AssetRipper_AssetRipper/Source/AssetRipper.AssemblyDumper/Passes/Pass501_MonoBehaviourImplementation.cs

using AssetRipper.AssemblyDumper.Documentation;
using AssetRipper.AssemblyDumper.InjectedTypes;
using AssetRipper.AssemblyDumper.Methods;
using AssetRipper.AssemblyDumper.Types;
using AssetRipper.Assets;

namespace AssetRipper.AssemblyDumper.Passes;

/// <summary>
/// Adds to the IMonoBehaviour and IScriptedImporter interfaces. Also fixes the read and yaml methods
/// </summary>
public static class Pass501_MonoBehaviourImplementation
{
	public static void DoPass()
	{
		TypeDefinition monoBehaviourHelperType = SharedState.Instance.InjectHelperType(typeof(MonoBehaviourHelper));
		TypeSignature propertyType = SharedState.Instance.Importer.ImportTypeSignature<IUnityAssetBase>();

		//MonoBehaviour
		ApplyChangesToGroup(SharedState.Instance.ClassGroups[114], monoBehaviourHelperType, propertyType);

		//ScriptedImporter
		ApplyChangesToGroup(SharedState.Instance.ClassGroups[2089858483], monoBehaviourHelperType, propertyType);
	}

	private static void ApplyChangesToGroup(ClassGroup group, TypeDefinition monoBehaviourHelperType, TypeSignature propertyType)
	{
		const string propertyName = "Structure";
		const string fieldName = "m_" + propertyName;

		PropertyDefinition interfaceProperty = group.Interface.AddFullProperty(propertyName, InterfaceUtils.InterfacePropertyDeclaration, propertyType)
			.AddNullableAttributesForMaybeNull();

		foreach (GeneratedClassInstance instance in group.Instances)
		{
			FieldDefinition structureField = instance.Type.AddField(fieldName, propertyType, visibility: Visibility.Internal);
			structureField
				.AddNullableAttributesForMaybeNull()
				.AddDebuggerBrowsableNeverAttribute();

			PropertyDefinition property = instance.Type.ImplementFullProperty(propertyName, InterfaceUtils.InterfacePropertyImplementation, null, structureField)
				.AddNullableAttributesForMaybeNull();

			DocumentationHandler.AddPropertyDefinitionLine(property, "The custom structure of this asset, based on the instance fields of its MonoScript.");

			instance.Type.AddWalkStructure(structureField, monoBehaviourHelperType, "Editor");
			instance.Type.AddWalkStructure(structureField, monoBehaviourHelperType, "Release");
			instance.Type.AddWalkStructure(structureField, monoBehaviourHelperType, "Standard");

			instance.Type.AddStructureFetchDependencies(structureField, monoBehaviourHelperType);

			instance.Type.AddStructureReset(structureField, monoBehaviourHelperType);

			instance.Type.AddStructureCopyValues(structureField, interfaceProperty, monoBehaviourHelperType);
		}
	}

	private static void AddWalkStructure(this TypeDefinition type, FieldDefinition field, TypeDefinition monoBehaviourHelperType, string walkType)
	{
		string targetMethodName = walkType switch
		{
			"Editor" => nameof(UnityAssetBase.WalkEditor),
			"Release" => nameof(UnityAssetBase.WalkRelease),
			"Standard" => nameof(UnityAssetBase.WalkStandard),
			_ => throw new ArgumentException(null, nameof(walkType)),
		};

		MethodDefinition method = type.Methods.Single(m => m.Name == targetMethodName);

		string injectedMethodName = walkType switch
		{
			"Editor" => nameof(MonoBehaviourHelper.MaybeWalkStructureEditor),
			"Release" => nameof(MonoBehaviourHelper.MaybeWalkStructureRelease),
			"Standard" => nameof(MonoBehaviourHelper.MaybeWalkStructureStandard),
			_ => throw new ArgumentException(null, nameof(walkType)),
		};

		IMethodDefOrRef walkStructureMethod = monoBehaviourHelperType.Methods.Single(m => m.Name == injectedMethodName);

		CilInstructionCollection instructions = method.CilMethodBody!.Instructions;

		int insertIndex = FindLastNop(instructions) + 1;

		//Insert the opcodes in reverse order, so that we don't have to adjust the insert index.
		instructions.Insert(insertIndex, CilOpCodes.Call, walkStructureMethod);
		instructions.Insert(insertIndex, CilOpCodes.Ldarg_1);//walker
		instructions.Insert(insertIndex, CilOpCodes.Ldfld, field);//the structure field
		instructions.Insert(insertIndex, CilOpCodes.Ldarg_0);//this
		instructions.Insert(insertIndex, CilOpCodes.Ldarg_0);//this

		static int FindLastNop(CilInstructionCollection instructions)
		{
			for (int i = instructions.Count - 1; i >= 0; i--)
			{
				if (instructions[i].OpCode == CilOpCodes.Nop)
				{
					return i;
				}
			}
			throw new Exception("No nop found");
		}
	}

	private static void AddStructureFetchDependencies(this TypeDefinition type, FieldDefinition field, TypeDefinition monoBehaviourHelperType)
	{
		MethodDefinition method = type.Methods.Single(m => m.Name == nameof(UnityAssetBase.FetchDependencies));
		IMethodDefOrRef fetchDependenciesMethod = monoBehaviourHelperType.Methods.Single(m => m.Name == nameof(MonoBehaviourHelper.MaybeAppendStructureDependencies));
		CilInstructionCollection instructions = method.CilMethodBody!.Instructions;
		instructions.Pop(); //pop the return value
		instructions.Add(CilOpCodes.Ldarg_0);//this
		instructions.Add(CilOpCodes.Ldfld, field);//the structure field
		instructions.Add(CilOpCodes.Call, fetchDependenciesMethod);
		instructions.Add(CilOpCodes.Ret);
	}

	private static void AddStructureReset(this TypeDefinition type, FieldDefinition field, TypeDefinition monoBehaviourHelperType)
	{
		MethodDefinition method = type.Methods.Single(m => m.Name == nameof(UnityAssetBase.Reset));
		IMethodDefOrRef resetMethod = monoBehaviourHelperType.Methods.Single(m => m.Name == nameof(MonoBehaviourHelper.ResetStructure));
		CilInstructionCollection instructions = method.CilMethodBody!.Instructions;
		instructions.Pop(); //pop the return value
		instructions.Add(CilOpCodes.Ldarg_0);//this
		instructions.Add(CilOpCodes.Ldfld, field);//the structure field
		instructions.Add(CilOpCodes.Call, resetMethod);
		instructions.Add(CilOpCodes.Ret);
	}

	private static void AddStructureCopyValues(this TypeDefinition type, FieldDefinition field, PropertyDefinition interfaceProperty, TypeDefinition monoBehaviourHelperType)
	{
		MethodDefinition method = type.Methods.Single(m => m.Name == nameof(UnityAssetBase.CopyValues) && m.IsFinal && m.Parameters.Count == 2);
		IMethodDefOrRef copyValuesMethod = monoBehaviourHelperType.Methods.Single(m => m.Name == nameof(MonoBehaviourHelper.CopyStructureValues));
		CilInstructionCollection instructions = method.CilMethodBody!.Instructions;
		instructions.Pop(); //pop the return value
		instructions.Add(CilOpCodes.Ldarg_0);//this
		instructions.Add(CilOpCodes.Ldflda, field);//the structure field
		instructions.Add(CilOpCodes.Ldarg_1);//source
		instructions.Add(CilOpCodes.Callvirt, interfaceProperty.GetMethod!);//the Structure property
		instructions.Add(CilOpCodes.Ldarg_2);//converter
		instructions.Add(CilOpCodes.Call, copyValuesMethod);
		instructions.Add(CilOpCodes.Ret);
	}
}