using System;
using System.Collections.Generic;
using System.Linq;
using Serilog;
using ShareeBike.Model.Connector;
using ShareeBike.Repository.Response;
using ShareeBike.Repository.Response.Stations;
using ShareeBike.Repository.Response.Stations.Station;

namespace ShareeBike.Repository
{
	[Flags]
	public enum UpdateTarget
	{
		None = 0,
		BikesAvailableResponse = 1,
		BikesReservedOccupiedResponse = 2,
		StationsAvailableResponse = 4,
		All = BikesAvailableResponse | BikesReservedOccupiedResponse | StationsAvailableResponse
	}

	/// <summary>
	/// Manages station and bikes information.
	/// Bike is kept in a response- oriented way which is redundant an has to be synchronized for this reason when updated.
	/// </summary>
	public class CopriResponseModel
	{
		public CopriResponseModel(
			BikesAvailableResponse bikesAll,
			BikesReservedOccupiedResponse bikesReservedOccupied,
			StationsAvailableResponse stations)
		{
			BikesAll = bikesAll ?? new BikesAvailableResponse();
			BikesReservedOccupied = bikesReservedOccupied ?? new BikesReservedOccupiedResponse();
			Stations = stations ?? new StationsAvailableResponse();
		}

		/// <summary>
		/// Holds
		/// - part of/ or all available bikes and
		/// - part of/ or all reserved bikes of logged in user if user is logged in and
		/// - part of/ or all occupied bikes of logged in user if user is logged in.
		/// </summary>
		/// <remarks>
		/// Available bikes: Full information is only contained in <see cref="BikesAll"/>.
		/// Available bikes: Count of available bikes per station is kept in <see cref="Stations"/>.
		/// Reserved and occupied bikes: Are contained as well in <see cref="BikesReservedOccupied"/>.
		/// Reserved and occupied bikes: Are contained as well in <see cref="Stations"/>.
		/// </remarks>
		public BikesAvailableResponse BikesAll { get; private set; }

		/// <summary>
		/// Holds all reserved and occupied bikes of logged in user if not used without being logged in.
		/// </summary>
		/// <remarks>
		/// Reserved and occupied bikes: Are contained as well in <see cref="BikesAll"/>.
		/// Reserved and occupied bikes: Are contained as well in <see cref="Stations"/>.
		/// </remarks>
		public BikesReservedOccupiedResponse BikesReservedOccupied { get; private set; }

		/// <summary>
		/// All bike stations, count of available bikes at each station
		/// and all reserved and occupied bikes of logged in user if not used without being logged in.
		/// </summary>
		/// <remarks>
		/// Count of available bikes a each station: Information contained in <see cref="BikesAll"/>.
		/// Reserved and occupied bikes: Are contained as well in <see cref="BikesReservedOccupied"/>.
		/// </remarks>
		public StationsAvailableResponse Stations { get; private set; }

		/// <summary>
		/// Updates model from response.
		/// </summary>
		/// <param name="bikesAll">
		/// Holds
		/// - part of/ or all available bikes and
		/// - part of/ or all reserved bikes of logged in user if user is logged in and
		/// - part of/ or all occupied bikes of logged in user if user is logged in.
		/// </param>
		/// <returns>Parts of model which have to be updated.</returns>
		public UpdateTarget Update(
			BikesAvailableResponse bikesAllResponse,
			string stationId = null,
			string bikeId = null)
		{
			try
			{
				if (!string.IsNullOrEmpty(stationId))
				{
					return UpdateFromBikesAtStation(
						bikesAllResponse,
						stationId);
				}

				if (!string.IsNullOrEmpty(bikeId))
				{
					return UpdateFromBikesAtStation(
						bikesAllResponse,
						bikesAllResponse.bikes.Values.FirstOrDefault(x => x.bike.ToUpper() == bikeId.ToUpper())?.station);
				}

				return UpdateTarget.None;
			}
			catch (System.Exception ex)
			{
				Log.ForContext<CopriResponseModel>().Error(
					"Updating response model form {@Type}  for station id {@StationId} and bike id {BikeId} failed. {@Exception}",
					nameof(BikesAvailableResponse),
					stationId,
					bikeId,
					ex);
				return UpdateTarget.None;
			}
		}

		/// <summary>
		/// Updates cache from bike which changed rental state from available or reserved to booked.
		/// </summary>
		/// <param name="response"></param>
		public UpdateTarget Update(BikeInfoReservedOrBooked response)
		{
			try
			{
				var updateTarget = UpdateTarget.None;
				if (response == null || string.IsNullOrEmpty(response.bike))
				{
					// Can nor update station or remove bike 
					return updateTarget;
				}

				// Update station if required i.e. decrease count of available bikes if required.
				updateTarget = UpdateAvailableBikesCount(
					BikesAll.bikes.Values.FirstOrDefault(b => b.bike == response?.bike)?.station,
					i => i - 1, // Decrease count of available bikes.
					updateTarget);

				// A booked bike is no more available.
				BikesAll.bikes.Remove(response.bike);

				// Update Stations with latest reserved/ rented bike.
				Stations.bikes_occupied.Remove(response.bike);
				Stations.bikes_occupied.Add(response.bike, response);

				// Update BikesAll with latest reserved/ rented bike.
				BikesAll.bikes_occupied.Remove(response.bike);
				BikesAll.bikes_occupied.Add(response.bike, response);

				// Update BikesReservedOccupied with latest reserved/ rented bike.
				BikesReservedOccupied.bikes_occupied.Remove(response.bike);
				BikesReservedOccupied.bikes_occupied.Add(response.bike, response);

				return updateTarget | UpdateTarget.BikesAvailableResponse | UpdateTarget.BikesReservedOccupiedResponse;
			} catch (System.Exception ex)
			{
				Log.ForContext<CopriResponseModel>().Error(
					"Updating response model form {@Type} failed. {@Exception}",
					nameof(BikeInfoReservedOrBooked),
					ex);

				return UpdateTarget.None;
			}
		}

		/// <summary> Updates cache from bike which changed rental state (reservation/ booking canceled). </summary>
		public UpdateTarget Update(BookingActionResponse response)
		{
			try
			{
				if (response == null || string.IsNullOrEmpty(response.bike))
				{
					// Can nor update station or remove bike 
					return UpdateTarget.None;
				}

				// Remove available bike from Stations.
				Stations.bikes_occupied.Remove(response.bike);

				// Remove available bike from BikesAll.
				BikesAll.bikes_occupied.Remove(response.bike);

				// Remove available bike from BikesReservedOccupied.
				BikesReservedOccupied.bikes_occupied.Remove(response.bike);

				return UpdateTarget.StationsAvailableResponse | UpdateTarget.BikesAvailableResponse | UpdateTarget.BikesReservedOccupiedResponse;
			}
			catch (System.Exception ex)
			{
				Log.ForContext<CopriResponseModel>().Error(
					"Updating response model form {@Type} failed. {@Exception}",
					nameof(BookingActionResponse),
					ex);

				return UpdateTarget.None;
			}
		}

		/// <summary>
		/// Updates model from response.
		/// </summary>
		/// <param name="bikesAll">
		/// Holds
		/// - all available bikes located at given station and
		/// - all reserved bikes of logged in user if user is logged in located at given and
		/// - all occupied bikes of logged in user if user is logged in located at given .
		/// </param>
		/// <returns>Parts of model which have to be updated.</returns>
		private UpdateTarget UpdateFromBikesAtStation(
			BikesAvailableResponse bikesAllResponse,
			string stationId)
		{
			/// <summary>
			/// Synchronizes a dictionary with another, i.e.
			/// - adds values which do not yet exist
			/// - updates existing values with new ones and  
			/// - removes bikes which do no more exist
			/// </summary>
			/// <param name="source">Source dictionary to be read from.</param>
			/// <param name="target">Target directory to be written to.</param>
			void Synchonize<T>(
				ComparableDictionary<T> sourceDict,
				ComparableDictionary<T> targetDict,
				Action updateRequiredAction) where T : BikeInfoBase, IEquatable<T>
			{
				if (targetDict == null)
				{
					// Nothing to do if target dictionary is empty.
					return;
				}

				// Add/ update bikes
				foreach (var sourceBike in sourceDict ?? new ComparableDictionary<T>())
				{
					// Check if bikes already exists.
					var targetBike = targetDict.Values.FirstOrDefault(x => x.bike == sourceBike.Value.bike);
					if (targetBike != null)
					{
						// Check if bikes equals
						if (sourceBike.Value.Equals(targetBike))
						{
							// Bikes equal, process next.
							continue;
						}

						// Remove all bikes from target which part of source to be added later.
						targetDict.Remove(sourceBike.Key);
					}

					targetDict.Add(sourceBike.Key, sourceBike.Value);
					updateRequiredAction?.Invoke();
				}

				// Remove bikes from target dictionary which are no more at station
				var bikesToRemove = targetDict
					.Where(x => x.Value.station == stationId)
					.Where(x => sourceDict?.Values?.FirstOrDefault(y => y.station == stationId) == null);

				foreach (var bike in bikesToRemove)
				{
					targetDict.Remove(bike.Key);
					updateRequiredAction?.Invoke();
				}
			}

			if (BikesAll == bikesAllResponse
				|| bikesAllResponse == null)
			{
				return UpdateTarget.None;
			}

			var updateTarget = UpdateTarget.None;

			// Update bikes all by updating existing bikes and adding new ones.
			Synchonize(
				bikesAllResponse.bikes,
				BikesAll.bikes,
				() => { updateTarget |= UpdateTarget.BikesAvailableResponse; });

			Synchonize(
				bikesAllResponse.bikes_occupied,
				BikesAll.bikes_occupied,
				() => { updateTarget |= UpdateTarget.BikesAvailableResponse; });

			// Update stations property count of available bikes for selected station.
			UpdateAvailableBikesCount(
				bikesAllResponse.bikes.Count,
				Stations.stations.Values.FirstOrDefault(x => x.station == stationId),
				() => updateTarget |= UpdateTarget.StationsAvailableResponse);

			// Add/ update stations bikes reserved and stations bikes occupied.
			Synchonize(
				bikesAllResponse.bikes_occupied,
				Stations.bikes_occupied,
				() => updateTarget |= UpdateTarget.StationsAvailableResponse);

			// Add/ update reserved and occupied bikes.
			Synchonize(
				bikesAllResponse.bikes_occupied,
				BikesReservedOccupied.bikes_occupied,
				() => updateTarget |= UpdateTarget.BikesReservedOccupiedResponse);

			// Remove available bikes from bikes available response if there are: A bike reserved or occupied can not be available at the same time.
			Remove(
				bikesAllResponse.bikes_occupied.Values.Select(x => x.bike).ToList(),
				BikesAll.bikes,
				() => updateTarget |= UpdateTarget.BikesAvailableResponse);

			// Remove reserved and occupied bikes from bikes available response if there are: A bike available can not be reserved or occupied at the same time.
			Remove(
				bikesAllResponse.bikes.Values.Select(x => x.bike).ToList(),
				BikesAll.bikes_occupied,
				() => updateTarget |= UpdateTarget.BikesAvailableResponse);

			// Remove reserved and occupied bikes from stations response if there are: A bike available can not be reserved or occupied at the same time.
			Remove(
				bikesAllResponse.bikes.Values.Select(x => x.bike).ToList(),
				Stations.bikes_occupied,
				() => updateTarget |= UpdateTarget.StationsAvailableResponse);

			return updateTarget;
		}

		/// <summary>
		/// Updates model from reserved and occupied bikes.
		/// </summary>
		/// <param name="bikesReservedOccupiedResponse">Bikes to update with.</param>
		/// <returns>Parts of model which have to be updated.</returns>
		public UpdateTarget Update(BikesReservedOccupiedResponse bikesReservedOccupiedResponse)
		{
			try
			{
				if (bikesReservedOccupiedResponse == BikesReservedOccupied
					|| bikesReservedOccupiedResponse == null)
				{
					return UpdateTarget.None;
				}

				var updateTarget = UpdateTarget.BikesReservedOccupiedResponse;
				BikesReservedOccupied = bikesReservedOccupiedResponse; ;

				// Update bikes reserved or occupied from bikes reserved or occupied response.
				Write(
					bikesReservedOccupiedResponse.bikes_occupied,
					BikesAll.bikes_occupied,
					() => updateTarget |= UpdateTarget.BikesAvailableResponse);

				// Update stations from bikes reserved or occupied response.
				Write(
					bikesReservedOccupiedResponse.bikes_occupied,
					Stations.bikes_occupied,
					() => updateTarget |= UpdateTarget.StationsAvailableResponse);

				// Remove available bikes from bikes available response: A bike reserved/ occupied can not be available at the same time.
				Remove(
					bikesReservedOccupiedResponse.bikes_occupied.Values.Select(x => x.bike).ToList(),
					BikesAll.bikes,
					() => updateTarget |= UpdateTarget.BikesAvailableResponse);

				// Due to possible change of bikes available from bikes available response (step above), count of bikes from stations might need to be updated.
				UpdateAvailableBikesCount(
					BikesAll.bikes,
					Stations.stations,
					() => updateTarget |= UpdateTarget.StationsAvailableResponse);

				return updateTarget;
			}
			catch (System.Exception ex)
			{
				Log.ForContext<CopriResponseModel>().Error(
					"Updating response model form {@Type} failed. {@Exception}",
					nameof(BikesReservedOccupiedResponse),
					ex);

				return UpdateTarget.None;
			}
		}

		/// <summary>
		/// Updates model from stations response.
		/// </summary>
		/// <param name="stationsResponse">Response to update from.</param>
		/// <returns></returns>
		public UpdateTarget Update(StationsAvailableResponse stationsResponse)
		{
			try
			{ 
				// Remove bike from dictionary if located at a list of stations.
				// This can only be done randomly because only the count of bikes without bike ids is known (task #901).
				void LimitAvailableBikesCountByStation(
					IList<StationInfo> stations,
					ComparableBikeDictionary<BikeInfoAvailable> bikes,
					Action updateRequiredAction)
				{
					// Group available bikes by station.
					var groupedBikes = bikes.GroupBy(x => x.Value.station).ToList();

					foreach (var station in stations)
					{
						var bikesAtStation = groupedBikes.FirstOrDefault(x => x.Key == station.station);

						var toReviseCount = bikesAtStation?.ToList()?.Count ?? 0;
						if (string.IsNullOrEmpty(bikesAtStation?.Key)
							|| !station.TryGetBikesAvailableCount(out var trueCount)
							|| toReviseCount <= trueCount)
						{
							// Either
							// - there is no bikes at current station or
							// - invalid format detected
							// - count of bikes is ok
							continue;
						}

						var surplus = toReviseCount - trueCount;

						// There are move bikes available at current station in bikes available response than the station object reports.
						// Randomly remove surplus bikes.
						var keys = bikesAtStation.Select(x => x.Key).ToList();
						for (var i = 0; i < surplus; i++)
						{
							bikes.Remove(keys[i]);
						}

						updateRequiredAction?.Invoke();
					}
				}

				if (Stations == stationsResponse
					|| stationsResponse == null)
				{
					return UpdateTarget.None;
				}

				var updateTarget = UpdateTarget.StationsAvailableResponse;
				Stations = stationsResponse;

				// Ensure that bikes which have become occupied are no more in list of available bikes
				foreach (var bike in Stations.bikes_occupied.Values)
				{
					if (!BikesAll.bikes.ContainsKey(bike.bike)) continue;

					BikesAll.bikes.Remove(bike.bike);
				}

				// Ensure that there are not more bikes assigned to one station in bikes available object than there are reported in station response.
				// An example for this case is that a bike is brought to garage.
				LimitAvailableBikesCountByStation(
					Stations.stations.Values.ToList(),
					BikesAll.bikes,
					() => updateTarget |= UpdateTarget.BikesAvailableResponse);

				// Update bikes reserved and bikes occupied from stations response.
				Write(
					Stations.bikes_occupied,
					BikesAll.bikes_occupied,
					() => updateTarget |= UpdateTarget.BikesAvailableResponse);

				// Update bikes reserved or occupied from stations response.
				Write(
					Stations.bikes_occupied,
					BikesReservedOccupied.bikes_occupied,
					() => updateTarget |= UpdateTarget.BikesReservedOccupiedResponse);

				return updateTarget;
			}
			catch (System.Exception ex)
			{
				Log.ForContext<CopriResponseModel>().Error(
					"Updating response model form {@Type} failed. {@Exception}",
					nameof(StationsAvailableResponse),
					ex);

				return UpdateTarget.None;
			}
		}

		/// <summary>
		/// Removes bikes from a dictionary.
		/// </summary>
		/// <typeparam name="T">Type of dictionary values to remove.</typeparam>
		/// <param name="bikesToRemove">Bikes to remove.</param>
		/// <param name="target">Dictionary to removed bikes from.</param>
		/// <param name="updateRequiredAction">Action to be invoked if any bike gets removed from dictionary.</param>
		private void Remove<T>(
			IList<string> bikesToRemove,
			ComparableDictionary<T> target,
			Action updateRequiredAction) where T : BikeInfoBase
		{
			if (target == null)
			{
				// Nothing to do.
				return;
			}

			foreach (var bike in bikesToRemove)
			{
				if (!target.Remove(bike))
				{
					continue;
				}

				updateRequiredAction?.Invoke();
			}
		}

		/// <summary>
		/// Writes a dictionary to another if required.
		/// </summary>
		/// <param name="source">Source dictionary to be read from.</param>
		/// <param name="target">Target directory to be written to.</param>
		void Write(
			ComparableDictionary<BikeInfoReservedOrBooked> source,
			ComparableDictionary<BikeInfoReservedOrBooked> target,
			Action updateRequiredAction)
		{
			if (target == null || source == target)
			{
				return;
			}

			target.Clear();

			foreach (var bike in source ?? new ComparableBikeDictionary<BikeInfoReservedOrBooked>())
			{
				target.Add(bike.Key, bike.Value);
			}

			updateRequiredAction?.Invoke();
		}

		private void UpdateAvailableBikesCount(
			ComparableBikeDictionary<BikeInfoAvailable> bikesAvailable,
			ComparableDictionary<StationInfo> stations,
			Action updateRequiredAction)
		{
			foreach (var station in stations.Values)
			{
				UpdateAvailableBikesCount(
					bikesAvailable.Values.Where(x => x.station == station.station).Count(),
					station,
					updateRequiredAction);
			}
		}

		/// <summary>
		/// Updates the count of available bikes of a given station.
		/// </summary>
		/// <param name="id">Id of the station to update count for.</param>
		/// <param name="countDelegate">Delegate to return the new count.</param>
		/// <param name="updateRequiredAction">Update action required</param>
		private UpdateTarget UpdateAvailableBikesCount(
			string id,
			Func<int, int> countDelegate,
			UpdateTarget currentUpdateTarget)
		{
			if (string.IsNullOrEmpty(id))
			{
				// Bike was not available before.
				return currentUpdateTarget;
			}

			var station = Stations.stations.Values.FirstOrDefault(s => s.station == id);
			if (station == null)
			{
				// There is no matching station.
				return currentUpdateTarget;
			}

			// Decrement count of stations.
			station.SetBikesAvailableCount(countDelegate(station.GetBikesAvailableCount() ?? 1));
			return currentUpdateTarget | UpdateTarget.StationsAvailableResponse;
		}
		private void UpdateAvailableBikesCount(
			int bikesAvailableCount,
			StationInfo station,
			Action updateRequiredAction)
		{
			if (station == null
				|| !station.TryGetBikesAvailableCount(out var targetBikesCount)
				|| targetBikesCount == bikesAvailableCount)
			{
				// Either
				// - there is no matching station or
				// - station count if not numeric or 
				// - count matches
				return;
			}

			station.SetBikesAvailableCount(bikesAvailableCount);
			updateRequiredAction?.Invoke();
		}
	}
}