// 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 'package:flutter_devicelab/framework/devices.dart';
import 'package:flutter_devicelab/framework/framework.dart';
import 'package:flutter_devicelab/framework/task_result.dart';
import 'package:flutter_devicelab/framework/utils.dart';
import 'package:path/path.dart' as path;
import 'package:xml/xml.dart';

Future<TaskResult> run() async {
  deviceOperatingSystem = DeviceOperatingSystem.macos;

  final Directory appDir = dir(path.join(flutterDirectory.path, 'examples/hello_world'));
  final String plistPath = path.join(appDir.path, 'macos', 'Runner', 'Info.plist');
  final plistFile = File(plistPath);

  if (!plistFile.existsSync()) {
    return TaskResult.failure('Info.plist not found at $plistPath');
  }

  var res = TaskResult.success(null);

  try {
    await inDirectory(appDir, () async {
      await flutter('packages', options: <String>['get']);

      // Step 1: Test without flag
      final Process process1 = await startFlutter(
        'run',
        options: <String>['--enable-impeller', '-d', 'macos'],
      );

      final completer1 = Completer<void>();
      var sawMetalMessage = false;

      final StreamSubscription<String> subscription1 = process1.stdout
          .transform(utf8.decoder)
          .transform(const LineSplitter())
          .listen((String line) {
            print('[STDOUT 1]: $line');
            if (line.contains('Using the Impeller rendering backend (Metal).')) {
              sawMetalMessage = true;
              if (!completer1.isCompleted) {
                completer1.complete();
              }
            }
          });

      await Future.any(<Future<void>>[
        completer1.future,
        Future<void>.delayed(const Duration(minutes: 2)),
      ]);

      process1.stdin.writeln('q');
      await process1.exitCode;
      await subscription1.cancel();

      if (!sawMetalMessage) {
        res = TaskResult.failure(
          'Did not see "Using the Impeller rendering backend (Metal)." in output',
        );
        return; // Exit early if first step fails
      }

      // Step 2: Modify Info.plist to enable SDFS
      final String xmlStr = plistFile.readAsStringSync();
      final xmlDoc = XmlDocument.parse(xmlStr);
      final XmlElement dictNode = xmlDoc.findAllElements('dict').first;

      dictNode.children.add(
        XmlElement(XmlName('key'), <XmlAttribute>[], <XmlNode>[
          XmlText('FLTEnableSDFs'),
        ], /*isSelfClosing=*/ false),
      );
      dictNode.children.add(XmlElement(XmlName('true')));

      plistFile.writeAsStringSync(xmlDoc.toXmlString(pretty: true, indent: '    '));

      // Run again with flag
      final Process process2 = await startFlutter(
        'run',
        options: <String>['--enable-impeller', '-d', 'macos'],
      );

      final completer2 = Completer<void>();
      var sawSdfsMessage = false;

      final StreamSubscription<String> subscription2 = process2.stdout
          .transform(utf8.decoder)
          .transform(const LineSplitter())
          .listen((String line) {
            print('[STDOUT 2]: $line');
            if (line.contains('Using the Impeller rendering backend (MetalSDF).')) {
              sawSdfsMessage = true;
              if (!completer2.isCompleted) {
                completer2.complete();
              }
            }
          });

      await Future.any(<Future<void>>[
        completer2.future,
        Future<void>.delayed(const Duration(minutes: 2)),
      ]);

      process2.stdin.writeln('q');
      await process2.exitCode;
      await subscription2.cancel();

      if (!sawSdfsMessage) {
        res = TaskResult.failure(
          'Did not see "Using the Impeller rendering backend (MetalSDF)." in output',
        );
      }
    });
  } catch (e) {
    res = TaskResult.failure('Test failed with exception: $e');
  } finally {
    // Restore Info.plist
    if (plistFile.existsSync()) {
      await exec('git', <String>['checkout', plistPath]);
    }
  }

  return res;
}

Future<void> main() async {
  await task(run);
}