// Copyright Epic Games, Inc. All Rights Reserved.

#pragma once

#include "CoreMinimal.h"

/** Data structure and algorithm to find all cycles in a UObject directed graph **/
struct FFindStronglyConnected
{
    struct NodeInfo
    {
        int32 IndexValue;
        int32 LowIndex;
        bool InStack;
    };

    TMultiMap<UObject*, UObject*> AllEdges;
    TMultiMap<UObject*, UObject*> Edges;
    TArray<UObject*> AllObjects;
    TSet<UObject*> PermanentObjects;
    TArray<UObject*> TempObjects;
    TMap<UObject*, NodeInfo> NodeIndex;
    int32 MasterIndex;
    TArray<UObject*> Stack;

    TArray<TArray<UObject*>> Components;
    TArray<TArray<UObject*>> SimpleCycles;

    FFindStronglyConnected()
        : MasterIndex(1)
    {
    }

    /** Find all cycles in the uobject reference graph **/
    void FindAllCycles();

    void FindSimpleCycleForComponent(TArray<UObject*>& Dest, const TArray<UObject*>& Component);

    void StrongConnect(UObject* Node);

private:
    bool FindSimpleCycleForComponentInner(TArray<UObject*>& Dest, const TArray<UObject*>& Component, UObject* Node);

    NodeInfo* StrongConnectInner(UObject* Node);
};