/*
 *  <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/framebuffer.h"
#include "blt/gfx/renderer/resource_manager.h"
#include "blt/gfx/renderer/postprocess.h"
#include <blt/std/hashmap.h>
#include <blt/std/memory_util.h>
#include <blt/math/vectors.h>
#include <string_view>
#include <vector>

namespace blt::gfx
{
    struct rectangle2d_t
    {
        vec2f pos, size;
        f32 rotation = 0;
        
        rectangle2d_t(const f32 x, const f32 y, const f32 width, const f32 height, const f32 rotation): pos(x, y), size(width, height),
                                                                                                        rotation(rotation)
        {}
        
        rectangle2d_t(const f32 x, const f32 y, const f32 width, const f32 height): pos(x, y), size(width, height)
        {}
        
        rectangle2d_t(const vec2f pos, const vec2f size, const f32 rotation): pos(pos), size(size), rotation(rotation)
        {}
        
        rectangle2d_t(const vec2f pos, const vec2f size): pos(pos), size(size)
        {}
    };
    
    struct line2d_t
    {
        vec2f p1;
        vec2f p2;
        f32 thickness = 1;
        
        line2d_t(const f32 px1, const f32 py1, const f32 px2, const f32 py2): p1(px1, py1), p2(px2, py2)
        {}
        
        line2d_t(const vec2f p1, const vec2f p2): p1(p1), p2(p2)
        {}
        
        line2d_t(const f32 px1, const f32 py1, const f32 px2, const f32 py2, const f32 thickness): p1(px1, py1), p2(px2, py2), thickness(thickness)
        {}
        
        line2d_t(const vec2f p1, const vec2f p2, const f32 thickness): p1(p1), p2(p2), thickness(thickness)
        {}
    };
    
    struct point2d_t
    {
        vec2f pos;
        float scale = 1;
        
        point2d_t(const float x, const float y, const float scale): pos(x, y), scale(scale)
        {}
        
        point2d_t(const float x, const float y): pos(x, y)
        {}
        
        point2d_t(const vec2f pos, const float scale): pos(pos), scale(scale)
        {}
        
        explicit point2d_t(const vec2f pos): pos(pos)
        {}
    };
    
    struct render_info_t
    {
        private:
            constexpr static color4 disabled = color4(0, 0, 0, 0);
            constexpr static vec4 empty{0, 0, 0, 1};
            constexpr static vec4 full{1, 1, 1, 1};
            
            render_info_t(const std::string_view texture, color4 color, color4 blend): texture_name(texture), color(color), blend(blend)
            {}
        
        public:
            // texture to use
            std::string texture_name;
            // color to use
            color4 color;
            // how much to blend the texture into the color? note blending is always additive!
            color4 blend;
            // should we outline this object?
            bool outline = false;
            // what color should we outline with?
            color4 outline_color;
            
            render_info_t() = default;
            
            static render_info_t make_info(const std::string_view texture, const color4 outline = disabled)
            {
                render_info_t info{texture, empty, full};
                if (outline != disabled)
                {
                    info.outline = true;
                    info.outline_color = outline;
                }
                return info;
            }
            
            static render_info_t make_info(const color4 color, const color4 outline = disabled)
            {
                render_info_t info{"", color, empty};
                if (outline != disabled)
                {
                    info.outline = true;
                    info.outline_color = outline;
                }
                return info;
            }
            
            static render_info_t make_info(const std::string_view texture, const color4 color, const color4 blend, const color4 outline = disabled)
            {
                render_info_t info{texture, color, blend};
                if (outline != disabled)
                {
                    info.outline = true;
                    info.outline_color = outline;
                }
                return info;
            }
    };
    
    class batch_renderer_2d
    {
        private:
            std::unique_ptr<pp_engine_t> engine;
            
            template<typename T>
            struct render_object_t
            {
                f32 z_index;
                T obj;
                
                render_object_t(const float z_index, const 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>;
            
            template<typename T>
            using object_container = hashmap_t<std::string, std::vector<std::pair<render_info_t, T>>>;
        
        private:
            std::unique_ptr<vertex_array_t> square_vao = nullptr;
            std::unique_ptr<vertex_array_t> line_vao = nullptr;
            std::unique_ptr<shader_t> square_shader = nullptr;
            std::unique_ptr<shader_t> point_shader = nullptr;
            resource_manager& resources;
            matrix_state_manager& state;
            // texture name -> draw info
            struct
            {
                object_container<rectangle2d_obj_t> complex_rectangles;
                object_container<point2d_obj_t> complex_points;
                object_container<line2d_obj_t> complex_lines;
                size_t draw_count = 0;
                f32 z_min = std::numeric_limits<f32>::max();
                f32 z_max = std::numeric_limits<f32>::min();
            } draw;
            
            template<typename E>
            static void insert_obj(object_container<E>& map, const render_info_t& info, const E& obj)
            {
                map[info.texture_name].emplace_back(info, obj);
            }
            
            // called at the end of the render function
            void render_reset();
            
            // called before invocation of draw_objects
            void pre_reset();
            
            // called after draw_objects()
            void post_reset();
            
            void draw_objects();
            
            inline void update_z_index(f32 z_index)
            {
                draw.z_min = std::min(draw.z_min, -z_index);
                draw.z_max = std::max(draw.z_max, -z_index);
            }
        
        public:
            explicit batch_renderer_2d(resource_manager& resources, matrix_state_manager& state): resources(resources), state(state)
            {
                engine = pp_engine_t::make_multi_pp(std::make_unique<pp_render_target_t>());
            }
            
            void create();
            
            void drawRectangleInternal(std::string_view texture, const rectangle2d_t& rectangle, f32 z_index = 0);
            
            void drawRectangleInternal(const vec4& color, const rectangle2d_t& rectangle, f32 z_index = 0);
            
            void drawRectangleInternal(const render_info_t& draw_info, const rectangle2d_t& rectangle, f32 z_index = 0);
            
            void drawLineInternal(std::string_view texture, const line2d_t& line, f32 z_index = 0);
            
            void drawLineInternal(const vec4& color, const line2d_t& line, f32 z_index = 0);
            
            void drawLineInternal(const render_info_t& draw_info, const line2d_t& line, f32 z_index = 0);
            
            void drawPointInternal(std::string_view texture, const point2d_t& point, f32 z_index = 0);
            
            void drawPointInternal(const vec4& color, const point2d_t& point, f32 z_index = 0);
            
            void drawPointInternal(const render_info_t& draw_info, const point2d_t& point, f32 z_index = 0);
            
            template<typename T, typename... P>
            void drawRectangle(const T& render_info, P... p)
            { drawRectangleInternal(render_info, {p...}); }
            
            template<typename T, typename... P>
            void drawPoint(const T& render_info, P... p)
            { drawPointInternal(render_info, {p...}); }
            
            template<typename T, typename... P>
            void drawLine(const T& render_info, P... p)
            { drawLineInternal(render_info, {p...}); }
            
            template<typename T, typename... P>
            void drawRectangle(const T& render_info, f32 z_index, P... p)
            { drawRectangleInternal(render_info, {p...}, z_index); }
            
            template<typename T, typename... P>
            void drawPoint(const T& render_info, f32 z_index, P... p)
            { drawPointInternal(render_info, {p...}, z_index); }
            
            template<typename T, typename... P>
            void drawLine(const T& render_info, f32 z_index, P... p)
            { drawLineInternal(render_info, {p...}, z_index); }
            
            void render(i32 width, i32 height, bool transparency = true);
            
            void cleanup();
            
            [[nodiscard]] size_t draw_count() const
            { return draw.draw_count; }
    };
}

#endif //BLT_WITH_GRAPHICS_BATCH_2D_RENDERER_H