// https://github.com/XtraCube/Reactor/blob/main/Reactor/Utilities/CompilerGeneratedObjectWrapper.cs

using System;
using System.Collections.Generic;
using System.Reflection;
using HarmonyLib;

namespace EHR.Modules;

/// <summary>
/// A safe wrapper around compiler generated classes like DisplayClass or IEnumerator state machines.
/// </summary>
public class CompilerGeneratedObjectWrapper
{
    /// <summary>
    /// Gets a reference to the compiler generated object.
    /// </summary>
    public object GeneratedObject { get; }

    /// <summary>
    /// Gets the type of the compiler generated object.
    /// </summary>
    protected Type GeneratedType { get; }

    /// <summary>
    /// Gets the property info cache for faster lookups.
    /// </summary>
    protected Dictionary<string, PropertyInfo> PropertyCache { get; }

    /// <summary>
    /// Initializes a new instance of the <see cref="CompilerGeneratedObjectWrapper"/> class.
    /// </summary>
    /// <param name="generatedObject">An instance of the compiler generated object.</param>
    public CompilerGeneratedObjectWrapper(object generatedObject)
    {
        GeneratedObject = generatedObject;
        GeneratedType = generatedObject.GetType();

        PropertyCache = [];
    }

    /// <summary>
    /// Gets the value of a field in the compiler generated object.
    /// </summary>
    /// <param name="fieldName">The name of the field to get.</param>
    /// <typeparam name="TField">The type of the field.</typeparam>
    /// <returns>>The value of the field.</returns>
    /// <exception cref="MissingMemberException">Thrown if the field does not exist.</exception>
    public TField GetField<TField>(string fieldName)
    {
        if (!PropertyCache.TryGetValue(fieldName, out var propertyInfo))
        {
            propertyInfo = AccessTools.Property(GeneratedType, fieldName);
            if (propertyInfo == null)
            {
                throw new MissingMemberException($"Could not find field '{fieldName}' in type '{GeneratedType}'.");
            }
            PropertyCache[fieldName] = propertyInfo;
        }

        return (TField) propertyInfo.GetValue(GeneratedObject)!;
    }

    /// <summary>
    /// Sets the value of a field in the compiler generated object.
    /// </summary>
    /// <param name="fieldName">The name of the field to set.</param>
    /// <param name="value">The value to set.</param>
    /// <typeparam name="TField">The type of the field.</typeparam>
    /// <exception cref="MissingMemberException">Thrown if the field does not exist.</exception>
    public void SetField<TField>(string fieldName, TField value)
    {
        if (!PropertyCache.TryGetValue(fieldName, out var propertyInfo))
        {
            propertyInfo = AccessTools.Property(GeneratedType, fieldName);
            if (propertyInfo == null)
            {
                throw new MissingMemberException($"Could not find field '{fieldName}' in type '{GeneratedType}'.");
            }
            PropertyCache[fieldName] = propertyInfo;
        }

        propertyInfo.SetValue(GeneratedObject, value);
    }
}