#include "application.h"

#include "rendering/renderer.h"
#include "rendering/vertex_array.h"
#include "rendering/vertex_buffer.h"
#include "rendering/index_buffer.h"
#include "rendering/shader.h"

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

namespace Donut
{
    Application* Application::s_instance = nullptr;

    Application::Application(const std::string& name, int width, int height)
        : m_running(true), m_minimized(false)
    {
        s_instance = this;

        m_window = std::make_unique<Window>(name, width, height);
        m_window->set_event_callback([this](Event& event) 
        {
            on_event(event);
        });

        on_init();
    }

    Application::~Application()
    {
        on_shutdown();
        s_instance = nullptr;
    }

    void Application::run()
    {
        while (m_running)
        {
            if (!m_minimized)
            {
                on_update();
                on_render();
            }

            m_window->on_update();
        }
    }

    void Application::close()
    {
        m_running = false;
    }

    void Application::on_event(Event& event)
    {
        EventDispatcher dispatcher(event);
        dispatcher.dispatch<WindowCloseEvent>([this, &event](WindowCloseEvent& e) 
        {
            m_running = false;
            event.handled = true;
            return true;
        });
        
        dispatcher.dispatch<WindowResizeEvent>([this, &event](WindowResizeEvent& e) 
        {
            if (e.get_width() == 0 || e.get_height() == 0)
                m_minimized = true;
            else
                m_minimized = false;
            
            if (m_camera)
                m_camera->set_projection(45.0f, (float)e.get_width() / (float)e.get_height(), 0.1f, 100.0f);
            
            event.handled = true;
            return true;
        });
        
        dispatcher.dispatch<WindowFocusEvent>([this, &event](WindowFocusEvent& e) 
        {
            m_first_mouse = true;
            m_mouse_dragging = false;
            event.handled = true;
            return true;
        });
        
        dispatcher.dispatch<WindowLostFocusEvent>([this, &event](WindowLostFocusEvent& e) 
        {
            m_mouse_dragging = false;
            event.handled = true;
            return true;
        });
        
        dispatcher.dispatch<KeyPressedEvent>([this, &event](KeyPressedEvent& e) 
        {
            m_keys[e.get_key_code()] = true;
            return true;
        });
        
        dispatcher.dispatch<KeyReleasedEvent>([this, &event](KeyReleasedEvent& e) 
        {
            m_keys[e.get_key_code()] = false;
            return true;
        });
        
        dispatcher.dispatch<MouseMovedEvent>([this, &event](MouseMovedEvent& e) 
        {
            if (!m_mouse_dragging)
                return true;
                
            if (m_first_mouse)
            {
                m_last_x = e.get_x();
                m_last_y = e.get_y();
                m_first_mouse = false;
            }

            float x_offset = m_last_x - e.get_x();
            float y_offset = e.get_y() - m_last_y;

            m_last_x = e.get_x();
            m_last_y = e.get_y();

            if (m_camera)
                m_camera->on_mouse_move(x_offset, y_offset);
            
            return true;
        });
        
        dispatcher.dispatch<MouseButtonPressedEvent>([this, &event](MouseButtonPressedEvent& e) 
        {
            if (e.get_mouse_button() == GLFW_MOUSE_BUTTON_LEFT)
            {
                m_mouse_dragging = true;
                m_first_mouse = true;
            }
            return true;
        });
        
        dispatcher.dispatch<MouseButtonReleasedEvent>([this, &event](MouseButtonReleasedEvent& e) 
        {
            if (e.get_mouse_button() == GLFW_MOUSE_BUTTON_LEFT)
                m_mouse_dragging = false;
            return true;
        });
    }

    void Application::on_init()     
    { 
        Renderer::init();

        m_camera = std::make_unique<Camera>(45.0f, 1280.0f / 720.0f, 0.1f, 100.0f);
        m_camera->set_position({ 0.0f, 0.0f, 3.0f });
        m_camera->set_mouse_sensitivity(0.1f);
        m_camera->set_movement_speed(5.0f);

        float vertices[] = 
        {
            -0.5f, -0.5f, -0.5f,  1.0f, 0.0f, 0.0f, 1.0f,
             0.5f, -0.5f, -0.5f,  0.0f, 1.0f, 0.0f, 1.0f,
             0.5f,  0.5f, -0.5f,  0.0f, 0.0f, 1.0f, 1.0f,
            -0.5f,  0.5f, -0.5f,  1.0f, 1.0f, 0.0f, 1.0f,
            -0.5f, -0.5f,  0.5f,  1.0f, 0.0f, 1.0f, 1.0f,
             0.5f, -0.5f,  0.5f,  0.0f, 1.0f, 1.0f, 1.0f,
             0.5f,  0.5f,  0.5f,  0.5f, 0.5f, 0.5f, 1.0f,
            -0.5f,  0.5f,  0.5f,  1.0f, 1.0f, 1.0f, 1.0f
        };

        uint32_t indices[] = 
        {
            0, 1, 2,  2, 3, 0,
            1, 5, 6,  6, 2, 1,
            5, 4, 7,  7, 6, 5,
            4, 0, 3,  3, 7, 4,
            3, 2, 6,  6, 7, 3,
            4, 5, 1,  1, 0, 4 
        };

        m_vertex_array = std::shared_ptr<VertexArray>(VertexArray::create());
        m_vertex_buffer = std::shared_ptr<VertexBuffer>(VertexBuffer::create(vertices, sizeof(vertices)));
        
        VertexBufferLayout layout;
        layout.push<float>(3);
        layout.push<float>(4);
        m_vertex_buffer->set_layout(layout);

        m_vertex_array->add_vertex_buffer(m_vertex_buffer);

        m_index_buffer = std::shared_ptr<IndexBuffer>(IndexBuffer::create(indices, 36));
        m_vertex_array->set_index_buffer(m_index_buffer);

        m_shader = std::shared_ptr<Shader>(Shader::create("assets/basic.glsl"));
    }

    void Application::on_shutdown() 
    { 
        Renderer::shutdown();
    }

    void Application::on_update()
    {
        float current_frame = (float)glfwGetTime();
        m_delta_time = current_frame - m_last_frame;
        m_last_frame = current_frame;

        if (m_camera)
        {
            if (m_keys[GLFW_KEY_W])
                m_camera->move_forward(m_delta_time);
            if (m_keys[GLFW_KEY_S])
                m_camera->move_backward(m_delta_time);
            if (m_keys[GLFW_KEY_A])
                m_camera->move_left(m_delta_time);
            if (m_keys[GLFW_KEY_D])
                m_camera->move_right(m_delta_time);
            if (m_keys[GLFW_KEY_SPACE])
                m_camera->move_up(m_delta_time);
            if (m_keys[GLFW_KEY_LEFT_SHIFT])
                m_camera->move_down(m_delta_time);
        }
    }

    void Application::on_render()
    {
        Renderer::set_clear_color({ 0.0f, 0.0f, 0.0f, 1.0f });
        Renderer::clear();

        glm::mat4 view_projection = m_camera ? m_camera->get_view_projection_matrix() : glm::mat4(1.0f);
        
        glm::vec3 center_pos(0.0f, 0.0f, 0.0f);
        glm::vec3 right_pos(2.0f, 0.0f, 0.0f);
        glm::vec3 left_pos(-2.0f, 0.0f, 0.0f);
        glm::vec3 up_pos(0.0f, 2.0f, 0.0f);
        glm::vec3 down_pos(0.0f, -2.0f, 0.0f);
        glm::vec3 forward_pos(0.0f, 0.0f, 2.0f);
        glm::vec3 back_pos(0.0f, 0.0f, -2.0f);
        
        glm::mat4 transform = glm::translate(glm::mat4(1.0f), center_pos);
        Renderer::submit(m_shader, m_vertex_array, transform, view_projection);
        transform = glm::translate(glm::mat4(1.0f), right_pos);
        Renderer::submit(m_shader, m_vertex_array, transform, view_projection);
        transform = glm::translate(glm::mat4(1.0f), left_pos);
        Renderer::submit(m_shader, m_vertex_array, transform, view_projection);
        transform = glm::translate(glm::mat4(1.0f), up_pos);
        Renderer::submit(m_shader, m_vertex_array, transform, view_projection);
        transform = glm::translate(glm::mat4(1.0f), down_pos);
        Renderer::submit(m_shader, m_vertex_array, transform, view_projection);
        transform = glm::translate(glm::mat4(1.0f), forward_pos);
        Renderer::submit(m_shader, m_vertex_array, transform, view_projection);
        transform = glm::translate(glm::mat4(1.0f), back_pos);
        Renderer::submit(m_shader, m_vertex_array, transform, view_projection);
    }
}