#include "Entrypoint/Backend.hpp"

#if BUILD_CORE_WITH_OPENGL2_BACKEND
#	include <glad/glad.h>

#	include <GLFW/glfw3.h>
#	include <backend/imgui_impl_glfw.h>
#	include <backend/imgui_impl_opengl2.h>
#	include <imgui.h>
#	include <stdexcept>
#	include <iostream>

#	define IMGUI_IMPL_OPENGL_LOADER_CUSTOM
#	include <backend/imgui_impl_opengl2.cpp>

class OpenGL2Backend : public RenderingBackend
{
private:
	GLFWwindow* mWindow;

public:
	OpenGL2Backend()
	{
		glfwSetErrorCallback(&GlfwErrorCallback);
		if (!glfwInit()) {
			throw std::runtime_error("Failed to initialize GLFW.");
		}

		mWindow = glfwCreateWindow(1280, 720, "Cplt", nullptr, nullptr);
		if (mWindow == nullptr) {
			throw std::runtime_error("Failed to create GLFW window.");
		}
		glfwMakeContextCurrent(mWindow);
		glfwSwapInterval(1); // Enable vsync

		if (gladLoadGLLoader((GLADloadproc)glfwGetProcAddress) == 0) {
			throw std::runtime_error("Failed to initialize OpenGL.");
		}

		IMGUI_CHECKVERSION();
		ImGui::CreateContext();

		ImGui_ImplGlfw_InitForOpenGL(mWindow, true);
		ImGui_ImplOpenGL2_Init();
	}

	virtual ~OpenGL2Backend()
	{
		ImGui_ImplOpenGL2_Shutdown();
		ImGui_ImplGlfw_Shutdown();
		ImGui::DestroyContext();

		glfwDestroyWindow(mWindow);
		glfwTerminate();
	}

	virtual void RunUntilWindowClose(void (*windowContent)())
	{
		while (!glfwWindowShouldClose(mWindow)) {
			glfwPollEvents();

			ImGui_ImplOpenGL2_NewFrame();
			ImGui_ImplGlfw_NewFrame();
			ImGui::NewFrame();

			windowContent();

			int displayWidth, displayHeight;
			glfwGetFramebufferSize(mWindow, &displayWidth, &displayHeight);
			glViewport(0, 0, displayWidth, displayHeight);

			const ImVec4 kClearColor = ImVec4(0.45f, 0.55f, 0.60f, 1.00f);
			glClearColor(kClearColor.x * kClearColor.w, kClearColor.y * kClearColor.w, kClearColor.z * kClearColor.w, kClearColor.w);
			glClear(GL_COLOR_BUFFER_BIT);

			ImGui::Render();
			ImGui_ImplOpenGL2_RenderDrawData(ImGui::GetDrawData());

			glfwMakeContextCurrent(mWindow);
			glfwSwapBuffers(mWindow);
		}
	}

	static void GlfwErrorCallback(int errorCode, const char* message)
	{
		std::cerr << "GLFW Error " << errorCode << ": " << message << "\n";
	}
};

std::unique_ptr<RenderingBackend> RenderingBackend::CreateOpenGL2Backend()
{
	try {
		return std::make_unique<OpenGL2Backend>();
	} catch (std::exception& e) {
		return nullptr;
	}
}

#else // ^^ BUILD_CORE_WITH_OPENGL2_BACKEND | !BUILD_CORE_WITH_OPENGL2_BACKEND vv

std::unique_ptr<RenderingBackend> RenderingBackend::CreateOpenGL2Backend()
{
	return nullptr;
}

#endif