integration/Plugins/BlueprintMCP/Source/BlueprintMCP/Handlers/StateMachine_AddTransition.h

#pragma once

#include "CoreMinimal.h"
#include "MCPServer.h"
#include "MCPHandler.h"
#include "MCPAssets.h"
#include "MCPUtils.h"
#include "Kismet2/KismetEditorUtilities.h"
#include "Animation/AnimBlueprint.h"
#include "AnimStateNode.h"
#include "AnimStateTransitionNode.h"
#include "AnimationStateMachineGraph.h"
#include "StateMachine_AddTransition.generated.h"


// ---------------------------------------------------------------------------
// ---------------------------------------------------------------------------
// ---------------------------------------------------------------------------

UCLASS()
class UMCP_StateMachine_AddTransition : public UObject, public IMCPHandler
{
	GENERATED_BODY()

public:
	UPROPERTY(meta=(Description="Animation Blueprint name or package path"))
	FString Blueprint;

	UPROPERTY(meta=(Description="State machine graph name"))
	FString Graph;

	UPROPERTY(meta=(Description="Name of the source state"))
	FString FromState;

	UPROPERTY(meta=(Description="Name of the target state"))
	FString ToState;

	UPROPERTY(meta=(Optional, Description="Crossfade duration in seconds"))
	float CrossfadeDuration = 0.0f;

	UPROPERTY(meta=(Optional, Description="Transition priority order"))
	int32 Priority = 0;

	UPROPERTY(meta=(Optional, Description="Whether the transition is bidirectional"))
	bool BBidirectional = false;

	virtual FString GetDescription() const override
	{
		return TEXT("Add a transition between two states in an animation state machine graph.");
	}

	virtual void Handle() override
	{
		MCPAssets<UAnimBlueprint> Assets;
		if (!Assets.Exact(Blueprint).ENone().ETwo().Load()) return;
		UAnimBlueprint* AnimBP = Assets.Object();

		UAnimationStateMachineGraph* SMGraph = MCPUtils::FindStateMachineGraph(AnimBP, Graph);
		if (!SMGraph)
		{
			UMCPServer::Printf(TEXT("ERROR: State machine graph '%s' not found in '%s'\n"), *Graph, *MCPUtils::FormatName(AnimBP));
			return;
		}

		UAnimStateNode* FromStateNode = MCPUtils::FindStateByName(SMGraph, FromState);
		if (!FromStateNode) return;

		UAnimStateNode* ToStateNode = MCPUtils::FindStateByName(SMGraph, ToState);
		if (!ToStateNode) return;

		// Create transition node
		UAnimStateTransitionNode* TransNode = NewObject<UAnimStateTransitionNode>(SMGraph);
		TransNode->CreateNewGuid();
		TransNode->PostPlacedNewNode();
		TransNode->AllocateDefaultPins();

		// Position between the two states
		TransNode->NodePosX = (FromStateNode->NodePosX + ToStateNode->NodePosX) / 2;
		TransNode->NodePosY = (FromStateNode->NodePosY + ToStateNode->NodePosY) / 2;

		SMGraph->AddNode(TransNode, false, false);
		TransNode->SetFlags(RF_Transactional);

		// Connect: FromState output -> Transition input, Transition output -> ToState input
		TransNode->CreateConnections(FromStateNode, ToStateNode);

		// Set optional properties
		TransNode->CrossfadeDuration = CrossfadeDuration;
		TransNode->PriorityOrder = Priority;
		TransNode->Bidirectional = BBidirectional;

		// Compile and save
		FKismetEditorUtilities::CompileBlueprint(AnimBP);
		MCPUtils::SaveBlueprintPackage(AnimBP);

		UMCPServer::Printf(TEXT("Created transition %s -> %s: %s\n"),
			*FromState, *ToState, *MCPUtils::FormatName(TransNode));
	}
};