using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;
using System.Threading;
using System.Threading.Tasks;
using Ionic.Zlib;
using TLSharp.Core.MTProto;
using TLSharp.Core.MTProto.Crypto;
using TLSharp.Core.Requests;
using TLSharp.Core.Utils;

namespace TLSharp.Core.Network
{
    public class MtProtoSender
    {
        //private ulong sessionId = GenerateRandomUlong();

        private readonly TcpTransport _transport;
        private readonly Session _session;

        public readonly List<ulong> needConfirmation = new List<ulong>();

        public MtProtoSender(TcpTransport transport, Session session)
        {
            _transport = transport;
            _session = session;
        }

        private int GenerateSequence(bool confirmed)
        {
            return confirmed ? _session.Sequence++ * 2 + 1 : _session.Sequence * 2;
        }

        public async Task Send(TeleSharp.TL.TLMethod request)
        {
            // TODO: refactor
            if (needConfirmation.Any())
            {
                var ackRequest = new AckRequest(needConfirmation);
                using (var memory = new MemoryStream())
                using (var writer = new BinaryWriter(memory))
                {
                    ackRequest.SerializeBody(writer);
                    await Send(memory.ToArray(), ackRequest);
                    needConfirmation.Clear();
                }
            }


            using (var memory = new MemoryStream())
            using (var writer = new BinaryWriter(memory))
            {
                request.SerializeBody(writer);
                await Send(memory.ToArray(), request);
            }

            _session.Save();
        }

        public async Task Send(byte[] packet, TeleSharp.TL.TLMethod request)
        {
            request.MessageId = _session.GetNewMessageId();

            byte[] msgKey;
            byte[] ciphertext;
            using (MemoryStream plaintextPacket = makeMemory(8 + 8 + 8 + 4 + 4 + packet.Length))
            {
                using (BinaryWriter plaintextWriter = new BinaryWriter(plaintextPacket))
                {
                    plaintextWriter.Write(_session.Salt);
                    plaintextWriter.Write(_session.Id);
                    plaintextWriter.Write(request.MessageId);
                    plaintextWriter.Write(GenerateSequence(request.Confirmed));
                    plaintextWriter.Write(packet.Length);
                    plaintextWriter.Write(packet);

                    msgKey = Helpers.CalcMsgKey(plaintextPacket.GetBuffer());
                    ciphertext = AES.EncryptAES(Helpers.CalcKey(_session.AuthKey.Data, msgKey, true), plaintextPacket.GetBuffer());
                }
            }

            using (MemoryStream ciphertextPacket = makeMemory(8 + 16 + ciphertext.Length))
            {
                using (BinaryWriter writer = new BinaryWriter(ciphertextPacket))
                {
                    writer.Write(_session.AuthKey.Id);
                    writer.Write(msgKey);
                    writer.Write(ciphertext);

                    await _transport.Send(ciphertextPacket.GetBuffer());
                }
            }
        }

        private Tuple<byte[], ulong, int> DecodeMessage(byte[] body)
        {
            byte[] message;
            ulong remoteMessageId;
            int remoteSequence;

            using (var inputStream = new MemoryStream(body))
            using (var inputReader = new BinaryReader(inputStream))
            {
                if (inputReader.BaseStream.Length < 8)
                    throw new InvalidOperationException($"Can't decode packet");

                ulong remoteAuthKeyId = inputReader.ReadUInt64(); // TODO: check auth key id
                byte[] msgKey = inputReader.ReadBytes(16); // TODO: check msg_key correctness
                AESKeyData keyData = Helpers.CalcKey(_session.AuthKey.Data, msgKey, false);

                byte[] plaintext = AES.DecryptAES(keyData, inputReader.ReadBytes((int)(inputStream.Length - inputStream.Position)));

                using (MemoryStream plaintextStream = new MemoryStream(plaintext))
                using (BinaryReader plaintextReader = new BinaryReader(plaintextStream))
                {
                    var remoteSalt = plaintextReader.ReadUInt64();
                    var remoteSessionId = plaintextReader.ReadUInt64();
                    remoteMessageId = plaintextReader.ReadUInt64();
                    remoteSequence = plaintextReader.ReadInt32();
                    int msgLen = plaintextReader.ReadInt32();
                    message = plaintextReader.ReadBytes(msgLen);
                }
            }
            return new Tuple<byte[], ulong, int>(message, remoteMessageId, remoteSequence);
        }

        public async Task<byte[]> Receive(TeleSharp.TL.TLMethod request)
        {
            while (!request.ConfirmReceived)
            {
                var result = DecodeMessage((await _transport.Receive()).Body);

                using (var messageStream = new MemoryStream(result.Item1, false))
                using (var messageReader = new BinaryReader(messageStream))
                {
                    processMessage(result.Item2, result.Item3, messageReader, request);
                }
            }

            return null;
        }

        public async Task SendPingAsync()
        {
            var pingRequest = new PingRequest();
            using (var memory = new MemoryStream())
            using (var writer = new BinaryWriter(memory))
            {
                pingRequest.SerializeBody(writer);
                await Send(memory.ToArray(), pingRequest);
            }

            await Receive(pingRequest);
        }

        private bool processMessage(ulong messageId, int sequence, BinaryReader messageReader, TeleSharp.TL.TLMethod request)
        {
            // TODO: check salt
            // TODO: check sessionid
            // TODO: check seqno

            //logger.debug("processMessage: msg_id {0}, sequence {1}, data {2}", BitConverter.ToString(((MemoryStream)messageReader.BaseStream).GetBuffer(), (int) messageReader.BaseStream.Position, (int) (messageReader.BaseStream.Length - messageReader.BaseStream.Position)).Replace("-","").ToLower());
            needConfirmation.Add(messageId);

            uint code = messageReader.ReadUInt32();
            messageReader.BaseStream.Position -= 4;
            switch (code)
            {
                case 0x73f1f8dc: // container
                                 //logger.debug("MSG container");
                    return HandleContainer(messageId, sequence, messageReader, request);
                case 0x7abe77ec: // ping
                                 //logger.debug("MSG ping");
                    return HandlePing(messageId, sequence, messageReader);
                case 0x347773c5: // pong
                                 //logger.debug("MSG pong");
                    return HandlePong(messageId, sequence, messageReader, request);
                case 0xae500895: // future_salts
                                 //logger.debug("MSG future_salts");
                    return HandleFutureSalts(messageId, sequence, messageReader);
                case 0x9ec20908: // new_session_created
                                 //logger.debug("MSG new_session_created");
                    return HandleNewSessionCreated(messageId, sequence, messageReader);
                case 0x62d6b459: // msgs_ack
                                 //logger.debug("MSG msds_ack");
                    return HandleMsgsAck(messageId, sequence, messageReader);
                case 0xedab447b: // bad_server_salt
                                 //logger.debug("MSG bad_server_salt");
                    return HandleBadServerSalt(messageId, sequence, messageReader, request);
                case 0xa7eff811: // bad_msg_notification
                                 //logger.debug("MSG bad_msg_notification");
                    return HandleBadMsgNotification(messageId, sequence, messageReader);
                case 0x276d3ec6: // msg_detailed_info
                                 //logger.debug("MSG msg_detailed_info");
                    return HandleMsgDetailedInfo(messageId, sequence, messageReader);
                case 0xf35c6d01: // rpc_result
                                 //logger.debug("MSG rpc_result");
                    return HandleRpcResult(messageId, sequence, messageReader, request);
                case 0x3072cfa1: // gzip_packed
                                 //logger.debug("MSG gzip_packed");
                    return HandleGzipPacked(messageId, sequence, messageReader, request);
                case 0xe317af7e:
                case 0xd3f45784:
                case 0x2b2fbd4e:
                case 0x78d4dec1:
                case 0x725b04c3:
                case 0x74ae4240:
                    return HandleUpdate(messageId, sequence, messageReader);
                default:
                    //logger.debug("unknown message: {0}", code);
                    return false;
            }
        }

        private bool HandleUpdate(ulong messageId, int sequence, BinaryReader messageReader)
        {
            return false;

            /*
			try
			{
				UpdatesEvent(TL.Parse<Updates>(messageReader));
				return true;
			}
			catch (Exception e)
			{
				logger.warning("update processing exception: {0}", e);
				return false;
			}
			*/
        }

        private bool HandleGzipPacked(ulong messageId, int sequence, BinaryReader messageReader, TeleSharp.TL.TLMethod request)
        {
            uint code = messageReader.ReadUInt32();
            byte[] packedData = GZipStream.UncompressBuffer(Serializers.Bytes.read(messageReader));
            using (MemoryStream packedStream = new MemoryStream(packedData, false))
            using (BinaryReader compressedReader = new BinaryReader(packedStream))
            {
                processMessage(messageId, sequence, compressedReader, request);
            }

            return true;
        }

        private bool HandleRpcResult(ulong messageId, int sequence, BinaryReader messageReader, TeleSharp.TL.TLMethod request)
        {
            uint code = messageReader.ReadUInt32();
            ulong requestId = messageReader.ReadUInt64();

            if (requestId == (ulong)request.MessageId)
                request.ConfirmReceived = true;

            //throw new NotImplementedException();
            /*
			lock (runningRequests)
			{
				if (!runningRequests.ContainsKey(requestId))
				{
					logger.warning("rpc response on unknown request: {0}", requestId);
					messageReader.BaseStream.Position -= 12;
					return false;
				}

				request = runningRequests[requestId];
				runningRequests.Remove(requestId);
			}
			*/

            uint innerCode = messageReader.ReadUInt32();
            if (innerCode == 0x2144ca19)
            { // rpc_error
                int errorCode = messageReader.ReadInt32();
                string errorMessage = Serializers.String.read(messageReader);

                if (errorMessage.StartsWith("FLOOD_WAIT_"))
                {
                    var resultString = Regex.Match(errorMessage, @"\d+").Value;
                    var seconds = int.Parse(resultString);
                    throw new FloodException(TimeSpan.FromSeconds(seconds));
                }
                else if (errorMessage.StartsWith("PHONE_MIGRATE_"))
                {
                    var resultString = Regex.Match(errorMessage, @"\d+").Value;
                    var dcIdx = int.Parse(resultString);
                    throw new PhoneMigrationException(dcIdx);
                }
                else if (errorMessage.StartsWith("FILE_MIGRATE_"))
                {
                    var resultString = Regex.Match(errorMessage, @"\d+").Value;
                    var dcIdx = int.Parse(resultString);
                    throw new FileMigrationException(dcIdx);
                }
                else if (errorMessage.StartsWith("USER_MIGRATE_"))
                {
                    var resultString = Regex.Match(errorMessage, @"\d+").Value;
                    var dcIdx = int.Parse(resultString);
                    throw new UserMigrationException(dcIdx);
                }
                else if (errorMessage.StartsWith("NETWORK_MIGRATE_"))
                {
                    var resultString = Regex.Match(errorMessage, @"\d+").Value;
                    var dcIdx = int.Parse(resultString);
                    throw new NetworkMigrationException(dcIdx);
                }
                else if (errorMessage == "PHONE_CODE_INVALID")
                {
                    throw new InvalidPhoneCodeException("The numeric code used to authenticate does not match the numeric code sent by SMS/Telegram");
                }
                else if (errorMessage == "SESSION_PASSWORD_NEEDED")
                {
                    throw new CloudPasswordNeededException("This Account has Cloud Password !");
                }
                else
                {
                    throw new InvalidOperationException(errorMessage);
                }

            }
            else if (innerCode == 0x3072cfa1)
            {
                try
                {
                    // gzip_packed
                    byte[] packedData = Serializers.Bytes.read(messageReader);
                    using (var ms = new MemoryStream())
                    {
                        using (var packedStream = new MemoryStream(packedData, false))
                        using (var zipStream = new GZipStream(packedStream, CompressionMode.Decompress))
                        {
                            zipStream.CopyTo(ms);
                            ms.Position = 0;
                        }
                        using (var compressedReader = new BinaryReader(ms))
                        {
                            request.DeserializeResponse(compressedReader);
                        }
                    }
                }
                catch (ZlibException ex)
                {

                }
            }
            else
            {
                messageReader.BaseStream.Position -= 4;
                request.DeserializeResponse(messageReader);
            }

            return false;
        }

        private bool HandleMsgDetailedInfo(ulong messageId, int sequence, BinaryReader messageReader)
        {
            return false;
        }

        private bool HandleBadMsgNotification(ulong messageId, int sequence, BinaryReader messageReader)
        {
            uint code = messageReader.ReadUInt32();
            ulong requestId = messageReader.ReadUInt64();
            int requestSequence = messageReader.ReadInt32();
            int errorCode = messageReader.ReadInt32();

            switch (errorCode)
            {
                case 16:
                    throw new InvalidOperationException("msg_id too low (most likely, client time is wrong; it would be worthwhile to synchronize it using msg_id notifications and re-send the original message with the “correct” msg_id or wrap it in a container with a new msg_id if the original message had waited too long on the client to be transmitted)");
                case 17:
                    throw new InvalidOperationException("msg_id too high (similar to the previous case, the client time has to be synchronized, and the message re-sent with the correct msg_id)");
                case 18:
                    throw new InvalidOperationException("incorrect two lower order msg_id bits (the server expects client message msg_id to be divisible by 4)");
                case 19:
                    throw new InvalidOperationException("container msg_id is the same as msg_id of a previously received message (this must never happen)");
                case 20:
                    throw new InvalidOperationException("message too old, and it cannot be verified whether the server has received a message with this msg_id or not");
                case 32:
                    throw new InvalidOperationException("msg_seqno too low (the server has already received a message with a lower msg_id but with either a higher or an equal and odd seqno)");
                case 33:
                    throw new InvalidOperationException(" msg_seqno too high (similarly, there is a message with a higher msg_id but with either a lower or an equal and odd seqno)");
                case 34:
                    throw new InvalidOperationException("an even msg_seqno expected (irrelevant message), but odd received");
                case 35:
                    throw new InvalidOperationException("odd msg_seqno expected (relevant message), but even received");
                case 48:
                    throw new InvalidOperationException("incorrect server salt (in this case, the bad_server_salt response is received with the correct salt, and the message is to be re-sent with it)");
                case 64:
                    throw new InvalidOperationException("invalid container");

            }
            throw new NotImplementedException("This should never happens");
            /*
			logger.debug("bad_msg_notification: msgid {0}, seq {1}, errorcode {2}", requestId, requestSequence,
						 errorCode);
			*/
            /*
			if (!runningRequests.ContainsKey(requestId))
			{
				logger.debug("bad msg notification on unknown request");
				return true;
			}
			*/

            //OnBrokenSessionEvent();
            //MTProtoRequest request = runningRequests[requestId];
            //request.OnException(new MTProtoBadMessageException(errorCode));

            return true;
        }

        private bool HandleBadServerSalt(ulong messageId, int sequence, BinaryReader messageReader, TeleSharp.TL.TLMethod request)
        {
            uint code = messageReader.ReadUInt32();
            ulong badMsgId = messageReader.ReadUInt64();
            int badMsgSeqNo = messageReader.ReadInt32();
            int errorCode = messageReader.ReadInt32();
            ulong newSalt = messageReader.ReadUInt64();

            //logger.debug("bad_server_salt: msgid {0}, seq {1}, errorcode {2}, newsalt {3}", badMsgId, badMsgSeqNo, errorCode, newSalt);

            _session.Salt = newSalt;

            //resend
            Send(request);
            /*
            if(!runningRequests.ContainsKey(badMsgId)) {
                logger.debug("bad server salt on unknown message");
                return true;
            }
            */


            //MTProtoRequest request = runningRequests[badMsgId];
            //request.OnException(new MTProtoBadServerSaltException(salt));

            return true;
        }

        private bool HandleMsgsAck(ulong messageId, int sequence, BinaryReader messageReader)
        {
            return false;
        }

        private bool HandleNewSessionCreated(ulong messageId, int sequence, BinaryReader messageReader)
        {
            return false;
        }

        private bool HandleFutureSalts(ulong messageId, int sequence, BinaryReader messageReader)
        {
            uint code = messageReader.ReadUInt32();
            ulong requestId = messageReader.ReadUInt64();

            messageReader.BaseStream.Position -= 12;

            throw new NotImplementedException("Handle future server salts function isn't implemented.");
            /*
			if (!runningRequests.ContainsKey(requestId))
			{
				logger.info("future salts on unknown request");
				return false;
			}
			*/

            //	MTProtoRequest request = runningRequests[requestId];
            //	runningRequests.Remove(requestId);
            //	request.OnResponse(messageReader);

            return true;
        }

        private bool HandlePong(ulong messageId, int sequence, BinaryReader messageReader, TeleSharp.TL.TLMethod request)
        {
            uint code = messageReader.ReadUInt32();
            ulong msgId = messageReader.ReadUInt64();

            if (msgId == (ulong)request.MessageId)
            {
                request.ConfirmReceived = true;
            }

            return false;
        }

        private bool HandlePing(ulong messageId, int sequence, BinaryReader messageReader)
        {
            return false;
        }

        private bool HandleContainer(ulong messageId, int sequence, BinaryReader messageReader, TeleSharp.TL.TLMethod request)
        {
            uint code = messageReader.ReadUInt32();
            int size = messageReader.ReadInt32();
            for (int i = 0; i < size; i++)
            {
                ulong innerMessageId = messageReader.ReadUInt64();
                int innerSequence = messageReader.ReadInt32();
                int innerLength = messageReader.ReadInt32();
                long beginPosition = messageReader.BaseStream.Position;
                try
                {
                    if (!processMessage(innerMessageId, sequence, messageReader, request))
                    {
                        messageReader.BaseStream.Position = beginPosition + innerLength;
                    }
                }
                catch (Exception e)
                {
                    //	logger.error("failed to process message in container: {0}", e);
                    messageReader.BaseStream.Position = beginPosition + innerLength;
                }
            }

            return false;
        }

        private MemoryStream makeMemory(int len)
        {
            return new MemoryStream(new byte[len], 0, len, true, true);
        }
    }

    public class FloodException : Exception
    {
        public TimeSpan TimeToWait { get; private set; }

        internal FloodException(TimeSpan timeToWait)
            : base($"Flood prevention. Telegram now requires your program to do requests again only after {timeToWait.TotalSeconds} seconds have passed ({nameof(TimeToWait)} property)." +
                    " If you think the culprit of this problem may lie in TLSharp's implementation, open a Github issue please.")
        {
            TimeToWait = timeToWait;
        }
    }

    internal abstract class DataCenterMigrationException : Exception
    {
        internal int DC { get; private set; }

        private const string REPORT_MESSAGE =
            " See: https://github.com/sochix/TLSharp#i-get-a-xxxmigrationexception-or-a-migrate_x-error";

        protected DataCenterMigrationException(string msg, int dc) : base (msg + REPORT_MESSAGE)
        {
            DC = dc;
        }
    }

    internal class PhoneMigrationException : DataCenterMigrationException
    {
        internal PhoneMigrationException(int dc)
            : base ($"Phone number registered to a different DC: {dc}.", dc)
        {
        }
    }

    internal class FileMigrationException : DataCenterMigrationException
    {
        internal FileMigrationException(int dc)
            : base ($"File located on a different DC: {dc}.", dc)
        {
        }
    }

    internal class UserMigrationException : DataCenterMigrationException
    {
        internal UserMigrationException(int dc)
            : base($"User located on a different DC: {dc}.", dc)
        {
        }
    }
    
    internal class NetworkMigrationException : DataCenterMigrationException
    {
        internal NetworkMigrationException(int dc)
            : base($"Network located on a different DC: {dc}.", dc)
        {
        }
    }
}