// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

// Copied from https://github.com/dotnet/runtime/blob/dcbf3413c5f7ae431a68fd0d3f09af095b525887/src/libraries/System.Net.ServerSentEvents/src/System/Net/ServerSentEvents/PooledByteBufferWriter.cs

using System.Buffers;
using System.Diagnostics;

namespace System.Net.ServerSentEvents;

internal sealed class PooledByteBufferWriter : IBufferWriter<byte>, IDisposable
{
    private const int MinimumBufferSize = 256;
    private ArrayBuffer _buffer = new(initialSize: 256, usePool: true);

    public void Advance(int count) => _buffer.Commit(count);

    public Memory<byte> GetMemory(int sizeHint = 0)
    {
        _buffer.EnsureAvailableSpace(Math.Max(sizeHint, MinimumBufferSize));
        return _buffer.AvailableMemory;
    }

    public Span<byte> GetSpan(int sizeHint = 0)
    {
        _buffer.EnsureAvailableSpace(Math.Max(sizeHint, MinimumBufferSize));
        return _buffer.AvailableSpan;
    }

    public ReadOnlyMemory<byte> WrittenMemory => _buffer.ActiveMemory;
    public int Capacity => _buffer.Capacity;
    public int WrittenCount => _buffer.ActiveLength;
    public void Reset() => _buffer.Discard(_buffer.ActiveLength);
    public void Dispose() => _buffer.Dispose();
}