using System;
using System.Collections.Generic;
using System.Linq;
using Xamarin.Essentials;

namespace TINK.Model
{
	/// <summary>
	/// Single whats new entry.
	/// </summary>
	public struct WhatsNewEntry
	{
		public readonly Version Version;
		public readonly string Message;
		public readonly IEnumerable<AppFlavor> Flavors;
		public readonly IEnumerable<DevicePlatform> Platforms;

		public WhatsNewEntry(
			string message,
			Version version,
			IEnumerable<AppFlavor> concernedFlavors,
			IEnumerable<DevicePlatform> concernedPlatforms)
		{
			Version = version;
			Message = message;
			Flavors = concernedFlavors;
			Platforms = concernedPlatforms;
		}
	}

	/// <summary>
	/// Manges whats new messages.
	/// </summary>
	public class WhatsNewMessages : List<WhatsNewEntry>, IEnumerable<WhatsNewEntry>
	{
		/// <summary>
		/// Add a new entry to whats new messages
		/// </summary>
		/// <param name="version">When change was introduced.</param>
		/// <param name="message">Text describing </param>
		/// <param name="concernedFlavors">List of apps to which the message appiles. Null or empty list if message applies to all flavors.</param>
		/// <param name="concernedPlatforms">List of platforms to which the message applies. Null or empty list if message applies to all platorms.</param>
		public void Add(
			Version version,
			string message,
			IEnumerable<AppFlavor> concernedFlavors = null,
			IEnumerable<DevicePlatform> concernedPlatforms = null)
		{
			if (string.IsNullOrEmpty(message?.Trim()))
			{
				// Igore enties which hold not text.
				return;
			}

			if (version == null || version == new Version())
			{
				// Igore enties which hold an invalid version.
				return;
			}

			Add(new WhatsNewEntry(
				message,
				version,
				concernedFlavors ?? new List<AppFlavor>(),
				concernedPlatforms ?? new List<DevicePlatform>()));
		}

		/// <summary>
		/// Filters messges for a given version of the app, a flavor of app and a given environment from object which holds all messages.
		/// </summary>
		/// <remarks>
		/// A log message might apply to all app flavors (sharee.bike, Lastenrad Bayern, ...) all OS and ís assigned to a version.
		/// </remarks>
		/// <param name="flavor">Flavor to filter for.</param>
		/// <param name="platform">Platform to filter for.</param>
		/// <returns>Filtered messages.</returns>
		public Dictionary<Version, string> GetFilteredMessages(
			AppFlavor flavor,
			DevicePlatform platform,
			Version shownInVersionOrLastVersion,
			Version currentVersion)
		{
			if (shownInVersionOrLastVersion == null
				|| shownInVersionOrLastVersion == new Version())
			{
				// Initial install detected.
				return new Dictionary<Version, string>();
			}

			if (currentVersion == null || currentVersion == new Version())
			{
				// Invalid state detected.
				return new Dictionary<Version, string>();
			}

			return this.Where(element =>
				shownInVersionOrLastVersion < element.Version /* do not show messages for old version */
				&& element.Version <= currentVersion /* do not show message entered for future versions */
				&& (element.Flavors.Count() == 0 || element.Flavors.Contains(flavor)) /* filter by app flavor */
				&& (element.Platforms.Count() == 0 || element.Platforms.Contains(platform))/* filter by platorm */ )
				.ToDictionary(element => element.Version, element => element.Message);
		}
	}
}