// 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.

// @dart = 2.8

import 'package:crypto/crypto.dart';
import 'package:meta/meta.dart';
import 'package:process/process.dart';
import 'package:xml/xml.dart';

import '../artifacts.dart';
import '../base/analyze_size.dart';
import '../base/common.dart';
import '../base/deferred_component.dart';
import '../base/file_system.dart';
import '../base/io.dart';
import '../base/logger.dart';
import '../base/platform.dart';
import '../base/process.dart';
import '../base/terminal.dart';
import '../base/utils.dart';
import '../build_info.dart';
import '../cache.dart';
import '../convert.dart';
import '../flutter_manifest.dart';
import '../project.dart';
import '../reporting/reporting.dart';
import 'android_builder.dart';
import 'android_studio.dart';
import 'gradle_errors.dart';
import 'gradle_utils.dart';

/// The directory where the APK artifact is generated.
Directory getApkDirectory(FlutterProject project) {
  return project.isModule
    ? project.android.buildDirectory
        .childDirectory('host')
        .childDirectory('outputs')
        .childDirectory('apk')
    : project.android.buildDirectory
        .childDirectory('app')
        .childDirectory('outputs')
        .childDirectory('flutter-apk');
}

/// The directory where the app bundle artifact is generated.
@visibleForTesting
Directory getBundleDirectory(FlutterProject project) {
  return project.isModule
    ? project.android.buildDirectory
        .childDirectory('host')
        .childDirectory('outputs')
        .childDirectory('bundle')
    : project.android.buildDirectory
        .childDirectory('app')
        .childDirectory('outputs')
        .childDirectory('bundle');
}

/// The directory where the repo is generated.
/// Only applicable to AARs.
Directory getRepoDirectory(Directory buildDirectory) {
  return buildDirectory
    .childDirectory('outputs')
    .childDirectory('repo');
}

/// Returns the name of Gradle task that starts with [prefix].
String _taskFor(String prefix, BuildInfo buildInfo) {
  final String buildType = camelCase(buildInfo.modeName);
  final String productFlavor = buildInfo.flavor ?? '';
  return '$prefix${toTitleCase(productFlavor)}${toTitleCase(buildType)}';
}

/// Returns the task to build an APK.
@visibleForTesting
String getAssembleTaskFor(BuildInfo buildInfo) {
  return _taskFor('assemble', buildInfo);
}

/// Returns the task to build an AAB.
@visibleForTesting
String getBundleTaskFor(BuildInfo buildInfo) {
  return _taskFor('bundle', buildInfo);
}

/// Returns the task to build an AAR.
@visibleForTesting
String getAarTaskFor(BuildInfo buildInfo) {
  return _taskFor('assembleAar', buildInfo);
}

/// Returns the output APK file names for a given [AndroidBuildInfo].
///
/// For example, when [splitPerAbi] is true, multiple APKs are created.
Iterable<String> _apkFilesFor(AndroidBuildInfo androidBuildInfo) {
  final String buildType = camelCase(androidBuildInfo.buildInfo.modeName);
  final String productFlavor = androidBuildInfo.buildInfo.lowerCasedFlavor ?? '';
  final String flavorString = productFlavor.isEmpty ? '' : '-$productFlavor';
  if (androidBuildInfo.splitPerAbi) {
    return androidBuildInfo.targetArchs.map<String>((AndroidArch arch) {
      final String abi = getNameForAndroidArch(arch);
      return 'app$flavorString-$abi-$buildType.apk';
    });
  }
  return <String>['app$flavorString-$buildType.apk'];
}

/// Tries to create `settings_aar.gradle` in an app project by removing the subprojects
/// from the existing `settings.gradle` file. This operation will fail if the existing
/// `settings.gradle` file has local edits.
@visibleForTesting
void createSettingsAarGradle(Directory androidDirectory, Logger logger) {
  final FileSystem fileSystem = androidDirectory.fileSystem;
  final File newSettingsFile = androidDirectory.childFile('settings_aar.gradle');
  if (newSettingsFile.existsSync()) {
    return;
  }
  final File currentSettingsFile = androidDirectory.childFile('settings.gradle');
  if (!currentSettingsFile.existsSync()) {
    return;
  }
  final String currentFileContent = currentSettingsFile.readAsStringSync();

  final String newSettingsRelativeFile = fileSystem.path.relative(newSettingsFile.path);
  final Status status = logger.startProgress('✏️  Creating `$newSettingsRelativeFile`...');

  final String flutterRoot = fileSystem.path.absolute(Cache.flutterRoot);
  final File legacySettingsDotGradleFiles = fileSystem.file(fileSystem.path.join(flutterRoot, 'packages','flutter_tools',
      'gradle', 'settings.gradle.legacy_versions'));
  assert(legacySettingsDotGradleFiles.existsSync());
  final String settingsAarContent = fileSystem.file(fileSystem.path.join(flutterRoot, 'packages','flutter_tools',
      'gradle', 'settings_aar.gradle.tmpl')).readAsStringSync();

  // Get the `settings.gradle` content variants that should be patched.
  final List<String> existingVariants = legacySettingsDotGradleFiles.readAsStringSync().split(';EOF');
  existingVariants.add(settingsAarContent);

  bool exactMatch = false;
  for (final String fileContentVariant in existingVariants) {
    if (currentFileContent.trim() == fileContentVariant.trim()) {
      exactMatch = true;
      break;
    }
  }
  if (!exactMatch) {
    status.cancel();
    logger.printStatus('${logger.terminal.warningMark} Flutter tried to create the file `$newSettingsRelativeFile`, but failed.');
    // Print how to manually update the file.
    logger.printStatus(fileSystem.file(fileSystem.path.join(flutterRoot, 'packages','flutter_tools',
        'gradle', 'manual_migration_settings.gradle.md')).readAsStringSync());
    throwToolExit('Please create the file and run this command again.');
  }
  // Copy the new file.
  newSettingsFile.writeAsStringSync(settingsAarContent);
  status.stop();
  logger.printStatus('${logger.terminal.successMark} `$newSettingsRelativeFile` created successfully.');
}

/// An implementation of the [AndroidBuilder] that delegates to gradle.
class AndroidGradleBuilder implements AndroidBuilder {
  AndroidGradleBuilder({
    @required Logger logger,
    @required ProcessManager processManager,
    @required FileSystem fileSystem,
    @required Artifacts artifacts,
    @required Usage usage,
    @required GradleUtils gradleUtils,
    @required Platform platform,
  }) : _logger = logger,
       _fileSystem = fileSystem,
       _artifacts = artifacts,
       _usage = usage,
       _gradleUtils = gradleUtils,
       _fileSystemUtils = FileSystemUtils(fileSystem: fileSystem, platform: platform),
       _processUtils = ProcessUtils(logger: logger, processManager: processManager);

  final Logger _logger;
  final ProcessUtils _processUtils;
  final FileSystem _fileSystem;
  final Artifacts _artifacts;
  final Usage _usage;
  final GradleUtils _gradleUtils;
  final FileSystemUtils _fileSystemUtils;

  /// Builds the AAR and POM files for the current Flutter module or plugin.
  @override
  Future<void> buildAar({
    @required FlutterProject project,
    @required Set<AndroidBuildInfo> androidBuildInfo,
    @required String target,
    @required String outputDirectoryPath,
    @required String buildNumber,
  }) async {
    Directory outputDirectory =
      _fileSystem.directory(outputDirectoryPath ?? project.android.buildDirectory);
    if (project.isModule) {
      // Module projects artifacts are located in `build/host`.
      outputDirectory = outputDirectory.childDirectory('host');
    }
    for (final AndroidBuildInfo androidBuildInfo in androidBuildInfo) {
      await buildGradleAar(
        project: project,
        androidBuildInfo: androidBuildInfo,
        target: target,
        outputDirectory: outputDirectory,
        buildNumber: buildNumber,
      );
    }
    printHowToConsumeAar(
      buildModes: androidBuildInfo
        .map<String>((AndroidBuildInfo androidBuildInfo) {
          return androidBuildInfo.buildInfo.modeName;
        }).toSet(),
      androidPackage: project.manifest.androidPackage,
      repoDirectory: getRepoDirectory(outputDirectory),
      buildNumber: buildNumber,
      logger: _logger,
      fileSystem: _fileSystem,
    );
  }

  /// Builds the APK.
  @override
  Future<void> buildApk({
    @required FlutterProject project,
    @required AndroidBuildInfo androidBuildInfo,
    @required String target,
  }) async {
    await buildGradleApp(
      project: project,
      androidBuildInfo: androidBuildInfo,
      target: target,
      isBuildingBundle: false,
      localGradleErrors: gradleErrors,
    );
  }

  /// Builds the App Bundle.
  @override
  Future<void> buildAab({
    @required FlutterProject project,
    @required AndroidBuildInfo androidBuildInfo,
    @required String target,
    bool validateDeferredComponents = true,
    bool deferredComponentsEnabled = false,
  }) async {
    await buildGradleApp(
      project: project,
      androidBuildInfo: androidBuildInfo,
      target: target,
      isBuildingBundle: true,
      localGradleErrors: gradleErrors,
      validateDeferredComponents: validateDeferredComponents,
      deferredComponentsEnabled: deferredComponentsEnabled,
    );
  }

  /// Builds an app.
  ///
  /// * [project] is typically [FlutterProject.current()].
  /// * [androidBuildInfo] is the build configuration.
  /// * [target] is the target dart entry point. Typically, `lib/main.dart`.
  /// * If [isBuildingBundle] is `true`, then the output artifact is an `*.aab`,
  ///   otherwise the output artifact is an `*.apk`.
  /// * The plugins are built as AARs if [shouldBuildPluginAsAar] is `true`. This isn't set by default
  ///   because it makes the build slower proportional to the number of plugins.
  /// * [retries] is the max number of build retries in case one of the [GradleHandledError] handler
  ///   returns [GradleBuildStatus.retry] or [GradleBuildStatus.retryWithAarPlugins].
  Future<void> buildGradleApp({
    @required FlutterProject project,
    @required AndroidBuildInfo androidBuildInfo,
    @required String target,
    @required bool isBuildingBundle,
    @required List<GradleHandledError> localGradleErrors,
    bool shouldBuildPluginAsAar = false,
    bool validateDeferredComponents = true,
    bool deferredComponentsEnabled = false,
    int retries = 1,
  }) async {
    assert(project != null);
    assert(androidBuildInfo != null);
    assert(target != null);
    assert(isBuildingBundle != null);
    assert(localGradleErrors != null);

    if (!project.android.isSupportedVersion) {
      _exitWithUnsupportedProjectMessage(_usage, _logger.terminal);
    }
    final Directory buildDirectory = project.android.buildDirectory;

    final bool usesAndroidX = isAppUsingAndroidX(project.android.hostAppGradleRoot);
    if (usesAndroidX) {
      BuildEvent('app-using-android-x', flutterUsage: _usage).send();
    } else if (!usesAndroidX) {
      BuildEvent('app-not-using-android-x', flutterUsage: _usage).send();
      _logger.printStatus("${_logger.terminal.warningMark} Your app isn't using AndroidX.", emphasis: true);
      _logger.printStatus(
        'To avoid potential build failures, you can quickly migrate your app '
            'by following the steps on https://goo.gl/CP92wY .',
        indent: 4,
      );
    }
    // The default Gradle script reads the version name and number
    // from the local.properties file.
    updateLocalProperties(project: project, buildInfo: androidBuildInfo.buildInfo);

    if (shouldBuildPluginAsAar) {
      // Create a settings.gradle that doesn't import the plugins as subprojects.
      createSettingsAarGradle(project.android.hostAppGradleRoot, _logger);
      await buildPluginsAsAar(
        project,
        androidBuildInfo,
        buildDirectory: buildDirectory.childDirectory('app'),
      );
    }

    final BuildInfo buildInfo = androidBuildInfo.buildInfo;
    final String assembleTask = isBuildingBundle
        ? getBundleTaskFor(buildInfo)
        : getAssembleTaskFor(buildInfo);

    final Status status = _logger.startProgress(
      "Running Gradle task '$assembleTask'...",
      multilineOutput: true,
    );

    final List<String> command = <String>[
      _gradleUtils.getExecutable(project),
    ];
    if (_logger.isVerbose) {
      command.add('-Pverbose=true');
    } else {
      command.add('-q');
    }
    if (!buildInfo.androidGradleDaemon) {
      command.add('--no-daemon');
    }
    if (_artifacts is LocalEngineArtifacts) {
      final LocalEngineArtifacts localEngineArtifacts = _artifacts as LocalEngineArtifacts;
      final Directory localEngineRepo = _getLocalEngineRepo(
        engineOutPath: localEngineArtifacts.engineOutPath,
        androidBuildInfo: androidBuildInfo,
        fileSystem: _fileSystem,
      );
      _logger.printTrace(
          'Using local engine: ${localEngineArtifacts.engineOutPath}\n'
              'Local Maven repo: ${localEngineRepo.path}'
      );
      command.add('-Plocal-engine-repo=${localEngineRepo.path}');
      command.add('-Plocal-engine-build-mode=${buildInfo.modeName}');
      command.add('-Plocal-engine-out=${localEngineArtifacts.engineOutPath}');
      command.add('-Ptarget-platform=${_getTargetPlatformByLocalEnginePath(
          localEngineArtifacts.engineOutPath)}');
    } else if (androidBuildInfo.targetArchs.isNotEmpty) {
      final String targetPlatforms = androidBuildInfo
          .targetArchs
          .map(getPlatformNameForAndroidArch).join(',');
      command.add('-Ptarget-platform=$targetPlatforms');
    }
    if (target != null) {
      command.add('-Ptarget=$target');
    }
    if (project.manifest.deferredComponents != null) {
      if (deferredComponentsEnabled) {
        command.add('-Pdeferred-components=true');
        androidBuildInfo.buildInfo.dartDefines.add('validate-deferred-components=$validateDeferredComponents');
      }
      // Pass in deferred components regardless of building split aot to satisfy
      // android dynamic features registry in build.gradle.
      final List<String> componentNames = <String>[];
      for (final DeferredComponent component in project.manifest.deferredComponents) {
        componentNames.add(component.name);
      }
      if (componentNames.isNotEmpty) {
        command.add('-Pdeferred-component-names=${componentNames.join(',')}');
        // Multi-apk applications cannot use shrinking. This is only relevant when using
        // android dynamic feature modules.
        _logger.printStatus(
          'Shrinking has been disabled for this build due to deferred components. Shrinking is '
          'not available for multi-apk applications. This limitation is expected to be removed '
          'when Gradle plugin 4.2+ is available in Flutter.', color: TerminalColor.yellow);
        command.add('-Pshrink=false');
      }
    }
    command.addAll(androidBuildInfo.buildInfo.toGradleConfig());
    if (buildInfo.fileSystemRoots != null && buildInfo.fileSystemRoots.isNotEmpty) {
      command.add('-Pfilesystem-roots=${buildInfo.fileSystemRoots.join('|')}');
    }
    if (buildInfo.fileSystemScheme != null) {
      command.add('-Pfilesystem-scheme=${buildInfo.fileSystemScheme}');
    }
    if (androidBuildInfo.splitPerAbi) {
      command.add('-Psplit-per-abi=true');
    }
    if (shouldBuildPluginAsAar) {
      // Pass a system flag instead of a project flag, so this flag can be
      // read from include_flutter.groovy.
      command.add('-Dbuild-plugins-as-aars=true');
      // Don't use settings.gradle from the current project since it includes the plugins as subprojects.
      command.add('--settings-file=settings_aar.gradle');
    }
    if (androidBuildInfo.fastStart) {
      command.add('-Pfast-start=true');
    }
    command.add(assembleTask);

    GradleHandledError detectedGradleError;
    String detectedGradleErrorLine;
    String consumeLog(String line) {
      // This message was removed from first-party plugins,
      // but older plugin versions still display this message.
      if (androidXPluginWarningRegex.hasMatch(line)) {
        // Don't pipe.
        return null;
      }
      if (detectedGradleError != null) {
        // Pipe stdout/stderr from Gradle.
        return line;
      }
      for (final GradleHandledError gradleError in localGradleErrors) {
        if (gradleError.test(line)) {
          detectedGradleErrorLine = line;
          detectedGradleError = gradleError;
          // The first error match wins.
          break;
        }
      }
      // Pipe stdout/stderr from Gradle.
      return line;
    }

    final Stopwatch sw = Stopwatch()
      ..start();
    int exitCode = 1;
    try {
      exitCode = await _processUtils.stream(
        command,
        workingDirectory: project.android.hostAppGradleRoot.path,
        allowReentrantFlutter: true,
        environment: <String, String>{
          if (javaPath != null)
            'JAVA_HOME': javaPath,
        },
        mapFunction: consumeLog,
      );
    } on ProcessException catch (exception) {
      consumeLog(exception.toString());
      // Rethrow the exception if the error isn't handled by any of the
      // `localGradleErrors`.
      if (detectedGradleError == null) {
        rethrow;
      }
    } finally {
      status.stop();
    }

    _usage.sendTiming('build', 'gradle', sw.elapsed);

    if (exitCode != 0) {
      if (detectedGradleError == null) {
        BuildEvent('gradle-unknown-failure', flutterUsage: _usage).send();
        throwToolExit(
          'Gradle task $assembleTask failed with exit code $exitCode',
          exitCode: exitCode,
        );
      } else {
        final GradleBuildStatus status = await detectedGradleError.handler(
          line: detectedGradleErrorLine,
          project: project,
          usesAndroidX: usesAndroidX,
          shouldBuildPluginAsAar: shouldBuildPluginAsAar,
        );

        if (retries >= 1) {
          final String successEventLabel = 'gradle-${detectedGradleError.eventLabel}-success';
          switch (status) {
            case GradleBuildStatus.retry:
              await buildGradleApp(
                project: project,
                androidBuildInfo: androidBuildInfo,
                target: target,
                isBuildingBundle: isBuildingBundle,
                localGradleErrors: localGradleErrors,
                shouldBuildPluginAsAar: shouldBuildPluginAsAar,
                retries: retries - 1,
              );
              BuildEvent(successEventLabel, flutterUsage: _usage).send();
              return;
            case GradleBuildStatus.retryWithAarPlugins:
              await buildGradleApp(
                project: project,
                androidBuildInfo: androidBuildInfo,
                target: target,
                isBuildingBundle: isBuildingBundle,
                localGradleErrors: localGradleErrors,
                shouldBuildPluginAsAar: true,
                retries: retries - 1,
              );
              BuildEvent(successEventLabel, flutterUsage: _usage).send();
              return;
            case GradleBuildStatus.exit:
            // noop.
          }
        }
        BuildEvent('gradle-${detectedGradleError.eventLabel}-failure', flutterUsage: _usage).send();
        throwToolExit(
          'Gradle task $assembleTask failed with exit code $exitCode',
          exitCode: exitCode,
        );
      }
    }

    if (isBuildingBundle) {
      final File bundleFile = findBundleFile(project, buildInfo, _logger, _usage);
      final String appSize = (buildInfo.mode == BuildMode.debug)
          ? '' // Don't display the size when building a debug variant.
          : ' (${getSizeAsMB(bundleFile.lengthSync())})';

      if (buildInfo.codeSizeDirectory != null) {
        await _performCodeSizeAnalysis('aab', bundleFile, androidBuildInfo);
      }

      _logger.printStatus(
        '${_logger.terminal.successMark} Built ${_fileSystem.path.relative(bundleFile.path)}$appSize.',
        color: TerminalColor.green,
      );
      return;
    }
    // Gradle produced an APK.
    final Iterable<String> apkFilesPaths = project.isModule
        ? findApkFilesModule(project, androidBuildInfo, _logger, _usage)
        : listApkPaths(androidBuildInfo);
    final Directory apkDirectory = getApkDirectory(project);
    final File apkFile = apkDirectory.childFile(apkFilesPaths.first);
    if (!apkFile.existsSync()) {
      _exitWithExpectedFileNotFound(
        project: project,
        fileExtension: '.apk',
        logger: _logger,
        usage: _usage,
      );
    }

    // Copy the first APK to app.apk, so `flutter run` can find it.
    // TODO(egarciad): Handle multiple APKs.
    apkFile.copySync(apkDirectory
        .childFile('app.apk')
        .path);
    _logger.printTrace('calculateSha: $apkDirectory/app.apk');

    final File apkShaFile = apkDirectory.childFile('app.apk.sha1');
    apkShaFile.writeAsStringSync(_calculateSha(apkFile));

    final String appSize = (buildInfo.mode == BuildMode.debug)
        ? '' // Don't display the size when building a debug variant.
        : ' (${getSizeAsMB(apkFile.lengthSync())})';
    _logger.printStatus(
      '${_logger.terminal.successMark}  Built ${_fileSystem.path.relative(apkFile.path)}$appSize.',
      color: TerminalColor.green,
    );

    if (buildInfo.codeSizeDirectory != null) {
      await _performCodeSizeAnalysis('apk', apkFile, androidBuildInfo);
    }
  }

  Future<void> _performCodeSizeAnalysis(String kind,
      File zipFile,
      AndroidBuildInfo androidBuildInfo,) async {
    final SizeAnalyzer sizeAnalyzer = SizeAnalyzer(
      fileSystem: _fileSystem,
      logger: _logger,
      flutterUsage: _usage,
    );
    final String archName = getNameForAndroidArch(androidBuildInfo.targetArchs.single);
    final BuildInfo buildInfo = androidBuildInfo.buildInfo;
    final File aotSnapshot = _fileSystem.directory(buildInfo.codeSizeDirectory)
        .childFile('snapshot.$archName.json');
    final File precompilerTrace = _fileSystem.directory(buildInfo.codeSizeDirectory)
        .childFile('trace.$archName.json');
    final Map<String, Object> output = await sizeAnalyzer.analyzeZipSizeAndAotSnapshot(
      zipFile: zipFile,
      aotSnapshot: aotSnapshot,
      precompilerTrace: precompilerTrace,
      kind: kind,
    );
    final File outputFile = _fileSystemUtils.getUniqueFile(
      _fileSystem
        .directory(_fileSystemUtils.homeDirPath)
        .childDirectory('.flutter-devtools'), '$kind-code-size-analysis', 'json',
    )
      ..writeAsStringSync(jsonEncode(output));
    // This message is used as a sentinel in analyze_apk_size_test.dart
    _logger.printStatus(
      'A summary of your ${kind.toUpperCase()} analysis can be found at: ${outputFile.path}',
    );

    // DevTools expects a file path relative to the .flutter-devtools/ dir.
    final String relativeAppSizePath = outputFile.path
        .split('.flutter-devtools/')
        .last
        .trim();
    _logger.printStatus(
        '\nTo analyze your app size in Dart DevTools, run the following command:\n'
            'flutter pub global activate devtools; flutter pub global run devtools '
            '--appSizeBase=$relativeAppSizePath'
    );
  }

  /// Builds AAR and POM files.
  ///
  /// * [project] is typically [FlutterProject.current()].
  /// * [androidBuildInfo] is the build configuration.
  /// * [outputDir] is the destination of the artifacts,
  /// * [buildNumber] is the build number of the output aar,
  Future<void> buildGradleAar({
    @required FlutterProject project,
    @required AndroidBuildInfo androidBuildInfo,
    @required String target,
    @required Directory outputDirectory,
    @required String buildNumber,
  }) async {
    assert(project != null);
    assert(target != null);
    assert(androidBuildInfo != null);
    assert(outputDirectory != null);

    final FlutterManifest manifest = project.manifest;
    if (!manifest.isModule && !manifest.isPlugin) {
      throwToolExit('AARs can only be built for plugin or module projects.');
    }

    final BuildInfo buildInfo = androidBuildInfo.buildInfo;
    final String aarTask = getAarTaskFor(buildInfo);
    final Status status = _logger.startProgress(
      "Running Gradle task '$aarTask'...",
      multilineOutput: true,
    );

    final String flutterRoot = _fileSystem.path.absolute(Cache.flutterRoot);
    final String initScript = _fileSystem.path.join(
      flutterRoot,
      'packages',
      'flutter_tools',
      'gradle',
      'aar_init_script.gradle',
    );
    final List<String> command = <String>[
      _gradleUtils.getExecutable(project),
      '-I=$initScript',
      '-Pflutter-root=$flutterRoot',
      '-Poutput-dir=${outputDirectory.path}',
      '-Pis-plugin=${manifest.isPlugin}',
      '-PbuildNumber=$buildNumber'
    ];
    if (_logger.isVerbose) {
      command.add('-Pverbose=true');
    } else {
      command.add('-q');
    }
    if (!buildInfo.androidGradleDaemon) {
      command.add('--no-daemon');
    }

    if (target != null && target.isNotEmpty) {
      command.add('-Ptarget=$target');
    }
    command.addAll(androidBuildInfo.buildInfo.toGradleConfig());
    if (buildInfo.dartObfuscation && buildInfo.mode != BuildMode.release) {
      _logger.printStatus(
        'Dart obfuscation is not supported in ${toTitleCase(buildInfo.friendlyModeName)}'
            ' mode, building as un-obfuscated.',
      );
    }

    if (_artifacts is LocalEngineArtifacts) {
      final LocalEngineArtifacts localEngineArtifacts = _artifacts as LocalEngineArtifacts;
      final Directory localEngineRepo = _getLocalEngineRepo(
        engineOutPath: localEngineArtifacts.engineOutPath,
        androidBuildInfo: androidBuildInfo,
        fileSystem: _fileSystem,
      );
      _logger.printTrace(
        'Using local engine: ${localEngineArtifacts.engineOutPath}\n'
        'Local Maven repo: ${localEngineRepo.path}'
      );
      command.add('-Plocal-engine-repo=${localEngineRepo.path}');
      command.add('-Plocal-engine-build-mode=${buildInfo.modeName}');
      command.add('-Plocal-engine-out=${localEngineArtifacts.engineOutPath}');

      // Copy the local engine repo in the output directory.
      try {
        copyDirectory(
          localEngineRepo,
          getRepoDirectory(outputDirectory),
        );
      } on FileSystemException catch (error, st) {
        throwToolExit(
            'Failed to copy the local engine ${localEngineRepo.path} repo '
                'in ${outputDirectory.path}: $error, $st'
        );
      }
      command.add('-Ptarget-platform=${_getTargetPlatformByLocalEnginePath(
          localEngineArtifacts.engineOutPath)}');
    } else if (androidBuildInfo.targetArchs.isNotEmpty) {
      final String targetPlatforms = androidBuildInfo.targetArchs
          .map(getPlatformNameForAndroidArch).join(',');
      command.add('-Ptarget-platform=$targetPlatforms');
    }

    command.add(aarTask);

    final Stopwatch sw = Stopwatch()
      ..start();
    RunResult result;
    try {
      result = await _processUtils.run(
        command,
        workingDirectory: project.android.hostAppGradleRoot.path,
        allowReentrantFlutter: true,
        environment: <String, String>{
          if (javaPath != null)
            'JAVA_HOME': javaPath,
        },
      );
    } finally {
      status.stop();
    }
    _usage.sendTiming('build', 'gradle-aar', sw.elapsed);

    if (result.exitCode != 0) {
      _logger.printStatus(result.stdout, wrap: false);
      _logger.printError(result.stderr, wrap: false);
      throwToolExit(
        'Gradle task $aarTask failed with exit code ${result.exitCode}.',
        exitCode: result.exitCode,
      );
    }
    final Directory repoDirectory = getRepoDirectory(outputDirectory);
    if (!repoDirectory.existsSync()) {
      _logger.printStatus(result.stdout, wrap: false);
      _logger.printError(result.stderr, wrap: false);
      throwToolExit(
        'Gradle task $aarTask failed to produce $repoDirectory.',
        exitCode: exitCode,
      );
    }
    _logger.printStatus(
      '${_logger.terminal.successMark} Built ${_fileSystem.path.relative(repoDirectory.path)}.',
      color: TerminalColor.green,
    );
  }

  /// Builds the plugins as AARs.
  @visibleForTesting
  Future<void> buildPluginsAsAar(
    FlutterProject flutterProject,
    AndroidBuildInfo androidBuildInfo, {
    Directory buildDirectory,
  }) async {
    final File flutterPluginFile = flutterProject.flutterPluginsFile;
    if (!flutterPluginFile.existsSync()) {
      return;
    }
    final List<String> plugins = flutterPluginFile.readAsStringSync().split('\n');
    for (final String plugin in plugins) {
      final List<String> pluginParts = plugin.split('=');
      if (pluginParts.length != 2) {
        continue;
      }
      final Directory pluginDirectory = _fileSystem.directory(pluginParts.last);
      assert(pluginDirectory.existsSync());

      final String pluginName = pluginParts.first;
      final File buildGradleFile = pluginDirectory.childDirectory('android').childFile('build.gradle');
      if (!buildGradleFile.existsSync()) {
        _logger.printTrace("Skipping plugin $pluginName since it doesn't have a android/build.gradle file");
        continue;
      }
      _logger.printStatus('Building plugin $pluginName...');
      try {
        await buildGradleAar(
          project: FlutterProject.fromDirectory(pluginDirectory),
          androidBuildInfo: AndroidBuildInfo(
            BuildInfo(
              BuildMode.release, // Plugins are built as release.
              null, // Plugins don't define flavors.
              treeShakeIcons: androidBuildInfo.buildInfo.treeShakeIcons,
              packagesPath: androidBuildInfo.buildInfo.packagesPath,
            ),
          ),
          target: '',
          outputDirectory: buildDirectory,
          buildNumber: '1.0'
        );
      } on ToolExit {
        // Log the entire plugin entry in `.flutter-plugins` since it
        // includes the plugin name and the version.
        BuildEvent('gradle-plugin-aar-failure', eventError: plugin, flutterUsage: _usage).send();
        throwToolExit('The plugin $pluginName could not be built due to the issue above.');
      }
    }
  }
}

/// Prints how to consume the AAR from a host app.
void printHowToConsumeAar({
  @required Set<String> buildModes,
  @required String androidPackage,
  @required Directory repoDirectory,
  @required Logger logger,
  @required FileSystem fileSystem,
  String buildNumber,
}) {
  assert(buildModes != null && buildModes.isNotEmpty);
  assert(androidPackage != null);
  assert(repoDirectory != null);
  buildNumber ??= '1.0';

  logger.printStatus('\nConsuming the Module', emphasis: true);
  logger.printStatus('''
  1. Open ${fileSystem.path.join('<host>', 'app', 'build.gradle')}
  2. Ensure you have the repositories configured, otherwise add them:

      String storageUrl = System.env.FLUTTER_STORAGE_BASE_URL ?: "https://storage.googleapis.com"
      repositories {
        maven {
            url '${repoDirectory.path}'
        }
        maven {
            url "\$storageUrl/download.flutter.io"
        }
      }

  3. Make the host app depend on the Flutter module:

    dependencies {''');

  for (final String buildMode in buildModes) {
    logger.printStatus("""
      ${buildMode}Implementation '$androidPackage:flutter_$buildMode:$buildNumber'""");
  }

  logger.printStatus('''
    }
''');

  if (buildModes.contains('profile')) {
    logger.printStatus('''

  4. Add the `profile` build type:

    android {
      buildTypes {
        profile {
          initWith debug
        }
      }
    }
''');
  }

  logger.printStatus('To learn more, visit https://flutter.dev/go/build-aar');
}

String _hex(List<int> bytes) {
  final StringBuffer result = StringBuffer();
  for (final int part in bytes) {
    result.write('${part < 16 ? '0' : ''}${part.toRadixString(16)}');
  }
  return result.toString();
}

String _calculateSha(File file) {
  final List<int> bytes = file.readAsBytesSync();
  return _hex(sha1.convert(bytes).bytes);
}

void _exitWithUnsupportedProjectMessage(Usage usage, Terminal terminal) {
  BuildEvent('unsupported-project', eventError: 'gradle-plugin', flutterUsage: usage).send();
  throwToolExit(
    '${terminal.warningMark} Your app is using an unsupported Gradle project. '
    'To fix this problem, create a new project by running `flutter create -t app <app-directory>` '
    'and then move the dart code, assets and pubspec.yaml to the new project.',
  );
}

/// Returns [true] if the current app uses AndroidX.
// TODO(egarciad): https://github.com/flutter/flutter/issues/40800
// Remove `FlutterManifest.usesAndroidX` and provide a unified `AndroidProject.usesAndroidX`.
bool isAppUsingAndroidX(Directory androidDirectory) {
  final File properties = androidDirectory.childFile('gradle.properties');
  if (!properties.existsSync()) {
    return false;
  }
  return properties.readAsStringSync().contains('android.useAndroidX=true');
}

/// Returns the APK files for a given [FlutterProject] and [AndroidBuildInfo].
@visibleForTesting
Iterable<String> findApkFilesModule(
  FlutterProject project,
  AndroidBuildInfo androidBuildInfo,
  Logger logger,
  Usage usage,
) {
  final Iterable<String> apkFileNames = _apkFilesFor(androidBuildInfo);
  final Directory apkDirectory = getApkDirectory(project);
  final Iterable<File> apks = apkFileNames.expand<File>((String apkFileName) {
    File apkFile = apkDirectory.childFile(apkFileName);
    if (apkFile.existsSync()) {
      return <File>[apkFile];
    }
    final BuildInfo buildInfo = androidBuildInfo.buildInfo;
    final String modeName = camelCase(buildInfo.modeName);
    apkFile = apkDirectory
      .childDirectory(modeName)
      .childFile(apkFileName);
    if (apkFile.existsSync()) {
      return <File>[apkFile];
    }
    if (buildInfo.flavor != null) {
      // Android Studio Gradle plugin v3 adds flavor to path.
      apkFile = apkDirectory
        .childDirectory(buildInfo.flavor)
        .childDirectory(modeName)
        .childFile(apkFileName);
      if (apkFile.existsSync()) {
        return <File>[apkFile];
      }
    }
    return const <File>[];
  });
  if (apks.isEmpty) {
    _exitWithExpectedFileNotFound(
      project: project,
      fileExtension: '.apk',
      logger: logger,
      usage: usage,
    );
  }
  return apks.map((File file) => file.path);
}

/// Returns the APK files for a given [FlutterProject] and [AndroidBuildInfo].
///
/// The flutter.gradle plugin will copy APK outputs into:
/// `$buildDir/app/outputs/flutter-apk/app-<abi>-<flavor-flag>-<build-mode-flag>.apk`
@visibleForTesting
Iterable<String> listApkPaths(
  AndroidBuildInfo androidBuildInfo,
) {
  final String buildType = camelCase(androidBuildInfo.buildInfo.modeName);
  final List<String> apkPartialName = <String>[
    if (androidBuildInfo.buildInfo.flavor?.isNotEmpty ?? false)
      androidBuildInfo.buildInfo.lowerCasedFlavor,
    '$buildType.apk',
  ];
  if (androidBuildInfo.splitPerAbi) {
    return <String>[
      for (AndroidArch androidArch in androidBuildInfo.targetArchs)
        <String>[
          'app',
          getNameForAndroidArch(androidArch),
          ...apkPartialName
        ].join('-')
    ];
  }
  return <String>[
    <String>[
      'app',
      ...apkPartialName,
    ].join('-')
  ];
}

@visibleForTesting
File findBundleFile(FlutterProject project, BuildInfo buildInfo, Logger logger, Usage usage) {
  final List<File> fileCandidates = <File>[
    getBundleDirectory(project)
      .childDirectory(camelCase(buildInfo.modeName))
      .childFile('app.aab'),
    getBundleDirectory(project)
      .childDirectory(camelCase(buildInfo.modeName))
      .childFile('app-${buildInfo.modeName}.aab'),
  ];
  if (buildInfo.flavor != null) {
    // The Android Gradle plugin 3.0.0 adds the flavor name to the path.
    // For example: In release mode, if the flavor name is `foo_bar`, then
    // the directory name is `foo_barRelease`.
    fileCandidates.add(
      getBundleDirectory(project)
        .childDirectory('${buildInfo.lowerCasedFlavor}${camelCase('_' + buildInfo.modeName)}')
        .childFile('app.aab'));

    // The Android Gradle plugin 3.5.0 adds the flavor name to file name.
    // For example: In release mode, if the flavor name is `foo_bar`, then
    // the file name name is `app-foo_bar-release.aab`.
    fileCandidates.add(
      getBundleDirectory(project)
        .childDirectory('${buildInfo.lowerCasedFlavor}${camelCase('_' + buildInfo.modeName)}')
        .childFile('app-${buildInfo.lowerCasedFlavor}-${buildInfo.modeName}.aab'));
  }
  for (final File bundleFile in fileCandidates) {
    if (bundleFile.existsSync()) {
      return bundleFile;
    }
  }
  _exitWithExpectedFileNotFound(
    project: project,
    fileExtension: '.aab',
    logger: logger,
    usage: usage,
  );
  return null;
}

/// Throws a [ToolExit] exception and logs the event.
void _exitWithExpectedFileNotFound({
  @required FlutterProject project,
  @required String fileExtension,
  @required Logger logger,
  @required Usage usage,
}) {
  assert(project != null);
  assert(fileExtension != null);

  final String androidGradlePluginVersion =
  getGradleVersionForAndroidPlugin(project.android.hostAppGradleRoot, logger);
  BuildEvent('gradle-expected-file-not-found',
    settings:
    'androidGradlePluginVersion: $androidGradlePluginVersion, '
      'fileExtension: $fileExtension',
    flutterUsage: usage,
  ).send();
  throwToolExit(
    'Gradle build failed to produce an $fileExtension file. '
    "It's likely that this file was generated under ${project.android.buildDirectory.path}, "
    "but the tool couldn't find it."
  );
}

void _createSymlink(String targetPath, String linkPath, FileSystem fileSystem) {
  final File targetFile = fileSystem.file(targetPath);
  if (!targetFile.existsSync()) {
    throwToolExit("The file $targetPath wasn't found in the local engine out directory.");
  }
  final File linkFile = fileSystem.file(linkPath);
  final Link symlink = linkFile.parent.childLink(linkFile.basename);
  try {
    symlink.createSync(targetPath, recursive: true);
  } on FileSystemException catch (exception) {
    throwToolExit(
      'Failed to create the symlink $linkPath->$targetPath: $exception'
    );
  }
}

String _getLocalArtifactVersion(String pomPath, FileSystem fileSystem) {
  final File pomFile = fileSystem.file(pomPath);
  if (!pomFile.existsSync()) {
    throwToolExit("The file $pomPath wasn't found in the local engine out directory.");
  }
  XmlDocument document;
  try {
    document = XmlDocument.parse(pomFile.readAsStringSync());
  } on XmlParserException {
    throwToolExit(
      'Error parsing $pomPath. Please ensure that this is a valid XML document.'
    );
  } on FileSystemException {
    throwToolExit(
      'Error reading $pomPath. Please ensure that you have read permission to this '
      'file and try again.');
  }
  final Iterable<XmlElement> project = document.findElements('project');
  assert(project.isNotEmpty);
  for (final XmlElement versionElement in document.findAllElements('version')) {
    if (versionElement.parent == project.first) {
      return versionElement.text;
    }
  }
  throwToolExit('Error while parsing the <version> element from $pomPath');
}

/// Returns the local Maven repository for a local engine build.
/// For example, if the engine is built locally at <home>/engine/src/out/android_release_unopt
/// This method generates symlinks in the temp directory to the engine artifacts
/// following the convention specified on https://maven.apache.org/pom.html#Repositories
Directory _getLocalEngineRepo({
  @required String engineOutPath,
  @required AndroidBuildInfo androidBuildInfo,
  @required FileSystem fileSystem,
}) {
  assert(engineOutPath != null);
  assert(androidBuildInfo != null);

  final String abi = _getAbiByLocalEnginePath(engineOutPath);
  final Directory localEngineRepo = fileSystem.systemTempDirectory
    .createTempSync('flutter_tool_local_engine_repo.');
  final String buildMode = androidBuildInfo.buildInfo.modeName;
  final String artifactVersion = _getLocalArtifactVersion(
    fileSystem.path.join(
      engineOutPath,
      'flutter_embedding_$buildMode.pom',
    ),
    fileSystem,
  );
  for (final String artifact in const <String>['pom', 'jar']) {
    // The Android embedding artifacts.
    _createSymlink(
      fileSystem.path.join(
        engineOutPath,
        'flutter_embedding_$buildMode.$artifact',
      ),
      fileSystem.path.join(
        localEngineRepo.path,
        'io',
        'flutter',
        'flutter_embedding_$buildMode',
        artifactVersion,
        'flutter_embedding_$buildMode-$artifactVersion.$artifact',
      ),
      fileSystem,
    );
    // The engine artifacts (libflutter.so).
    _createSymlink(
      fileSystem.path.join(
        engineOutPath,
        '${abi}_$buildMode.$artifact',
      ),
      fileSystem.path.join(
        localEngineRepo.path,
        'io',
        'flutter',
        '${abi}_$buildMode',
        artifactVersion,
        '${abi}_$buildMode-$artifactVersion.$artifact',
      ),
      fileSystem,
    );
  }
  for (final String artifact in <String>['flutter_embedding_$buildMode', '${abi}_$buildMode']) {
    _createSymlink(
      fileSystem.path.join(
        engineOutPath,
        '$artifact.maven-metadata.xml',
      ),
      fileSystem.path.join(
        localEngineRepo.path,
        'io',
        'flutter',
        artifact,
        'maven-metadata.xml',
      ),
      fileSystem,
    );
  }
  return localEngineRepo;
}

String _getAbiByLocalEnginePath(String engineOutPath) {
  String result = 'armeabi_v7a';
  if (engineOutPath.contains('x86')) {
    result = 'x86';
  } else if (engineOutPath.contains('x64')) {
    result = 'x86_64';
  } else if (engineOutPath.contains('arm64')) {
    result = 'arm64_v8a';
  }
  return result;
}

String _getTargetPlatformByLocalEnginePath(String engineOutPath) {
  String result = 'android-arm';
  if (engineOutPath.contains('x86')) {
    result = 'android-x86';
  } else if (engineOutPath.contains('x64')) {
    result = 'android-x64';
  } else if (engineOutPath.contains('arm64')) {
    result = 'android-arm64';
  }
  return result;
}