// Copyright (c) 2004-2008 MySQL AB, 2008-2009 Sun Microsystems, Inc.
//
// MySQL Connector/NET is licensed under the terms of the GPLv2
// <http://www.gnu.org/licenses/old-licenses/gpl-2.0.html>, like most 
// MySQL Connectors. There are special exceptions to the terms and 
// conditions of the GPLv2 as it is applied to this software, see the 
// FLOSS License Exception
// <http://www.mysql.com/about/legal/licensing/foss-exception.html>.
//
// This program is free software; you can redistribute it and/or modify 
// it under the terms of the GNU General Public License as published 
// by the Free Software Foundation; version 2 of the License.
//
// This program is distributed in the hope that it will be useful, but 
// WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
// or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 
// for more details.
//
// You should have received a copy of the GNU General Public License along 
// with this program; if not, write to the Free Software Foundation, Inc., 
// 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA

using System;
using System.Collections;
using System.Diagnostics;
using System.IO;
using MySql.Data.Common;
using MySql.Data.Types;
using System.Security.Cryptography.X509Certificates;
using MySql.Data.MySqlClient.Properties;
using System.Text;
#if !CF
using System.Net.Security;
using System.Security.Authentication;
using System.Globalization;
#endif

namespace MySql.Data.MySqlClient
{
    /// <summary>
    /// Summary description for Driver.
    /// </summary>
    internal class NativeDriver : IDriver
    {
        private DBVersion version;
        private int threadId;
        protected String encryptionSeed;
        protected ServerStatusFlags serverStatus;
        protected MySqlStream stream;
        protected Stream baseStream;
        private BitArray nullMap;
        private MySqlPacket packet;
        private ClientFlags connectionFlags;
        private Driver owner;
        private int warnings;

        // Windows authentication method string, used by the protocol.
        // Also known as "client plugin name".
        const string AuthenticationWindowsPlugin = "authentication_windows_client";

        // Predefined username for IntegratedSecurity
        const string AuthenticationWindowsUser = "auth_windows";

        public NativeDriver(Driver owner)
        {
            this.owner = owner;
            threadId = -1;
        }

        public ClientFlags Flags
        {
            get { return connectionFlags; }
        }

        public int ThreadId
        {
            get { return threadId; }
        }

        public DBVersion Version
        {
            get { return version; }
        }

        public ServerStatusFlags ServerStatus
        {
            get { return serverStatus; }
        }

        public int WarningCount
        {
            get { return warnings; }
        }

        public MySqlPacket Packet
        {
            get { return packet; }
        }

        private MySqlConnectionStringBuilder Settings
        {
            get { return owner.Settings; }
        }

        private Encoding Encoding
        {
            get { return owner.Encoding; }
        }

        private void HandleException(MySqlException ex)
        {
            if (ex.IsFatal)
                owner.Close();
        }

        private void ReadOk(bool read)
        {
            try
            {
                if (read)
                    packet = stream.ReadPacket();
                byte marker = (byte) packet.ReadByte();
                if (marker != 0)
                {
                    throw new MySqlException("Out of sync with server", true, null);
                }

                packet.ReadFieldLength(); /* affected rows */
                packet.ReadFieldLength(); /* last insert id */
                if (packet.HasMoreData)
                {
                    serverStatus = (ServerStatusFlags) packet.ReadInteger(2);
                    packet.ReadInteger(2);  /* warning count */
                    if (packet.HasMoreData)
                    {
                        packet.ReadLenString();  /* message */
                    }
                }
            }
            catch (MySqlException ex)
            {
                HandleException(ex);
                throw;
            }
        }

        /// <summary>
        /// Sets the current database for the this connection
        /// </summary>
        /// <param name="dbName"></param>
        public void SetDatabase(string dbName)
        {
            byte[] dbNameBytes = Encoding.GetBytes(dbName);

            packet.Clear();
            packet.WriteByte((byte)DBCmd.INIT_DB);
            packet.Write(dbNameBytes);
            ExecutePacket(packet);

            ReadOk(true);
        }

        public void Configure()
        {
            stream.MaxPacketSize = (ulong)owner.MaxPacketSize;
            stream.Encoding = Encoding;
        }

        public void Open()
        {
            // connect to one of our specified hosts
            try
            {
#if !CF
                if (Settings.ConnectionProtocol == MySqlConnectionProtocol.SharedMemory)
                {
                    SharedMemoryStream str = new SharedMemoryStream(Settings.SharedMemoryName);
                    str.Open(Settings.ConnectionTimeout);
                    baseStream = str;
                }
                else
                {
#endif
                    string pipeName = Settings.PipeName;
                    if (Settings.ConnectionProtocol != MySqlConnectionProtocol.NamedPipe)
                        pipeName = null;
                    StreamCreator sc = new StreamCreator(Settings.Server, Settings.Port, pipeName,
                        Settings.Keepalive);
                    baseStream = sc.GetStream(Settings.ConnectionTimeout);
#if !CF
                }
#endif
            }
            catch (Exception ex)
            {
                throw new MySqlException(Resources.UnableToConnectToHost, 
                    (int) MySqlErrorCode.UnableToConnectToHost, ex);
            }

            if (baseStream == null)
                throw new MySqlException(Resources.UnableToConnectToHost,
                    (int)MySqlErrorCode.UnableToConnectToHost);

            int maxSinglePacket = 255*255*255;
            stream = new MySqlStream(baseStream, Encoding, false);

            stream.ResetTimeout((int)Settings.ConnectionTimeout*1000);

            // read off the welcome packet and parse out it's values
            packet = stream.ReadPacket();
            int protocol = packet.ReadByte();
            string versionString = packet.ReadString();
            version = DBVersion.Parse(versionString);
            if (!version.isAtLeast(5, 0, 0))
                throw new NotSupportedException(Resources.ServerTooOld);
            threadId = packet.ReadInteger(4);
            encryptionSeed = packet.ReadString();

            maxSinglePacket = (256*256*256) - 1;

            // read in Server capabilities if they are provided
            ClientFlags serverCaps = 0;
            if (packet.HasMoreData)
                serverCaps = (ClientFlags) packet.ReadInteger(2);

            /* New protocol with 16 bytes to describe server characteristics */
            owner.ConnectionCharSetIndex = (int)packet.ReadByte();

            serverStatus = (ServerStatusFlags) packet.ReadInteger(2);

            // Since 5.5, high bits of server caps are stored after status.
            // Previously, it was part of reserved always 0x00 13-byte filler.
            uint serverCapsHigh = (uint)packet.ReadInteger(2);
            serverCaps |= (ClientFlags)(serverCapsHigh << 16);

            packet.Position += 11;
            string seedPart2 = packet.ReadString();
            encryptionSeed += seedPart2;

            string authenticationMethod = ""; 
            if ((serverCaps & ClientFlags.PLUGIN_AUTH)!=0)
            {
                authenticationMethod = packet.ReadString();
            }
            
            // based on our settings, set our connection flags
            SetConnectionFlags(serverCaps);

            packet.Clear();
            packet.WriteInteger((int) connectionFlags, 4);

#if !CF
            if ((serverCaps & ClientFlags.SSL) ==0)
            {
                if ((Settings.SslMode != MySqlSslMode.None)
                && (Settings.SslMode != MySqlSslMode.Preferred))
                {
                    // Client requires SSL connections.
                    string message = String.Format(Resources.NoServerSSLSupport,
                        Settings.Server);
                    throw new MySqlException(message);
                }
            }
            else if (Settings.SslMode != MySqlSslMode.None)
            {
                stream.SendPacket(packet);
                StartSSL();
                packet.Clear();
                packet.WriteInteger((int) connectionFlags, 4);
            }
#endif

            packet.WriteInteger(maxSinglePacket, 4);
            packet.WriteByte(8);
            packet.Write(new byte[23]);

            Authenticate(false);

            // if we are using compression, then we use our CompressedStream class
            // to hide the ugliness of managing the compression
            if ((connectionFlags & ClientFlags.COMPRESS) != 0)
                stream = new MySqlStream(baseStream, Encoding, true);

            // give our stream the server version we are connected to.  
            // We may have some fields that are read differently based 
            // on the version of the server we are connected to.
            packet.Version = version;
            stream.MaxBlockSize = maxSinglePacket;
        }

#if !CF

        #region SSL

        /// <summary>
        /// Retrieve client SSL certificates. Dependent on connection string 
        /// settings we use either file or store based certificates.
        /// </summary>
        private X509CertificateCollection GetClientCertificates()
        {
            X509CertificateCollection certs = new X509CertificateCollection();

            // Check for file-based certificate
            if (Settings.CertificateFile != null)
            {
                if (!Version.isAtLeast(5, 1, 0))
                    throw new MySqlException(Properties.Resources.FileBasedCertificateNotSupported);

                X509Certificate2 clientCert = new X509Certificate2(Settings.CertificateFile,
                    Settings.CertificatePassword);
                certs.Add(clientCert);
                return certs;
            }

            if (Settings.CertificateStoreLocation == MySqlCertificateStoreLocation.None)
                return certs;

            StoreLocation location =
                (Settings.CertificateStoreLocation == MySqlCertificateStoreLocation.CurrentUser) ?
                StoreLocation.CurrentUser : StoreLocation.LocalMachine;

            // Check for store-based certificate
            X509Store store = new X509Store(StoreName.My, location);
            store.Open(OpenFlags.ReadOnly | OpenFlags.OpenExistingOnly);


            if (Settings.CertificateThumbprint == null)
            {
                // Return all certificates from the store.
                certs.AddRange(store.Certificates);
                return certs;
            }

            // Find certificate with given thumbprint
            certs.AddRange(store.Certificates.Find(X509FindType.FindByThumbprint,
                      Settings.CertificateThumbprint, true));

            if (certs.Count == 0)
            {
                throw new MySqlException("Certificate with Thumbprint " +
                   Settings.CertificateThumbprint + " not found");
            }
            return certs;
        }


        private void StartSSL()
        {
            RemoteCertificateValidationCallback sslValidateCallback =
                new RemoteCertificateValidationCallback(ServerCheckValidation);
            SslStream ss = new SslStream(baseStream, true, sslValidateCallback, null);
            X509CertificateCollection certs = GetClientCertificates();
            ss.AuthenticateAsClient(Settings.Server, certs, SslProtocols.Default, false);
            baseStream = ss;
            stream = new MySqlStream(ss, Encoding, false);
            stream.SequenceByte = 2;

        }

        private bool ServerCheckValidation(object sender, X509Certificate certificate,
                                                  X509Chain chain, SslPolicyErrors sslPolicyErrors)
        {
            if (sslPolicyErrors == SslPolicyErrors.None)
                return true;

            if (Settings.SslMode == MySqlSslMode.Preferred ||
                Settings.SslMode == MySqlSslMode.Required)
            {
                //Tolerate all certificate errors.
                return true;
            }

            if (Settings.SslMode == MySqlSslMode.VerifyCA && 
                sslPolicyErrors == SslPolicyErrors.RemoteCertificateNameMismatch)
            {
                // Tolerate name mismatch in certificate, if full validation is not requested.
                return true;
            }

            return false;
        }


        #endregion

#endif

        #region Authentication

        /// <summary>
        /// Return the appropriate set of connection flags for our
        /// server capabilities and our user requested options.
        /// </summary>
        private void SetConnectionFlags(ClientFlags serverCaps)
        {
            // allow load data local infile
            ClientFlags flags = ClientFlags.LOCAL_FILES;

            if (!Settings.UseAffectedRows)
                flags |= ClientFlags.FOUND_ROWS;

            flags |= ClientFlags.PROTOCOL_41;
            // Need this to get server status values
            flags |= ClientFlags.TRANSACTIONS;

            // user allows/disallows batch statements
            if (Settings.AllowBatch)
                flags |= ClientFlags.MULTI_STATEMENTS;

            // We always allow multiple result sets
            flags |= ClientFlags.MULTI_RESULTS;

            // if the server allows it, tell it that we want long column info
            if ((serverCaps & ClientFlags.LONG_FLAG) != 0)
                flags |= ClientFlags.LONG_FLAG;

            // if the server supports it and it was requested, then turn on compression
            if ((serverCaps & ClientFlags.COMPRESS) != 0 && Settings.UseCompression)
                flags |= ClientFlags.COMPRESS;

            flags |= ClientFlags.LONG_PASSWORD; // for long passwords

            // did the user request an interactive session?
            if (Settings.InteractiveSession)
                flags |= ClientFlags.INTERACTIVE;

            // if the server allows it and a database was specified, then indicate
            // that we will connect with a database name
            if ((serverCaps & ClientFlags.CONNECT_WITH_DB) != 0 &&
                Settings.Database != null && Settings.Database.Length > 0)
                flags |= ClientFlags.CONNECT_WITH_DB;

            // if the server is requesting a secure connection, then we oblige
            if ((serverCaps & ClientFlags.SECURE_CONNECTION) != 0)
                flags |= ClientFlags.SECURE_CONNECTION;

#if !CF
            // if the server is capable of SSL and the user is requesting SSL
            if ((serverCaps & ClientFlags.SSL) != 0 && Settings.SslMode != MySqlSslMode.None)
                flags |= ClientFlags.SSL;
#endif

            // if the server supports output parameters, then we do too
            if ((serverCaps & ClientFlags.PS_MULTI_RESULTS) != 0)
                flags |= ClientFlags.PS_MULTI_RESULTS;

            if(Settings.IntegratedSecurity)
            {
                if ((serverCaps & ClientFlags.PLUGIN_AUTH) != 0)
                    flags |= ClientFlags.PLUGIN_AUTH;
            }
            connectionFlags = flags;
        }


        private void AuthenticateSSPI()
        {

            string targetName = ""; // target name (required by Kerberos)

            // First packet sent by server should include target name (for
            // Kerberos) as UTF8 string. It might however be prepended by junk 
            // at the start of the string (0xfe"authentication_win_client"\0,
            // see Bug#57442), this junk will be ignored. Target name can also 
            // be an empty string if server is not running in a domain environment, 
            // in this case authentication will fallback to NTLM.

            // Note that 0xfe byte at the start could also indicate that windows
            // authentication is not supported by srver, we throw an exception
            // if this happens.

            packet = stream.ReadPacket();
            byte b = packet.ReadByte();
            if (b == 0xfe)
            {
                string authMethod = packet.ReadString();
                if (authMethod.Equals(AuthenticationWindowsPlugin))
                {
                    targetName = packet.ReadString(Encoding.UTF8);
                }
                else
                {
                    // User has requested Windows authentication,  bail out.
                    throw new MySqlException("unexpected authentication method " +
                        authMethod);
                }
            }
            else
            {
                targetName = Encoding.UTF8.GetString(packet.Buffer, 0, packet.Buffer.Length);
            }

            // Do SSPI authentication handshake
            SSPI sspi = new SSPI(targetName, stream.BaseStream, stream.SequenceByte);
            sspi.AuthenticateClient();

            // read ok packet.
            packet = stream.ReadPacket();
            ReadOk(false);
        }

        /// <summary>
        /// Perform an authentication against a 4.1.1 server
        /// <param name="reset">
        /// True, if this function is called as part of CHANGE_USER request
        /// (connection reset)
        /// False, for first-time logon
        /// </param>
        /// </summary>
        private void AuthenticateNew(bool reset)
        {
            if ((connectionFlags & ClientFlags.SECURE_CONNECTION) == 0)
                AuthenticateOld();

            packet.Write(Crypt.Get411Password(Settings.Password, encryptionSeed));
            if ((connectionFlags & ClientFlags.CONNECT_WITH_DB) != 0 && Settings.Database != null)
                packet.WriteString(Settings.Database);
            else
                packet.WriteString(""); // Add a null termination to the string.

            
            if (Settings.IntegratedSecurity)
            {
                // Append authentication method after the database name in the 
                // handshake authentication packet.If we're sending CHANGE_USER
                // also write charset number after database name prior to plugin name
                if (reset)
                {
                    packet.WriteInteger(8, 2); // Charset number
                }
                packet.WriteString(AuthenticationWindowsPlugin);
                stream.SendPacket(packet);
                AuthenticateSSPI();
                return;
            }
            else
            {
                stream.SendPacket(packet);
            }

            // this result means the server wants us to send the password using
            // old encryption
            packet = stream.ReadPacket();
            if (packet.IsLastPacket)
            {
                packet.Clear();
                packet.WriteString(Crypt.EncryptPassword(
                                       Settings.Password, encryptionSeed.Substring(0, 8), true));
                stream.SendPacket(packet);
                ReadOk(true);
            }
            ReadOk(false);
        }

        private void AuthenticateOld()
        {
            packet.WriteString(Crypt.EncryptPassword(
                                   Settings.Password, encryptionSeed, true));
            if ((connectionFlags & ClientFlags.CONNECT_WITH_DB) != 0 && Settings.Database != null)
                packet.WriteString(Settings.Database);

            stream.SendPacket(packet);
            ReadOk(true);
        }


        public void Authenticate(bool reset)
        {
            if (Settings.IntegratedSecurity)
            {
                packet.WriteString(AuthenticationWindowsUser);
            }
            else
            {
              // write the user id to the auth packet
              packet.WriteString(Settings.UserID);
            }
            AuthenticateNew(reset);
        }

        #endregion

        public void Reset()
        {
            warnings = 0;
            stream.Encoding = this.Encoding;
            stream.SequenceByte = 0;
            packet.Clear();
            packet.WriteByte((byte)DBCmd.CHANGE_USER);
            Authenticate(true);
        }

        /// <summary>
        /// Query is the method that is called to send all queries to the server
        /// </summary>
        public void SendQuery(MySqlPacket queryPacket)
        {
            warnings = 0;
            queryPacket.Buffer[4] = (byte)DBCmd.QUERY;
            ExecutePacket(queryPacket);
            // the server will respond in one of several ways with the first byte indicating
            // the type of response.
            // 0 == ok packet.  This indicates non-select queries
            // 0xff == error packet.  This is handled in stream.OpenPacket
            // > 0 = number of columns in select query
            // We don't actually read the result here since a single query can generate
            // multiple resultsets and we don't want to duplicate code.  See ReadResult
            // Instead we set our internal server status flag to indicate that we have a query waiting.
            // This flag will be maintained by ReadResult
            serverStatus |= ServerStatusFlags.AnotherQuery;
        }

        public void Close(bool isOpen)
        {
            try
            {
                if (isOpen)
                {
                    try
                    {
                        packet.Clear();
                        packet.WriteByte((byte)DBCmd.QUIT);
                        ExecutePacket(packet);
                    }
                    catch (Exception)
                    {
                        // Eat exception here. We should try to closing 
                        // the stream anyway.
                    }
                }

                if (stream != null)
                    stream.Close();
                stream = null;
            }
            catch (Exception)
            {
                // we are just going to eat any exceptions
                // generated here
            }
        }

        public bool Ping()
        {
            try
            {
                packet.Clear();
                packet.WriteByte((byte)DBCmd.PING);
                ExecutePacket(packet);
                ReadOk(true);
                return true;
            }
            catch (Exception)
            {
                return false;
            }
        }

        public int GetResult(ref int affectedRow, ref int insertedId)
        {
            try
            {
                packet = stream.ReadPacket();
            }
            catch (TimeoutException)
            {
                // Do not reset serverStatus, allow to reenter, e.g when
                // ResultSet is closed.
                throw;
            }
            catch (Exception)
            {
                serverStatus = 0;
                throw;
            }

            int fieldCount = (int)packet.ReadFieldLength();
            if (-1 == fieldCount)
            {
                string filename = packet.ReadString();
                SendFileToServer(filename);

                return GetResult(ref affectedRow, ref insertedId);
            }
            else if (fieldCount == 0)
            {
                // the code to read last packet will set these server status vars 
                // again if necessary.
                serverStatus &= ~(ServerStatusFlags.AnotherQuery |
                                  ServerStatusFlags.MoreResults);
                affectedRow = (int)packet.ReadFieldLength();
                insertedId = (int)packet.ReadFieldLength();

                serverStatus = (ServerStatusFlags)packet.ReadInteger(2);
                warnings += packet.ReadInteger(2);
                if (packet.HasMoreData)
                {
                    packet.ReadLenString(); //TODO: server message
                }
            }
            return fieldCount;
        }

        /// <summary>
        /// Sends the specified file to the server. 
        /// This supports the LOAD DATA LOCAL INFILE
        /// </summary>
        /// <param name="filename"></param>
        private void SendFileToServer(string filename)
        {
            byte[] buffer = new byte[8196];

            long len = 0;
            try
            {
                using (FileStream fs = new FileStream(filename, FileMode.Open,
                    FileAccess.Read))
                {
                    len = fs.Length;
                    while (len > 0)
                    {
                        int count = fs.Read(buffer, 4, (int)(len > 8192 ? 8192 : len));
                        stream.SendEntirePacketDirectly(buffer, count);
                        len -= count;
                    }
                    stream.SendEntirePacketDirectly(buffer, 0);
                }
            }
            catch (Exception ex)
            {
                throw new MySqlException("Error during LOAD DATA LOCAL INFILE", ex);
            }
        }

        private void ReadNullMap(int fieldCount)
        {
            // if we are binary, then we need to load in our null bitmap
            nullMap = null;
            byte[] nullMapBytes = new byte[(fieldCount + 9)/8];
            packet.ReadByte();
            packet.Read(nullMapBytes, 0, nullMapBytes.Length);
            nullMap = new BitArray(nullMapBytes);
        }

        public IMySqlValue ReadColumnValue(int index, MySqlField field, IMySqlValue valObject)
        {
            long length = -1;
            bool isNull;

            if (nullMap != null)
                isNull = nullMap[index + 2];
            else
            {
                length = packet.ReadFieldLength();
                isNull = length == -1;
            }

            packet.Encoding = field.Encoding;
            packet.Version = version;
            return valObject.ReadValue(packet, length, isNull);
        }

        public void SkipColumnValue(IMySqlValue valObject)
        {
            int length = -1;
            if (nullMap == null)
            {
                length = (int)packet.ReadFieldLength();
                if (length == -1) return;
            }
            if (length > -1)
                packet.Position += length;
            else
                valObject.SkipValue(packet);
        }

        public void GetColumnsData(MySqlField[] columns)
        {
            for (int i = 0; i < columns.Length; i++)
                GetColumnData(columns[i]);
            ReadEOF();
        }

        private void GetColumnData(MySqlField field)
        {
            stream.Encoding = Encoding;
            packet = stream.ReadPacket();
            field.Encoding = Encoding;
            field.CatalogName = packet.ReadLenString();
            field.DatabaseName = packet.ReadLenString();
            field.TableName = packet.ReadLenString();
            field.RealTableName = packet.ReadLenString();
            field.ColumnName = packet.ReadLenString();
            field.OriginalColumnName = packet.ReadLenString();
            packet.ReadByte();
            field.CharacterSetIndex = packet.ReadInteger(2);
            field.ColumnLength = packet.ReadInteger(4);
            MySqlDbType type = (MySqlDbType)packet.ReadByte();
            ColumnFlags colFlags;
            if ((connectionFlags & ClientFlags.LONG_FLAG) != 0)
                colFlags = (ColumnFlags)packet.ReadInteger(2);
            else
                colFlags = (ColumnFlags)packet.ReadByte();
            field.Scale = (byte)packet.ReadByte();

            if (packet.HasMoreData)
            {
                packet.ReadInteger(2); // reserved
            }

            if (type == MySqlDbType.Decimal || type == MySqlDbType.NewDecimal)
            {
                field.Precision = (byte)(field.ColumnLength - 2);
                if ((colFlags & ColumnFlags.UNSIGNED) != 0)
                    field.Precision++;
            }

            field.SetTypeAndFlags(type, colFlags);
        }

        private void ExecutePacket(MySqlPacket packetToExecute)
        {
            try
            {
                warnings = 0;
                stream.SequenceByte = 0;
                stream.SendPacket(packetToExecute);
            }
            catch (MySqlException ex)
            {
                HandleException(ex);
                throw;
            }
        }

        public void ExecuteStatement(MySqlPacket packetToExecute)
        {
            warnings = 0;
            packetToExecute.Buffer[4] = (byte)DBCmd.EXECUTE;
            ExecutePacket(packetToExecute);
            serverStatus |= ServerStatusFlags.AnotherQuery;
        }

        private void CheckEOF()
        {
            if (!packet.IsLastPacket)
                throw new MySqlException("Expected end of data packet");

            packet.ReadByte(); // read off the 254

            if (packet.HasMoreData)
            {
                warnings += packet.ReadInteger(2);
                serverStatus = (ServerStatusFlags)packet.ReadInteger(2);

                // if we are at the end of this cursor based resultset, then we remove
                // the last row sent status flag so our next fetch doesn't abort early
                // and we remove this command result from our list of active CommandResult objects.
                //                if ((serverStatus & ServerStatusFlags.LastRowSent) != 0)
                //              {
                //                serverStatus &= ~ServerStatusFlags.LastRowSent;
                //              commandResults.Remove(lastCommandResult);
                //        }
            }
        }

        private void ReadEOF()
        {
            packet = stream.ReadPacket();
            CheckEOF();
        }

        public int PrepareStatement(string sql, ref MySqlField[] parameters)
        {
            //TODO: check this
            //ClearFetchedRow();

            packet.Length = sql.Length*4 + 5;
            byte[] buffer = packet.Buffer;
            int len = Encoding.GetBytes(sql, 0, sql.Length, packet.Buffer, 5);
            packet.Position = len + 5;
            buffer[4] = (byte)DBCmd.PREPARE;
            ExecutePacket(packet);

            packet = stream.ReadPacket();

            int marker = packet.ReadByte();
            if (marker != 0)
                throw new MySqlException("Expected prepared statement marker");

            int statementId = packet.ReadInteger(4);
            int numCols = packet.ReadInteger(2);
            int numParams = packet.ReadInteger(2);
            //TODO: find out what this is needed for
            packet.ReadInteger(3);
            if (numParams > 0)
            {
                parameters = owner.GetColumns(numParams);
                // we set the encoding for each parameter back to our connection encoding
                // since we can't trust what is coming back from the server
                for (int i = 0; i < parameters.Length; i++)
                    parameters[i].Encoding = Encoding;
            }

            if (numCols > 0)
            {
                while (numCols-- > 0)
                {
                    packet = stream.ReadPacket();
                    //TODO: handle streaming packets
                }

                ReadEOF();
            }

            return statementId;
        }

        //		private void ClearFetchedRow() 
        //		{
        //			if (lastCommandResult == 0) return;

        //TODO
        /*			CommandResult result = (CommandResult)commandResults[lastCommandResult];
					result.ReadRemainingColumns();

					stream.OpenPacket();
					if (! stream.IsLastPacket)
						throw new MySqlException("Cursor reading out of sync");

					ReadEOF(false);
					lastCommandResult = 0;*/
        //		}

        /// <summary>
        /// FetchDataRow is the method that the data reader calls to see if there is another 
        /// row to fetch.  In the non-prepared mode, it will simply read the next data packet.
        /// In the prepared mode (statementId > 0), it will 
        /// </summary>
        public bool FetchDataRow(int statementId, int columns)
        {
            /*			ClearFetchedRow();

						if (!commandResults.ContainsKey(statementId)) return false;

						if ( (serverStatus & ServerStatusFlags.LastRowSent) != 0)
							return false;

						stream.StartPacket(9, true);
						stream.WriteByte((byte)DBCmd.FETCH);
						stream.WriteInteger(statementId, 4);
						stream.WriteInteger(1, 4);
						stream.Flush();

						lastCommandResult = statementId;
							*/
            packet = stream.ReadPacket();
            if (packet.IsLastPacket)
            {
                CheckEOF();
                return false;
            }
            nullMap = null;
            if (statementId > 0)
                ReadNullMap(columns);

			return true;
		}

        public void CloseStatement(int statementId)
        {
            packet.Clear();
            packet.WriteByte((byte)DBCmd.CLOSE_STMT);
            packet.WriteInteger((long)statementId, 4);
            stream.SequenceByte = 0;
            stream.SendPacket(packet);
        }

        /// <summary>
        /// Execution timeout, in milliseconds. When the accumulated time for network IO exceeds this value
        /// TimeoutException is thrown. This timeout needs to be reset for every new command
        /// </summary>
        /// 
        public void ResetTimeout(int timeout)
        {
            if (stream != null)
                stream.ResetTimeout(timeout);
        }

    }
 
}