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

namespace MUnique.OpenMU.ConnectServer;

using System.Buffers;
using System.Net;
using System.Threading;
using Microsoft.Extensions.Logging;
using MUnique.OpenMU.ConnectServer.PacketHandler;
using MUnique.OpenMU.Network;
using MUnique.OpenMU.Network.Packets.ConnectServer;
using Nito.AsyncEx.Synchronous;

/// <summary>
/// The client which connected to the connect server.
/// </summary>
internal sealed class Client : IDisposable
{
    private readonly ILogger<Client> _logger;
    private readonly byte[] _receiveBuffer;
    private readonly Timer _onlineTimer;
    private readonly IPacketHandler<Client> _packetHandler;

    private bool _disposed;

    private DateTime _lastReceive;

    /// <summary>
    /// Initializes a new instance of the <see cref="Client" /> class.
    /// </summary>
    /// <param name="connection">The connection.</param>
    /// <param name="timeout">The timeout.</param>
    /// <param name="packetHandler">The packet handler.</param>
    /// <param name="maxPacketSize">Maximum size of the packet. This value is also used to initialize the receive buffer.</param>
    /// <param name="logger">The logger.</param>
    public Client(IConnection connection, TimeSpan timeout, IPacketHandler<Client> packetHandler, byte maxPacketSize, ILogger<Client> logger)
    {
        this.Connection = connection;
        this.Connection.PacketReceived += this.OnPacketReceivedAsync;
        this.Timeout = timeout;
        this._packetHandler = packetHandler;
        this._logger = logger;
        this._lastReceive = DateTime.Now;
        var checkInterval = new TimeSpan(0, 0, 20);
        this._onlineTimer = new Timer(this.OnOnlineTimerElapsed, null, checkInterval, checkInterval);
        this._receiveBuffer = new byte[maxPacketSize];
    }

    /// <summary>
    /// Gets or sets the timeout after which the client gets disconnected if he is inactive.
    /// </summary>
    public TimeSpan Timeout { get; set; }

    /// <summary>
    /// Gets or sets the server information request count.
    /// </summary>
    /// <remarks>Used for DOS protection.</remarks>
    public int ServerInfoRequestCount { get; set; }

    /// <summary>
    /// Gets or sets the FTP request count.
    /// </summary>
    /// <remarks>Used for DOS protection.</remarks>
    public int FtpRequestCount { get; set; }

    /// <summary>
    /// Gets or sets the server list request count.
    /// </summary>
    /// <remarks>Used for DOS protection.</remarks>
    public int ServerListRequestCount { get; set; }

    /// <summary>
    /// Gets or sets the ip from which the client is connecting.
    /// </summary>
    public IPAddress Address { get; set; } = IPAddress.None;

    /// <summary>
    /// Gets or sets the port from which the client is connecting.
    /// </summary>
    public int Port { get; set; }

    /// <summary>
    /// Gets the connection from/to the client.
    /// </summary>
    internal IConnection Connection { get; }

    /// <inheritdoc/>
    public void Dispose()
    {
        if (!this._disposed)
        {
            this._disposed = true;
            this._onlineTimer.Dispose();
            this.Connection.Dispose();
        }
    }

    /// <summary>
    /// Sends the hello packet.
    /// </summary>
    internal ValueTask SendHelloAsync()
    {
        return this.Connection.SendHelloAsync();
    }

    private void OnOnlineTimerElapsed(object? state)
    {
        try
        {
            if (this.Connection.Connected && DateTime.Now.Subtract(this._lastReceive) > this.Timeout)
            {
                this._logger.LogDebug("Connection Timeout ({0}): Address {1}:{2} will be disconnected.", this.Timeout, this.Address, this.Port);
                this.Connection.DisconnectAsync().AsTask().WaitAndUnwrapException();
            }
        }
        catch (Exception ex)
        {
            this._logger.LogError(ex, "Error when disconnecting client.  Address {1}:{2}", this.Address, this.Port);
        }
    }

    private async ValueTask OnPacketReceivedAsync(ReadOnlySequence<byte> sequence)
    {
        this._lastReceive = DateTime.Now;
        if (sequence.Length > this._receiveBuffer.Length)
        {
            this._logger.LogInformation($"Client {this.Address}:{this.Port} will be disconnected because it sent a packet which was too big (size of {sequence.Length}");
            await this.Connection.DisconnectAsync().ConfigureAwait(false);
        }

        sequence.CopyTo(this._receiveBuffer);
        await this._packetHandler
            .HandlePacketAsync(this, this._receiveBuffer.AsMemory(0, this._receiveBuffer.GetPacketSize()))
            .ConfigureAwait(false);
    }
}