using System;
using System.Text;

namespace AuthTest
{
    internal class BitWriter
    {
        private readonly byte[] _buffer;
        private int _numBits;

        internal BitWriter(int capacity)
        {
            _buffer = new byte[capacity];
        }

        internal byte[] Buffer
        {
            get { return _buffer; }
        }

        internal int NumBits
        {
            get { return _numBits; }
        }

        internal int Length
        {
            get
            {
                int pos7 = (WritePos & 7);
                int bitsLeft = 8 - pos7;

                if (bitsLeft == 0)
                    return NumBits / 8;
                return (_numBits + bitsLeft)/8;
            }
        }

        internal int WritePos { get; set; }

        private static int Shift<T>(T left, int right)
        {
            if (typeof (T).Name == "Int32")
                return Convert.ToInt32(left) >> right;

            if (typeof (T).Name == "UInt32")
                return (int) (Convert.ToUInt32(left) >> right);

            return 0;
        }

        private void AlignToNextByte()
        {
            WritePos = (WritePos + 7) & ~7;
        }

        internal void WriteBytes( byte[] bytes )
        {
            AlignToNextByte();

            foreach (var b in bytes)
            {
                WriteBits((int)b, 8);
            }
        }

        private void WriteBytes( byte[] bytes, int length )
        {
            var buf = new byte[length];
            Array.Copy(bytes, 0, buf, 0, length);
            WriteBytes(buf);
        }

        public void WriteBuffer(byte[] bytes, int byteLength, int sizeBitCount)
        {
            WriteBits(byteLength, sizeBitCount);
            WriteBytes(bytes, byteLength);
        }

        internal void WriteInt32( int intVal )
        {
            WriteBits(intVal, 32);
        }

        internal void WriteBits<T>(T valz, int numBits)
        {
            if (numBits > 0)
            {
                _numBits += numBits;
                while (true)
                {
                    int pos7 = (WritePos & 7);
                    int unk = 8 - pos7;
                    var lShift = (char) (1 << unk);
                    int subNum;

                    if (unk < numBits)
                        subNum = unk;
                    else
                    {
                        lShift = (char) (1 << numBits);
                        subNum = numBits;
                    }

                    numBits -= subNum;

                    var firstHalf = (char) (~((lShift - 1) << pos7));

                    var shifted = (char) Shift(valz, numBits);
                    var secondHalf = (char) (((lShift - 1) & shifted) << pos7);

                    Buffer[WritePos >> 3] = (byte) (Buffer[WritePos >> 3] & firstHalf | secondHalf);

                    WritePos += subNum;

                    if (numBits == 0)
                        return;
                }
            }
        }

        internal void WriteFourCC(string fourCC)
        {
            byte[] arr = Encoding.ASCII.GetBytes(fourCC);
            Array.Reverse(arr);

            if (arr.Length < 4)
            {
                byte[] backup = arr;
                arr = new byte[arr.Length + 1];
                backup.CopyTo(arr, 0);
            }
            int test = BitConverter.ToInt32(arr, 0);
            WriteInt32(BitConverter.ToInt32(arr,0));
        }

        internal void WriteHeader( int packetId, int channelId )
        {
            WriteBits(packetId, 6);
            WriteBits(1, 1);
            WriteBits(channelId, 4);
        }

        public override string ToString()
        {
            string str = "";
            int numBytes = _numBits/8;

            if (_numBits % 8 > 0)
                numBytes++;

            for( int i = 0; i < numBytes; i++)
            {
                if (i > 0 && i % 16 == 0)
                    str += Environment.NewLine;

                str += string.Format("{0:x2} ", Buffer[i]);
            }
            return str;
        }
    }
}