// <copyright file="BaseGuildInfoPlugIn.cs" company="MUnique">
// Licensed under the MIT License. See LICENSE file in the project root for full license information.
// </copyright>

namespace MUnique.OpenMU.GameServer.RemoteView.Guild;

using System.Collections.Concurrent;
using MUnique.OpenMU.GameLogic;
using MUnique.OpenMU.GameLogic.Views.Guild;
using MUnique.OpenMU.Interfaces;

/// <summary>
/// Abstract base class for a <see cref="IShowGuildInfoPlugIn" /> which allows to cache serialized guild infos.
/// </summary>
/// <typeparam name="T">The type of the actual <see cref="IShowGuildInfoPlugIn"/>. Required, so there is one cache per type.</typeparam>
// ReSharper disable once UnusedTypeParameter we just use it to get type specific static fields.
public abstract class BaseGuildInfoPlugIn<T>
{
    /// <summary>
    /// The cache for already serialized guilds. This data doesn't change, but is requested often.
    /// </summary>
    // ReSharper disable once StaticMemberInGenericType That's what we want
    private static readonly ConcurrentDictionary<uint, Memory<byte>> Cache = new();

    // ReSharper disable once StaticMemberInGenericType That's what we want
    private static readonly HashSet<IGameServerContext> AppendedGuildDeletedSenders = new();

    /// <summary>
    /// Initializes a new instance of the <see cref="BaseGuildInfoPlugIn{T}"/> class.
    /// </summary>
    /// <param name="player">The player.</param>
    protected BaseGuildInfoPlugIn(RemotePlayer player)
    {
        this.Player = player;
        lock (AppendedGuildDeletedSenders)
        {
            if (AppendedGuildDeletedSenders.Add(player.GameServerContext))
            {
                // to make sure we just add one event handler
                this.Player.GameServerContext.GuildDeleted += OnGuildChanged;
                this.Player.GameServerContext.GuildChanged += OnGuildChanged;
            }
        }
    }

    /// <summary>
    /// Gets the player.
    /// </summary>
    /// <value>
    /// The player.
    /// </value>
    protected RemotePlayer Player { get; }

    /// <summary>
    /// Serializes the specified guild.
    /// </summary>
    /// <param name="guild">The guild.</param>
    /// <param name="guildId">The guild identifier.</param>
    /// <returns>The serialized guild data packet.</returns>
    protected abstract Memory<byte> Serialize(Guild guild, uint guildId);

    /// <summary>
    /// Returns the Guild Info Data of a Guild. It will either
    /// take the data out of the Cache, or get it from the database and serializes it.
    /// </summary>
    /// <param name="guildId">The id of the guild.</param>
    /// <returns>
    /// The data of the guild.
    /// </returns>
    protected async ValueTask<Memory<byte>> GetGuildDataAsync(uint guildId)
    {
        if (Cache.TryGetValue(guildId, out var guildInfo))
        {
            return guildInfo;
        }

        var guild = await this.Player.GameServerContext.GuildServer.GetGuildAsync(guildId).ConfigureAwait(false);
        if (guild is null)
        {
            return Memory<byte>.Empty;
        }

        var data = this.Serialize(guild, guildId);
        Cache.TryAdd(guildId, data);
        return data;
    }

    private static void OnGuildChanged(object? sender, GuildEventArgs args)
    {
        Cache.TryRemove(args.GuildId, out _);
    }
}