using System.Collections.Concurrent;
using System.Net.Sockets;
using System.Security.Cryptography;
using Microsoft.AspNetCore.Connections;
using Microsoft.AspNetCore.Server.Kestrel.Transport.Sockets;
using PCC.App.Networking;
using PCC.App.Security;
using PCC.Common.EventBus;
using PCC.Common.Networking;

namespace PCC.App.Tpm;

internal class LocalPeerManager
{
    private readonly KestrelTcpServer _listener;

    private readonly SocketConnectionContextFactory _sckConnectionContextFactory;
    private readonly TimestampNonceManager _nonceManager;
    private readonly IEventBus _eventBus;

    private readonly ILocalPeerInfo _localPeer;

    private readonly ConcurrentDictionary<string, IRemotePeerInfo> _trustedRemotePeers;

    private readonly ConcurrentDictionary<string, EncryptedTcpPeer> _connectedInbound = new();
    private readonly ConcurrentDictionary<string, EncryptedTcpPeer> _connectedOutbound = new();

    public LocalPeerManager(SocketConnectionContextFactory sckConnectionContextFactory, TimestampNonceManager nonceManager, ILocalPeerInfo localPeer, IEventBus eventBus, ILogger<TrustedPeerManager> logger)
    {
        _sckConnectionContextFactory = sckConnectionContextFactory;
        _nonceManager = nonceManager;
        _localPeer = localPeer;
        _eventBus = eventBus;

        _listener = new(localPeer.Address, localPeer.Port, HandleInboundConnection, (ILogger<KestrelTcpServer>)logger);
        _trustedRemotePeers = new(localPeer.TrustedRemotePeers.ToDictionary(p => p.PeerId));
    }

    private async Task HandleInboundConnection(ConnectionContext connection)
    {
        _eventBus.Publish(new TPM_EVT_INBOUND_CON_ACCEPTED(_localPeer.PeerId, connection.ConnectionId, connection.RemoteEndPoint));

        string? remotePeerId = null;
        EncryptedTcpPeer? epRemote = null;
        try
        {
            // handshake as server
            {
                var tpRemote = new TcpPeer(connection);
                //rx handshake1
                IRemotePeerInfo peerPeerInfo;
                byte[] payloadOfHandshake1;
                {
                    var receivedBlock = await tpRemote.RxBlockAsync(new CancellationTokenSource(TimeSpan.FromSeconds(10)).Token);
                    if (receivedBlock == null) return;

                    var handshake1 = RsaUtility.Decrypt(_localPeer.PrivateKey, receivedBlock);

                    var (nonceResult, _, payload) = _nonceManager.CheckValidAndExtractPayload(handshake1);
                    if (nonceResult != TimestampNonceResult.OK)
                    {
                        if (nonceResult == TimestampNonceResult.ReplayAttackDetected)
                            _eventBus.Publish(new TPM_EVT_INBOUND_CON_STATUS_CHANGED(TPM_EVT_INBOUND_CON_STATUS.SECURE_ALERT_REPLAY_ATTACK_DETECT, _localPeer.PeerId, connection.ConnectionId, null));

                        if (nonceResult == TimestampNonceResult.TimestampSkew)
                            _eventBus.Publish(new TPM_EVT_INBOUND_CON_STATUS_CHANGED(TPM_EVT_INBOUND_CON_STATUS.SECURE_WARN_TIMESTAMP_SKEW, _localPeer.PeerId, connection.ConnectionId, null));

                        return;
                    }

                    remotePeerId = Convert.ToHexString(payload.Span);

                    // Kick if non-trusted
                    if (_trustedRemotePeers.TryGetValue(remotePeerId, out peerPeerInfo!) == false)
                    {
                        _eventBus.Publish(new TPM_EVT_INBOUND_CON_STATUS_CHANGED(TPM_EVT_INBOUND_CON_STATUS.HANDSHAKE_FAIL_NOT_TRUSTED, _localPeer.PeerId, connection.ConnectionId, remotePeerId));
                        return;
                    }

                    // verify signature
                    payloadOfHandshake1 = RsaUtility.DecryptAndVerifySignature(_localPeer.PrivateKey, receivedBlock, peerPeerInfo.PublicKey);
                }

                //tx handshake2
                {
                    epRemote = new EncryptedTcpPeer(_localPeer.PrivateKey, peerPeerInfo.PublicKey, tpRemote);
                    var payloadOfHandshake2 = SHA256.HashData(payloadOfHandshake1);
                    var (handshake2, _) = _nonceManager.NewNonceWithPayload(payloadOfHandshake2);
                    await epRemote.SendBlockAsync(handshake2);
                }

                _eventBus.Publish(new TPM_EVT_INBOUND_CON_STATUS_CHANGED(TPM_EVT_INBOUND_CON_STATUS.HANDSHAKE_OK, _localPeer.PeerId, connection.ConnectionId, remotePeerId));
            }

            //replace exist connection
            if (_connectedInbound.Remove(remotePeerId, out var exist)) exist.Disconnect();
            _connectedInbound[remotePeerId] = epRemote;

            // start RxCycle
            while (true)
            {
                var receivedBlock = await epRemote.RxBlockAsync();
                if (receivedBlock == null) break;

                var (nonceResult, senderTimestamp, payload) = _nonceManager.CheckValidAndExtractPayload(receivedBlock);
                if (nonceResult != TimestampNonceResult.OK)
                {
                    if (nonceResult == TimestampNonceResult.ReplayAttackDetected)
                        _eventBus.Publish(new TPM_EVT_INBOUND_CON_STATUS_CHANGED(TPM_EVT_INBOUND_CON_STATUS.SECURE_ALERT_REPLAY_ATTACK_DETECT, _localPeer.PeerId, connection.ConnectionId, remotePeerId));

                    if (nonceResult == TimestampNonceResult.TimestampSkew)
                        _eventBus.Publish(new TPM_EVT_INBOUND_CON_STATUS_CHANGED(TPM_EVT_INBOUND_CON_STATUS.SECURE_WARN_TIMESTAMP_SKEW, _localPeer.PeerId, connection.ConnectionId, remotePeerId));

                    break;
                }

                _eventBus.Publish(new TPM_EVT_INBOUND_RX(_localPeer.PeerId, remotePeerId, senderTimestamp, payload));
            }
        }
        catch (Exception exception)
        {
            _eventBus.Publish(new TPM_EVT_INBOUND_CON_ERROR(_localPeer.PeerId, connection.ConnectionId, remotePeerId, exception));
        }
        finally
        {
            _eventBus.Publish(new TPM_EVT_INBOUND_CON_STATUS_CHANGED(TPM_EVT_INBOUND_CON_STATUS.DISCONNECTED, _localPeer.PeerId, connection.ConnectionId, remotePeerId));
            epRemote?.Disconnect();

            if (remotePeerId != null) _connectedInbound.Remove(remotePeerId, out _);
        }
    }

    public bool ConnectToRemotePeer(string remotePeerId)
    {
        if (_trustedRemotePeers.TryGetValue(remotePeerId, out var peerInfo) == false) return false;

        _ = Task.Run(async () =>
        {
            EncryptedTcpPeer? epOutbound = null;
            try
            {
                //Create Peer client and connect to server
                {
                    var sckOutbound = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

                    _eventBus.Publish(new TPM_EVT_OUTBOUND_CON_STATUS_CHANGED(TPM_EVT_OUTBOUND_CON_STATUS.CONNECTION_ATTEMPT, _localPeer.PeerId, remotePeerId));
                    await sckOutbound.ConnectAsync(peerInfo.Host, peerInfo.Port);

                    var connOutbound = _sckConnectionContextFactory.Create(sckOutbound);
                    var tcpPeerOutbound = new TcpPeer(connOutbound);
                    epOutbound = new EncryptedTcpPeer(_localPeer.PrivateKey, peerInfo.PublicKey, tcpPeerOutbound);

                    // handshake as client
                    _eventBus.Publish(new TPM_EVT_OUTBOUND_CON_STATUS_CHANGED(TPM_EVT_OUTBOUND_CON_STATUS.HANDSHAKE_ATTEMPT, _localPeer.PeerId, remotePeerId));

                    // ☞ tx handshake 1
                    var (handshake1, _) = _nonceManager.NewNonceWithPayload(Convert.FromHexString(_localPeer.PeerId));
                    await epOutbound.SendBlockAsync(handshake1);

                    // ☞ rx handshake 2
                    var handshake2 = await epOutbound.RxBlockAsync(new CancellationTokenSource(TimeSpan.FromSeconds(10)).Token);
                    if (handshake2 == null)
                    {
                        return;
                    } // timeout or disconnect

                    var (nonceResult, _, pl) = _nonceManager.CheckValidAndExtractPayload(handshake2);
                    if (nonceResult != TimestampNonceResult.OK)
                    {
                        if (nonceResult == TimestampNonceResult.ReplayAttackDetected)
                            _eventBus.Publish(new TPM_EVT_OUTBOUND_CON_STATUS_CHANGED(TPM_EVT_OUTBOUND_CON_STATUS.SECURE_ALERT_REPLAY_ATTACK_DETECT, _localPeer.PeerId, remotePeerId));

                        if (nonceResult == TimestampNonceResult.TimestampSkew)
                            _eventBus.Publish(new TPM_EVT_OUTBOUND_CON_STATUS_CHANGED(TPM_EVT_OUTBOUND_CON_STATUS.SECURE_WARN_TIMESTAMP_SKEW, _localPeer.PeerId, remotePeerId));

                        epOutbound.Disconnect();
                        return;
                    }

                    // handshake not match, disconnect
                    if (pl.Span.SequenceEqual(SHA256.HashData(handshake1.Span)) != true)
                    {
                        _eventBus.Publish(new TPM_EVT_OUTBOUND_CON_STATUS_CHANGED(TPM_EVT_OUTBOUND_CON_STATUS.HANDSHAKE_FAIL_ACK_NOT_MATCHED, _localPeer.PeerId, remotePeerId));

                        return;
                    }

                    _eventBus.Publish(new TPM_EVT_OUTBOUND_CON_STATUS_CHANGED(TPM_EVT_OUTBOUND_CON_STATUS.HANDSHAKE_OK, _localPeer.PeerId, remotePeerId));
                }

                //replace exist connection
                if (_connectedOutbound.Remove(remotePeerId, out var exist)) exist.Disconnect();

                _connectedOutbound[remotePeerId] = epOutbound;

                while (true) // start RxCycle
                {
                    var rxb = await epOutbound.RxBlockAsync();
                    if (rxb == null) break;

                    var (nonceResult, senderTimestamp, payload) = _nonceManager.CheckValidAndExtractPayload(rxb);
                    if (nonceResult != TimestampNonceResult.OK)
                    {
                        if (nonceResult == TimestampNonceResult.ReplayAttackDetected)
                            _eventBus.Publish(new TPM_EVT_OUTBOUND_CON_STATUS_CHANGED(TPM_EVT_OUTBOUND_CON_STATUS.SECURE_ALERT_REPLAY_ATTACK_DETECT, _localPeer.PeerId, remotePeerId));

                        if (nonceResult == TimestampNonceResult.TimestampSkew)
                            _eventBus.Publish(new TPM_EVT_OUTBOUND_CON_STATUS_CHANGED(TPM_EVT_OUTBOUND_CON_STATUS.SECURE_WARN_TIMESTAMP_SKEW, _localPeer.PeerId, remotePeerId));

                        break;
                    }

                    _eventBus.Publish(new TPM_EVT_OUTBOUND_RX(_localPeer.PeerId, remotePeerId, senderTimestamp, payload));
                }
            }
            catch (Exception ex)
            {
                _eventBus.Publish(new TPM_EVT_OUTBOUND_CON_ERROR(_localPeer.PeerId, remotePeerId, ex));
            }
            finally
            {
                _eventBus.Publish(new TPM_EVT_OUTBOUND_CON_STATUS_CHANGED(TPM_EVT_OUTBOUND_CON_STATUS.DISCONNECTED, _localPeer.PeerId, remotePeerId));

                _connectedOutbound.Remove(remotePeerId, out _);

                epOutbound?.Disconnect();
            }
        });

        return true;
    }

    public bool DisconnectRemotePeer(string remotePeerId)
    {
        var flag = false;

        if (_connectedInbound.Remove(remotePeerId, out var inbound))
        {
            flag = true;
            inbound.Disconnect();
        }

        if (_connectedOutbound.Remove(remotePeerId, out var outbound))
        {
            flag = true;
            outbound.Disconnect();
        }

        return flag;
    }

    public void AddOrReplaceRemotePeer(IRemotePeerInfo peerInfo)
    {
        _trustedRemotePeers[peerInfo.PeerId] = peerInfo;
    }

    public bool RemoveRemotePeer(string remotePeerId)
    {
        DisconnectRemotePeer(remotePeerId);
        return _trustedRemotePeers.Remove(remotePeerId, out _);
    }

    public void Start()
    {
        Task.Run(async () =>
        {
            try
            {
                _eventBus.Publish(new TPM_EVT_LISTENER_STATUS_CHANGED(_localPeer.PeerId, TPM_EVT_INBOUND_LISTEN_STATUS.STARTING));
                await _listener.StartAsync();
                _eventBus.Publish(new TPM_EVT_LISTENER_STATUS_CHANGED(_localPeer.PeerId, TPM_EVT_INBOUND_LISTEN_STATUS.STARTED));
            }
            catch (Exception ex)
            {
                _eventBus.Publish(new TPM_EVT_LISTENER_STATUS_CHANGED(_localPeer.PeerId, TPM_EVT_INBOUND_LISTEN_STATUS.START_FAIL, ex));
            }
        });
    }

    public void Stop()
    {
        Task.Run(async () =>
        {
            try
            {
                _eventBus.Publish(new TPM_EVT_LISTENER_STATUS_CHANGED(_localPeer.PeerId, TPM_EVT_INBOUND_LISTEN_STATUS.STOPPING));
                await _listener.StopAsync();
                _eventBus.Publish(new TPM_EVT_LISTENER_STATUS_CHANGED(_localPeer.PeerId, TPM_EVT_INBOUND_LISTEN_STATUS.STOPPED));
            }
            catch (Exception ex)
            {
                _eventBus.Publish(new TPM_EVT_LISTENER_STATUS_CHANGED(_localPeer.PeerId, TPM_EVT_INBOUND_LISTEN_STATUS.STOP_FAIL, ex));
            }
        });

        foreach (var item in _connectedInbound) item.Value.Disconnect();
        _connectedInbound.Clear();

        foreach (var item in _connectedOutbound) item.Value.Disconnect();
        _connectedOutbound.Clear();
    }

    public bool SendToRemotePeer(string remotePeerId, byte[] payload)
    {
        bool isOutbound;
        if (_connectedOutbound.TryGetValue(remotePeerId, out var remote) == false)
        {
            if (_connectedInbound.TryGetValue(remotePeerId, out remote))
                isOutbound = false;
            else
                return false;
        }
        else
        {
            isOutbound = true;
        }

        Task.Run(async () =>
        {
            var (payloadAndNonce, timestamp) = _nonceManager.NewNonceWithPayload(payload);

            await remote.SendBlockAsync(payloadAndNonce);

            if (isOutbound)
            {
                _eventBus.Publish(new TPM_EVT_OUTBOUND_TX(_localPeer.PeerId, remotePeerId, timestamp, payload));
            }
            else
            {
                _eventBus.Publish(new TPM_EVT_INBOUND_TX(_localPeer.PeerId, remotePeerId, timestamp, payload));
            }
        });

        return true;
    }
}