using System;
using System.IO;
using System.Threading;
using System.Threading.Tasks;

namespace Xtremegaida.DataStructures;

public class DataQueueReadStream : Stream
{
	private readonly IDataQueueReader owner;
	private readonly bool keepReaderOpen;

	public override bool CanRead => true;
	public override bool CanSeek => false;
	public override bool CanWrite => false;
	public override long Length => owner.TotalBytesRead + owner.UnreadLength;
	public override long Position { get => owner.TotalBytesRead; set => throw new NotSupportedException(); }

	public DataQueueReadStream(IDataQueueReader owner, bool keepReaderOpen = false)
	{
		this.owner = owner;
		this.keepReaderOpen = keepReaderOpen;
	}

	public override void Flush() { }
	public override void Write(byte[] buffer, int offset, int count) { throw new NotSupportedException(); }
	public override long Seek(long offset, SeekOrigin origin) { throw new NotSupportedException(); }
	public override void SetLength(long value) { throw new NotSupportedException(); }

	public override int Read(byte[] buffer, int offset, int count)
	{
		var task = owner.ReadAsync(new Memory<byte>(buffer, offset, count));
		if (task.IsCompletedSuccessfully) { return task.Result; }
		return task.AsTask().Result;
	}

	public override int ReadByte()
	{
		var task = owner.ReadByteAsync();
		if (task.IsCompletedSuccessfully) { return task.Result; }
		return task.AsTask().Result;
	}

	public override Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
	{
		var task = owner.ReadAsync(new Memory<byte>(buffer, offset, count), false, cancellationToken);
		if (task.IsCompletedSuccessfully) { return Task.FromResult(task.Result); }
		return task.AsTask();
	}

	public override ValueTask<int> ReadAsync(Memory<byte> buffer, CancellationToken cancellationToken = default)
	{
		return owner.ReadAsync(buffer, false, cancellationToken);
	}

	public override void Close()
	{
		if (!keepReaderOpen) { owner.Dispose(); }
	}
}