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 * Copyright (c) 2005-2025 The OPC Foundation, Inc. All rights reserved.
 *
 * OPC Foundation MIT License 1.00
 *
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 * obtaining a copy of this software and associated documentation
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 * ======================================================================*/

using System;
using System.Buffers;
using System.IO;
using NUnit.Framework;
using Opc.Ua.Bindings;
using Opc.Ua.Tests;

namespace Opc.Ua.Types.Buffers.Tests
{
    /// <summary>
    /// Tests for <see cref="ArrayPoolBufferWriter{T}"/> where T is <see cref="byte"/>.
    /// </summary>
    [Parallelizable(ParallelScope.All)]
    public class ArraySegmentStreamTests
    {
        /// <summary>
        /// Test the default behavior of <see cref="ArrayPoolMemoryStream"/>.
        /// </summary>
        [Test]
        public void ArraySegmentStreamWhenConstructedWithDefaultOptionsShouldNotThrow()
        {
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();

            // Arrange
            var bufferManager = new BufferManager(
                nameof(ArraySegmentStreamWhenConstructedWithDefaultOptionsShouldNotThrow),
                0x10000 - 1,
                telemetry);
            var stream = new ArraySegmentStream(bufferManager);

            // Act
            Action act = stream.Dispose;
            byte[] buffer = [0x55];

            // Assert
            Assert.That(stream.CanRead, Is.True);
            Assert.That(stream.CanWrite, Is.True);
            Assert.That(stream.CanSeek, Is.True);
            Assert.Throws<NotSupportedException>(() => stream.SetLength(0));
            Assert.Throws<IOException>(() => stream.Seek(-1, SeekOrigin.Begin));
            Assert.Throws<IOException>(() => stream.Seek(0, (SeekOrigin)66));

            Assert.That(stream.Seek(0, SeekOrigin.Begin), Is.Zero);
            Assert.That(stream.ReadByte(), Is.EqualTo(-1));
            Assert.That(stream.Read(buffer, 0, 1), Is.Zero);
#if NET5_0_OR_GREATER
            Assert.That(stream.Read(buffer.AsSpan(0, 1)), Is.Zero);
#endif
            stream.Position = 0;
            Assert.That(stream.Position, Is.Zero);

            Assert.That(stream.Length, Is.Zero);

            Assert.That(stream.Seek(0, SeekOrigin.Begin), Is.Zero);
            stream.WriteByte(0xaa);
            stream.Write(buffer, 0, 1);
#if NET5_0_OR_GREATER
            stream.Write(buffer.AsSpan(0, 1));
#else
            stream.Write(buffer, 0, 1);
#endif
            stream.Flush();
            Assert.That(stream.Length, Is.EqualTo(3));
            Assert.That(stream.Position, Is.EqualTo(3));
            Assert.That(stream.Length, Is.EqualTo(3));

            Assert.That(stream.Seek(-3, SeekOrigin.Current), Is.Zero);
            Assert.That(stream.ReadByte(), Is.EqualTo(0xaa));
            Assert.That(stream.Length, Is.EqualTo(3));
            Assert.That(stream.Position, Is.EqualTo(1));
            Assert.That(stream.Read(buffer, 0, 1), Is.EqualTo(1));
            Assert.That(stream.Position, Is.EqualTo(2));
            Assert.That(stream.Length, Is.EqualTo(3));
            Assert.That(buffer[0], Is.EqualTo(0x55));
#if NET5_0_OR_GREATER
            Assert.That(stream.Read(buffer.AsSpan(0, 1)), Is.EqualTo(1));
#else
            Assert.That(stream.Read(buffer, 0, 1), Is.EqualTo(1));
#endif
            Assert.That(stream.Position, Is.EqualTo(3));
            Assert.That(stream.Length, Is.EqualTo(3));
            Assert.That(buffer[0], Is.EqualTo(0x55));
            Assert.That(stream.ReadByte(), Is.EqualTo(-1));
            Assert.That(stream.Read(buffer, 0, 1), Is.Zero);
#if NET5_0_OR_GREATER
            Assert.That(stream.Read(buffer.AsSpan(0, 1)), Is.Zero);
#endif

            byte[] array = stream.ToArray();
            Assert.That(array, Has.Length.EqualTo(3));
            Assert.That(array[0], Is.EqualTo(0xaa));
            Assert.That(array[1], Is.EqualTo(0x55));
            Assert.That(array[2], Is.EqualTo(0x55));

            // now buffer sequence owns the buffers
            using (BufferSequence bufferSequence = stream.GetSequence("Test"))
            {
                ReadOnlySequence<byte> sequence = bufferSequence.Sequence;
                Assert.That(sequence.Length, Is.EqualTo(3));
                Assert.That(sequence.Slice(0, 1).First.Span[0], Is.EqualTo(0xaa));
                Assert.That(sequence.Slice(1, 1).First.Span[0], Is.EqualTo(0x55));
                Assert.That(sequence.Slice(2, 1).First.Span[0], Is.EqualTo(0x55));
            }

            act();

            Assert.Throws<ObjectDisposedException>(() => stream.ToArray());
        }

        /// <summary>
        /// Test the default behavior of <see cref="ArraySegmentStream"/>.
        /// </summary>
        [Theory]
        public void ArraySegmentStreamWrite(
            [Values(0, 1, 16, 17, 128, 333, 777, 1024, 4096)] int chunkSize,
            [Values(16, 128, 333, 1024, 4096, 65536)] int defaultBufferSize)
        {
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();

            int length;
            byte[] buffer = new byte[chunkSize];

            // Arrange
            var bufferManager = new BufferManager(
                nameof(ArraySegmentStreamWhenConstructedWithDefaultOptionsShouldNotThrow),
                defaultBufferSize,
                telemetry);
            using var writer = new ArraySegmentStream(bufferManager);
            // Act
            for (int i = 0; i <= byte.MaxValue; i++)
            {
                // fill chunk with a byte
                for (int v = 0; v < chunkSize; v++)
                {
                    buffer[v] = (byte)i;
                }

                // write next chunk
                switch (UnsecureRandom.Shared.Next(3))
                {
                    case 0:
                        for (int v = 0; v < chunkSize; v++)
                        {
                            writer.WriteByte((byte)i);
                        }

                        break;
                    case 1:
                        writer.Write(buffer, 0, chunkSize);
                        break;
#if NET5_0_OR_GREATER
                    default:
                        writer.Write(buffer.AsSpan(0, chunkSize));
                        break;
#else
                    default:
                        writer.Write(buffer, 0, chunkSize);
                        break;
#endif
                }
            }

            length = (byte.MaxValue + 1) * chunkSize;
            long result = writer.Seek(0, SeekOrigin.Begin);
            Assert.That(result, Is.Zero);

            result = writer.Seek(0, SeekOrigin.End);
            Assert.That(result, Is.EqualTo(length));

            // read back from writer MemoryStream
            result = writer.Seek(0, SeekOrigin.Begin);
            Assert.That(result, Is.Zero);

            Assert.That(writer.Length, Is.EqualTo(length));

            long position;
            for (int i = 0; i <= byte.MaxValue; i++)
            {
                if (UnsecureRandom.Shared.Next(2) == 0)
                {
                    position = writer.Seek(chunkSize * i, SeekOrigin.Begin);
                    Assert.That(position, Is.EqualTo(chunkSize * i));
                }

                int bytesRead;
                switch (UnsecureRandom.Shared.Next(3))
                {
                    case 0:
                        for (int v = 0; v < chunkSize; v++)
                        {
                            Assert.That(writer.ReadByte(), Is.EqualTo((byte)i));
                        }
                        break;
                    case 1:
                        bytesRead = writer.Read(buffer, 0, chunkSize);
                        Assert.That(chunkSize, Is.EqualTo(bytesRead));
                        for (int v = 0; v < chunkSize; v++)
                        {
                            Assert.That(buffer[v], Is.EqualTo((byte)i));
                        }
                        break;
                    default:
#if NET5_0_OR_GREATER
                        bytesRead = writer.Read(buffer.AsSpan(0, chunkSize));
                        Assert.That(chunkSize, Is.EqualTo(bytesRead));
                        for (int v = 0; v < chunkSize; v++)
                        {
                            Assert.That(buffer[v], Is.EqualTo((byte)i));
                        }
                        break;
#else
                        goto case 1;
#endif
                }
            }

            position = writer.Seek(0, SeekOrigin.Begin);
            Assert.That(position, Is.Zero);

            using BufferSequence bufferSequence = writer.GetSequence("Test");
            ReadOnlySequence<byte> sequence = bufferSequence.Sequence;
            buffer = sequence.ToArray();

            // Assert sequence properties
            Assert.That(buffer, Has.Length.EqualTo(length));
            Assert.That(sequence.Length, Is.EqualTo(length));

            for (int i = 0; i < buffer.Length; i++)
            {
                Assert.That(buffer[i], Is.EqualTo((byte)(i / chunkSize)));
            }

            for (int i = 0; i <= byte.MaxValue; i++)
            {
                ReadOnlySequence<byte> chunkSequence = sequence.Slice(i * chunkSize, chunkSize);
                Assert.That(chunkSequence.Length, Is.EqualTo((long)chunkSize));

                buffer = chunkSequence.ToArray();
                for (int v = 0; v < chunkSize; v++)
                {
                    Assert.That(buffer[v], Is.EqualTo((byte)i));
                }
            }
        }
    }
}