using H.Pipes;
using H.Pipes.AccessControl;
using H.Pipes.Args;
using InABox.Core;
using InABox.IPC;
using InABox.Rpc;
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.IO.Pipes;
using System.Linq;
using System.Security.Principal;
using System.Text;
using System.Threading.Tasks;

namespace InABox.Server;

internal class InternalServerSession : IRpcSession
{
    public Guid ID { get; set; }

    public Platform Platform { get; set; }

    public string? Version { get; set; }

    public string UserID { get; set; }

    public Guid UserGuid { get; set; }

    public PipeConnection<RpcMessage?> Connection { get; set; }
}

/// <summary>
/// This is the main server the database engine runs, which the proxies connect to.
/// </summary>
public class InternalServer : IPusher, IRpcServer
{
    private PipeServer<RpcMessage?> _transport;

    public event LogEvent? OnLog;

    public bool IsSecure() => false;

    public InternalServer(string name)
    {
        _transport = new PipeServer<RpcMessage?>(name);

        #if WINDOWS
        SetPipeSecurity();
        #endif
        
        _transport.ClientConnected += Transport_OnConnected;
        _transport.ClientDisconnected += Transport_OnDisconnected;
        _transport.MessageReceived += Transport_OnMessage;
        _transport.ExceptionOccurred += Transport_OnException;

        AddHandler(new OpenSessionHandler(this));
        AddHandler(new CloseSessionHandler(this));

        AddHandler(new RpcPingHandler(this));
        AddHandler(new RpcInfoHandler(this));

        AddHandler(new RpcValidateHandler(this));
        AddHandler(new RpcCheck2FAHandler(this));

        AddHandler(new RpcQueryHandler(this));
        AddHandler(new RpcSaveHandler(this));
        AddHandler(new RpcDeleteHandler(this));

        AddHandler(new RpcVersionHandler(this));
        AddHandler(new RpcInstallerHandler(this));
        AddHandler(new RpcReleaseNotesHandler(this));
    }

    #region Handlers

    private Dictionary<string, IRpcCommandHandler> _handlers = new Dictionary<string, IRpcCommandHandler>();

    public void AddHandler<TSender, TCommand, TProperties, TResult>(RpcCommandHandler<TSender, TCommand, TProperties, TResult> handler)
        where TSender : class
        where TCommand : IRpcCommand<TProperties, TResult>
        where TProperties : IRpcCommandParameters, new()
        where TResult : IRpcCommandResult, new()
    {
        _handlers[typeof(TCommand).Name] = handler;
    }

    #endregion

    #region Sessions

    private ConcurrentDictionary<Guid, InternalServerSession> _sessions = new ConcurrentDictionary<Guid, InternalServerSession>();

    private class OpenSessionHandler : RpcCommandHandler<InternalServer, OpenSessionCommand, OpenSessionParameters, OpenSessionResult>
    {
        public OpenSessionHandler(InternalServer server) : base(server)
        {
        }

        protected override OpenSessionResult Execute(IRpcSession session, OpenSessionParameters parameters)
        {
            return new OpenSessionResult
            {
                SessionID = session.ID
            };
        }
    }

    private class CloseSessionHandler : RpcCommandHandler<InternalServer, CloseSessionCommand, CloseSessionParameters, CloseSessionResult>
    {
        public CloseSessionHandler(InternalServer server) : base(server)
        {
        }

        protected override CloseSessionResult Execute(IRpcSession session, CloseSessionParameters parameters)
        {
            Sender.DeleteSession(session.ID);
            return new CloseSessionResult();
        }
    }

    private InternalServerSession GetSession(Guid sessionID, PipeConnection<RpcMessage?> connection)
    {
        if(sessionID == Guid.Empty)
        {
            sessionID = Guid.NewGuid();
        }
        if(!_sessions.TryGetValue(sessionID, out var session))
        {
            session = new InternalServerSession
            {
                ID = sessionID,
                Connection = connection
            };
            _sessions.TryAdd(sessionID, session);
        }
        return session;
    }

    private InternalServerSession? DeleteSession(Guid sessionID)
    {
        _sessions.Remove(sessionID, out InternalServerSession? session);
        return session;
    }

    #endregion

    #region Transport Stuff

    private void SetPipeSecurity()
    {

        #pragma warning disable CA1416
        
        var pipeSecurity = new PipeSecurity();

        pipeSecurity.AddAccessRule(new PipeAccessRule(new SecurityIdentifier(WellKnownSidType.LocalSid, null), PipeAccessRights.ReadWrite, System.Security.AccessControl.AccessControlType.Allow));
        pipeSecurity.AddAccessRule(new PipeAccessRule(new SecurityIdentifier(WellKnownSidType.LocalServiceSid, null), PipeAccessRights.ReadWrite, System.Security.AccessControl.AccessControlType.Allow));
        pipeSecurity.AddAccessRule(new PipeAccessRule(new SecurityIdentifier(WellKnownSidType.LocalSystemSid, null), PipeAccessRights.ReadWrite, System.Security.AccessControl.AccessControlType.Allow));

        _transport.SetPipeSecurity(pipeSecurity);
        
        #pragma warning restore CA1416

    }

    public void Start()
    {
        _transport.StartAsync().Wait();
    }

    public void Stop()
    {
        _transport.StopAsync().Wait();
    }
    
    private void Transport_OnConnected(object? sender, H.Pipes.Args.ConnectionEventArgs<RpcMessage?> e)
    {
        OnLog?.Invoke(LogType.Information, "", $"Client Connected");
    }

    private void Transport_OnMessage(object? sender, H.Pipes.Args.ConnectionMessageEventArgs<RpcMessage?> e)
    {
        Task.Run(() =>
        {
            var response = DoMessage(e.Connection, e.Message);
            e.Connection.WriteAsync(response);
        });
    }

    private void Transport_OnDisconnected(object? sender, H.Pipes.Args.ConnectionEventArgs<RpcMessage?> e)
    {
        OnLog?.Invoke(LogType.Information, "", $"Client Disconnected");

        foreach(var session in _sessions.Where(x => x.Value.Connection == e.Connection))
        {
            DeleteSession(session.Key);
        }

        e.Connection.DisposeAsync();
    }

    private void Transport_OnException(object? sender, H.Pipes.Args.ExceptionEventArgs e)
    {
        DoException(null, e.Exception);
    }
    
    protected void DoException(IRpcSession? session, Exception e)
    {
        if ((session?.ID ?? Guid.Empty) != Guid.Empty)
            OnLog?.Invoke(LogType.Error, $"", $"Exception Occurred in {session?.ID}: {e.Message}");
    }

    #endregion

    /// <summary>
    /// Handle a message from a client.
    /// </summary>
    /// <param name="connection">The client connection.</param>
    /// <param name="message">The message to be handled.</param>
    /// <returns>The response to be sent back to the client.</returns>
    public RpcMessage? DoMessage(PipeConnection<RpcMessage?>? connection, RpcMessage? message)
    {
        if(message is null)
        {
            DoException(null, new Exception("NULL Message Received"));
            return null;
        }
        if(connection is null)
        {
            DoException(null, new Exception("NULL connection"));
            return null;
        }
        var response = new RpcMessage() { Id = message.Id, Command = message.Command };
        try
        {
            var data = Serialization.ReadBinary<InternalServerMessage>(message.Payload, BinarySerializationSettings.Latest);

            var session = GetSession(data.Session, connection);

            response = new RpcMessage() { Id = message.Id, Command = message.Command };

            if (_handlers.TryGetValue(message.Command, out var command))
            {
                try
                {
                    response.Payload = command.Execute(session, data.Payload);
                }
                catch (RpcException err)
                {
                    response.Payload = Encoding.UTF8.GetBytes(err.Message);
                    response.Error = err.Error;
                }
            }
            else
            {
                DoException(session, new Exception("Command Not Found"));
                response.Error = RpcError.COMMANDNOTFOUND;
            }
        }
        catch(Exception e)
        {
            DoException(null, e);
            response.Payload = Encoding.UTF8.GetBytes(e.Message);
            response.Error = RpcError.SERVERERROR;
        }

        return response;
    }

    /// <summary>
    /// Send a message to a particular client connection.
    /// </summary>
    /// <param name="connection">The connection to send to.</param>
    /// <param name="message">The message to send.</param>
    public void Send(PipeConnection<RpcMessage?> connection, RpcMessage message)
    {
        connection.WriteAsync(message);
    }

    #region Pusher Stuff

    public void PushToAll<TPush>(TPush push) where TPush : BaseObject
    {
        var internalMessage = new InternalServerMessage
        {
            Session = Guid.Empty,
            Payload = RpcPush.Create(push).WriteBinary(BinarySerializationSettings.Latest)
        };
        var message = new RpcMessage(Guid.NewGuid(), "Push", internalMessage.WriteBinary(BinarySerializationSettings.Latest));

        foreach (var connection in _transport.ConnectedClients)
        {
            Send(connection, message);
        }
    }

    public void PushToSession<TPush>(Guid session, TPush push) where TPush : BaseObject
    {
        var internalMessage = new InternalServerMessage
        {
            Session = session,
            Payload = RpcPush.Create(push).WriteBinary(BinarySerializationSettings.Latest)
        };
        var message = new RpcMessage(Guid.NewGuid(), "Push", internalMessage.WriteBinary(BinarySerializationSettings.Latest));

        var sessionConnection = _sessions.FirstOrDefault(x => x.Value.ID == session).Value.Connection;
        if(sessionConnection is not null)
        {
            Send(sessionConnection, message);
        }
    }

    public void PushToSession(Guid session, Type TPush, BaseObject push)
    {
        var internalMessage = new InternalServerMessage
        {
            Session = session,
            Payload = new RpcPush
            {
                Object = push,
                Type = TPush
            }.WriteBinary(BinarySerializationSettings.Latest)
        };
        var message = new RpcMessage(Guid.NewGuid(), "Push", internalMessage.WriteBinary(BinarySerializationSettings.Latest));

        var sessionConnection = _sessions.FirstOrDefault(x => x.Value.ID == session).Value.Connection;
        if (sessionConnection is not null)
        {
            Send(sessionConnection, message);
        }
    }

    public IEnumerable<Guid> GetUserSessions(Guid user) =>
        _sessions.Values.Where(x => x.UserGuid == user).Select(x => x.ID);

    public IEnumerable<Guid> GetSessions(Platform platform) =>
        _sessions.Values.Where(x => x.Platform == platform).Select(x => x.ID);

    #endregion

    public void Dispose()
    {
        _transport.DisposeAsync().AsTask().Wait();
    }
    
    ~InternalServer()
    {
        Dispose();
    }
}