#nullable disable
// LzOutWindow.cs

namespace SevenZip.Compression.LZ
{
	public class OutWindow
	{
		byte[] _buffer = null;
		uint _pos;
		uint _windowSize = 0;
		uint _streamPos;
		System.IO.Stream _stream;

		public uint TrainSize = 0;

		public void Create( uint windowSize )
		{
			if ( _windowSize != windowSize )
			{
				// System.GC.Collect();
				_buffer = new byte[windowSize];
			}
			_windowSize = windowSize;
			_pos = 0;
			_streamPos = 0;
		}

		public void Init( System.IO.Stream stream, bool solid )
		{
			ReleaseStream();
			_stream = stream;
			if ( !solid )
			{
				_streamPos = 0;
				_pos = 0;
				TrainSize = 0;
			}
		}

		public bool Train( System.IO.Stream stream )
		{
			long len = stream.Length;
			uint size = (len < _windowSize) ? (uint)len : _windowSize;
			TrainSize = size;
			stream.Position = len - size;
			_streamPos = _pos = 0;
			while ( size > 0 )
			{
				uint curSize = _windowSize - _pos;
				if ( size < curSize )
					curSize = size;
				int numReadBytes = stream.Read( _buffer, (int)_pos, (int)curSize );
				if ( numReadBytes == 0 )
					return false;
				size -= (uint)numReadBytes;
				_pos += (uint)numReadBytes;
				_streamPos += (uint)numReadBytes;
				if ( _pos == _windowSize )
					_streamPos = _pos = 0;
			}
			return true;
		}

		public void ReleaseStream()
		{
			Flush();
			_stream = null;
		}

		public void Flush()
		{
			uint size = _pos - _streamPos;
			if ( size == 0 )
				return;
			_stream.Write( _buffer, (int)_streamPos, (int)size );
			if ( _pos >= _windowSize )
				_pos = 0;
			_streamPos = _pos;
		}

		public void CopyBlock( uint distance, uint len )
		{
			uint pos = _pos - distance - 1;
			if ( pos >= _windowSize )
				pos += _windowSize;
			for ( ; len > 0; len-- )
			{
				if ( pos >= _windowSize )
					pos = 0;
				_buffer[_pos++] = _buffer[pos++];
				if ( _pos >= _windowSize )
					Flush();
			}
		}

		public void PutByte( byte b )
		{
			_buffer[_pos++] = b;
			if ( _pos >= _windowSize )
				Flush();
		}

		public byte GetByte( uint distance )
		{
			uint pos = _pos - distance - 1;
			if ( pos >= _windowSize )
				pos += _windowSize;
			return _buffer[pos];
		}
	}
}