// =============================================
//  Aster: light_manager.h
//  Copyright (c) 2020-2024 Anish Bhobe
// =============================================

#pragma once

#include "aster/aster.h"

// TODO: Separate files so you only import handles.
#include "render_resource_manager.h"

struct Environment;

struct DirectionalLight
{
    vec3 m_Direction;
    u32 m_UnusedPadding0_;
    u32 m_Color_; // LSB is used for flags. (R G B Flags)
    f32 m_Intensity;
};

struct PointLight
{
    vec3 m_Position;
    f32 m_Range;
    u32 m_Color_; // LSB is used for flags. (R G B Flags)
    f32 m_Intensity;
};

struct LightHandle
{
    u8 m_Type;
    u8 m_Generation;
    u16 m_Index;
};

struct Light;

struct LightManager
{
    constexpr static u16 MAX_LIGHTS = MaxValue<u16>;
    struct LightMetaInfo
    {
        TextureHandle m_Skybox;    // 04   04
        TextureHandle m_Diffuse;   // 04   08
        TextureHandle m_Prefilter; // 04   12
        TextureHandle m_BrdfLut;   // 04   16

        // The number of directional lights is relatively low (1 - 2) and will almost never change in a scene.
        // We can use that with Offset = 0, and point light at further offsets.
        // This way we don't need to move point lights often.
        BufferHandle m_LightBuffer;     // 04   20
        u16 m_PointLightMaxCount;       // 02   22
        u16 m_PointLightOffset;         // 02   24
        u16 m_DirectionalLightMaxCount; // 02   26
        u16 m_UnusedPadding0 = 0;       // 02   28
        u32 m_UnusedPadding1 = 0;       // 04   32
    };

    RenderResourceManager *m_ResourceManager;
    eastl::vector<Light> m_Lights;

    // We don't need a Directional Light free list. We will just brute force iterate.
    u16 m_DirectionalLightCount;
    // TODO: A point light free list. We will brute force until we have a lot (100+) of point lights.
    u16 m_PointLightCount;

    LightMetaInfo m_MetaInfo;
    // Using lower bit for flags. Use CAPACITY_MASK for value.
    u16 m_GpuBufferCapacity_;

    // Using lower bit. Capacity can be directly a multiple of 2
    // Thus, range is up to MaxValue<u16>
    constexpr static u16 UPDATE_REQUIRED_BIT = 1;
    constexpr static u16 CAPACITY_MASK = ~(UPDATE_REQUIRED_BIT);

    LightHandle AddDirectional(const vec3 &direction, const vec3 &color, f32 intensity);
    LightHandle AddPoint(const vec3 &position, const vec3 &color, f32 radius, f32 intensity);
    void Update();
    void RemoveLight(LightHandle handle);

    void SetEnvironment(Environment *environment);

    explicit LightManager(RenderResourceManager *resourceManager);
    ~LightManager();

    LightManager(LightManager &&other) noexcept;
    LightManager &operator=(LightManager &&other) noexcept;

    DISALLOW_COPY_AND_ASSIGN(LightManager);
};