// Copyright 2017 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 UIKit
import Flutter

@UIApplicationMain
@objc class AppDelegate: FlutterAppDelegate, FlutterStreamHandler {
  private var eventSink: FlutterEventSink?

  override func application(
    _ application: UIApplication,
    didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
    GeneratedPluginRegistrant.register(with: self)
    let controller: FlutterViewController = window?.rootViewController as! FlutterViewController
    let batteryChannel = FlutterMethodChannel(name: "samples.flutter.io/battery",
                                              binaryMessenger: controller)
    batteryChannel.setMethodCallHandler({
      (call: FlutterMethodCall, result: FlutterResult) -> Void in
      if "getBatteryLevel" == call.method {
        self.receiveBatteryLevel(result: result)
      } else {
        result(FlutterMethodNotImplemented)
      }
    })

    let chargingChannel = FlutterEventChannel(name: "samples.flutter.io/charging",
                                              binaryMessenger: controller)
    chargingChannel.setStreamHandler(self)
    return super.application(application, didFinishLaunchingWithOptions: launchOptions)
  }

  private func receiveBatteryLevel(result: FlutterResult) {
    let device = UIDevice.current
    device.isBatteryMonitoringEnabled = true
    if device.batteryState == UIDeviceBatteryState.unknown {
      result(FlutterError(code: "UNAVAILABLE",
                          message: "Battery info unavailable",
                          details: nil))
    } else {
      result(Int(device.batteryLevel * 100))
    }
  }

  public func onListen(withArguments arguments: Any?,
                       eventSink: @escaping FlutterEventSink) -> FlutterError? {
    self.eventSink = eventSink
    UIDevice.current.isBatteryMonitoringEnabled = true
    sendBatteryStateEvent()
    NotificationCenter.default.addObserver(
      self,
      selector: #selector(onBatteryStateDidChange),
      name: NSNotification.Name.UIDeviceBatteryStateDidChange,
      object: nil)
    return nil
  }

  @objc private func onBatteryStateDidChange(notification: NSNotification) {
    sendBatteryStateEvent()
  }

  private func sendBatteryStateEvent() {
    if eventSink == nil {
      return
    }

    let state = UIDevice.current.batteryState
    switch state {
    case UIDeviceBatteryState.full:
      eventSink!("charging")
    case UIDeviceBatteryState.charging:
      eventSink!("charging")
    case UIDeviceBatteryState.unplugged:
      eventSink!("discharging")
    default:
      eventSink!(FlutterError(code: "UNAVAILABLE",
                              message: "Charging status unavailable",
                              details: nil))
    }
  }

  public func onCancel(withArguments arguments: Any?) -> FlutterError? {
    NotificationCenter.default.removeObserver(self)
    eventSink = nil
    return nil
  }
}