#include <memory>
#include <iostream>
#include <cstdlib>

#include <imgui.h>
#include <imgui_impl_glfw_gl3.h>
#include <GL/gl3w.h>
#include <GLFW/glfw3.h>

#include "gui.h"
#include "state.h"
#include "notify.h"

#define CLEAR_COLOR 0.0, 0.0, 0.0, 1.0

static void glfw_error_callback(int error, const char* description) {
	std::cerr << "GLFW error " << error << " " << description << '\n';
}

// static void glfw_key_callback(GLFWwindow *window, int key, int scancode, int action, int mods) {
// 	if (key == GLFW_KEY_R && mods == GLFW_MOD_CONTROL && action == GLFW_PRESS) {
// 		printf("...\n");
// 	}
// }

int main(int argc, char* argv[]) {
	glfwSetErrorCallback(glfw_error_callback);

	if (!glfwInit()){
		// glfw init failed; crash out
		std::clog << "GLFW: init failed; exiting.\n";
		std::exit(-1);
	}

	// request at least OpenGL v3.3
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
	glfwWindowHint(GLFW_OPENGL_DEBUG_CONTEXT, 1);

	auto window = glfwCreateWindow(1024, 768, "Zinnia", NULL, NULL);
	if (!window) {
		// window creation failed
		glfwTerminate();
		std::clog << "GLFW: failed to create window; exiting.\n";
		return EXIT_FAILURE;
	}

	glfwMakeContextCurrent(window);
	glfwSwapInterval(1);
	if (gl3wInit()) {
		std::clog << "Failed to initialize OpenGL\n";
		return EXIT_FAILURE;
	}

	std::cout << "[GL] OpenGL v" << glGetString(GL_VERSION)
		<< ", GLSL v" << glGetString(GL_SHADING_LANGUAGE_VERSION) << '\n';

	ImGui_ImplGlfwGL3_Init(window, true);

	// demo state
	auto config = Config::from_file("../config.toml");
	auto state = DemoState(std::make_shared<Config>(config));
	auto inotify = NotifyService();

	// set up a GUI state
	auto gui = Gui(&state);

	if (argc == 2) {
		auto proj = Project::fromFile(std::string(argv[1]));
		inotify.watch(*proj);
		state.current_project = std::move(proj);
	}

	const GLfloat v_quad[][2] = {
		{1, 1}, {1, -1}, {-1, -1}, {-1, 1},
	};
	const GLuint i_quad[] = {
		0, 1, 3,
		1, 2, 3,
	};
	GLuint vao, vbo, ebo;
	glGenVertexArrays(1, &vao);

	glGenBuffers(1, &ebo);
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(i_quad), i_quad, GL_STATIC_DRAW);

	glBindVertexArray(vao);
		glGenBuffers(1, &vbo);
		glBindBuffer(GL_ARRAY_BUFFER, vbo);
		glBufferData(GL_ARRAY_BUFFER, sizeof(v_quad), v_quad, GL_STATIC_DRAW);

		glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, 0);
		glEnableVertexAttribArray(0);
	glBindVertexArray(0);

	double t, t_prev, dt;
	unsigned long frame_n = 0;
	glfwSetTime(0); t_prev = glfwGetTime();
	while(!glfwWindowShouldClose(window) && state.running) {
		t = glfwGetTime();
		dt = t - t_prev; t_prev = t;

		glfwPollEvents();
		ImGui_ImplGlfwGL3_NewFrame();

		glfwGetFramebufferSize(window, &state.width, &state.height);
		state.ratio = (float)state.width / (float)state.height;

		glViewport(0, 0, (float)state.width, (float)state.height);
		glClearColor(CLEAR_COLOR);
		glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT|GL_STENCIL_BUFFER_BIT);

		if (state.current_project != nullptr) {
			if (state.current_project->scene_loaded) {
				auto prog = *state.current_project->current_scene->shader_p;
				auto u_resolution = glGetUniformLocation(prog, "u_Resolution");
				auto u_mouse = glGetUniformLocation(prog, "u_Mouse");
				auto u_time = glGetUniformLocation(prog, "u_Time");

				double m_x, m_y;
				glfwGetCursorPos(window, &m_x, &m_y);

				glUseProgram(prog);
				glUniform2f(u_resolution, (float)state.width, (float)state.height);
				glUniform4f(u_mouse, m_x, m_y, 0., 0.);
				glUniform1f(u_time, t);
				glBindVertexArray(vao);
				glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
					glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
				glBindVertexArray(0);
			}
		}

		gui.render();
		ImGui::Render();

		glfwSwapBuffers(window);

		if ((frame_n % 10) == 0) {
			inotify._poll();
		}

		std::cout << std::flush;
		std::cerr << std::flush;

		frame_n++;
	}

	ImGui_ImplGlfwGL3_Shutdown();

	glfwDestroyWindow(window);
	glfwTerminate();
	return 0;
}