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);
        }
    }
}