// Copyright 2013 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 = 2.6
part of engine;

/// The HTML engine used by the current browser.
enum BrowserEngine {
  /// The engine that powers Chrome, Samsung Internet Browser, UC Browser,
  /// Microsoft Edge, Opera, and others.
  blink,

  /// The engine that powers Safari.
  webkit,

  /// The engine that powers Firefox.
  firefox,

  /// The engine that powers Edge.
  edge,

  /// The engine that powers Internet Explorer 11.
  ie11,

  /// We were unable to detect the current browser engine.
  unknown,
}

/// Lazily initialized current browser engine.
BrowserEngine _browserEngine;

/// Override the value of [browserEngine].
///
/// Setting this to `null` lets [browserEngine] detect the browser that the
/// app is running on.
///
/// This is intended to be used for testing and debugging only.
BrowserEngine debugBrowserEngineOverride;

/// Returns the [BrowserEngine] used by the current browser.
///
/// This is used to implement browser-specific behavior.
BrowserEngine get browserEngine {
  if (debugBrowserEngineOverride != null) {
    return debugBrowserEngineOverride;
  }
  return _browserEngine ??= _detectBrowserEngine();
}

BrowserEngine _detectBrowserEngine() {
  final String vendor = html.window.navigator.vendor;
  final String agent = html.window.navigator.userAgent.toLowerCase();
  if (vendor == 'Google Inc.') {
    return BrowserEngine.blink;
  } else if (vendor == 'Apple Computer, Inc.') {
    return BrowserEngine.webkit;
  } else if (agent.contains('edge/')) {
    return BrowserEngine.edge;
  } else if (agent.contains('trident/7.0')) {
    return BrowserEngine.ie11;
  } else if (vendor == '' && agent.contains('firefox')) {
    // An empty string means firefox:
    // https://developer.mozilla.org/en-US/docs/Web/API/Navigator/vendor
    return BrowserEngine.firefox;
  }

  // Assume blink otherwise, but issue a warning.
  print('WARNING: failed to detect current browser engine.');
  return BrowserEngine.unknown;
}

/// Operating system where the current browser runs.
///
/// Taken from the navigator platform.
/// <https://developer.mozilla.org/en-US/docs/Web/API/NavigatorID/platform>
enum OperatingSystem {
  /// iOS: <http://www.apple.com/ios/>
  iOs,

  /// Android: <https://www.android.com/>
  android,

  /// Linux: <https://www.linux.org/>
  linux,

  /// Windows: <https://www.microsoft.com/windows/>
  windows,

  /// MacOs: <https://www.apple.com/macos/>
  macOs,

  /// We were unable to detect the current operating system.
  unknown,
}

/// Lazily initialized current operating system.
OperatingSystem _operatingSystem;

/// Returns the [OperatingSystem] the current browsers works on.
///
/// This is used to implement operating system specific behavior such as
/// soft keyboards.
OperatingSystem get operatingSystem {
  if (debugOperatingSystemOverride != null) {
    return debugOperatingSystemOverride;
  }
  return _operatingSystem ??= _detectOperatingSystem();
}

/// Override the value of [operatingSystem].
///
/// Setting this to `null` lets [operatingSystem] detect the real OS that the
/// app is running on.
///
/// This is intended to be used for testing and debugging only.
OperatingSystem debugOperatingSystemOverride;

OperatingSystem _detectOperatingSystem() {
  final String platform = html.window.navigator.platform;
  final String userAgent = html.window.navigator.userAgent;

  if (platform.startsWith('Mac')) {
    return OperatingSystem.macOs;
  } else if (platform.toLowerCase().contains('iphone') ||
      platform.toLowerCase().contains('ipad') ||
      platform.toLowerCase().contains('ipod')) {
    return OperatingSystem.iOs;
  } else if (userAgent.contains('Android')) {
    // The Android OS reports itself as "Linux armv8l" in
    // [html.window.navigator.platform]. So we have to check the user-agent to
    // determine if the OS is Android or not.
    return OperatingSystem.android;
  } else if (platform.startsWith('Linux')) {
    return OperatingSystem.linux;
  } else if (platform.startsWith('Win')) {
    return OperatingSystem.windows;
  } else {
    return OperatingSystem.unknown;
  }
}

/// List of Operating Systems we know to be working on laptops/desktops.
///
/// These devices tend to behave differently on many core issues such as events,
/// screen readers, input devices.
const Set<OperatingSystem> _desktopOperatingSystems = {
  OperatingSystem.macOs,
  OperatingSystem.linux,
  OperatingSystem.windows,
};

/// A flag to check if the current operating system is a laptop/desktop
/// operating system.
///
/// See [_desktopOperatingSystems].
bool get isDesktop => _desktopOperatingSystems.contains(operatingSystem);