else if (!suiteConfig.runSkipped && entry.metadata.skip) {
            await _runSkippedTest(suiteController, entry as Test, parents);
          } else {
            var test = entry as Test;
            await _runLiveTest(suiteController,
                test.load(suiteController.liveSuite.suite, groups: parents));
          }
        }
      }

      // Even if we're closed or setUpAll failed, we want to run all the
      // teardowns to ensure that any state is properly cleaned up.
      if (!skipGroup && group.tearDownAll != null) {
        var liveTest = group.tearDownAll!
            .load(suiteController.liveSuite.suite, groups: parents);
        await _runLiveTest(suiteController, liveTest, countSuccess: false);
        if (_closed) await liveTest.close();
      }
    } finally {
      parents.remove(group);
    }
  }

  /// Runs [liveTest] using [suiteController].
  ///
  /// If [countSuccess] is `true` (the default), the test is put into [passed]
  /// if it succeeds. Otherwise, it's removed from [liveTests] entirely.
  Future _runLiveTest(LiveSuiteController suiteController, LiveTest liveTest,
      {bool countSuccess = true}) async {
    await _onUnpaused;
    _active.add(liveTest);

    // If there were no active non-load tests, the current active test would
    // have been a load test. In that case, remove it, since now we have a
    // non-load test to add.
    if (_active.first.suite is LoadSuite) _active.removeFirst();

    late StreamSubscription subscription;
    subscription = liveTest.onStateChange.listen((state) {
      if (state.status != Status.complete) return;
      _active.remove(liveTest);

      // If we're out of non-load tests, surface a load test.
      if (_active.isEmpty && _activeLoadTests.isNotEmpty) {
        _active.add(_activeLoadTests.first);
      }
    }, onDone: () {
      _subscriptions.remove(subscription);
    });
    _subscriptions.add(subscription);

    suiteController.reportLiveTest(liveTest, countSuccess: countSuccess);

    // Schedule a microtask to ensure that [onTestStarted] fires before the
    // first [LiveTest.onStateChange] event.
    await Future.microtask(liveTest.run);

    // Once the test finishes, use [new Future] to do a coarse-grained event
    // loop pump to avoid starving non-microtask events.
    await Future(() {});

    if (!_restarted.contains(liveTest)) return;
    await _runLiveTest(suiteController, liveTest.copy(),
        countSuccess: countSuccess);
    _restarted.remove(liveTest);
  }

  /// Runs a dummy [LiveTest] for a test marked as "skip".
  ///
  /// [suiteController] is the controller for the suite that contains [test].
  /// [parents] is a list of groups that contain [test].
  Future _runSkippedTest(LiveSuiteController suiteController, Test test,
      List<Group> parents) async {
    await _onUnpaused;
    var skipped = LocalTest(test.name, test.metadata, () {}, trace: test.trace);

    late LiveTestController controller;
    controller =
        LiveTestController(suiteController.liveSuite.suite, skipped, () {
      controller.setState(const State(Status.running, Result.success));
      controller.setState(const State(Status.running, Result.skipped));

      if (skipped.metadata.skipReason != null) {
        controller
            .message(Message.skip('Skip: ${skipped.metadata.skipReason}'));
      }

      controller.setState(const State(Status.complete, Result.skipped));
      controller.completer.complete();
    }, () {}, groups: parents);

    return await _runLiveTest(suiteController, controller);
  }

  /// Closes [liveTest] and tells the engine to re-run it once it's done
  /// running.
  ///
  /// Returns the same future as [LiveTest.close].
  Future restartTest(LiveTest liveTest) async {
    if (_activeLoadTests.contains(liveTest)) {
      throw ArgumentError("Can't restart a load test.");
    }

    if (!_active.contains(liveTest)) {
      throw StateError("Can't restart inactive test "
          '\"${liveTest.test.name}\".');
    }

    _restarted.add(liveTest);
    _active.remove(liveTest);
    await liveTest.close();
  }

  /// Runs [suite] and returns the [LiveSuiteController] for the suite it loads.
  ///
  /// Returns `null` if the suite fails to load.
  Future<LiveSuiteController?> _addLoadSuite(LoadSuite suite) async {
    var controller = LiveSuiteController(suite);
    _addLiveSuite(controller.liveSuite);

    var liveTest = suite.test.load(suite);
    _activeLoadTests.add(liveTest);

    // Only surface the load test if there are no other tests currently running.
    if (_active.isEmpty) _active.add(liveTest);

    late StreamSubscription subscription;
    subscription = liveTest.onStateChange.listen((state) {
      if (state.status != Status.complete) return;
      _activeLoadTests.remove(liveTest);

      // Only one load test will be active at any given time, and it will always
      // be the only active test. Remove it and, if possible, surface another
      // load test.
      if (_active.isNotEmpty && _active.first.suite == suite) {
        _active.remove(liveTest);
        if (_activeLoadTests.isNotEmpty) _active.add(_activeLoadTests.last);
      }
    }, onDone: () {
      _subscriptions.remove(subscription);
    });
    _subscriptions.add(subscription);

    controller.reportLiveTest(liveTest, countSuccess: false);
    controller.noMoreLiveTests();

    // Schedule a microtask to ensure that [onTestStarted] fires before the
    // first [LiveTest.onStateChange] event.
    await Future.microtask(liveTest.run);

    var innerSuite = await suite.suite;
    if (innerSuite == null) return null;

    var innerController = LiveSuiteController(innerSuite);
    unawaited(innerController.liveSuite.onClose.whenComplete(() {
      // When the main suite is closed, close the load suite and its test as
      // well. This doesn't release any resources, but it does close streams
      // which indicates that the load test won't experience an error in the
      // future.
      liveTest.close();
      controller.close();
    }));

    return innerController;
  }

  /// Add [liveSuite] and the information it exposes to the engine's
  /// informational streams and collections.
  void _addLiveSuite(LiveSuite liveSuite) {
    _liveSuites.add(liveSuite);
    _onSuiteStartedController.add(liveSuite);

    _onTestStartedGroup.add(liveSuite.onTestStarted);
    _passedGroup.add(liveSuite.passed);
    _skippedGroup.add(liveSuite.skipped);
    _failedGroup.add(liveSuite.failed);
  }

  /// Pauses the engine.
  ///
  /// This pauses all streams and keeps any new suites from being loaded or
  /// tests from being run until [resume] is called.
  ///
  /// This does nothing if the engine is already paused. Pauses are *not*
  /// cumulative.
  void pause() {
    if (_pauseCompleter != null) return;
    _pauseCompleter = Completer();
    for (var subscription in _subscriptions) {
      subscription.pause();
    }
  }

  void resume() {
    if (_pauseCompleter == null) return;
    _pauseCompleter!.complete();
    _pauseCompleter = null;
    for (var subscription in _subscriptions) {
      subscription.resume();
    }
  }

  /// Signals that the caller is done paying attention to test results and the
  /// engine should release any resources it has allocated.
  ///
  /// Any actively-running tests are also closed. VM tests are allowed to finish
  /// running so that any modifications they've made to the filesystem can be
  /// cleaned up.
  ///
  /// **Note that closing the engine is not the same as closing [suiteSink].**
  /// Closing [suiteSink] indicates that no more input will be provided, closing
  /// the engine indicates that no more output should be emitted.
  Future close() async {
    _closed = true;
    if (_closedBeforeDone != null) _closedBeforeDone = true;
    await _suiteController.close();
    await _onSuiteAddedController.close();

    // Close the running tests first so that we're sure to wait for them to
    // finish before we close their suites and cause them to become unloaded.
    var allLiveTests = liveTests.toSet()..addAll(_activeLoadTests);
    var futures = allLiveTests.map((liveTest) => liveTest.close()).toList();

    // Closing the run pool will close the test suites as soon as their tests
    // are done. For browser suites this is effectively immediate since their
    // tests shut down as soon as they're closed, but for VM suites we may need
    // to wait for tearDowns or tearDownAlls to run.
    futures.add(_runPool.close());
    await Future.wait(futures, eagerError: true);
  }
}