// Copyright 2014 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:convert';
import 'dart:io';
import 'dart:math' as math;

import 'package:googleapis/bigquery/v2.dart' as bq;
import 'package:googleapis_auth/auth_io.dart' as auth;
import 'package:http/http.dart' as http;
import 'package:meta/meta.dart';
import 'package:path/path.dart' as path;

import 'browser.dart';
import 'flutter_compact_formatter.dart';
import 'run_command.dart';
import 'utils.dart';

typedef ShardRunner = Future<void> Function();

/// A function used to validate the output of a test.
///
/// If the output matches expectations, the function shall return null.
///
/// If the output does not match expectations, the function shall return an
/// appropriate error message.
typedef OutputChecker = String Function(CapturedOutput);

final String exe = Platform.isWindows ? '.exe' : '';
final String bat = Platform.isWindows ? '.bat' : '';
final String flutterRoot = path.dirname(path.dirname(path.dirname(path.fromUri(Platform.script))));
final String flutter = path.join(flutterRoot, 'bin', 'flutter$bat');
final String dart = path.join(flutterRoot, 'bin', 'cache', 'dart-sdk', 'bin', 'dart$exe');
final String pub = path.join(flutterRoot, 'bin', 'cache', 'dart-sdk', 'bin', 'pub$bat');
final String pubCache = path.join(flutterRoot, '.pub-cache');
final String toolRoot = path.join(flutterRoot, 'packages', 'flutter_tools');
final String engineVersionFile = path.join(flutterRoot, 'bin', 'internal', 'engine.version');

String get platformFolderName {
  if (Platform.isWindows)
    return 'windows-x64';
  if (Platform.isMacOS)
    return 'darwin-x64';
  if (Platform.isLinux)
    return 'linux-x64';
  throw UnsupportedError('The platform ${Platform.operatingSystem} is not supported by this script.');
}
final String flutterTester = path.join(flutterRoot, 'bin', 'cache', 'artifacts', 'engine', platformFolderName, 'flutter_tester$exe');

/// The arguments to pass to `flutter test` (typically the local engine
/// configuration) -- prefilled with the arguments passed to test.dart.
final List<String> flutterTestArgs = <String>[];

final bool useFlutterTestFormatter = Platform.environment['FLUTTER_TEST_FORMATTER'] == 'true';

/// The number of Cirrus jobs that run host-only devicelab tests in parallel.
///
/// WARNING: if you change this number, also change .cirrus.yml
/// and make sure it runs _all_ shards.
const int kDeviceLabShardCount = 4;

/// The number of Cirrus jobs that run build tests in parallel.
///
/// WARNING: if you change this number, also change .cirrus.yml
/// and make sure it runs _all_ shards.
const int kBuildTestShardCount = 2;

/// The number of Cirrus jobs that run Web tests in parallel.
///
/// The default is 8 shards. Typically .cirrus.yml would define the
/// WEB_SHARD_COUNT environment variable rather than relying on the default.
///
/// WARNING: if you change this number, also change .cirrus.yml
/// and make sure it runs _all_ shards.
///
/// The last shard also runs the Web plugin tests.
int get webShardCount => Platform.environment.containsKey('WEB_SHARD_COUNT')
  ? int.parse(Platform.environment['WEB_SHARD_COUNT'])
  : 8;

/// Tests that we don't run on Web for various reasons.
//
// TODO(yjbanov): we're getting rid of this blacklist as part of https://github.com/flutter/flutter/projects/60
const List<String> kWebTestFileBlacklist = <String>[
  // This test doesn't compile because it depends on code outside the flutter package.
  'test/examples/sector_layout_test.dart',
  // This test relies on widget tracking capability in the VM.
  'test/widgets/widget_inspector_test.dart',

  'test/widgets/selectable_text_test.dart',
  'test/widgets/color_filter_test.dart',
  'test/widgets/editable_text_cursor_test.dart',
  'test/widgets/editable_text_test.dart',
  'test/material/animated_icons_private_test.dart',
  'test/material/data_table_test.dart',
  'test/cupertino/nav_bar_transition_test.dart',
  'test/cupertino/refresh_test.dart',
  'test/cupertino/text_field_test.dart',
  'test/cupertino/route_test.dart',
];

/// When you call this, you can pass additional arguments to pass custom
/// arguments to flutter test. For example, you might want to call this
/// script with the parameter --local-engine=host_debug_unopt to
/// use your own build of the engine.
///
/// To run the tool_tests part, run it with SHARD=tool_tests
///
/// Examples:
/// SHARD=tool_tests bin/cache/dart-sdk/bin/dart dev/bots/test.dart
/// bin/cache/dart-sdk/bin/dart dev/bots/test.dart --local-engine=host_debug_unopt
Future<void> main(List<String> args) async {
  print('$clock STARTING ANALYSIS');
  try {
    flutterTestArgs.addAll(args);
    if (Platform.environment.containsKey(CIRRUS_TASK_NAME))
      print('Running task: ${Platform.environment[CIRRUS_TASK_NAME]}');
    print('═' * 80);
    await _runSmokeTests();
    print('═' * 80);
    await selectShard(const <String, ShardRunner>{
      'add_to_app_tests': _runAddToAppTests,
      'add_to_app_life_cycle_tests': _runAddToAppLifeCycleTests,
      'build_tests': _runBuildTests,
      'firebase_test_lab_tests': _runFirebaseTestLabTests,
      'framework_coverage': _runFrameworkCoverage,
      'framework_tests': _runFrameworkTests,
      'hostonly_devicelab_tests': _runHostOnlyDeviceLabTests,
      'tool_coverage': _runToolCoverage,
      'tool_tests': _runToolTests,
      'web_tests': _runWebUnitTests,
      'web_integration_tests': _runWebIntegrationTests,
    });
  } on ExitException catch (error) {
    error.apply();
  }
  print('$clock ${bold}Test successful.$reset');
}

/// Verify the Flutter Engine is the revision in
/// bin/cache/internal/engine.version.
Future<void> _validateEngineHash() async {
  final String luciBotId = Platform.environment['SWARMING_BOT_ID'] ?? '';
  if (luciBotId.startsWith('luci-dart-')) {
    // The Dart HHH bots intentionally modify the local artifact cache
    // and then use this script to run Flutter's test suites.
    // Because the artifacts have been changed, this particular test will return
    // a false positive and should be skipped.
    print('${yellow}Skipping Flutter Engine Version Validation for swarming '
          'bot $luciBotId.');
    return;
  }
  final String expectedVersion = File(engineVersionFile).readAsStringSync().trim();
  final CapturedOutput flutterTesterOutput = CapturedOutput();
  await runCommand(flutterTester, <String>['--help'], output: flutterTesterOutput, outputMode: OutputMode.capture);
  final String actualVersion = flutterTesterOutput.stderr.split('\n').firstWhere((final String line) {
    return line.startsWith('Flutter Engine Version:');
  });
  if (!actualVersion.contains(expectedVersion)) {
    print('${red}Expected "Flutter Engine Version: $expectedVersion", '
          'but found "$actualVersion".');
    exit(1);
  }
}

Future<void> _runSmokeTests() async {
  print('${green}Running smoketests...$reset');

  await _validateEngineHash();

  // Verify that the tests actually return failure on failure and success on
  // success.
  final String automatedTests = path.join(flutterRoot, 'dev', 'automated_tests');
  // We run the "pass" and "fail" smoke tests first, and alone, because those
  // are particularly critical and sensitive. If one of these fails, there's no
  // point even trying the others.
  await _runFlutterTest(automatedTests,
    script: path.join('test_smoke_test', 'pass_test.dart'),
    printOutput: false,
  );
  await _runFlutterTest(automatedTests,
    script: path.join('test_smoke_test', 'fail_test.dart'),
    expectFailure: true,
    printOutput: false,
  );
  // We run the timeout tests individually because they are timing-sensitive.
  await _runFlutterTest(automatedTests,
    script: path.join('test_smoke_test', 'timeout_pass_test.dart'),
    expectFailure: false,
    printOutput: false,
  );
  await _runFlutterTest(automatedTests,
    script: path.join('test_smoke_test', 'timeout_fail_test.dart'),
    expectFailure: true,
    printOutput: false,
  );
  await _runFlutterTest(automatedTests,
    script: path.join('test_smoke_test', 'pending_timer_fail_test.dart'),
    expectFailure: true,
    printOutput: false,
    outputChecker: (CapturedOutput output) {
      return output.stdout.contains('failingPendingTimerTest')
        ? null
        : 'Failed to find the stack trace for the pending Timer.';
    }
  );
  // We run the remaining smoketests in parallel, because they each take some
  // time to run (e.g. compiling), so we don't want to run them in series,
  // especially on 20-core machines...
  await Future.wait<void>(
    <Future<void>>[
      _runFlutterTest(automatedTests,
        script: path.join('test_smoke_test', 'crash1_test.dart'),
        expectFailure: true,
        printOutput: false,
      ),
      _runFlutterTest(automatedTests,
        script: path.join('test_smoke_test', 'crash2_test.dart'),
        expectFailure: true,
        printOutput: false,
      ),
      _runFlutterTest(automatedTests,
        script: path.join('test_smoke_test', 'syntax_error_test.broken_dart'),
        expectFailure: true,
        printOutput: false,
      ),
      _runFlutterTest(automatedTests,
        script: path.join('test_smoke_test', 'missing_import_test.broken_dart'),
        expectFailure: true,
        printOutput: false,
      ),
      _runFlutterTest(automatedTests,
        script: path.join('test_smoke_test', 'disallow_error_reporter_modification_test.dart'),
        expectFailure: true,
        printOutput: false,
      ),
      runCommand(flutter,
        <String>['drive', '--use-existing-app', '-t', path.join('test_driver', 'failure.dart')],
        workingDirectory: path.join(flutterRoot, 'packages', 'flutter_driver'),
        expectNonZeroExit: true,
        outputMode: OutputMode.discard,
      ),
    ],
  );

  // Verify that we correctly generated the version file.
  final String versionError = await verifyVersion(File(path.join(flutterRoot, 'version')));
  if (versionError != null)
    exitWithError(<String>[versionError]);
}

Future<bq.BigqueryApi> _getBigqueryApi() async {
  if (!useFlutterTestFormatter) {
    return null;
  }
  // TODO(dnfield): How will we do this on LUCI?
  final String privateKey = Platform.environment['GCLOUD_SERVICE_ACCOUNT_KEY'];
  // If we're on Cirrus and a non-collaborator is doing this, we can't get the key.
  if (privateKey == null || privateKey.isEmpty || privateKey.startsWith('ENCRYPTED[')) {
    return null;
  }
  try {
    final auth.ServiceAccountCredentials accountCredentials = auth.ServiceAccountCredentials(
      'flutter-ci-test-reporter@flutter-infra.iam.gserviceaccount.com',
      auth.ClientId.serviceAccount('114390419920880060881.apps.googleusercontent.com'),
      '-----BEGIN PRIVATE KEY-----\n$privateKey\n-----END PRIVATE KEY-----\n',
    );
    final List<String> scopes = <String>[bq.BigqueryApi.BigqueryInsertdataScope];
    final http.Client client = await auth.clientViaServiceAccount(accountCredentials, scopes);
    return bq.BigqueryApi(client);
  } catch (e) {
    print('${red}Failed to get BigQuery API client.$reset');
    print(e);
    return null;
  }
}

Future<void> _runToolCoverage() async {
  await _pubRunTest(
    toolRoot,
    testPaths: <String>[
      path.join('test', 'general.shard'),
      path.join('test', 'commands.shard', 'hermetic'),
    ],
    coverage: 'coverage',
  );
  await runCommand(pub,
    <String>[
      'run',
      'coverage:format_coverage',
      '--lcov',
      '--in=coverage',
      '--out=coverage/lcov.info',
      '--packages=.packages',
      '--report-on=lib/'
    ],
    workingDirectory: toolRoot,
    outputMode: OutputMode.discard,
  );
}

Future<void> _runToolTests() async {
  final bq.BigqueryApi bigqueryApi = await _getBigqueryApi();

  const String kDotShard = '.shard';
  const String kTest = 'test';
  final String toolsPath = path.join(flutterRoot, 'packages', 'flutter_tools');

  final Map<String, ShardRunner> subshards = Map<String, ShardRunner>.fromIterable(
    Directory(path.join(toolsPath, kTest))
      .listSync()
      .map<String>((FileSystemEntity entry) => entry.path)
      .where((String name) => name.endsWith(kDotShard))
      .map<String>((String name) => path.basenameWithoutExtension(name)),
    // The `dynamic` on the next line is because Map.fromIterable isn't generic.
    value: (dynamic subshard) => () async {
      // Due to https://github.com/flutter/flutter/issues/46180, skip the hermetic directory
      // on Windows.
      final String suffix = Platform.isWindows && subshard == 'commands'
        ? 'permeable'
        : '';
      await _pubRunTest(
        toolsPath,
        testPaths: <String>[path.join(kTest, '$subshard$kDotShard', suffix)],
        tableData: bigqueryApi?.tabledata,
        enableFlutterToolAsserts: true,
        // Detect unit test time regressions (poor time delay handling, etc).
        perTestTimeout: (subshard == 'general') ? const Duration(seconds: 2) : null,
      );
    },
  );

  await selectSubshard(subshards);
}

/// Verifies that APK, and IPA (if on macOS) builds the examples apps
/// without crashing. It does not actually launch the apps. That happens later
/// in the devicelab. This is just a smoke-test. In particular, this will verify
/// we can build when there are spaces in the path name for the Flutter SDK and
/// target app.
Future<void> _runBuildTests() async {
  final List<FileSystemEntity> exampleDirectories = Directory(path.join(flutterRoot, 'examples')).listSync()
    ..add(Directory(path.join(flutterRoot, 'dev', 'integration_tests', 'non_nullable')))
    ..add(Directory(path.join(flutterRoot, 'dev', 'integration_tests', 'flutter_gallery')));

  final String branch = Platform.environment['CIRRUS_BRANCH'];
  // The tests are randomly distributed into subshards so as to get a uniform
  // distribution of costs, but the seed is fixed so that issues are reproducible.
  final List<ShardRunner> tests = <ShardRunner>[
    for (final FileSystemEntity exampleDirectory in exampleDirectories)
        () => _runExampleProjectBuildTests(exampleDirectory),
    if (branch != 'beta' && branch != 'stable')
      ...<ShardRunner>[
        // Web compilation tests.
          () =>  _flutterBuildDart2js(
          path.join('dev', 'integration_tests', 'web'),
          path.join('lib', 'main.dart'),
        ),
        // Should not fail to compile with dart:io.
          () =>  _flutterBuildDart2js(
          path.join('dev', 'integration_tests', 'web_compile_tests'),
          path.join('lib', 'dart_io_import.dart'),
        ),
      ],
  ]..shuffle(math.Random(0));

  await _selectIndexedSubshard(tests, kBuildTestShardCount);
}

Future<void> _runExampleProjectBuildTests(FileSystemEntity exampleDirectory) async {
  // Only verify caching with flutter gallery.
  final bool verifyCaching = exampleDirectory.path.contains('flutter_gallery');
  if (exampleDirectory is! Directory) {
    return;
  }
  final String examplePath = exampleDirectory.path;
  final bool hasNullSafety = File(path.join(examplePath, 'null_safety')).existsSync();
  final List<String> additionalArgs = hasNullSafety
    ? <String>['--enable-experiment', 'non-nullable', '--no-sound-null-safety']
    : <String>[];
  if (Directory(path.join(examplePath, 'android')).existsSync()) {
    await _flutterBuildApk(examplePath, release: false, additionalArgs: additionalArgs, verifyCaching: verifyCaching);
    await _flutterBuildApk(examplePath, release: true, additionalArgs: additionalArgs, verifyCaching: verifyCaching);
  } else {
    print('Example project ${path.basename(examplePath)} has no android directory, skipping apk');
  }
  if (Platform.isMacOS) {
    if (Directory(path.join(examplePath, 'ios')).existsSync()) {
      await _flutterBuildIpa(examplePath, release: false, additionalArgs: additionalArgs, verifyCaching: verifyCaching);
      await _flutterBuildIpa(examplePath, release: true, additionalArgs: additionalArgs, verifyCaching: verifyCaching);
    } else {
      print('Example project ${path.basename(examplePath)} has no ios directory, skipping ipa');
    }
  }
}

Future<void> _flutterBuildApk(String relativePathToApplication, {
  @required bool release,
  bool verifyCaching = false,
  List<String> additionalArgs = const <String>[],
}) async {
  print('${green}Testing APK build$reset for $cyan$relativePathToApplication$reset...');
  await runCommand(flutter,
    <String>[
      'build',
      'apk',
      ...additionalArgs,
      if (release)
        '--release'
      else
        '--debug',
      '-v',
    ],
    workingDirectory: path.join(flutterRoot, relativePathToApplication),
  );

  if (verifyCaching) {
    print('${green}Testing APK cache$reset for $cyan$relativePathToApplication$reset...');
    await runCommand(flutter,
      <String>[
        'build',
        'apk',
        '--performance-measurement-file=perf.json',
        ...additionalArgs,
        if (release)
          '--release'
        else
          '--debug',
        '-v',
      ],
      workingDirectory: path.join(flutterRoot, relativePathToApplication),
    );
    final File file = File(path.join(flutterRoot, relativePathToApplication, 'perf.json'));
    if (!_allTargetsCached(file)) {
      print('${red}Not all build targets cached after second run.$reset');
      print('The target performance data was: ${file.readAsStringSync()}');
      exit(1);
    }
  }
}

Future<void> _flutterBuildIpa(String relativePathToApplication, {
  @required bool release,
  List<String> additionalArgs = const <String>[],
  bool verifyCaching = false,
}) async {
  assert(Platform.isMacOS);
  print('${green}Testing IPA build$reset for $cyan$relativePathToApplication$reset...');
  // Install Cocoapods.  We don't have these checked in for the examples,
  // and build ios doesn't take care of it automatically.
  final File podfile = File(path.join(flutterRoot, relativePathToApplication, 'ios', 'Podfile'));
  if (podfile.existsSync()) {
    await runCommand('pod',
      <String>['install'],
      workingDirectory: podfile.parent.path,
      environment: <String, String>{
        'LANG': 'en_US.UTF-8',
      },
    );
  }
  await runCommand(flutter,
    <String>[
      'build',
      'ios',
      ...additionalArgs,
      '--no-codesign',
      if (release)
        '--release'
      else
        '--debug',
      '-v',
    ],
    workingDirectory: path.join(flutterRoot, relativePathToApplication),
  );
  if (verifyCaching) {
    print('${green}Testing IPA cache$reset for $cyan$relativePathToApplication$reset...');
    await runCommand(flutter,
      <String>[
        'build',
        'ios',
        '--performance-measurement-file=perf.json',
        ...additionalArgs,
        '--no-codesign',
        if (release)
          '--release'
        else
          '--debug',
        '-v',
      ],
      workingDirectory: path.join(flutterRoot, relativePathToApplication),
    );
    final File file = File(path.join(flutterRoot, relativePathToApplication, 'perf.json'));
    if (!_allTargetsCached(file)) {
      print('${red}Not all build targets cached after second run.$reset');
      print('The target performance data was: ${file.readAsStringSync()}');
      exit(1);
    }
  }
}

bool _allTargetsCached(File performanceFile) {
  final Map<String, Object> data = json.decode(performanceFile.readAsStringSync())
    as Map<String, Object>;
  final List<Map<String, Object>> targets = (data['targets'] as List<Object>)
    .cast<Map<String, Object>>();
  return targets.every((Map<String, Object> element) => element['skipped'] == true);
}

Future<void> _flutterBuildDart2js(String relativePathToApplication, String target, { bool expectNonZeroExit = false }) async {
  print('${green}Testing Dart2JS build$reset for $cyan$relativePathToApplication$reset...');
  await runCommand(flutter,
    <String>['build', 'web', '-v', '--target=$target'],
    workingDirectory: path.join(flutterRoot, relativePathToApplication),
    expectNonZeroExit: expectNonZeroExit,
    environment: <String, String>{
      'FLUTTER_WEB': 'true',
    },
  );
}

Future<void> _runAddToAppTests() async {
  if (Platform.isMacOS) {
    print('${green}Running add-to-app iOS integration tests$reset...');
    final String addToAppDir = path.join(flutterRoot, 'dev', 'integration_tests', 'ios_add2app');
    await runCommand('./build_and_test.sh',
      <String>[],
      workingDirectory: addToAppDir,
    );
  }
}

Future<void> _runAddToAppLifeCycleTests() async {
  if (Platform.isMacOS) {
    print('${green}Running add-to-app life cycle iOS integration tests$reset...');
    final String addToAppDir = path.join(flutterRoot, 'dev', 'integration_tests', 'ios_add2app_life_cycle');
    await runCommand('./build_and_test.sh',
      <String>[],
      workingDirectory: addToAppDir,
    );
  }
}

Future<void> _runFrameworkTests() async {
  final bq.BigqueryApi bigqueryApi = await _getBigqueryApi();
  final List<String> nullSafetyOptions = <String>['--enable-experiment=non-nullable', '--no-sound-null-safety'];
  final List<String> trackWidgetCreationAlternatives = <String>['--track-widget-creation', '--no-track-widget-creation'];

  Future<void> runWidgets() async {
    print('${green}Running packages/flutter tests for$reset: ${cyan}test/widgets/$reset');
    for (final String trackWidgetCreationOption in trackWidgetCreationAlternatives) {
      await _runFlutterTest(
        path.join(flutterRoot, 'packages', 'flutter'),
        options: <String>[trackWidgetCreationOption, ...nullSafetyOptions],
        tableData: bigqueryApi?.tabledata,
        tests: <String>[ path.join('test', 'widgets') + path.separator ],
      );
    }
    // Try compiling code outside of the packages/flutter directory with and without --track-widget-creation
    for (final String trackWidgetCreationOption in trackWidgetCreationAlternatives) {
      await _runFlutterTest(
        path.join(flutterRoot, 'dev', 'integration_tests', 'flutter_gallery'),
        options: <String>[trackWidgetCreationOption],
        tableData: bigqueryApi?.tabledata,
      );
    }
  }

  Future<void> runLibraries() async {
    final List<String> tests = Directory(path.join(flutterRoot, 'packages', 'flutter', 'test'))
      .listSync(followLinks: false, recursive: false)
      .whereType<Directory>()
      .where((Directory dir) => dir.path.endsWith('widgets') == false)
      .map<String>((Directory dir) => path.join('test', path.basename(dir.path)) + path.separator)
      .toList();
    print('${green}Running packages/flutter tests$reset for: $cyan${tests.join(", ")}$reset');
    for (final String trackWidgetCreationOption in trackWidgetCreationAlternatives) {
      await _runFlutterTest(
        path.join(flutterRoot, 'packages', 'flutter'),
        options: <String>[trackWidgetCreationOption, ...nullSafetyOptions],
        tableData: bigqueryApi?.tabledata,
        tests: tests,
      );
    }
  }

  Future<void> runMisc() async {
    print('${green}Running package tests$reset for directories other than packages/flutter');
    await _pubRunTest(path.join(flutterRoot, 'dev', 'bots'), tableData: bigqueryApi?.tabledata);
    await _pubRunTest(path.join(flutterRoot, 'dev', 'devicelab'), tableData: bigqueryApi?.tabledata);
    await _pubRunTest(path.join(flutterRoot, 'dev', 'snippets'), tableData: bigqueryApi?.tabledata);
    await _pubRunTest(path.join(flutterRoot, 'dev', 'tools'), tableData: bigqueryApi?.tabledata);
    await _runFlutterTest(path.join(flutterRoot, 'dev', 'integration_tests', 'android_semantics_testing'), tableData: bigqueryApi?.tabledata);
    await _runFlutterTest(path.join(flutterRoot, 'dev', 'manual_tests'), tableData: bigqueryApi?.tabledata);
    await _runFlutterTest(path.join(flutterRoot, 'dev', 'tools', 'vitool'), tableData: bigqueryApi?.tabledata);
    await _runFlutterTest(path.join(flutterRoot, 'examples', 'catalog'), tableData: bigqueryApi?.tabledata);
    await _runFlutterTest(path.join(flutterRoot, 'examples', 'hello_world'), tableData: bigqueryApi?.tabledata);
    await _runFlutterTest(path.join(flutterRoot, 'examples', 'layers'), tableData: bigqueryApi?.tabledata);
    await _runFlutterTest(path.join(flutterRoot, 'dev', 'benchmarks', 'test_apps', 'stocks'), tableData: bigqueryApi?.tabledata);
    await _runFlutterTest(path.join(flutterRoot, 'packages', 'flutter_driver'), tableData: bigqueryApi?.tabledata, tests: <String>[path.join('test', 'src', 'real_tests')]);
    await _runFlutterTest(path.join(flutterRoot, 'packages', 'flutter_goldens'), tableData: bigqueryApi?.tabledata);
    await _runFlutterTest(path.join(flutterRoot, 'packages', 'flutter_localizations'), tableData: bigqueryApi?.tabledata);
    await _runFlutterTest(path.join(flutterRoot, 'packages', 'flutter_test'), tableData: bigqueryApi?.tabledata);
    await _runFlutterTest(path.join(flutterRoot, 'packages', 'fuchsia_remote_debug_protocol'), tableData: bigqueryApi?.tabledata);
    await _runFlutterTest(path.join(flutterRoot, 'dev', 'integration_tests', 'non_nullable'), options: nullSafetyOptions);
    await _runFlutterTest(
      path.join(flutterRoot, 'dev', 'tracing_tests'),
      options: <String>['--enable-vmservice'],
      tableData: bigqueryApi?.tabledata,
    );
    const String httpClientWarning =
      'Warning: At least one test in this suite creates an HttpClient. When\n'
      'running a test suite that uses TestWidgetsFlutterBinding, all HTTP\n'
      'requests will return status code 400, and no network request will\n'
      'actually be made. Any test expecting a real network connection and\n'
      'status code will fail.\n'
      'To test code that needs an HttpClient, provide your own HttpClient\n'
      'implementation to the code under test, so that your test can\n'
      'consistently provide a testable response to the code under test.';
    await _runFlutterTest(
      path.join(flutterRoot, 'packages', 'flutter_test'),
      script: path.join('test', 'bindings_test_failure.dart'),
      expectFailure: true,
      printOutput: false,
      outputChecker: (CapturedOutput output) {
        final Iterable<Match> matches = httpClientWarning.allMatches(output.stdout);
        if (matches == null || matches.isEmpty || matches.length > 1) {
          return 'Failed to print warning about HttpClientUsage, or printed it too many times.\n'
                 'stdout:\n${output.stdout}';
        }
        return null;
      },
      tableData: bigqueryApi?.tabledata,
    );
  }

  await selectSubshard(<String, ShardRunner>{
    'widgets': runWidgets,
    'libraries': runLibraries,
    'misc': runMisc,
  });
}

Future<void> _runFirebaseTestLabTests() async {
  // Firebase Lab tests take ~20 minutes per integration test,
  // so only one test is run per shard. Therefore, there are as
  // many shards available as there are integration tests in this list.
  // If you add a new test, add a corresponding firebase_test_lab-#-linux
  // to .cirrus.yml
  final List<String> integrationTests = <String>[
    'release_smoke_test',
    'abstract_method_smoke_test',
    'android_embedding_v2_smoke_test',
  ];

  final String firebaseScript = path.join(flutterRoot, 'dev', 'bots', 'firebase_testlab.sh');
  final String integrationTestDirectory = path.join(flutterRoot, 'dev', 'integration_tests');

  final List<ShardRunner> tests = integrationTests.map((String integrationTest) =>
    () => runCommand(firebaseScript, <String>[ path.join(integrationTestDirectory, integrationTest) ])
  ).toList();

  await _selectIndexedSubshard(tests, integrationTests.length);
}

Future<void> _runFrameworkCoverage() async {
  final File coverageFile = File(path.join(flutterRoot, 'packages', 'flutter', 'coverage', 'lcov.info'));
  if (!coverageFile.existsSync()) {
    print('${red}Coverage file not found.$reset');
    print('Expected to find: $cyan${coverageFile.absolute}$reset');
    print('This file is normally obtained by running `${green}flutter update-packages$reset`.');
    exit(1);
  }
  coverageFile.deleteSync();
  await _runFlutterTest(path.join(flutterRoot, 'packages', 'flutter'),
    options: const <String>['--coverage'],
  );
  if (!coverageFile.existsSync()) {
    print('${red}Coverage file not found.$reset');
    print('Expected to find: $cyan${coverageFile.absolute}$reset');
    print('This file should have been generated by the `${green}flutter test --coverage$reset` script, but was not.');
    exit(1);
  }
}

Future<void> _runWebUnitTests() async {
  final Map<String, ShardRunner> subshards = <String, ShardRunner>{};

  final Directory flutterPackageDirectory = Directory(path.join(flutterRoot, 'packages', 'flutter'));
  final Directory flutterPackageTestDirectory = Directory(path.join(flutterPackageDirectory.path, 'test'));

  final List<String> allTests = flutterPackageTestDirectory
    .listSync()
    .whereType<Directory>()
    .expand((Directory directory) => directory
      .listSync(recursive: true)
      .where((FileSystemEntity entity) => entity.path.endsWith('_test.dart'))
    )
    .whereType<File>()
    .map<String>((File file) => path.relative(file.path, from: flutterPackageDirectory.path))
    .where((String filePath) => !kWebTestFileBlacklist.contains(filePath))
    .toList()
    // Finally we shuffle the list because we want the average cost per file to be uniformly
    // distributed. If the list is not sorted then different shards and batches may have
    // very different characteristics.
    // We use a constant seed for repeatability.
    ..shuffle(math.Random(0));

  assert(webShardCount >= 1);
  final int testsPerShard = (allTests.length / webShardCount).ceil();
  assert(testsPerShard * webShardCount >= allTests.length);

  // This for loop computes all but the last shard.
  for (int index = 0; index < webShardCount - 1; index += 1) {
    subshards['$index'] = () => _runFlutterWebTest(
      flutterPackageDirectory.path,
      allTests.sublist(
        index * testsPerShard,
        (index + 1) * testsPerShard,
      ),
    );
  }

  // The last shard also runs the flutter_web_plugins tests.
  //
  // We make sure the last shard ends in _last so it's easier to catch mismatches
  // between `.cirrus.yml` and `test.dart`.
  subshards['${webShardCount - 1}_last'] = () async {
    await _runFlutterWebTest(
      flutterPackageDirectory.path,
      allTests.sublist(
        (webShardCount - 1) * testsPerShard,
        allTests.length,
      ),
    );
    await _runFlutterWebTest(
      path.join(flutterRoot, 'packages', 'flutter_web_plugins'),
      <String>['test'],
    );
    await _runFlutterWebTest(
        path.join(flutterRoot, 'packages', 'flutter_driver'),
        <String>[path.join('test', 'src', 'web_tests', 'web_extension_test.dart')],
    );
  };

  await selectSubshard(subshards);
}

Future<void> _runWebIntegrationTests() async {
  await _runWebStackTraceTest('profile');
  await _runWebStackTraceTest('release');
  await _runWebDebugTest('lib/stack_trace.dart');
  await _runWebDebugTest('lib/web_directory_loading.dart');
  await _runWebDebugTest('test/test.dart');
  await _runWebDebugTest('lib/null_safe_main.dart', enableNullSafety: true);
  await _runWebDebugTest('lib/web_define_loading.dart',
    additionalArguments: <String>[
      '--dart-define=test.valueA=Example',
      '--dart-define=test.valueB=Value',
    ]
  );
  await _runWebReleaseTest('lib/web_define_loading.dart',
    additionalArguments: <String>[
      '--dart-define=test.valueA=Example',
      '--dart-define=test.valueB=Value',
    ]
  );
}

Future<void> _runWebStackTraceTest(String buildMode) async {
  final String testAppDirectory = path.join(flutterRoot, 'dev', 'integration_tests', 'web');
  final String appBuildDirectory = path.join(testAppDirectory, 'build', 'web');

  // Build the app.
  await runCommand(
    flutter,
    <String>[ 'clean' ],
    workingDirectory: testAppDirectory,
  );
  await runCommand(
    flutter,
    <String>[
      'build',
      'web',
      '--$buildMode',
      '-t',
      'lib/stack_trace.dart',
    ],
    workingDirectory: testAppDirectory,
    environment: <String, String>{
      'FLUTTER_WEB': 'true',
    },
  );

  // Run the app.
  final String result = await evalTestAppInChrome(
    appUrl: 'http://localhost:8080/index.html',
    appDirectory: appBuildDirectory,
  );

  if (result.contains('--- TEST SUCCEEDED ---')) {
    print('${green}Web stack trace integration test passed.$reset');
  } else {
    print(result);
    print('${red}Web stack trace integration test failed.$reset');
    exit(1);
  }
}

/// Run a web integration test in release mode.
Future<void> _runWebReleaseTest(String target, {
  List<String> additionalArguments = const<String>[],
}) async {
  final String testAppDirectory = path.join(flutterRoot, 'dev', 'integration_tests', 'web');
  final String appBuildDirectory = path.join(testAppDirectory, 'build', 'web');

  // Build the app.
  await runCommand(
    flutter,
    <String>[ 'clean' ],
    workingDirectory: testAppDirectory,
  );
  await runCommand(
    flutter,
    <String>[
      'build',
      'web',
      '--release',
      ...additionalArguments,
      '-t',
      target,
    ],
    workingDirectory: testAppDirectory,
    environment: <String, String>{
      'FLUTTER_WEB': 'true',
    },
  );

  // Run the app.
  final String result = await evalTestAppInChrome(
    appUrl: 'http://localhost:8080/index.html',
    appDirectory: appBuildDirectory,
  );

  if (result.contains('--- TEST SUCCEEDED ---')) {
    print('${green}Web release mode test passed.$reset');
  } else {
    print(result);
    print('${red}Web release mode test failed.$reset');
    exit(1);
  }
}

/// Debug mode is special because `flutter build web` doesn't build in debug mode.
///
/// Instead, we use `flutter run --debug` and sniff out the standard output.
Future<void> _runWebDebugTest(String target, {
  bool enableNullSafety = false,
  List<String> additionalArguments = const<String>[],
}) async {
  final String testAppDirectory = path.join(flutterRoot, 'dev', 'integration_tests', 'web');
  final CapturedOutput output = CapturedOutput();
  bool success = false;
  await runCommand(
    flutter,
    <String>[
      'run',
      '--debug',
      if (enableNullSafety)
        ...<String>[
          '--enable-experiment',
          'non-nullable',
          '--no-sound-null-safety'
        ],
      '-d',
      'chrome',
      '--web-run-headless',
      ...additionalArguments,
      '-t',
      target,
    ],
    output: output,
    outputMode: OutputMode.capture,
    outputListener: (String line, Process process) {
      if (line.contains('--- TEST SUCCEEDED ---')) {
        success = true;
      }
      if (success || line.contains('--- TEST FAILED ---')) {
        process.stdin.add('q'.codeUnits);
      }
    },
    workingDirectory: testAppDirectory,
    environment: <String, String>{
      'FLUTTER_WEB': 'true',
    },
  );

  if (success) {
    print('${green}Web stack trace integration test passed.$reset');
  } else {
    print(output.stdout);
    print('${red}Web stack trace integration test failed.$reset');
    exit(1);
  }
}

Future<void> _runFlutterWebTest(String workingDirectory, List<String> tests) async {
  await runCommand(
    flutter,
    <String>[
      'test',
      if (ciProvider == CiProviders.cirrus)
        '--concurrency=1',  // do not parallelize on Cirrus, to reduce flakiness
      '-v',
      '--platform=chrome',
      ...?flutterTestArgs,
      ...tests,
    ],
    workingDirectory: workingDirectory,
    environment: <String, String>{
      'FLUTTER_WEB': 'true',
      'FLUTTER_LOW_RESOURCE_MODE': 'true',
    },
  );
}

Future<void> _pubRunTest(String workingDirectory, {
  List<String> testPaths,
  bool enableFlutterToolAsserts = true,
  bool useBuildRunner = false,
  String coverage,
  bq.TabledataResourceApi tableData,
  bool forceSingleCore = false,
  Duration perTestTimeout,
}) async {
  int cpus;
  final String cpuVariable = Platform.environment['CPU']; // CPU is set in cirrus.yml
  if (cpuVariable != null) {
    cpus = int.tryParse(cpuVariable, radix: 10);
    if (cpus == null) {
      print('${red}The CPU environment variable, if set, must be set to the integer number of available cores.$reset');
      print('Actual value: "$cpuVariable"');
      exit(1);
    }
  } else {
    cpus = 2; // Don't default to 1, otherwise we won't catch race conditions.
  }
  // Integration tests that depend on external processes like chrome
  // can get stuck if there are multiple instances running at once.
  if (forceSingleCore) {
    cpus = 1;
  }

  final List<String> args = <String>[
    'run',
    'test',
    if (useFlutterTestFormatter)
      '-rjson'
    else
      '-rcompact',
    '-j$cpus',
    if (!hasColor)
      '--no-color',
    if (coverage != null)
      '--coverage=$coverage',
    if (perTestTimeout != null)
      '--timeout=${perTestTimeout.inMilliseconds.toString()}ms',
    if (testPaths != null)
      for (final String testPath in testPaths)
        testPath,
  ];
  final Map<String, String> pubEnvironment = <String, String>{
    'FLUTTER_ROOT': flutterRoot,
  };
  if (Directory(pubCache).existsSync()) {
    pubEnvironment['PUB_CACHE'] = pubCache;
  }
  if (enableFlutterToolAsserts) {
    // If an existing env variable exists append to it, but only if
    // it doesn't appear to already include enable-asserts.
    String toolsArgs = Platform.environment['FLUTTER_TOOL_ARGS'] ?? '';
    if (!toolsArgs.contains('--enable-asserts'))
      toolsArgs += ' --enable-asserts';
    pubEnvironment['FLUTTER_TOOL_ARGS'] = toolsArgs.trim();
    // The flutter_tool will originally have been snapshotted without asserts.
    // We need to force it to be regenerated with them enabled.
    deleteFile(path.join(flutterRoot, 'bin', 'cache', 'flutter_tools.snapshot'));
    deleteFile(path.join(flutterRoot, 'bin', 'cache', 'flutter_tools.stamp'));
  }
  if (useFlutterTestFormatter) {
    final FlutterCompactFormatter formatter = FlutterCompactFormatter();
    Stream<String> testOutput;
    try {
      testOutput = runAndGetStdout(
        pub,
        args,
        workingDirectory: workingDirectory,
        environment: pubEnvironment,
      );
    } finally {
      formatter.finish();
    }
    await _processTestOutput(formatter, testOutput, tableData);
  } else {
    await runCommand(
      pub,
      args,
      workingDirectory: workingDirectory,
      environment: pubEnvironment,
      removeLine: useBuildRunner ? (String line) => line.startsWith('[INFO]') : null,
    );
  }
}

Future<void> _runFlutterTest(String workingDirectory, {
  String script,
  bool expectFailure = false,
  bool printOutput = true,
  OutputChecker outputChecker,
  List<String> options = const <String>[],
  bool skip = false,
  bq.TabledataResourceApi tableData,
  Map<String, String> environment,
  List<String> tests = const <String>[],
}) async {
  assert(!printOutput || outputChecker == null, 'Output either can be printed or checked but not both');

  final List<String> args = <String>[
    'test',
    ...options,
    ...?flutterTestArgs,
  ];

  final bool shouldProcessOutput = useFlutterTestFormatter && !expectFailure && !options.contains('--coverage');
  if (shouldProcessOutput)
    args.add('--machine');

  if (script != null) {
    final String fullScriptPath = path.join(workingDirectory, script);
    if (!FileSystemEntity.isFileSync(fullScriptPath)) {
      print('${red}Could not find test$reset: $green$fullScriptPath$reset');
      print('Working directory: $cyan$workingDirectory$reset');
      print('Script: $green$script$reset');
      if (!printOutput)
        print('This is one of the tests that does not normally print output.');
      if (skip)
        print('This is one of the tests that is normally skipped in this configuration.');
      exit(1);
    }
    args.add(script);
  }

  args.addAll(tests);

  if (!shouldProcessOutput) {
    OutputMode outputMode = OutputMode.discard;
    CapturedOutput output;

    if (outputChecker != null) {
      outputMode = OutputMode.capture;
      output = CapturedOutput();
    } else if (printOutput) {
      outputMode = OutputMode.print;
    }

    await runCommand(
      flutter,
      args,
      workingDirectory: workingDirectory,
      expectNonZeroExit: expectFailure,
      outputMode: outputMode,
      output: output,
      skip: skip,
      environment: environment,
    );

    if (outputChecker != null) {
      final String message = outputChecker(output);
      if (message != null)
        exitWithError(<String>[message]);
    }
    return;
  }

  if (useFlutterTestFormatter) {
    final FlutterCompactFormatter formatter = FlutterCompactFormatter();
    Stream<String> testOutput;
    try {
      testOutput = runAndGetStdout(
        flutter,
        args,
        workingDirectory: workingDirectory,
        expectNonZeroExit: expectFailure,
        environment: environment,
      );
    } finally {
      formatter.finish();
    }
    await _processTestOutput(formatter, testOutput, tableData);
  } else {
    await runCommand(
      flutter,
      args,
      workingDirectory: workingDirectory,
      expectNonZeroExit: expectFailure,
    );
  }
}

Map<String, String> _initGradleEnvironment() {
  final String androidSdkRoot = (Platform.environment['ANDROID_HOME']?.isEmpty ?? true)
      ? Platform.environment['ANDROID_SDK_ROOT']
      : Platform.environment['ANDROID_HOME'];
  if (androidSdkRoot == null || androidSdkRoot.isEmpty) {
    print('${red}Could not find Android SDK; set ANDROID_SDK_ROOT (or ANDROID_HOME).$reset');
    exit(1);
  }
  return <String, String>{
    'ANDROID_HOME': androidSdkRoot,
    'ANDROID_SDK_ROOT': androidSdkRoot,
  };
}

final Map<String, String> gradleEnvironment = _initGradleEnvironment();

Future<void> _runHostOnlyDeviceLabTests() async {
  // Please don't add more tests here. We should not be using the devicelab
  // logic to run tests outside devicelab, that's just confusing.
  // Instead, create tests that are not devicelab tests, and run those.

  // TODO(ianh): Move the tests that are not running on devicelab any more out
  // of the device lab directory.

  const Map<String, String> kChromeVariables = <String, String>{
    // This is required to be able to run Chrome on Cirrus and LUCI.
    'CHROME_NO_SANDBOX': 'true',
    // Causes Chrome to run in headless mode in environments without displays,
    // such as Cirrus and LUCI. Do not use this variable when recording actual
    // benchmark numbers.
    'UNCALIBRATED_SMOKE_TEST': 'true',
  };

  // List the tests to run.
  // We split these into subshards. The tests are randomly distributed into
  // those subshards so as to get a uniform distribution of costs, but the
  // seed is fixed so that issues are reproducible.
  final List<ShardRunner> tests = <ShardRunner>[
    // Keep this in alphabetical order.
    () => _runDevicelabTest('build_aar_module_test', environment: gradleEnvironment),
    if (Platform.isMacOS) () => _runDevicelabTest('flutter_create_offline_test_mac'),
    if (Platform.isLinux) () => _runDevicelabTest('flutter_create_offline_test_linux'),
    if (Platform.isWindows) () => _runDevicelabTest('flutter_create_offline_test_windows'),
    () => _runDevicelabTest('gradle_fast_start_test', environment: gradleEnvironment),
    // TODO(ianh): Fails on macOS looking for "dexdump", https://github.com/flutter/flutter/issues/42494
    if (!Platform.isMacOS) () => _runDevicelabTest('gradle_jetifier_test', environment: gradleEnvironment),
    () => _runDevicelabTest('gradle_non_android_plugin_test', environment: gradleEnvironment),
    () => _runDevicelabTest('gradle_deprecated_settings_test', environment: gradleEnvironment),
    () => _runDevicelabTest('gradle_plugin_bundle_test', environment: gradleEnvironment),
    () => _runDevicelabTest('gradle_plugin_fat_apk_test', environment: gradleEnvironment),
    () => _runDevicelabTest('gradle_plugin_light_apk_test', environment: gradleEnvironment),
    () => _runDevicelabTest('gradle_r8_test', environment: gradleEnvironment),

    () => _runDevicelabTest('module_host_with_custom_build_test', environment: gradleEnvironment, testEmbeddingV2: true),
    () => _runDevicelabTest('module_custom_host_app_name_test', environment: gradleEnvironment),
    () => _runDevicelabTest('module_test', environment: gradleEnvironment, testEmbeddingV2: true),
    () => _runDevicelabTest('plugin_dependencies_test', environment: gradleEnvironment),

    if (Platform.isMacOS) () => _runDevicelabTest('module_test_ios'),
    if (Platform.isMacOS) () => _runDevicelabTest('build_ios_framework_module_test'),
    if (Platform.isMacOS) () => _runDevicelabTest('plugin_lint_mac'),
    () => _runDevicelabTest('plugin_test', environment: gradleEnvironment),
    if (Platform.isLinux) () => _runDevicelabTest('web_benchmarks_html', environment: kChromeVariables),
    if (Platform.isLinux) () => _runDevicelabTest('web_benchmarks_canvaskit', environment: kChromeVariables),
  ]..shuffle(math.Random(0));

  await _selectIndexedSubshard(tests, kDeviceLabShardCount);
}

Future<void> _runDevicelabTest(String testName, {
  Map<String, String> environment,
  // testEmbeddingV2 is only supported by certain specific devicelab tests.
  // Don't use it unless you're sure the test actually supports it.
  // You can check by looking to see if the test examines the environment
  // for the ENABLE_ANDROID_EMBEDDING_V2 variable.
  bool testEmbeddingV2 = false,
}) async {
  await runCommand(
    dart,
    <String>['bin/run.dart', '-t', testName],
    workingDirectory: path.join(flutterRoot, 'dev', 'devicelab'),
    environment: <String, String>{
      ...?environment,
      if (testEmbeddingV2)
        'ENABLE_ANDROID_EMBEDDING_V2': 'true',
    },
  );
}

void deleteFile(String path) {
  // This is technically a race condition but nobody else should be running
  // while this script runs, so we should be ok. (Sadly recursive:true does not
  // obviate the need for existsSync, at least on Windows.)
  final File file = File(path);
  if (file.existsSync())
    file.deleteSync();
}

enum CiProviders {
  cirrus,
  luci,
}

Future<void> _processTestOutput(
  FlutterCompactFormatter formatter,
  Stream<String> testOutput,
  bq.TabledataResourceApi tableData,
) async {
  final Timer heartbeat = Timer.periodic(const Duration(seconds: 30), (Timer timer) {
    print('Processing...');
  });

  await testOutput.forEach(formatter.processRawOutput);
  heartbeat.cancel();
  formatter.finish();
  if (tableData == null || formatter.tests.isEmpty) {
    return;
  }
  final bq.TableDataInsertAllRequest request = bq.TableDataInsertAllRequest();
  final String authors = await _getAuthors();
  request.rows = List<bq.TableDataInsertAllRequestRows>.from(
    formatter.tests.map<bq.TableDataInsertAllRequestRows>((TestResult result) =>
      bq.TableDataInsertAllRequestRows.fromJson(<String, dynamic> {
        'json': <String, dynamic>{
          'source': <String, dynamic>{
            'provider': ciProviderName,
            'url': ciUrl,
            'platform': <String, dynamic>{
              'os': Platform.operatingSystem,
              'version': Platform.operatingSystemVersion,
            },
          },
          'test': <String, dynamic>{
            'name': result.name,
            'result': result.status.toString(),
            'file': result.path,
            'line': result.line,
            'column': result.column,
            'time': result.totalTime,
          },
          'git': <String, dynamic>{
            'author': authors,
            'pull_request': prNumber,
            'commit': gitHash,
            'organization': 'flutter',
            'repository': 'flutter',
          },
          'error': result.status != TestStatus.failed ? null : <String, dynamic>{
            'message': result.errorMessage,
            'stack_trace': result.stackTrace,
          },
          'information': result.messages,
        },
      }),
    ),
    growable: false,
  );
  final bq.TableDataInsertAllResponse response = await tableData.insertAll(request, 'flutter-infra', 'tests', 'ci');
  if (response.insertErrors != null && response.insertErrors.isNotEmpty) {
    print('${red}BigQuery insert errors:');
    print(response.toJson());
    print(reset);
  }
}

CiProviders get ciProvider {
  if (Platform.environment['CIRRUS_CI'] == 'true') {
    return CiProviders.cirrus;
  }
  if (Platform.environment['LUCI_CONTEXT'] != null) {
    return CiProviders.luci;
  }
  return null;
}

String get ciProviderName {
  switch (ciProvider) {
    case CiProviders.cirrus:
      return 'cirrusci';
    case CiProviders.luci:
      return 'luci';
  }
  return 'unknown';
}

int get prNumber {
  switch (ciProvider) {
    case CiProviders.cirrus:
      return Platform.environment['CIRRUS_PR'] == null
          ? -1
          : int.tryParse(Platform.environment['CIRRUS_PR']);
    case CiProviders.luci:
      return -1; // LUCI doesn't know about this.
  }
  return -1;
}

Future<String> _getAuthors() async {
  final String author = await runAndGetStdout(
    'git$exe', <String>['-c', 'log.showSignature=false', 'log', gitHash, '--pretty="%an <%ae>"'],
    workingDirectory: flutterRoot,
  ).first;
  return author;
}

String get ciUrl {
  switch (ciProvider) {
    case CiProviders.cirrus:
      return 'https://cirrus-ci.com/task/${Platform.environment['CIRRUS_TASK_ID']}';
    case CiProviders.luci:
      return 'https://ci.chromium.org/p/flutter/g/framework/console'; // TODO(dnfield): can we get a direct link to the actual build?
  }
  return '';
}

String get gitHash {
  switch(ciProvider) {
    case CiProviders.cirrus:
      return Platform.environment['CIRRUS_CHANGE_IN_REPO'];
    case CiProviders.luci:
      return 'HEAD'; // TODO(dnfield): Set this in the env for LUCI.
  }
  return '';
}

/// Checks the given file's contents to determine if they match the allowed
/// pattern for version strings.
///
/// Returns null if the contents are good. Returns a string if they are bad.
/// The string is an error message.
Future<String> verifyVersion(File file) async {
  final RegExp pattern = RegExp(
    r'^(\d+)\.(\d+)\.(\d+)((-\d+\.\d+)?\.pre(\.\d+)?)?$');
  final String version = await file.readAsString();
  if (!file.existsSync())
    return 'The version logic failed to create the Flutter version file.';
  if (version == '0.0.0-unknown')
    return 'The version logic failed to determine the Flutter version.';
  if (!version.contains(pattern))
    return 'The version logic generated an invalid version string: "$version".';
  return null;
}

/// Parse (zero-)index-named subshards and equally distribute [tests]
/// between them. Last shard should end in "_last" to catch mismatches
/// between `.cirrus.yml` and `test.dart`. See [selectShard] for naming details.
///
/// Examples:
/// build_tests-0-linux
/// build_tests-1-linux
/// build_tests-2_last-linux
Future<void> _selectIndexedSubshard(List<ShardRunner> tests, int numberOfShards) async {
  final int testsPerShard = tests.length ~/ numberOfShards;
  final Map<String, ShardRunner> subshards = <String, ShardRunner>{};

  for (int subshard = 0; subshard < numberOfShards; subshard += 1) {
    String last = '';
    List<ShardRunner> sublist;
    if (subshard < numberOfShards - 1) {
      sublist = tests.sublist(subshard * testsPerShard, (subshard + 1) * testsPerShard);
    } else {
      sublist = tests.sublist(subshard * testsPerShard, tests.length);
      // We make sure the last shard ends in _last.
      last = '_last';
    }
    subshards['$subshard$last'] = () async {
      for (final ShardRunner test in sublist)
        await test();
    };
  }

  await selectSubshard(subshards);
}

/// If the CIRRUS_TASK_NAME environment variable exists, we use that to determine
/// the shard and sub-shard (parsing it in the form shard-subshard-platform, ignoring
/// the platform).
///
/// However, for local testing you can just set the SHARD and SUBSHARD
/// environment variables. For example, to run all the framework tests you can
/// just set SHARD=framework_tests. To run specifically the third subshard of
/// the Web tests you can set SHARD=web_tests SUBSHARD=2 (it's zero-based).
Future<void> selectShard(Map<String, ShardRunner> shards) => _runFromList(shards, 'SHARD', 'shard', 0);
Future<void> selectSubshard(Map<String, ShardRunner> subshards) => _runFromList(subshards, 'SUBSHARD', 'subshard', 1);

const String CIRRUS_TASK_NAME = 'CIRRUS_TASK_NAME';

Future<void> _runFromList(Map<String, ShardRunner> items, String key, String name, int positionInTaskName) async {
  String item = Platform.environment[key];
  if (item == null && Platform.environment.containsKey(CIRRUS_TASK_NAME)) {
    final List<String> parts = Platform.environment[CIRRUS_TASK_NAME].split('-');
    assert(positionInTaskName < parts.length);
    item = parts[positionInTaskName];
  }
  if (item == null) {
    for (final String currentItem in items.keys) {
      print('$bold$key=$currentItem$reset');
      await items[currentItem]();
      print('');
    }
  } else {
    if (!items.containsKey(item)) {
      print('${red}Invalid $name: $item$reset');
      print('The available ${name}s are: ${items.keys.join(", ")}');
      exit(1);
    }
    print('$bold$key=$item$reset');
    await items[item]();
  }
}