#include "Backend.hpp"

#if BUILD_CORE_WITH_OPENGL3_BACKEND
#	include <glad/glad.h>

#	include <GLFW/glfw3.h>
#	include <iostream>
#	include <backend/imgui_impl_glfw.h>
#	include <backend/imgui_impl_opengl3.h>
#	include <imgui.h>
#	include <stdexcept>

#	define IMGUI_IMPL_OPENGL_LOADER_CUSTOM
#	include <backend/imgui_impl_opengl3.cpp>

class OpenGL3Backend : public RenderingBackend {
private:
	GLFWwindow* mWindow;

public:
	OpenGL3Backend() {
		glfwSetErrorCallback(&GlfwErrorCallback);
		if (!glfwInit()) {
			throw std::runtime_error("Failed to initialize GLFW.");
		}

#	if defined(__APPLE__)
		// GL 3.2 + GLSL 150
		const char* glslVersion = "#version 150";
		glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
		glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 2);
		glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE); // 3.2+ only
		glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); // Required on Mac
#	else
		// GL 3.0 + GLSL 130
		const char* glslVersion = "#version 130";
		glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
		glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0);
		// glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);  // 3.2+ only
		// glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);            // 3.0+ only
#	endif

		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_ImplOpenGL3_Init(glslVersion);
	}

	virtual ~OpenGL3Backend() {
		ImGui_ImplOpenGL3_Shutdown();
		ImGui_ImplGlfw_Shutdown();
		ImGui::DestroyContext();

		glfwDestroyWindow(mWindow);
		glfwTerminate();
	}

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

			ImGui_ImplOpenGL3_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_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());

			glfwSwapBuffers(mWindow);
		}
	}

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

std::unique_ptr<RenderingBackend> RenderingBackend::CreateOpenGL3Backend() {
	try {
		return std::make_unique<OpenGL3Backend>();
	} catch (std::exception& e) {
		return nullptr;
	}
}

#else // ^^ BUILD_CORE_WITH_OPENGL3_BACKEND | !BUILD_CORE_WITH_OPENGL3_BACKEND vv

std::unique_ptr<RenderingBackend> RenderingBackend::CreateOpenGL3Backend() {
	return nullptr;
}

#endif