using System;
using System.Threading;
using System.Threading.Tasks;
using Serilog;
using TINK.Model.Device;
using Xamarin.Essentials;

namespace TINK.Services.Geolocation
{
	public class LastKnownGeolocationService : IGeolocationService
	{
		private IGeolodationDependent Dependent { get; }

		public LastKnownGeolocationService(IGeolodationDependent dependent)
		{
			Dependent = dependent;
		}

		/// <summary> Gets the current location.</summary>
		/// <param name="cancelationToken">Token to cancel request for geolocation.</param>
		/// <param name="timeStamp">Time when geolocation is of interest. Is used to determine whether cached geolocation can be used or not.</param>
		public async Task<IGeolocation> GetAsync(CancellationToken? cancelationToken = null, DateTime? timeStamp = null)
		{
			IGeolocation location;
			try
			{
				location = (await Xamarin.Essentials.Geolocation.GetLastKnownLocationAsync()).ToGeolocation();
			}
			catch (FeatureNotSupportedException fnsEx)
			{
				// Handle not supported on device exception
				Log.ForContext<LastKnownGeolocationService>().Error("Retrieving Geolocation not supported on device. {Exception}", fnsEx);
				throw new Exception("Abfrage Standort nicht möglich auf Gerät.", fnsEx);
			}
			catch (FeatureNotEnabledException fneEx)
			{
				// Handle not enabled on device exception
				Log.ForContext<LastKnownGeolocationService>().Error("Retrieving Geolocation not enabled on device. {Exception}", fneEx);
				throw new Exception("Abfrage Standort nicht aktiviert auf Gerät.", fneEx);
			}
			catch (PermissionException pEx)
			{
				// Handle permission exception
				Log.ForContext<LastKnownGeolocationService>().Error("Retrieving Geolocation not permitted on device. {Exception}", pEx);
				throw new Exception("Berechtiung für Abfrage Standort nicht erteilt für App.", pEx);
			}
			catch (Exception ex)
			{
				// Unable to get location
				Log.ForContext<LastKnownGeolocationService>().Error("Retrieving Geolocation failed. {Exception}", ex);
				throw new Exception("Abfrage Standort fehlgeschlagen.", ex);
			}

			if (location != null // Cached location is available.
				&& (timeStamp == null || timeStamp.Value.Subtract(location.Timestamp.DateTime) < MaxAge))
			{
				// No time stamp available or location not too old.
				return location;
			}

			return await new GeolocationAccuracyMediumService(Dependent).GetAsync(cancelationToken, timeStamp);
		}

		/// <summary> If true location data returned is simulated.</summary>
		public bool IsSimulation { get => false; }

		/// <summary> Maximum age allowed for location info. </summary>
		public TimeSpan MaxAge => new TimeSpan(0, 3 /*minutes*/, 0);

		public bool IsGeolcationEnabled => Dependent.IsGeolcationEnabled;
	}
}