// Copyright (c) 2004, 2021, Oracle and/or its affiliates.
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License, version 2.0, as
// published by the Free Software Foundation.
//
// This program is also distributed with certain software (including
// but not limited to OpenSSL) that is licensed under separate terms,
// as designated in a particular file or component or in included license
// documentation.  The authors of MySQL hereby grant you an
// additional permission to link the program and your derivative works
// with the separately licensed software that they have included with
// MySQL.
//
// Without limiting anything contained in the foregoing, this file,
// which is part of MySQL Connector/NET, is also subject to the
// Universal FOSS Exception, version 1.0, a copy of which can be found at
// http://oss.oracle.com/licenses/universal-foss-exception.
//
// 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, version 2.0, 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.IO;
using System.Text;
using MySql.Data.Common;
using Sog.Properties;

namespace MySql.Data.MySqlClient
{
    class MySqlPacket
    {
        private byte[] _tempBuffer = new byte[256];
        private Encoding _encoding;
        private readonly MemoryStream _buffer = new MemoryStream(5);

        private MySqlPacket()
        {
            this.Clear();
        }

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

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

        #region Properties

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

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

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

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

        public bool IsLastPacket
        {
            get
            {
                byte[] bits = this._buffer.GetBuffer();

                return bits[0] == 0xfe && this.Length <= 5;
            }
        }

        public byte[] Buffer
        {
            get
            {
                byte[] bits = this._buffer.GetBuffer();

                return bits;
            }
        }

        public DBVersion Version { get; set; }

        #endregion

        public void Clear()
        {
            this.Position = 4;
        }


        #region Byte methods

        public byte ReadByte()
        {
            return (byte)this._buffer.ReadByte();
        }

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

        public void WriteByte(byte b)
        {
            this._buffer.WriteByte(b);
        }

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

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

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

            return this.ReadInteger(c);
        }

        public void SetByte(long position, byte value)
        {
            long currentPosition = this._buffer.Position;
            this._buffer.Position = position;
            this._buffer.WriteByte(value);
            this._buffer.Position = currentPosition;
        }

        #endregion

        #region Integer methods

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

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

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

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

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

            this._buffer.Position += numbytes;
            return value;
        }

        public long ReadLong(int numbytes)
        {
            Debug.Assert((this._buffer.Position + numbytes) <= this._buffer.Length);

            byte[] bits = this._buffer.GetBuffer();
            int pos = (int)this._buffer.Position;
            this._buffer.Position += numbytes;

            switch (numbytes)
            {
                case 2: return BitConverter.ToUInt16(bits, pos);
                case 4: return BitConverter.ToUInt32(bits, pos);
                case 8: return BitConverter.ToInt64(bits, pos);
            }

            throw new NotSupportedException("Only byte lengths of 2, 4, or 8 are supported");
        }

        public ulong ReadULong(int numbytes)
        {
            Debug.Assert((this._buffer.Position + numbytes) <= this._buffer.Length);

            byte[] bits = this._buffer.GetBuffer();

            int pos = (int)this._buffer.Position;
            this._buffer.Position += numbytes;

            switch (numbytes)
            {
                case 2: return BitConverter.ToUInt16(bits, pos);
                case 4: return BitConverter.ToUInt32(bits, pos);
                case 8: return BitConverter.ToUInt64(bits, pos);
            }

            throw new NotSupportedException("Only byte lengths of 2, 4, or 8 are supported");
        }

        public int Read3ByteInt()
        {
            int value = 0;

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

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

            this._buffer.Position += 3;
            return value;
        }

        public int ReadInteger(int numbytes)
        {
            if (numbytes == 3)
            {
                return this.Read3ByteInt();
            }

            Debug.Assert(numbytes <= 4);
            return (int)this.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++)
            {
                this._tempBuffer[x] = (byte)(val & 0xff);
                val >>= 8;
            }

            this.Write(this._tempBuffer, 0, numbytes);
        }

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

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

        public void WriteLength(long length)
        {
            if (length < 251)
            {
                this.WriteByte((byte)length);
            }
            else if (length < 65536L)
            {
                this.WriteByte(252);
                this.WriteInteger(length, 2);
            }
            else if (length < 16777216L)
            {
                this.WriteByte(253);
                this.WriteInteger(length, 3);
            }
            else
            {
                this.WriteByte(254);
                this.WriteInteger(length, 8);
            }
        }

        #endregion

        #region String methods

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

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

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

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

        public string ReadAsciiString(long length)
        {
            if (length == 0)
            {
                return String.Empty;
            }

            // byte[] buf = new byte[length];
            this.Read(this._tempBuffer, 0, (int)length);
            return Encoding.GetEncoding("us-ascii").GetString(this._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 (this._tempBuffer == null || length > this._tempBuffer.Length)
            {
                this._tempBuffer = new byte[length];
            }

            this.Read(this._tempBuffer, 0, (int)length);
            return this._encoding.GetString(this._tempBuffer, 0, (int)length);
        }

        public string ReadString()
        {
            return this.ReadString(this._encoding);
        }

        public string ReadString(Encoding theEncoding)
        {
            byte[] bytes = this.ReadStringAsBytes();
            string s = theEncoding.GetString(bytes, 0, bytes.Length);
            return s;
        }

        public byte[] ReadStringAsBytes()
        {
            byte[] readBytes;
            byte[] bits = this._buffer.GetBuffer();
            int end = (int)this._buffer.Position;
            byte[] tempBuffer = bits;

            while (end < (int)this._buffer.Length &&
                tempBuffer[end] != 0 && (int)tempBuffer[end] != -1)
            {
                end++;
            }

            readBytes = new byte[end - this._buffer.Position];
            Array.Copy(tempBuffer, (int)this._buffer.Position, readBytes, 0, (int)(end - this._buffer.Position));
            this._buffer.Position = end + 1;

            return readBytes;
        }

        #endregion
    }
}