namespace Nonemm.Spotting.Tests;

/// A stream that hands out bytes a test prepared and keeps whatever is written
/// back, so the telnet negotiation can be checked without a socket. Each read
/// returns one prepared block, the way a socket hands over one packet.
public sealed class FakeTelnetStream : Stream
{
    private readonly Queue<byte[]> blocks;
    private readonly List<byte> written = [];

    public FakeTelnetStream(params byte[][] blocks) => this.blocks = new Queue<byte[]>(blocks);

    public IReadOnlyList<byte> Written => written;

    public override bool CanRead => true;

    public override bool CanSeek => false;

    public override bool CanWrite => true;

    public override long Length => throw new NotSupportedException();

    public override long Position
    {
        get => throw new NotSupportedException();
        set => throw new NotSupportedException();
    }

    public override int Read(byte[] buffer, int offset, int count)
    {
        if (blocks.Count == 0)
        {
            return 0;
        }
        byte[] block = blocks.Dequeue();
        block.CopyTo(buffer, offset);
        return block.Length;
    }

    public override void Write(byte[] buffer, int offset, int count) =>
        written.AddRange(buffer.Skip(offset).Take(count));

    public override void Flush()
    {
    }

    public override long Seek(long offset, SeekOrigin origin) => throw new NotSupportedException();

    public override void SetLength(long value) => throw new NotSupportedException();
}