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

#pragma once

#include "CoreMinimal.h"
#include "Engine/Brush.h"
#include "Engine/Polys.h"

class AVolume;
class UModel;

class FBSPOps
{
public:
    /** Quality level for rebuilding Bsp. */
    enum EBspOptimization
    {
        BSP_Lame,
        BSP_Good,
        BSP_Optimal
    };

    /** Possible positions of a child Bsp node relative to its parent (for BspAddToNode) */
    enum ENodePlace
    {
        NODE_Back  = 0,  // Node is in back of parent              -> Bsp[iParent].iBack.
        NODE_Front = 1,  // Node is in front of parent             -> Bsp[iParent].iFront.
        NODE_Plane = 2,  // Node is coplanar with parent           -> Bsp[iParent].iPlane.
        NODE_Root  = 3,  // Node is the Bsp root and has no parent -> Bsp[0].
    };

    UNREALED_API static void csgPrepMovingBrush(ABrush* Actor);
    UNREALED_API static void csgCopyBrush(ABrush* Dest, ABrush* Src, uint32 PolyFlags, EObjectFlags ResFlags, bool bNeedsPrep, bool bCopyPosRotScale, bool bAllowEmpty = false);
    UNREALED_API static ABrush* csgAddOperation(ABrush* Actor, uint32 PolyFlags, EBrushType BrushType);

    static int32 bspAddVector(UModel* Model, FVector* V, bool Exact);
    static int32 bspAddPoint(UModel* Model, FVector* V, bool Exact);
    UNREALED_API static void bspBuild(UModel* Model, enum EBspOptimization Opt, int32 Balance, int32 PortalBias, int32 RebuildSimplePolys, int32 iNode);
    UNREALED_API static void bspRefresh(UModel* Model, bool NoRemapSurfs);

    UNREALED_API static void bspBuildBounds(UModel* Model);

    static void bspValidateBrush(UModel* Brush, bool ForceValidate, bool DoStatusUpdate);
    UNREALED_API static void bspUnlinkPolys(UModel* Brush);
    static int32 bspAddNode(UModel* Model, int32 iParent, enum ENodePlace ENodePlace, uint32 NodeFlags, FPoly* EdPoly);

    /**
     * Rebuild some brush internals
     */
    UNREALED_API static void RebuildBrush(UModel* Brush);

    static FPoly BuildInfiniteFPoly(UModel* Model, int32 iNode);

    /**
     * Rotates the specified brush's vertices.
     */
    static void RotateBrushVerts(ABrush* Brush, const FRotator& Rotation, bool bClearComponents);

    /** Called when an AVolume shape is changed*/
    static void HandleVolumeShapeChanged(AVolume& Volume);

    /** Errors encountered in Csg operation. */
    static int32 GErrors;
    static bool GFastRebuild;

protected:
    static void SplitPolyList(
        UModel* Model,
        int32 iParent,
        ENodePlace NodePlace,
        int32 NumPolys,
        FPoly** PolyList,
        EBspOptimization Opt,
        int32 Balance,
        int32 PortalBias,
        int32 RebuildSimplePolys);
};

/** @todo: remove when uses of ENodePlane have been replaced with FBSPOps::ENodePlace. */
typedef FBSPOps::ENodePlace ENodePlace;

struct FBspPointsKey
{
    int32 X;
    int32 Y;
    int32 Z;

    FBspPointsKey(int32 InX, int32 InY, int32 InZ)
        : X(InX), Y(InY), Z(InZ)
    {}

    friend FORCEINLINE bool operator==(const FBspPointsKey& A, const FBspPointsKey& B)
    {
        return A.X == B.X && A.Y == B.Y && A.Z == B.Z;
    }

    friend FORCEINLINE uint32 GetTypeHash(const FBspPointsKey& Key)
    {
        return HashCombine(static_cast<uint32>(Key.X), HashCombine(static_cast<uint32>(Key.Y), static_cast<uint32>(Key.Z)));
    }
};

struct FBspIndexedPoint
{
    FBspIndexedPoint(const FVector& InPoint, int32 InIndex)
        : Point(InPoint), Index(InIndex)
    {}

    FVector Point;
    int32 Index;
};

struct FBspPointsGridItem
{
    TArray<FBspIndexedPoint, TInlineAllocator<16>> IndexedPoints;
};

// Represents a sparse granular 3D grid into which points are added for quick (~O(1)) lookup.
// The 3D space is divided into a grid with a given granularity.
// Points are considered to have a given radius (threshold) and are added to the grid cube they fall in, and to up to seven neighbours if they overlap.
class FBspPointsGrid
{
public:
    FBspPointsGrid(float InGranularity, float InThreshold, int32 InitialSize = 0)
        : OneOverGranularity(1.0f / InGranularity), Threshold(InThreshold)
    {
        check(InThreshold / InGranularity <= 0.5f);
        Clear(InitialSize);
    }

    void Clear(int32 InitialSize = 0);

    int32 FindOrAddPoint(const FVector& Point, int32 Index, float Threshold);

    static FBspPointsGrid* GBspPoints;
    static FBspPointsGrid* GBspVectors;

private:
    float OneOverGranularity;
    float Threshold;

    typedef TMap<FBspPointsKey, FBspPointsGridItem> FGridMap;
    FGridMap GridMap;
};