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

#pragma once

#include "CoreMinimal.h"
#include "UObject/ObjectMacros.h"
#include "UObject/Object.h"
#include "ChunkDependencyInfo.generated.h"

/** A single dependency, read from ini file */
USTRUCT()
struct FChunkDependency
{
    GENERATED_USTRUCT_BODY()

    /** The child chunk */
    UPROPERTY(EditAnywhere, Category = ChunkInfo)
    int32 ChunkID = 0;

    /** Parent chunk, anything in both Parent and Child is only placed into Parent */
    UPROPERTY(EditAnywhere, Category = ChunkInfo)
    int32 ParentChunkID = 0;

    bool operator==(const FChunkDependency& RHS)
    {
        return ChunkID == RHS.ChunkID;
    }
};

/** In memory structure used for dependency tree */
struct FChunkDependencyTreeNode
{
    FChunkDependencyTreeNode(int32 InChunkID = 0)
        : ChunkID(InChunkID)
    {}

    int32 ChunkID;

    TArray<FChunkDependencyTreeNode> ChildNodes;
};

/** This is read out of config and defines a tree of chunk dependencies */
UCLASS(config = Engine, defaultconfig)
class UNREALED_API UChunkDependencyInfo: public UObject
{
    GENERATED_UCLASS_BODY()

    /** Will return an existing dependency graph, or build if it necessary */
    const FChunkDependencyTreeNode* GetOrBuildChunkDependencyGraph(int32 HighestChunk = 0);

    /** Will create a dependency tree starting with RootTreeNode. If HighestChunk is == 0 it will only add dependencies on 0 for chunks already in the dependencies list */
    const FChunkDependencyTreeNode* BuildChunkDependencyGraph(int32 HighestChunk);

    /** Removes redundant chunks from a chunk list */
    void RemoveRedundantChunks(TArray<int32>& ChunkIDs) const;

    /** List of dependencies used to remove redundant chunks */
    UPROPERTY(config)
    TArray<FChunkDependency> DependencyArray;

private:
    /** Fills out the Dependency Tree starting with Node */
    void AddChildrenRecursive(FChunkDependencyTreeNode& Node, TArray<FChunkDependency>& DepInfo, TSet<int32> Parents);

    /** Root of tree, this will be valid after calling BuildChunkDependencyGraph */
    FChunkDependencyTreeNode RootTreeNode;

    /** Map of child chunks to all parent chunks, computed in BuildChunkDependencyGraph */
    TMap<int32, TSet<int32>> ChildToParentMap;

    /** Cached value of HighestChunk at time of building */
    int32 CachedHighestChunk;
};