StabilityMatrix/StabilityMatrix.Core/Extensions/ObjectExtensions.cs

using System.Reflection;
using RockLib.Reflection.Optimized;

namespace StabilityMatrix.Core.Extensions;

public static class ObjectExtensions
{
    /// <summary>
    /// Cache of Types to named field getters
    /// </summary>
    private static readonly Dictionary<
        Type,
        Dictionary<string, Func<object, object>>
    > FieldGetterTypeCache = new();

    /// <summary>
    /// Cache of Types to named field setters
    /// </summary>
    private static readonly Dictionary<
        Type,
        Dictionary<string, Action<object, object>>
    > FieldSetterTypeCache = new();

    /// <summary>
    /// Get the value of a named private field from an object
    /// </summary>
    public static T? GetPrivateField<T>(this object obj, string fieldName)
    {
        // Check cache
        var fieldGetterCache = FieldGetterTypeCache.GetOrAdd(obj.GetType());

        if (!fieldGetterCache.TryGetValue(fieldName, out var fieldGetter))
        {
            // Get the field
            var field = obj.GetType()
                .GetField(fieldName, BindingFlags.Instance | BindingFlags.NonPublic);
            // Try get from parent
            field ??= obj.GetType()
                .BaseType?.GetField(fieldName, BindingFlags.Instance | BindingFlags.NonPublic);

            if (field is null)
            {
                throw new ArgumentException(
                    $"Field {fieldName} not found on type {obj.GetType().Name}"
                );
            }

            // Create a getter for the field
            fieldGetter = field.CreateGetter();

            // Add to cache
            fieldGetterCache.Add(fieldName, fieldGetter);
        }

        return (T?)fieldGetter(obj);
    }

    /// <summary>
    /// Set the value of a named private field on an object
    /// </summary>
    public static void SetPrivateField(this object obj, string fieldName, object value)
    {
        // Check cache
        var fieldSetterCache = FieldSetterTypeCache.GetOrAdd(obj.GetType());

        if (!fieldSetterCache.TryGetValue(fieldName, out var fieldSetter))
        {
            // Get the field
            var field = obj.GetType()
                .GetField(fieldName, BindingFlags.Instance | BindingFlags.NonPublic);
            // Try get from parent
            field ??= obj.GetType()
                .BaseType?.GetField(fieldName, BindingFlags.Instance | BindingFlags.NonPublic);

            if (field is null)
            {
                throw new ArgumentException(
                    $"Field {fieldName} not found on type {obj.GetType().Name}"
                );
            }

            // Create a setter for the field
            fieldSetter = field.CreateSetter();

            // Add to cache
            fieldSetterCache.Add(fieldName, fieldSetter);
        }

        fieldSetter(obj, value);
    }

    /// <summary>
    /// Set the value of a named private field on an object
    /// </summary>
    public static void SetPrivateField<T>(this object obj, string fieldName, T? value)
    {
        // Check cache
        var fieldSetterCache = FieldSetterTypeCache.GetOrAdd(obj.GetType());

        if (!fieldSetterCache.TryGetValue(fieldName, out var fieldSetter))
        {
            // Get the field
            var field = obj.GetType()
                .GetField(fieldName, BindingFlags.Instance | BindingFlags.NonPublic);
            // Try get from parent
            field ??= obj.GetType()
                .BaseType?.GetField(fieldName, BindingFlags.Instance | BindingFlags.NonPublic);

            if (field is null)
            {
                throw new ArgumentException(
                    $"Field {fieldName} not found on type {obj.GetType().Name}"
                );
            }

            // Create a setter for the field
            fieldSetter = field.CreateSetter();

            // Add to cache
            fieldSetterCache.Add(fieldName, fieldSetter);
        }

        fieldSetter(obj, value!);
    }
}