/*
 
Copyright (c) 2017 Ahmed Kh. Zamil

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

*/

using Esiur.Data;
using Esiur.Security.Authority;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;

namespace Esiur.Net.Packets
{
    class IIPAuthPacket : Packet
    {
        public enum IIPAuthPacketCommand : byte
        {
            Action = 0,
            Declare,
            Acknowledge,
            Error,
        }

        public enum IIPAuthPacketAction : byte
        {
            // Authenticate
            AuthenticateHash,


            //Challenge,
            //CertificateRequest,
            //CertificateReply,
            //EstablishRequest,
            //EstablishReply

            NewConnection = 0x20,
            ResumeConnection,

            ConnectionEstablished = 0x28
        }




        public IIPAuthPacketCommand Command
        {
            get;
            set;
        }
        public IIPAuthPacketAction Action
        {
            get;
            set;
        }

        public byte ErrorCode { get; set; }
        public string ErrorMessage { get; set; }

        public AuthenticationMethod LocalMethod
        {
            get;
            set;
        }

        public byte[] SourceInfo
        {
            get;
            set;
        }

        public byte[] Hash
        {
            get;
            set;
        }

        public byte[] SessionId
        {
            get;
            set;
        }

        public AuthenticationMethod RemoteMethod
        {
            get;
            set;
        }

        public string Domain
        {
            get;
            set;
        }

        public long CertificateId
        {
            get; set;
        }

        public string LocalUsername
        {
            get;
            set;
        }

        public string RemoteUsername
        {
            get;
            set;
        }

        public byte[] LocalPassword
        {
            get;
            set;
        }
        public byte[] RemotePassword
        {
            get;
            set;
        }

        public byte[] LocalToken
        {
            get;
            set;
        }

        public byte[] RemoteToken
        {
            get;
            set;
        }

        public byte[] AsymetricEncryptionKey
        {
            get;
            set;
        }

        public byte[] LocalNonce
        {
            get;
            set;
        }

        public byte[] RemoteNonce
        {
            get;
            set;
        }

        public ulong RemoteTokenIndex { get; set; }

        private uint dataLengthNeeded;

        bool NotEnough(uint offset, uint ends, uint needed)
        {
            if (offset + needed > ends)
            {
                dataLengthNeeded = needed - (ends - offset);
                return true;
            }
            else
                return false;
        }

        public override string ToString()
        {
            return Command.ToString() + " " + Action.ToString();
        }

        public override long Parse(byte[] data, uint offset, uint ends)
        {
            var oOffset = offset;

            if (NotEnough(offset, ends, 1))
                return -dataLengthNeeded;

            Command = (IIPAuthPacketCommand)(data[offset] >> 6);

            if (Command == IIPAuthPacketCommand.Action)
            {
                Action = (IIPAuthPacketAction)(data[offset++] & 0x3f);

                if (Action == IIPAuthPacketAction.AuthenticateHash)
                {
                    if (NotEnough(offset, ends, 32))
                        return -dataLengthNeeded;

                    Hash = data.Clip(offset, 32);

                    //var hash = new byte[32];
                    //Buffer.BlockCopy(data, (int)offset, hash, 0, 32);
                    //Hash = hash;

                    offset += 32;
                }
                else if (Action == IIPAuthPacketAction.NewConnection)
                {
                    if (NotEnough(offset, ends, 2))
                        return -dataLengthNeeded;

                    var length = data.GetUInt16(offset);

                    offset += 2;

                    if (NotEnough(offset, ends, length))
                        return -dataLengthNeeded;

                    SourceInfo = data.Clip(offset, length);

                    //var sourceInfo = new byte[length];
                    //Buffer.BlockCopy(data, (int)offset, sourceInfo, 0, length);
                    //SourceInfo = sourceInfo;

                    offset += 32;
                }
                else if (Action == IIPAuthPacketAction.ResumeConnection
                     || Action == IIPAuthPacketAction.ConnectionEstablished)
                {
                    //var sessionId = new byte[32];

                    if (NotEnough(offset, ends, 32))
                        return -dataLengthNeeded;

                    SessionId = data.Clip(offset, 32);

                    //Buffer.BlockCopy(data, (int)offset, sessionId, 0, 32);
                    //SessionId = sessionId;

                    offset += 32;
                }
            }
            else if (Command == IIPAuthPacketCommand.Declare)
            {
                RemoteMethod = (AuthenticationMethod)((data[offset] >> 4) & 0x3);
                LocalMethod = (AuthenticationMethod)((data[offset] >> 2) & 0x3);
                var encrypt = ((data[offset++] & 0x2) == 0x2);


                if (NotEnough(offset, ends, 1))
                    return -dataLengthNeeded;

                var domainLength = data[offset++];
                if (NotEnough(offset, ends, domainLength))
                    return -dataLengthNeeded;

                var domain = data.GetString(offset, domainLength);

                Domain = domain;

                offset += domainLength;


                if (RemoteMethod == AuthenticationMethod.Credentials)
                {
                    if (LocalMethod == AuthenticationMethod.None)
                    {
                        if (NotEnough(offset, ends, 33))
                            return -dataLengthNeeded;

                        //var remoteNonce = new byte[32];
                        //Buffer.BlockCopy(data, (int)offset, remoteNonce, 0, 32);
                        //RemoteNonce = remoteNonce;

                        RemoteNonce = data.Clip(offset, 32);

                        offset += 32;

                        var length = data[offset++];

                        if (NotEnough(offset, ends, length))
                            return -dataLengthNeeded;

                        RemoteUsername = data.GetString(offset, length);


                        offset += length;
                    }
                }
                else if (RemoteMethod == AuthenticationMethod.Token)
                {
                    if (LocalMethod == AuthenticationMethod.None)
                    {
                        if (NotEnough(offset, ends, 37))
                            return -dataLengthNeeded;

                        RemoteNonce = data.Clip(offset, 32);

                        offset += 32;

                        RemoteTokenIndex = data.GetUInt64(offset);
                        offset += 8;
                    }
                }

                if (encrypt)
                {
                    if (NotEnough(offset, ends, 2))
                        return -dataLengthNeeded;

                    var keyLength = data.GetUInt16(offset);

                    offset += 2;

                    if (NotEnough(offset, ends, keyLength))
                        return -dataLengthNeeded;

                    //var key = new byte[keyLength];
                    //Buffer.BlockCopy(data, (int)offset, key, 0, keyLength);
                    //AsymetricEncryptionKey = key;

                    AsymetricEncryptionKey = data.Clip(offset, keyLength);

                    offset += keyLength;
                }
            }
            else if (Command == IIPAuthPacketCommand.Acknowledge)
            {
                RemoteMethod = (AuthenticationMethod)((data[offset] >> 4) & 0x3);
                LocalMethod = (AuthenticationMethod)((data[offset] >> 2) & 0x3);
                var encrypt = ((data[offset++] & 0x2) == 0x2);

                if (RemoteMethod == AuthenticationMethod.None)
                {
                    if (LocalMethod == AuthenticationMethod.None)
                    {
                        // do nothing
                    }
                }
                else if (RemoteMethod == AuthenticationMethod.Credentials
                       || RemoteMethod == AuthenticationMethod.Token)
                {
                    if (LocalMethod == AuthenticationMethod.None)
                    {
                        if (NotEnough(offset, ends, 32))
                            return -dataLengthNeeded;

                        RemoteNonce = data.Clip(offset, 32);
                        offset += 32;

                    }
                }

                if (encrypt)
                {
                    if (NotEnough(offset, ends, 2))
                        return -dataLengthNeeded;

                    var keyLength = data.GetUInt16(offset);

                    offset += 2;

                    if (NotEnough(offset, ends, keyLength))
                        return -dataLengthNeeded;

                    //var key = new byte[keyLength];
                    //Buffer.BlockCopy(data, (int)offset, key, 0, keyLength);
                    //AsymetricEncryptionKey = key;

                    AsymetricEncryptionKey = data.Clip(offset, keyLength);

                    offset += keyLength;
                }
            }
            else if (Command == IIPAuthPacketCommand.Error)
            {
                if (NotEnough(offset, ends, 4))
                    return -dataLengthNeeded;

                offset++;
                ErrorCode = data[offset++];


                var cl = data.GetUInt16(offset);
                offset += 2;

                if (NotEnough(offset, ends, cl))
                    return -dataLengthNeeded;

                ErrorMessage = data.GetString(offset, cl);
                offset += cl;

            }


            return offset - oOffset;

        }

    }
}