/*
 *  <Short Description>
 *  Copyright (C) 2023  Brett Terpstra
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

#ifndef BLT_WITH_GRAPHICS_BATCH_2D_RENDERER_H
#define BLT_WITH_GRAPHICS_BATCH_2D_RENDERER_H

#include "blt/gfx/model.h"
#include "blt/gfx/shader.h"
#include "blt/gfx/renderer/resource_manager.h"
#include <blt/std/hashmap.h>
#include <blt/std/memory_util.h>
#include <blt/math/vectors.h>
#include <string_view>
#include <vector>
#include <memory>
#include <map>
#include <variant>

namespace blt::gfx
{
    struct rectangle2d_t
    {
        blt::vec2f pos, size;
        blt::f32 rotation = 0;
        
        rectangle2d_t(blt::f32 x, blt::f32 y, blt::f32 width, blt::f32 height, blt::f32 rotation): pos(x, y), size(width, height), rotation(rotation)
        {}
        
        rectangle2d_t(blt::f32 x, blt::f32 y, blt::f32 width, blt::f32 height): pos(x, y), size(width, height)
        {}
        
        rectangle2d_t(blt::vec2f pos, blt::vec2f size, blt::f32 rotation): pos(pos), size(size), rotation(rotation)
        {}
        
        rectangle2d_t(blt::vec2f pos, blt::vec2f size): pos(pos), size(size)
        {}
    };
    
    struct line2d_t
    {
        blt::vec2f p1;
        blt::vec2f p2;
        blt::f32 thickness = 1;
        
        line2d_t(blt::f32 px1, blt::f32 py1, blt::f32 px2, blt::f32 py2): p1(px1, py1), p2(px2, py2)
        {}
        
        line2d_t(blt::vec2f p1, blt::vec2f p2): p1(p1), p2(p2)
        {}
        
        line2d_t(blt::f32 px1, blt::f32 py1, blt::f32 px2, blt::f32 py2, blt::f32 thickness): p1(px1, py1), p2(px2, py2), thickness(thickness)
        {}
        
        line2d_t(blt::vec2f p1, blt::vec2f p2, blt::f32 thickness): p1(p1), p2(p2), thickness(thickness)
        {}
    };
    
    struct point2d_t
    {
        blt::vec2f pos;
        float scale = 1;
        
        point2d_t(float x, float y, float scale): pos(x, y), scale(scale)
        {}
        
        point2d_t(float x, float y): pos(x, y)
        {}
        
        point2d_t(vec2f pos, float scale): pos(pos), scale(scale)
        {}
        
        explicit point2d_t(vec2f pos): pos(pos)
        {}
    };
    
    struct draw_state
    {
        // texture to use
        std::string texture_name;
        // color to use
        blt::color4 color;
        // how much to blend the texture into the color? note blending is always additive!
        blt::color4 blend;
        // should we outline this object?
        bool outline;
        // what color should we outline with?
        blt::color4 outline_color;
    };
    
    class batch_renderer_2d
    {
        private:
            struct vec_hash
            {
                std::size_t operator()(const blt::vec4& key) const
                {
                    using namespace blt::mem;
                    return type_cast<blt::i32>(key.x()) ^ type_cast<blt::i32>(key.y()) ^ type_cast<blt::i32>(key.y()) ^ type_cast<blt::i32>(key.z());
                }
            };
            
            template<typename T>
            struct render_object_t
            {
                blt::f32 z_index;
                T obj;
                
                render_object_t(float z_index, T obj): z_index(z_index), obj(obj)
                {}
            };
            
            using rectangle2d_obj_t = render_object_t<rectangle2d_t>;
            using point2d_obj_t = render_object_t<point2d_t>;
            using line2d_obj_t = render_object_t<line2d_t>;
        private:
            vertex_array* square_vao = nullptr;
            vertex_array* line_vao = nullptr;
            shader_t* square_shader = nullptr;
            shader_t* point_shader = nullptr;
            resource_manager& resources;
            // texture -> color -> blend factor -> list of rectangles
            blt::hashmap_t<std::string, blt::hashmap_t<blt::vec4, blt::hashmap_t<blt::vec4, std::vector<rectangle2d_obj_t>, vec_hash>, vec_hash>> complex_rectangles;
            blt::hashmap_t<std::string, blt::hashmap_t<blt::vec4, blt::hashmap_t<blt::vec4, std::vector<point2d_obj_t>, vec_hash>, vec_hash>> complex_points;
            blt::hashmap_t<std::string, blt::hashmap_t<blt::vec4, blt::hashmap_t<blt::vec4, std::vector<line2d_obj_t>, vec_hash>, vec_hash>> complex_lines;
            size_t draw_count_ = 0;
        public:
            explicit batch_renderer_2d(resource_manager& resources): resources(resources)
            {}
            
            void create();
            
            inline void drawRectangleInternal(std::string_view texture, const rectangle2d_t& rectangle, blt::f32 z_index = 0)
            {
                const static blt::vec4 empty{0, 0, 0, 1};
                const static blt::vec4 full{1, 1, 1, 1};
                complex_rectangles[texture][empty][full].emplace_back(-z_index, rectangle);
            }
            
            inline void drawRectangleInternal(const blt::vec4& color, const rectangle2d_t& rectangle, blt::f32 z_index = 0)
            {
                const static blt::vec4 empty{0, 0, 0, 0};
                complex_rectangles[""][color][empty].emplace_back(-z_index, rectangle);
            }
            
            inline void drawRectangleInternal(const draw_state& draw_info, const rectangle2d_t& rectangle, blt::f32 z_index = 0)
            {
                complex_rectangles[draw_info.texture_name][draw_info.color][draw_info.blend].emplace_back(-z_index, rectangle);
            }
            
            inline void drawLineInternal(std::string_view texture, const line2d_t& line, blt::f32 z_index = 0)
            {
                const static blt::vec4 empty{0, 0, 0, 1};
                const static blt::vec4 full{1, 1, 1, 1};
                complex_lines[texture][empty][full].emplace_back(-z_index, line);
            }
            
            inline void drawLineInternal(const blt::vec4& color, const line2d_t& line, blt::f32 z_index = 0)
            {
                const static blt::vec4 empty{0, 0, 0, 0};
                complex_lines[""][color][empty].emplace_back(-z_index, line);
            }
            
            inline void drawLineInternal(const draw_state& draw_info, const line2d_t& line, blt::f32 z_index = 0)
            {
                complex_lines[draw_info.texture_name][draw_info.color][draw_info.blend].emplace_back(-z_index, line);
            }
            
            inline void drawPointInternal(std::string_view texture, const point2d_t& point, blt::f32 z_index = 0)
            {
                const static blt::vec4 empty{0, 0, 0, 1};
                const static blt::vec4 full{1, 1, 1, 1};
                complex_points[texture][empty][full].emplace_back(-z_index, point);
            }
            
            inline void drawPointInternal(const blt::vec4& color, const point2d_t& point, blt::f32 z_index = 0)
            {
                const static blt::vec4 empty{0, 0, 0, 0};
                complex_points[""][color][empty].emplace_back(-z_index, point);
            }
            
            inline void drawPointInternal(const draw_state& draw_info, const point2d_t& point, blt::f32 z_index = 0)
            {
                complex_points[draw_info.texture_name][draw_info.color][draw_info.blend].emplace_back(-z_index, point);
            }
            
            template<typename T, typename... P>
            inline void drawRectangle(const T& render_info, P... p)
            {
                drawRectangleInternal(render_info, {p...});
            }
            
            template<typename T, typename... P>
            inline void drawPoint(const T& render_info, P... p)
            {
                drawPointInternal(render_info, {p...});
            }
            
            template<typename T, typename... P>
            inline void drawLine(const T& render_info, P... p)
            {
                drawLineInternal(render_info, {p...});
            }
            
            template<typename T, typename... P>
            inline void drawRectangle(const T& render_info, blt::f32 z_index, P... p)
            {
                drawRectangleInternal(render_info, {p...}, z_index);
            }
            
            template<typename T, typename... P>
            inline void drawPoint(const T& render_info, blt::f32 z_index, P... p)
            {
                drawPointInternal(render_info, {p...}, z_index);
            }
            
            template<typename T, typename... P>
            inline void drawLine(const T& render_info, blt::f32 z_index, P... p)
            {
                drawLineInternal(render_info, {p...}, z_index);
            }
            
            void render(bool transparency = true);
            
            void cleanup();
            
            [[nodiscard]] inline size_t draw_count() const
            {
                return draw_count_;
            }
    };
    
}

#endif //BLT_WITH_GRAPHICS_BATCH_2D_RENDERER_H