#include "OpenGL2.hpp"

#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>

OpenGL2Backend::OpenGL2Backend() {
#if IMGUI_INCLUDE_OPENGL2_BACKEND
	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();
#else
	throw std::runtime_error("Backend opengl2 is not available in this build.\n");
#endif
}

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

	glfwDestroyWindow(mWindow);
	glfwTerminate();
}

void OpenGL2Backend::BeginFrame() {
	glfwPollEvents();

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

void OpenGL2Backend::EndFrame() {
	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);
}