// ----------------------------------------------------------------------------
//
//  Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ----------------------------------------------------------------------------

using System;
using System.Collections.Generic;
using System.Text;
using Microsoft.Singularity;
using Microsoft.SingSharp;
using Microsoft.Singularity.Channels;

namespace Smb.Shared
{
    public class ByteWriter
    {
        byte[]! _buffer;
        int _length;
        int _pos;
        
        // requires _pos >= 0;
        // requires _pos <= _length;
        // requires _length <= _buffer.Length;

        public ByteWriter()
        {
            _buffer = new byte[0x100];
            _length = 0;
            _pos = 0;
        }

        public int Position
        {
            get { return _pos; }
            set { _pos = value; }
        }

        public int Length
        {
            get
				// ensures _length >= 0;
			{ return _length; }
				
            set
				requires value >= 0;
            {
                if (value < 0)
                    throw new Exception("Length cannot be negative");
                InsureCapacity(value);
                _length = value;
            }
        }

        public void InsureCapacity(int capacity)
			requires capacity >= 0;
        {
            if (capacity < 0)
                throw new Exception("Capacity cannot be negative");

            if (capacity <= _buffer.Length)
                return;

            int newsize = capacity * 3 / 2 + 0x20;
            byte[] newbuffer = new byte[newsize];
            if (_length > 0)
                Buffer.BlockCopy(_buffer, 0, newbuffer, 0, _length);
            _buffer = newbuffer;
        }

        public void Write(byte b)
        {
            if (_pos < _length) {
                _buffer[_pos++] = b;
                return;
            }

            if (_length == _buffer.Length)
                InsureCapacity(_length + 1);
            _buffer[_length] = b;
            _length++;
            _pos = _length;
        }

        public void WriteZero(int count)
        {
            if (count == 0)
                return;
            if (count < 0)
                throw new Exception("Count cannot be negative.");

            InsureCapacity(_pos + count);
            for (int i = 0; i < count; i++)
                _buffer[_pos + i] = 0;
            _pos += count;
            if (_pos > _length)
                _length = _pos;
        }

#if ENABLE_GENERICS
        public void Write(ArraySpan<byte> span)
        {
            Write(span.ContainingArray, span.Offset, span.Length);
        }
#else
        public void Write(ArraySpan_byte span)
        {
            Write(span.ContainingArray, span.Offset, span.Length);
        }		
#endif

        public void Write(byte[]! data, int offset, int length)
        {
            if (length == 0)
                return;
            if (length < 0)
                throw new Exception("Length cannot be negative.");
            if (offset < 0)
                throw new Exception("Index cannot be negative.");
            if (offset + length > data.Length)
                throw new Exception("Length and offset exceed the length of the input buffer.");

            InsureCapacity(_pos + length);
            Buffer.BlockCopy(data, offset, _buffer, _pos, length);
            _pos += length;
            if (_pos > _length)
                _length = _pos;
        }
        
        public void Write(ByteWriter! data)
        {
			Write(data._buffer, 0, data._length);
        }

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

        public void WriteUInt64Le(ulong value)
        {
            Write((byte)(value & 0xff));
            Write((byte)((value >> 0x08) & 0xff));
            Write((byte)((value >> 0x10) & 0xff));
            Write((byte)((value >> 0x18) & 0xff));
            Write((byte)((value >> 0x20) & 0xff));
            Write((byte)((value >> 0x28) & 0xff));
            Write((byte)((value >> 0x30) & 0xff));
            Write((byte)((value >> 0x38) & 0xff));
        }

        public void WriteUInt32Le(uint value)
        {
            Write((byte)(value & 0xff));
            Write((byte)((value >> 8) & 0xff));
            Write((byte)((value >> 16) & 0xff));
            Write((byte)((value >> 24) & 0xff));
        }

        public void WriteUInt16Le(ushort value)
        {
            Write((byte)(value & 0xff));
            Write((byte)((value >> 8) & 0xff));
        }



        //
        //typedef struct _STRING32 {
        //  USHORT   Length;
        //  USHORT   MaximumLength;
        //  ULONG  Buffer;
        //} STRING32;
        //typedef STRING32 *PSTRING32;
        //

        // This writes a STRING32 header into the buffer at the specified position
        // offset - the offset of the string data (somewhere else)
        // length - the total length
        public void WriteCountedHeader(int offset, int length)
        {
            WriteUInt16Le((ushort)length); // Length
            WriteUInt16Le((ushort)length); // MaximumLength
            WriteUInt16Le((ushort)offset);
            WriteUInt16Le(0);
        }


        public byte[]! ToArray()
        {
            byte[]! result = new byte[_length];
            Buffer.BlockCopy(_buffer, 0, result, 0, _length);
            return result;
        }

        public byte[]! in ExHeap ToArrayEx()
        {
            return Bitter.FromByteArray(_buffer, 0, _length);
        }
        
        public void CopyTo(byte[]! in ExHeap dest, int dest_offset, int src_offset, int length)
			requires dest_offset >= 0;
			requires length >= 0;
			requires dest_offset + length <= dest.Length;
			requires src_offset >= 0;
			requires src_offset + length <= Length;
        {
			Bitter.FromByteArray(dest, dest_offset, length, _buffer, 0);
        }

		public void CopyTo(byte[]! in ExHeap dest, int dest_offset)
			requires dest_offset >= 0;
			// requires dest_offset + _length <= dest.Length;
		{
			Bitter.FromByteArray(dest, dest_offset, _length, _buffer, 0);
		}        

        public void WriteStringUnicode(string! text, bool terminate)
		{
			for (int i = 0; i < text.Length; i++) {
				char c = text[i];
				Write((byte)(c & 0xff));
				Write((byte)(c >> 8));
			}

            if (terminate) {
                Write((byte)0);
                Write((byte)0);
            }
		}

        public void WriteStringAscii(string! text, bool terminate)
        {
            for (int i = 0; i < text.Length; i++) {
                char c = text[i];
                Write((byte)(c & 0xff));
            }

            if (terminate) {
                Write((byte)0);
            }
        }
        
	}

}