// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'dart:io';

import 'package:code_assets/code_assets.dart';
import 'package:hooks/hooks.dart';
import 'package:logging/logging.dart';

const objCFlags = ['-x', 'objective-c', '-fobjc-arc'];

const assetName = 'objective_c.dylib';

final logger = Logger('')
  ..level = Level.INFO
  ..onRecord.listen((record) {
    print('${record.level.name}: ${record.time}: ${record.message}');
  });

void main(List<String> args) async {
  await build(args, (input, output) async {
    if (!input.config.buildCodeAssets) {
      // Don't build any other asset types.
      return;
    }

    const supportedOSs = {OS.iOS, OS.macOS};
    final codeConfig = input.config.code;
    final os = codeConfig.targetOS;
    if (!supportedOSs.contains(os)) {
      // Nothing to do.
      return;
    }

    if (codeConfig.linkModePreference == LinkModePreference.static) {
      throw UnsupportedError('LinkModePreference.static is not supported.');
    }

    final packageName = input.packageName;
    final assetPath = input.outputDirectory.resolve(assetName);
    final srcDir = Directory.fromUri(input.packageRoot.resolve('src/'));
    final target = toTargetTriple(codeConfig);

    final cFiles = <String>[];
    final mFiles = <String>[];
    final hFiles = <String>[];
    for (final file in srcDir.listSync(recursive: true)) {
      if (file is File) {
        final path = file.path;
        if (path.endsWith('.c')) cFiles.add(path);
        if (path.endsWith('.m')) mFiles.add(path);
        if (path.endsWith('.h')) hFiles.add(path);
      }
    }

    final testMode = input.userDefines['include_test_utils'] == true;
    if (testMode) {
      mFiles.add(input.packageRoot.resolve('test/gc_inject.m').toFilePath());
      mFiles.add(
        input.packageRoot.resolve('test/reference_tracker.m').toFilePath(),
      );
    }

    final sysroot = sdkPath(codeConfig);
    final minVersion = minOSVersion(codeConfig);

    // TODO(https://github.com/flutter/flutter/issues/186856): Remove this
    // workaround and just use -target. Atm this is necessary for AOT testing.
    final useArm64e =
        testMode && codeConfig.targetArchitecture == Architecture.arm64;

    final cFlags = <String>[
      '-isysroot',
      sysroot,
      if (useArm64e) ...['-arch', 'arm64e'] else ...['-target', target],
      minVersion,
    ];
    final mFlags = [...cFlags, ...objCFlags];
    final linkFlags = cFlags;

    final builder = await Builder.create(input, input.packageRoot.toFilePath());

    final objectFiles = await Future.wait(<Future<String>>[
      for (final src in cFiles) builder.buildObject(src, cFlags),
      for (final src in mFiles) builder.buildObject(src, mFlags),
    ]);
    await builder.linkLib(objectFiles, assetPath.toFilePath(), linkFlags);

    output.dependencies.addAll(cFiles.map(Uri.file));
    output.dependencies.addAll(mFiles.map(Uri.file));
    output.dependencies.addAll(hFiles.map(Uri.file));

    output.assets.code.add(
      CodeAsset(
        package: packageName,
        name: assetName,
        file: assetPath,
        linkMode: DynamicLoadingBundled(),
      ),
    );
  });
}

class Builder {
  final String _compiler;
  final String _rootDir;
  final Uri _tempOutDir;
  Builder._(this._compiler, this._rootDir, this._tempOutDir);

  static Future<Builder> create(BuildInput input, String rootDir) async {
    return Builder._(
      await _findCompiler(input.config.code),
      rootDir,
      input.outputDirectory.resolve('obj/'),
    );
  }

  static Future<String> _findCompiler(CodeConfig codeConfig) async {
    final compiler = codeConfig.cCompiler?.compiler.toFilePath();
    if (compiler != null) {
      assert(await File(compiler).exists());
      logger.info('Using compiler $compiler from BuildInput.cCompiler.cc.');
      return compiler;
    }
    logger.info(
      'No compiler set in BuildInput.cCompiler.cc. Falling back to '
      'assuming clang is in the PATH.',
    );
    return 'clang';
  }

  Future<String> buildObject(String input, List<String> flags) async {
    assert(input.startsWith(_rootDir));
    final relativeInput = input.substring(_rootDir.length);
    final output = '${_tempOutDir.resolve(relativeInput).toFilePath()}.o';
    File(output).parent.createSync(recursive: true);
    await _compile([
      ...flags,
      '-c',
      input,
      '-fpic',
      '-gline-tables-only',
      '-I',
      'src',
    ], output);
    return output;
  }

  Future<void> linkLib(
    List<String> objects,
    String output,
    List<String> flags,
  ) => _compile([
    '-shared',
    '-Wl,-encryptable',
    '-undefined',
    'dynamic_lookup',
    ...flags,
    ...objects,
  ], output);

  Future<void> _compile(List<String> flags, String output) async {
    final args = [...flags, '-o', output];
    logger.info('Running: $_compiler ${args.join(" ")}');
    final proc = await Process.run(_compiler, args);
    logger.info(proc.stdout);
    logger.info(proc.stderr);
    if (proc.exitCode != 0) {
      exitCode = proc.exitCode;
      throw Exception('Command failed: $_compiler ${args.join(" ")}');
    }
    logger.info('Generated $output');
  }
}

String sdkPath(CodeConfig codeConfig) {
  final String target;
  if (codeConfig.targetOS == OS.iOS) {
    if (codeConfig.iOS.targetSdk == IOSSdk.iPhoneOS) {
      target = 'iphoneos';
    } else {
      target = 'iphonesimulator';
    }
  } else {
    assert(codeConfig.targetOS == OS.macOS);
    target = 'macosx';
  }
  return firstLineOfStdout('xcrun', ['--show-sdk-path', '--sdk', target]);
}

String firstLineOfStdout(String cmd, List<String> args) {
  final result = Process.runSync(cmd, args);
  assert(result.exitCode == 0);
  return (result.stdout as String)
      .split('\n')
      .where((line) => line.isNotEmpty)
      .first;
}

String minOSVersion(CodeConfig codeConfig) {
  if (codeConfig.targetOS == OS.iOS) {
    final targetVersion = codeConfig.iOS.targetVersion;
    return '-mios-version-min=$targetVersion';
  }
  assert(codeConfig.targetOS == OS.macOS);
  final targetVersion = codeConfig.macOS.targetVersion;
  return '-mmacos-version-min=$targetVersion';
}

String toTargetTriple(CodeConfig codeConfig) {
  final architecture = codeConfig.targetArchitecture;
  if (codeConfig.targetOS == OS.iOS) {
    return appleClangIosTargetFlags[architecture]![codeConfig.iOS.targetSdk]!;
  }
  assert(codeConfig.targetOS == OS.macOS);
  return appleClangMacosTargetFlags[architecture]!;
}

const appleClangMacosTargetFlags = {
  Architecture.arm64: 'arm64-apple-darwin',
  Architecture.x64: 'x86_64-apple-darwin',
};

const appleClangIosTargetFlags = {
  Architecture.arm64: {
    IOSSdk.iPhoneOS: 'arm64-apple-ios',
    IOSSdk.iPhoneSimulator: 'arm64-apple-ios-simulator',
  },
  Architecture.x64: {IOSSdk.iPhoneSimulator: 'x86_64-apple-ios-simulator'},
};