// Copyright (c) Wojciech Figat. All rights reserved.

#pragma once

#include "Engine/Core/Math/Transform.h"
#include "Engine/Core/Math/BoundingSphere.h"
#include "Engine/Core/Math/Half.h"
#include "Engine/Core/Math/Matrix.h"

/// <summary>
/// Foliage instanced mesh instance. Packed data with very little of logic. Managed by the foliage chunks and foliage actor itself.
/// </summary>
API_STRUCT(NoPod, NoDefault) struct FLAXENGINE_API FoliageInstance
{
    DECLARE_SCRIPTING_TYPE_MINIMAL(FoliageInstance);

    /// <summary>
    /// The local-space transformation of the mesh relative to the foliage actor.
    /// </summary>
    API_FIELD() Transform Transform;

    /// <summary>
    /// The cached instance bounds (in world space).
    /// </summary>
    API_FIELD() BoundingSphere Bounds;

    /// <summary>
    /// The previous frame index. In sync with Engine::FrameCount used to detect new frames and rendering gaps to reset state.
    /// </summary>
    uint64 DrawStatePrevFrame = 0;

    /// <summary>
    /// The foliage type index. Foliage types are hold in foliage actor and shared by instances using the same model.
    /// </summary>
    API_FIELD() uint16 Type;

    /// <summary>
    /// The lightmap index for the foliage instance. -1 if unused.
    /// </summary>
    int8 LightmapTextureIndex = -1;

    /// <summary>
    /// The previous frame model LOD index used. It's locked during LOD transition to cache the transition start LOD.
    /// </summary>
    char DrawStatePrevLOD = -1;

    /// <summary>
    /// The LOD transition timer.
    /// </summary>
    byte DrawStateLODTransition = 255;

    /// <summary>
    /// Flag used to indicate whether CachedDrawWorld contains valid data.
    /// </summary>
    byte CachedDrawWorldValid = 0;

    /// <summary>
    /// The per-instance random value from range [0;1].
    /// </summary>
    API_FIELD() float Random;

    /// <summary>
    /// The cull distance for this instance.
    /// </summary>
    float CullDistance;

    /// <summary>
    /// Lightmap UVs area that entry occupies (packed Rectangle into Half4).
    /// </summary>
    Half4 LightmapUVsArea;

    /// <summary>
    /// Cached local-to-world transformation matrix for the instance used during rendering. Relative to the last rendering context origin. Valid only if CachedDrawWorldValid flag is set.
    /// </summary>
    Matrix CachedDrawWorld;

public:
    bool operator==(const FoliageInstance& v) const
    {
        return Type == v.Type && Random == v.Random && Transform == v.Transform;
    }

    /// <summary>
    /// Determines whether this foliage instance has valid lightmap data.
    /// </summary>
    FORCE_INLINE bool HasLightmap() const
    {
        return LightmapTextureIndex != INVALID_INDEX;
    }

    /// <summary>
    /// Removes the lightmap data from the foliage instance.
    /// </summary>
    FORCE_INLINE void RemoveLightmap()
    {
        LightmapTextureIndex = INVALID_INDEX;
    }
};