#ifndef ENGINE_H
#define ENGINE_H

#include <iostream>
#include <vector>
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include "imgui.h"
#include "imgui_impl_opengl3.h"
#include "imgui_impl_glfw.h"
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>

#include "Components/Component.h"
#include "Components/Camera.h"

// Forward declaration of Entity.
class Entity;

class Engine {
public:
    // Main window.
    static GLFWwindow* window;

    // Initializes GLFW, GLEW, and sets up the main window and offscreen framebuffer.
    static bool Init();
    // Returns the main GLFW window.
    static GLFWwindow* GetWindow();
    // Clean up resources and shutdown GLFW.
    static void Shutdown();

    // Offscreen render function that uses the provided camera parameters and renders the scene 
    // (with entities) offscreen. Returns the color attachment as an ImTextureID.
    static ImTextureID RenderScene(const glm::mat4 &view, const glm::mat4 &projection, const glm::vec3 &viewPos, const std::vector<Entity*>& entities);

    // Resizes the offscreen framebuffer to the given dimensions.
    static void ResizeFramebuffer(int width, int height);

    // Retrieves the final rendered texture.
    static ImTextureID GetFinalRenderingTexture();

    // --- Billboard Rendering for 3D Icons ---
    // Billboard shader and VAO for drawing icons (e.g., light icons) as billboards in 3D space.
    static GLuint billboardShaderProgram;
    static GLuint billboardVAO;
    // Sets up billboard resources.
    static bool SetupBillboard();
    // Draws a billboarded icon at the given world position with a specified size.
    static void DrawIconIn3DSpace(const glm::vec3 &worldPos, const glm::vec2 &size, ImTextureID texture, const glm::mat4 &view, const glm::mat4 &projection);
    // Iterates over entities and draws icons for those of the appropriate type.
    static void DrawIconsIn3DSpace(const std::vector<Entity*>& entities, const glm::mat4 &view, const glm::mat4 &projection, ImTextureID iconTexture);

private:
    // Offscreen framebuffer and its attachments.
    static GLuint framebuffer;
    static GLuint colorTexture;
    static GLuint depthRenderbuffer;
    // Geometry for a simple cube.
    static GLuint cubeVAO;
    static GLuint cubeVBO;
    // Shader program used for rendering the scene.
    static GLuint shaderProgram;
    // Rotation angle for the spinning cube (or animated models).
    static float rotationAngle;
    // Current offscreen framebuffer dimensions.
    static int fbWidth;
    static int fbHeight;

    // Helper function to compile and link shaders.
    static GLuint CompileShader(const char* vertexSrc, const char* fragmentSrc);
    // Sets up cube geometry and shader (called during initialization).
    static bool SetupScene();
};

#endif // ENGINE_H