sdk/pkg/frontend_server_client/example/web_client.dart

// Copyright 2020 The Dart 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:convert';
import 'dart:io';

import 'package:async/async.dart';
import 'package:frontend_server_client/frontend_server_client.dart';
import 'package:path/path.dart' as p;
import 'package:shelf/shelf.dart';
import 'package:shelf/shelf_io.dart' as shelf_io;
import 'package:shelf_packages_handler/shelf_packages_handler.dart';
import 'package:shelf_static/shelf_static.dart';

void main(List<String> args) async {
  // Change to package root so relative paths work in CI
  final scriptDir = p.dirname(p.fromUri(Platform.script));
  final packageRoot = p.dirname(scriptDir);
  Directory.current = packageRoot;

  try {
    watch.start();
    if (args.isNotEmpty) {
      throw ArgumentError('No command line args are supported');
    }

    _print('compiling the dart sdk');
    final sdkCompileResult = await Process.run(Platform.resolvedExecutable, [
      'compile',
      'js-dev',
      '--multi-root-scheme=org-dartlang-sdk',
      '--modules=amd',
      '--module-name=dart_sdk',
      '-o',
      dartSdkJs,
      p.url.join(sdkDir, sdkKernelPath),
    ]);
    if (sdkCompileResult.exitCode != 0) {
      _print(
        'Failed to compile the dart sdk to JS:\n'
        '${sdkCompileResult.stdout}\n'
        '${sdkCompileResult.stderr}',
      );
      exit(sdkCompileResult.exitCode);
    }

    _print('starting frontend server');
    final packagesPath = findNearestPackageConfigPath();
    final client = await DartDevcFrontendServerClient.start(
      'org-dartlang-root:///$app',
      outputDill,
      // Use an absolute filesystem root so org-dartlang-root:/// URIs resolve reliably in CI
      fileSystemRoots: [Directory.current.path],
      fileSystemScheme: 'org-dartlang-root',
      platformKernel: p.toUri(sdkKernelPath).toString(),
      packagesJson: packagesPath ?? '.dart_tool/package_config.json',
      verbose: true,
    );

    _print('compiling $app');
    await client.compile([]);
    client.accept();
    _print('done compiling $app');

    _print('starting shelf server');
    final cascade = Cascade()
        .add(_clientHandler(client))
        .add(createStaticHandler(Directory.current.path))
        .add(createFileHandler(dartSdkJs, url: 'example/app/dart_sdk.js'))
        .add(
          createFileHandler(
            p.join(
              sdkDir,
              'lib',
              'dev_compiler',
              'web',
              'dart_stack_trace_mapper.js',
            ),
            url: 'example/app/dart_stack_trace_mapper.js',
          ),
        )
        .add(
          createFileHandler(
            p.join(sdkDir, 'lib', 'dev_compiler', 'amd', 'require.js'),
            url: 'example/app/require.js',
          ),
        )
        .add(packagesDirHandler());
    final server = await shelf_io.serve(cascade.handler, 'localhost', 8080);
    _print('server ready');

    // The file we will be editing in the repl
    final appFile = File(app);
    final originalContent = await appFile.readAsString();
    final appLines = const LineSplitter().convert(originalContent);
    final getterText = 'String get message =>';
    final messageLine = appLines.indexWhere(
      (line) => line.startsWith(getterText),
    );

    final stdinQueue = StreamQueue(
      stdin.transform(utf8.decoder).transform(const LineSplitter()),
    );
    _prompt();
    while (await stdinQueue.hasNext) {
      final newMessage = await stdinQueue.next;
      if (newMessage == 'quit') {
        await server.close();
        await stdinQueue.cancel();
        break;
      } else if (newMessage == 'reset') {
        print('resetting');
        client.reset();
        _print('restoring $app');
        await appFile.writeAsString(originalContent);
      } else {
        _print('editing $app');
        appLines[messageLine] = '$getterText "$newMessage";';
        final newContent = appLines.join('\n');
        await appFile.writeAsString(newContent);

        _print('recompiling $app with edits');
        final result = await client.compile([
          Uri.parse('org-dartlang-root:///$app'),
        ]);
        if (result.errorCount > 0) {
          print('Compile errors: \n${result.compilerOutputLines.join('\n')}');
          await client.reject();
        } else {
          _print('Recompile succeeded for $app');
          client.accept();
          // TODO: support hot restart
          print('reload app to see the new message');
        }
      }

      _prompt();
    }

    _print('restoring $app');
    await appFile.writeAsString(originalContent);
    _print('exiting');
    await client.shutdown();
  } finally {
    Directory(p.join('.dart_tool', 'out')).deleteSync(recursive: true);
  }
}

Handler _clientHandler(DartDevcFrontendServerClient client) {
  return (Request request) {
    var path = request.url.path;
    final packagesIndex = path.indexOf('/packages/');
    if (packagesIndex > 0) {
      path = request.url.path.substring(packagesIndex);
    } else {
      path = request.url.path;
    }
    if (!path.startsWith('/')) path = '/$path';
    if (path.endsWith('.dart.js') && path != '/example/app/main.dart.js') {
      path = path.replaceFirst('.dart.js', '.dart.lib.js', path.length - 8);
    }
    final assetBytes = client.assetBytes(path);
    if (assetBytes == null) return Response.notFound('path not found');
    return Response.ok(
      assetBytes,
      headers: {HttpHeaders.contentTypeHeader: 'application/javascript'},
    );
  };
}

void _print(String message) {
  print('${watch.elapsed}: $message');
}

void _prompt() => stdout.write(
  'Enter a new message to print and recompile, or type `quit` to exit:',
);

final app = 'example/app/main.dart';
final dartSdkJs = p.join('.dart_tool', 'out', 'dart_sdk.js');
final outputDill = p.join('.dart_tool', 'out', 'example_app.dill');
final sdkDir = p.dirname(p.dirname(Platform.resolvedExecutable));
final sdkKernelPath = p.join(sdkDir, 'lib', '_internal', 'ddc_platform.dill');
final watch = Stopwatch();