MemberMethodProvider.cs

// Copyright (c) Six Labors.
// Licensed under the Six Labors Split License.

using System.Reflection;
using SixLabors.ImageSharp.PixelFormats;
using Xunit.Abstractions;

namespace SixLabors.ImageSharp.Tests;

/// <summary>
/// Provides <see cref="Image{TPixel}" /> instances for parametric unit tests.
/// </summary>
/// <typeparam name="TPixel">The pixel format of the image</typeparam>
public abstract partial class TestImageProvider<TPixel> : IXunitSerializable
    where TPixel : unmanaged, IPixel<TPixel>
{
    private class MemberMethodProvider : TestImageProvider<TPixel>
    {
        private string declaringTypeName;
        private string methodName;
        private Func<Image<TPixel>> factoryFunc;

        public MemberMethodProvider()
        {
        }

        public MemberMethodProvider(string declaringTypeName, string methodName)
        {
            this.declaringTypeName = declaringTypeName;
            this.methodName = methodName;
        }

        public override Image<TPixel> GetImage()
        {
            this.factoryFunc ??= this.GetFactory();
            return this.factoryFunc();
        }

        public override void Serialize(IXunitSerializationInfo info)
        {
            base.Serialize(info);

            info.AddValue(nameof(this.declaringTypeName), this.declaringTypeName);
            info.AddValue(nameof(this.methodName), this.methodName);
        }

        public override void Deserialize(IXunitSerializationInfo info)
        {
            base.Deserialize(info);

            this.methodName = info.GetValue<string>(nameof(this.methodName));
            this.declaringTypeName = info.GetValue<string>(nameof(this.declaringTypeName));
        }

        private Func<Image<TPixel>> GetFactory()
        {
            var declaringType = Type.GetType(this.declaringTypeName);
            MethodInfo m = declaringType.GetMethod(this.methodName);
            Type pixelType = typeof(TPixel);
            Type imgType = typeof(Image<>).MakeGenericType(pixelType);
            Type funcType = typeof(Func<>).MakeGenericType(imgType);
            MethodInfo genericMethod = m.MakeGenericMethod(pixelType);
            return (Func<Image<TPixel>>)genericMethod.CreateDelegate(funcType);
        }
    }
}