#pragma once

#include <vector>
#include <numbers>
#include <iostream>
#include <fstream>
#include <sstream>
#include <chrono>
#include <cmath>

#include "core/camera.h"
#include "object.h"

#include "rendering/renderer.h"
#include "rendering/shader.h"
#include "rendering/vertex_array.h"
#include "rendering/texture.h"
#include "rendering/uniform_buffer.h"
#include "rendering/texture_manager.h"

#include <GLFW/glfw3.h>
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>

namespace Donut
{
    const double c = 299792458.0;
    const double G = 6.67430e-11;

    struct BlackHole
    {
        glm::vec3 m_position;
        double m_mass;
        double m_radius;
        double m_rs;

        BlackHole(glm::vec3 pos, float mass) 
            : m_position(pos), m_mass(mass)
        {
            m_rs = 2.0 * G * m_mass / (c * c);
        }

        bool intercept(float px, float py, float pz) const
        {
            double dx = double(px) - double(m_position.x);
            double dy = double(py) - double(m_position.y);
            double dz = double(pz) - double(m_position.z);
            double dist2 = dx * dx + dy * dy + dz * dz;
            return dist2 < m_rs * m_rs;
        }
    };

    struct ObjectData
    {
        glm::vec4 m_pos_radius;
        glm::vec4 m_color;
        float     m_mass;
        glm::vec3 m_velocity = glm::vec3(0.0f, 0.0f, 0.0f);
    };

    class Engine
    {
    public:
        Engine();
        ~Engine() = default;

        void draw_full_screen_quad();
        void dispatch_compute(const Camera& cam);
        void upload_camera_ubo(const Camera& cam);
        void upload_objects_ubo(const std::vector<ObjectData>& objs);
        void upload_disk_ubo();
        void upload_simulation_ubo();
        void render_scene();
        void update_physics(float delta_time);
        void update_window_dimensions();
        void set_window_dimensions(int width, int height);

        int get_width()  const { return m_width;  }
        int get_height() const { return m_height; }

        std::vector<ObjectData>& get_objects() { return m_objects; }
        BlackHole&               get_sag_a()    { return m_sag_a;    }
        Camera&                  get_camera()  { return m_camera;  }
        bool&                    get_gravity() { return m_gravity; }

        void  update_performance(float delta_time);
        void  set_target_fps(int fps)        { m_target_fps = fps;                             }
        int   get_target_fps()         const { return m_target_fps;                            }
        float get_current_fps()        const { return m_current_fps;                           }
        void  set_compute_height(int height) { m_compute_height = height;                      }
        int   get_compute_height()     const { return m_compute_height;                        }
        int   get_compute_width()      const { return (m_width * m_compute_height) / m_height; }
        void  update_compute_dimensions();
        
        int   get_max_steps_moving()    const { return m_max_steps_moving; }
        int   get_max_steps_static()    const { return m_max_steps_static; }
        float get_early_exit_distance() const { return m_early_exit_distance; }
        void  set_max_steps_moving(int steps) { m_max_steps_moving = steps; }
        void  set_max_steps_static(int steps) { m_max_steps_static = steps; }
        void  set_early_exit_distance(float distance) { m_early_exit_distance = distance; }
        
        float get_disk_thickness() const { return m_disk_thickness; }
        void  set_disk_thickness(float thickness) { m_disk_thickness = thickness; }
        
        float get_disk_density() const { return m_disk_density; }
        void  set_disk_density(float density) { m_disk_density = density; }
        
        float get_rotation_speed() const { return m_rotation_speed; }
        void  set_rotation_speed(float speed) { m_rotation_speed = speed; }
        
        void load_objects_from_scene(const std::vector<Donut::Object>& objects);
        void export_high_res_frame(const std::string& filename, int width = 4096, int height = 3072);
        void print_object_info() const;
    private:
        Ref<Shader> create_compute_program(const char* path);
        std::pair<Ref<VertexArray>, Ref<Texture2D>> quad_vao();
    private:
        Ref<VertexArray>   m_quad_vao;
        Ref<Texture2D>     m_texture;
        Ref<Shader>        m_shader_program;
        Ref<Shader>        m_compute_program;
        Ref<UniformBuffer> m_camera_ubo;
        Ref<UniformBuffer> m_disk_ubo;
        Ref<UniformBuffer> m_objects_ubo;
        Ref<UniformBuffer> m_simulation_ubo;

        int   m_width;
        int   m_height;
        float m_width_f = 100*10e10f;
        float m_height_f = 75*10e10f;

        int   m_target_fps     = 60;
        float m_current_fps    = 60.0f;
        float m_last_frame_time = 0.0f;
        int   m_compute_height = 150;

        std::vector<ObjectData> m_objects;
        BlackHole               m_sag_a;
        Camera                  m_camera;
        bool                    m_gravity = false;
        
        int   m_max_steps_moving    = 60000;
        int   m_max_steps_static    = 30000;
        float m_early_exit_distance = 5e11f;
        
        float m_disk_thickness = 0.1;    
        float m_disk_density   = 1.2f;
        float m_rotation_speed = 1.0f;
    };
};