// 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.

library test.runner.engine;

import 'dart:async';
import 'dart:collection';

import 'package:async/async.dart' hide Result;
import 'package:collection/collection.dart';
import 'package:pool/pool.dart';

import '../backend/group.dart';
import '../backend/invoker.dart';
import '../backend/live_test.dart';
import '../backend/live_test_controller.dart';
import '../backend/state.dart';
import '../backend/group_entry.dart';
import '../backend/test.dart';
import 'load_suite.dart';
import 'runner_suite.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.
  var _closedBeforeDone;

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

  /// A pool that limits the number of test suites loaded concurrently.
  ///
  /// Once this reaches its limit, loading any additional test suites will cause
  /// previous suites to be unloaded in the order they completed.
  final Pool _loadPool;

  /// Whether all tests passed.
  ///
  /// 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 _group.future;
    if (_closedBeforeDone) return null;
    return liveTests.every((liveTest) =>
        liveTest.state.result == Result.success);
  }

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

  /// 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 => new DelegatingSink(_suiteController.sink);
  final _suiteController = new StreamController<RunnerSuite>();

  /// All the currently-known tests that have run, are running, or will run.
  ///
  /// 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.
  List<LiveTest> get liveTests => new UnmodifiableListView(_liveTests);
  final _liveTests = new List<LiveTest>();

  /// 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 => _onTestStartedController.stream;
  final _onTestStartedController = new StreamController<LiveTest>.broadcast();

  /// The set of tests that have completed and been marked as passing.
  Set<LiveTest> get passed => new UnmodifiableSetView(_passed);
  final _passed = new Set<LiveTest>();

  /// The set of tests that have completed and been marked as skipped.
  Set<LiveTest> get skipped => new UnmodifiableSetView(_skipped);
  final _skipped = new Set<LiveTest>();

  /// The set of tests that have completed and been marked as failing or error.
  Set<LiveTest> get failed => new UnmodifiableSetView(_failed);
  final _failed = new Set<LiveTest>();

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

  /// Creates an [Engine] that will run all tests provided via [suiteSink].
  ///
  /// [concurrency] controls how many suites are run at once, and defaults to 1.
  /// [maxSuites] controls how many suites are *loaded* at once, and defaults to
  /// four times [concurrency].
  Engine({int concurrency, int maxSuites})
      : _runPool = new Pool(concurrency == null ? 1 : concurrency),
        _loadPool = new Pool(maxSuites == null
            ? (concurrency == null ? 2 : concurrency * 2)
            : maxSuites) {
    _group.future.then((_) {
      if (_closedBeforeDone == null) _closedBeforeDone = false;
    }).catchError((_) {
      // Don't top-level errors. They'll be thrown via [success] anyway.
    });
  }

  /// Creates an [Engine] that will run all tests in [suites].
  ///
  /// [concurrency] controls how many suites are run at once. An engine
  /// constructed this way will automatically close its [suiteSink], meaning
  /// that no further suites may be provided.
  factory Engine.withSuites(List<RunnerSuite> suites, {int concurrency}) {
    var engine = new Engine(concurrency: concurrency);
    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.
  Future<bool> run() {
    if (_runCalled) {
      throw new StateError("Engine.run() may not be called more than once.");
    }
    _runCalled = true;

    _suiteController.stream.listen((suite) {
      _group.add(new Future.sync(() async {
        var loadResource = await _loadPool.request();

        if (suite is LoadSuite) {
          suite = await _addLoadSuite(suite);
          if (suite == null) {
            loadResource.release();
            return;
          }
        }

        await _runPool.withResource(() async {
          if (_closed) return;
          await _runGroup(suite, suite.group);
          loadResource.allowRelease(() => suite.close());
        });
      }));
    }, onDone: _group.close);

    return success;
  }

  /// Runs all the entries in [entries] in sequence.
  Future _runGroup(RunnerSuite suite, Group group) async {
    if (group.metadata.skip) {
      await _runLiveTest(_skippedTest(suite, group));
      return;
    }

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

      if (entry is Group) {
        await _runGroup(suite, entry);
      } else if (entry.metadata.skip) {
        await _runLiveTest(_skippedTest(suite, entry));
      } else {
        var test = entry as Test;
        await _runLiveTest(test.load(suite));
      }
    }
  }

  /// Returns a dummy [LiveTest] for a test or group marked as "skip".
  LiveTest _skippedTest(RunnerSuite suite, GroupEntry entry) {
    // The netry name will be `null` for the root group.
    var test = new LocalTest(entry.name ?? "(suite)", entry.metadata, () {});

    var controller;
    controller = new LiveTestController(suite, test, () {
      controller.setState(const State(Status.running, Result.success));
      controller.setState(const State(Status.complete, Result.success));
      controller.completer.complete();
    }, () {});
    return controller.liveTest;
  }

  /// Runs [liveTest].
  Future _runLiveTest(LiveTest liveTest) async {
    _liveTests.add(liveTest);
    _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.isNotEmpty && _active.first.suite is LoadSuite) {
      _liveTests.remove(_active.removeFirst());
    }

    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);
        _liveTests.add(_activeLoadTests.first);
      }

      if (state.result != Result.success) {
        _passed.remove(liveTest);
        _failed.add(liveTest);
      } else if (liveTest.test.metadata.skip) {
        _skipped.add(liveTest);
      } else {
        _passed.add(liveTest);
      }
    });

    _onTestStartedController.add(liveTest);

    // First, schedule a microtask to ensure that [onTestStarted] fires before
    // the first [LiveTest.onStateChange] event. Once the test finishes, use
    // [new Future] to do a coarse-grained event loop pump to avoid starving
    // non-microtask events.
    await new Future.microtask(liveTest.run);
    await new Future(() {});
  }

  /// Adds listeners for [suite].
  ///
  /// Load suites have specific logic apart from normal test suites.
  Future<RunnerSuite> _addLoadSuite(LoadSuite suite) async {
    var liveTest = await suite.test.load(suite);

    _activeLoadTests.add(liveTest);

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

    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);
        _liveTests.remove(liveTest);

        if (_activeLoadTests.isNotEmpty) {
          _active.add(_activeLoadTests.last);
          _liveTests.add(_activeLoadTests.last);
        }
      }

      // Surface the load test if it fails so that the user can see the failure.
      if (state.result == Result.success) return;
      _failed.add(liveTest);
      _liveTests.add(liveTest);
    });

    // Run the test immediately. We don't want loading to be blocked on suites
    // that are already running.
    _onTestStartedController.add(liveTest);
    await liveTest.run();

    return suite.suite;
  }

  /// 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;
    _suiteController.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);
    await Future.wait(allLiveTests.map((liveTest) => liveTest.close()));

    var allSuites = allLiveTests.map((liveTest) => liveTest.suite).toSet();
    await Future.wait(allSuites.map((suite) => suite.close()));
  }
}