// Copyright 2016 The Chromium 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:io';
import 'dart:math' as math;

import 'package:path/path.dart' as path;

import 'utils.dart';

typedef Future<Adb> AdbGetter();

/// Get an instance of [Adb].
///
/// See [realAdbGetter] for signature. This can be overwritten for testing.
AdbGetter adb = realAdbGetter;

Adb _currentDevice;

/// Picks a random Android device out of connected devices and sets it as
/// [_currentDevice].
Future<Null> pickNextDevice() async {
  List<Adb> allDevices =
      (await Adb.deviceIds).map((String id) => new Adb(deviceId: id)).toList();

  if (allDevices.length == 0) throw 'No Android devices detected';

  // TODO(yjbanov): filter out and warn about those with low battery level
  _currentDevice = allDevices[new math.Random().nextInt(allDevices.length)];
}

Future<Adb> realAdbGetter() async {
  if (_currentDevice == null) await pickNextDevice();
  return _currentDevice;
}

/// Gets the ID of an unlocked device, unlocking it if necessary.
// TODO(yjbanov): abstract away iOS from Android.
Future<String> getUnlockedDeviceId({ bool ios: false }) async {
  if (ios) {
    // We currently do not have a way to lock/unlock iOS devices, or even to
    // pick one out of many. So we pick the first random iPhone and assume it's
    // already unlocked. For now we'll just keep them at minimum screen
    // brightness so they don't drain battery too fast.
    List<String> iosDeviceIds =
        grep('UniqueDeviceID', from: await eval('ideviceinfo', <String>[]))
            .map((String line) => line.split(' ').last)
            .toList();

    if (iosDeviceIds.isEmpty) throw 'No connected iOS devices found.';

    return iosDeviceIds.first;
  }

  Adb device = await adb();
  await device.unlock();
  return device.deviceId;
}

/// Android Debug Bridge (`adb`) client that exposes a subset of functions
/// relevant to on-device testing.
class Adb {
  Adb({ this.deviceId });

  final String deviceId;

  // Parses information about a device. Example:
  //
  // 015d172c98400a03       device usb:340787200X product:nakasi model:Nexus_7 device:grouper
  static final RegExp _kDeviceRegex = new RegExp(r'^(\S+)\s+(\S+)(.*)');

  /// Reports connection health for every device.
  static Future<Map<String, HealthCheckResult>> checkDevices() async {
    Map<String, HealthCheckResult> results = <String, HealthCheckResult>{};
    for (String deviceId in await deviceIds) {
      try {
        Adb device = new Adb(deviceId: deviceId);
        // Just a smoke test that we can read wakefulness state
        // TODO(yjbanov): also check battery level
        await device._getWakefulness();
        results['android-device-$deviceId'] = new HealthCheckResult.success();
      } catch (e, s) {
        results['android-device-$deviceId'] = new HealthCheckResult.error(e, s);
      }
    }
    return results;
  }

  /// Kills the `adb` server causing it to start a new instance upon next
  /// command.
  ///
  /// Restarting `adb` helps with keeping device connections alive. When `adb`
  /// runs non-stop for too long it loses connections to devices.
  static Future<Null> restart() async {
    await exec(adbPath, <String>['kill-server'], canFail: false);
  }

  /// List of device IDs visible to `adb`.
  static Future<List<String>> get deviceIds async {
    List<String> output =
        (await eval(adbPath, <String>['devices', '-l'], canFail: false))
            .trim()
            .split('\n');
    List<String> results = <String>[];
    for (String line in output) {
      // Skip lines like: * daemon started successfully *
      if (line.startsWith('* daemon ')) continue;

      if (line.startsWith('List of devices')) continue;

      if (_kDeviceRegex.hasMatch(line)) {
        Match match = _kDeviceRegex.firstMatch(line);

        String deviceID = match[1];
        String deviceState = match[2];

        if (!const <String>['unauthorized', 'offline'].contains(deviceState)) {
          results.add(deviceID);
        }
      } else {
        throw 'Failed to parse device from adb output: $line';
      }
    }

    return results;
  }

  /// Whether the device is awake.
  Future<bool> isAwake() async {
    return await _getWakefulness() == 'Awake';
  }

  /// Whether the device is asleep.
  Future<bool> isAsleep() async {
    return await _getWakefulness() == 'Asleep';
  }

  /// Wake up the device if it is not awake using [togglePower].
  Future<Null> wakeUp() async {
    if (!(await isAwake())) await togglePower();
  }

  /// Send the device to sleep mode if it is not asleep using [togglePower].
  Future<Null> sendToSleep() async {
    if (!(await isAsleep())) await togglePower();
  }

  /// Sends `KEYCODE_POWER` (26), which causes the device to toggle its mode
  /// between awake and asleep.
  Future<Null> togglePower() async {
    await shellExec('input', const <String>['keyevent', '26']);
  }

  /// Unlocks the device by sending `KEYCODE_MENU` (82).
  ///
  /// This only works when the device doesn't have a secure unlock pattern.
  Future<Null> unlock() async {
    await wakeUp();
    await shellExec('input', const <String>['keyevent', '82']);
  }

  /// Retrieves device's wakefulness state.
  ///
  /// See: https://android.googlesource.com/platform/frameworks/base/+/master/core/java/android/os/PowerManagerInternal.java
  Future<String> _getWakefulness() async {
    String powerInfo = await shellEval('dumpsys', <String>['power']);
    String wakefulness =
        grep('mWakefulness=', from: powerInfo).single.split('=')[1].trim();
    return wakefulness;
  }

  /// Executes [command] on `adb shell` and returns its exit code.
  Future<Null> shellExec(String command, List<String> arguments,
      { Map<String, String> env }) async {
    await exec(adbPath, <String>['shell', command]..addAll(arguments),
        env: env, canFail: false);
  }

  /// Executes [command] on `adb shell` and returns its standard output as a [String].
  Future<String> shellEval(String command, List<String> arguments,
      { Map<String, String> env }) {
    return eval(adbPath, <String>['shell', command]..addAll(arguments),
        env: env, canFail: false);
  }
}

/// Path to the `adb` executable.
String get adbPath {
  String androidHome = Platform.environment['ANDROID_HOME'];

  if (androidHome == null)
    throw 'ANDROID_HOME environment variable missing. This variable must '
        'point to the Android SDK directory containing platform-tools.';

  File adbPath = file(path.join(androidHome, 'platform-tools/adb'));

  if (!adbPath.existsSync()) throw 'adb not found at: $adbPath';

  return adbPath.absolute.path;
}