// Copyright © 2004,2010, Oracle and/or its affiliates.  All rights reserved.
//
// 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.Diagnostics;
using System.Text;
using System.IO;
using MySql.Data.Common;
using MySql.Data.MySqlClient.Properties;

namespace MySql.Data.MySqlClient
{
    class MySqlPacket
    {
        private byte[] tempBuffer = new byte[256];
        private Encoding encoding;
        private MemoryStream buffer = new MemoryStream(5);
        private DBVersion version;

        private MySqlPacket()
        {
            Clear();
        }

        public MySqlPacket(Encoding enc) : this()
        {
            Encoding = enc;
        }

        public MySqlPacket(MemoryStream stream)
            : this()
        {
            buffer = stream;
        }

        #region Properties

        public Encoding Encoding
        {
            get { return encoding; }
            set 
            {
                Debug.Assert(value != null);
                encoding = value; 
            }
        }

        public bool HasMoreData
        {
            get { return buffer.Position < buffer.Length; }
        }

        public int Position
        {
            get { return (int)buffer.Position; }
            set { buffer.Position = (long)value; }
        }

        public int Length 
        {
            get { return (int)buffer.Length; }
            set { buffer.SetLength(value); }
        }

        public bool IsLastPacket
        {
            get 
            {
                byte[] bits = buffer.GetBuffer();
                return bits[0] == 0xfe && Length <= 5; 
            }
        }

        public byte[] Buffer
        {
            get { return buffer.GetBuffer(); }
        }

        public DBVersion Version
        {
            get { return version; }
            set { version = value; }
        }

        #endregion

        public void Clear()
        {
            Position = 4;
        }


        #region Byte methods

        public byte ReadByte()
        {
            return (byte)buffer.ReadByte();
        }

        public int Read(byte[] byteBuffer, int offset, int count)
        {
            return buffer.Read(byteBuffer, offset, count);
        }

        public void WriteByte(byte b)
        {
            buffer.WriteByte(b);
        }

        public void Write(byte[] bytesToWrite)
        {
            Write(bytesToWrite, 0, bytesToWrite.Length);
        }

        public void Write(byte[] bytesToWrite, int offset, int countToWrite)
        {
            buffer.Write(bytesToWrite, offset, countToWrite);
        }

        public int ReadNBytes()
        {
            byte c = ReadByte();
            if (c < 1 || c > 4)
                throw new MySqlException(Resources.IncorrectTransmission);
            return ReadInteger(c);
        }

        #endregion

        #region Integer methods

        public long ReadFieldLength()
        {
            byte c = ReadByte();

            switch (c)
            {
                case 251: return -1;
                case 252: return ReadInteger(2);
                case 253: return ReadInteger(3);
                case 254: return ReadLong(8);
                default: return c;
            }
        }

        public ulong ReadBitValue(int numbytes)
        {
            ulong value = 0;

            int pos = (int)buffer.Position;
            byte[] bits = buffer.GetBuffer();
            int shift = 0;

            for (int i = 0; i < numbytes; i++)
            {
                value <<= shift;
                value |= bits[pos++];
                shift = 8;
            }
            buffer.Position += numbytes;
            return value;
        }

        public long ReadLong(int numbytes)
        {
            Debug.Assert((buffer.Position + numbytes) <= buffer.Length);
            byte[] bytes = buffer.GetBuffer();
            int pos = (int)buffer.Position;
            buffer.Position += numbytes;
            switch (numbytes)
            {
                case 2: return BitConverter.ToUInt16(bytes, pos);
                case 4: return BitConverter.ToUInt32(bytes, pos);
                case 8: return BitConverter.ToInt64(bytes, pos);
            }
            throw new NotSupportedException("Only byte lengths of 2, 4, or 8 are supported");
        }

        public ulong ReadULong(int numbytes)
        {
            Debug.Assert((buffer.Position + numbytes) <= buffer.Length);
            byte[] bytes = buffer.GetBuffer();
            int pos = (int)buffer.Position;
            buffer.Position += numbytes;
            switch (numbytes)
            {
                case 2: return BitConverter.ToUInt16(bytes, pos);
                case 4: return BitConverter.ToUInt32(bytes, pos);
                case 8: return BitConverter.ToUInt64(bytes, pos);
            }
            throw new NotSupportedException("Only byte lengths of 2, 4, or 8 are supported");
        }

        public int Read3ByteInt()
        {
            int value = 0;

            int pos = (int)buffer.Position;
            byte[] bits = buffer.GetBuffer();
            int shift = 0;

            for (int i = 0; i < 3; i++)
            {
                value |= (int)(bits[pos++] << shift);
                shift += 8;
            }
            buffer.Position += 3;
            return value;
        }

        public int ReadInteger(int numbytes)
        {
            if (numbytes == 3)
                return Read3ByteInt();
            Debug.Assert(numbytes <= 4);
            return (int)ReadLong(numbytes);
        }

        /// <summary>
        /// WriteInteger
        /// </summary>
        /// <param name="v"></param>
        /// <param name="numbytes"></param>
        public void WriteInteger(long v, int numbytes)
        {
            long val = v;

            Debug.Assert(numbytes > 0 && numbytes < 9);

            for (int x = 0; x < numbytes; x++)
            {
                tempBuffer[x] = (byte)(val & 0xff);
                val >>= 8;
            }
            Write(tempBuffer, 0, numbytes);
        }

        public int ReadPackedInteger()
        {
            byte c = ReadByte();

            switch (c)
            {
                case 251: return -1;
                case 252: return ReadInteger(2);
                case 253: return ReadInteger(3);
                case 254: return ReadInteger(4);
                default: return c;
            }
        }

        public void WriteLength(long length)
        {
            if (length < 251)
                WriteByte((byte)length);
            else if (length < 65536L)
            {
                WriteByte(252);
                WriteInteger(length, 2);
            }
            else if (length < 16777216L)
            {
                WriteByte(253);
                WriteInteger(length, 3);
            }
            else
            {
                WriteByte(254);
                WriteInteger(length, 4);
            }
        }

        #endregion

        #region String methods

        public void WriteLenString(string s)
        {
            byte[] bytes = encoding.GetBytes(s);
            WriteLength(bytes.Length);
            Write(bytes, 0, bytes.Length);            
        }

        public void WriteStringNoNull(string v)
        {
            byte[] bytes = encoding.GetBytes(v);
            Write(bytes, 0, bytes.Length);
        }

        public void WriteString(string v)
        {
            WriteStringNoNull(v);
            WriteByte(0);
        }

        public string ReadLenString()
        {
            long len = ReadPackedInteger();
            return ReadString(len);
        }

        public string ReadAsciiString(long length)
        {
            if (length == 0)
                return String.Empty;
            //            byte[] buf = new byte[length];
            Read(tempBuffer, 0, (int)length);
            return ASCIIEncoding.ASCII.GetString(tempBuffer, 0, (int)length);
            //return encoding.GetString(tempBuffer, 0, (int)length); //buf.Length);
        }

        public string ReadString(long length)
        {
            if (length == 0)
                return String.Empty;
            if (tempBuffer == null || length > tempBuffer.Length)
                tempBuffer = new byte[length];
            Read(tempBuffer, 0, (int)length);
            return encoding.GetString(tempBuffer, 0, (int)length);
        }

        public string ReadString(Encoding enc)
        {
            byte[] bits = buffer.GetBuffer();
            int end = (int)buffer.Position;

            while (end < (int)buffer.Length &&
                bits[end] != 0 && (int)bits[end] != -1)
                end++;

            string s = enc.GetString(bits, 
                (int)buffer.Position, end - (int)buffer.Position);
            buffer.Position = end + 1;
            return s;
        }

        public string ReadString()
        {
            return ReadString(this.encoding);
        }
        #endregion        
    }
}