// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using System.IO;
using CommunityToolkit.HighPerformance.Buffers;
using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace CommunityToolkit.HighPerformance.UnitTests.Extensions;

[TestClass]
public class Test_IMemoryOwnerExtensions
{
    [TestMethod]
    public void Test_IMemoryOwnerExtensions_EmptyIMemoryOwnerStream()
    {
        MemoryOwner<byte> buffer = MemoryOwner<byte>.Empty;

        Stream stream = buffer.AsStream();

        Assert.IsNotNull(stream);
        Assert.AreEqual(buffer.Length, 0);
        Assert.AreEqual(stream.Length, 0);
        Assert.IsTrue(stream.CanWrite);
    }

    [TestMethod]
    public void Test_MemoryExtensions_IMemoryOwnerStream()
    {
        MemoryOwner<byte> buffer = MemoryOwner<byte>.Allocate(1024);

        Stream stream = buffer.AsStream();

        Assert.IsNotNull(stream);
        Assert.AreEqual(stream.Length, buffer.Length);
        Assert.IsTrue(stream.CanWrite);
    }

    [TestMethod]
    public void Test_MemoryExtensions_IMemoryOwnerStream_DoesNotAlterExistingData()
    {
        MemoryOwner<byte> buffer = MemoryOwner<byte>.Allocate(1024);

        // Fill the buffer with sample data
        for (int i = 0; i < buffer.Length; i++)
        {
            buffer.Span[i] = unchecked((byte)(i & byte.MaxValue));
        }

        Stream stream = buffer.AsStream();

        Assert.IsNotNull(stream);
        Assert.AreEqual(stream.Length, buffer.Length);
        Assert.IsTrue(stream.CanWrite);

        // Validate that creating the stream doesn't alter the underlying buffer
        for (int i = 0; i < buffer.Length; i++)
        {
            Assert.AreEqual(buffer.Span[i], unchecked((byte)(i & byte.MaxValue)));
        }
    }
}