Smart Stickers

import CoreLocation
import Foundation

/// A `WeatherProvider` for the https://openweathermap.org service.
@objcMembers @objc(PESDKOpenWeatherProvider) public class OpenWeatherProvider: NSObject, WeatherProvider, CLLocationManagerDelegate {

  // MARK: - Properties

  /// The used API key. If `nil` or empty the sample API is used.
  public let apiKey: String?

  /// The minimum update interval to request new data from the service. It defaults to one hour.
  public var updateInterval: TimeInterval = 60 * 60

  // MARK: - Initializers

  /// Create a new `OpenWeatherProvider`.
  /// - Parameters:
  ///   - apiKey: The used API key. If `nil` or empty the sample API is used.
  ///   - unit: The temperature format that should be used for displaying temperature measurements to the user.
  public init(apiKey: String?, unit: TemperatureFormat) {
    self.apiKey = apiKey
    temperatureFormat = unit
    super.init()
    locationManager.startUpdatingLocation()
  }

  deinit {
    locationManager.stopUpdatingLocation()
  }

  // MARK: - WeatherProvider

  private var url: URL? {
    guard let location = lastLocation else {
      return nil
    }
    let domain, appid: String
    if let apiKey = apiKey, !apiKey.isEmpty {
      domain = "api.openweathermap.org"
      appid = apiKey
    } else {
      domain = "samples.openweathermap.org"
      appid = "_"
    }
    let lat = location.coordinate.latitude
    let lon = location.coordinate.longitude
    let url = "https://\(domain)/data/2.5/weather?lat=\(lat)&lon=\(lon)&appid=\(appid)"
    return URL(string: url)
  }

  private var lastTemperature: Temperature?
  private var lastUpdate: Date?
  private var lastTask: URLSessionTask?

  private struct WeatherData: Codable {
    let main: Main
  }

  private struct Main: Codable {
    let temp: Double
  }

  /// The temperature format that should be used for displaying temperature measurements to the user.
  public var temperatureFormat: TemperatureFormat

  /// The temperature measurement.
  public var temperature: Temperature? { lastTemperature }

  /// Request to update the weather data.
  public func updateData() {
    guard let url = url else {
      return
    }
    if let lastTask = lastTask {
      switch lastTask.state {
      case .running:
        return
      case .suspended:
        lastTask.resume()
        return
      default:
        break
      }
    }
    if let lastUpdate = lastUpdate, lastUpdate.timeIntervalSinceNow < updateInterval {
      return
    }

    let session = URLSession.shared
    let task = session.dataTask(with: url) { data, _, _ in
      guard let data = data, let weatherData = try? JSONDecoder().decode(WeatherData.self, from: data) else {
        return
      }
      DispatchQueue.main.async {
        self.lastUpdate = Date()
        self.lastTemperature = Temperature(value: weatherData.main.temp, unit: .kelvin)
      }
    }
    task.resume()
    lastTask = task
  }

  // MARK: - CoreLocation

  private var lastLocation: CLLocation?

  private lazy var locationManager: CLLocationManager = {
    let locationManager = CLLocationManager()
    locationManager.delegate = self
    locationManager.distanceFilter = 10
    return locationManager
  }()

  /// When this closure is called, the SDK has determined that location access has not been granted
  /// to the host app yet. Within this closure you should then request appropriate permissions from
  /// the passed in `CLLocationManager` object. Location access is used to request weather data
  /// for the current location for weather stickers.
  ///
  /// - Attention: Starting Spring 2019, all apps submitted to the App Store that access user data
  ///   are required to include a purpose string as soon as location permissions requests appear
  ///   somewhere in the binary. Since we do not want to force developers integrating the SDK into
  ///   their app to include a purpose string even with weather stickers disabled, this closure was
  ///   introduced, so that developers can decide for themselves if it is appropriate to request
  ///   location access. Simply set this property like this:
  ///   ````
  ///   openWeatherProvider.locationAccessRequestClosure = { locationManager in
  ///     locationManager.requestWhenInUseAuthorization()
  ///   }
  ///   ````
  public var locationAccessRequestClosure: ((CLLocationManager) -> Void)? {
    didSet {
      if CLLocationManager.authorizationStatus() == .notDetermined {
        locationAccessRequestClosure?(locationManager)
      }
    }
  }

  /// :nodoc:
  public func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
    lastLocation = locations.last
    updateData()
  }
}