/* See LICENSE file for copyright and license details. */
#include <sys/timerfd.h>
#include <stdatomic.h>
#include <libsimple.h>
#include <libsimple-arg.h>
#if defined(__GNUC__)
# pragma GCC diagnostic push
# pragma GCC diagnostic ignored "-Wdeprecated-declarations"
# pragma GCC diagnostic ignored "-Wstrict-prototypes"
#endif
#include <gtk/gtk.h>
#include <gdk/gdkkeysyms.h>
#if defined(__GNUC__)
# pragma GCC diagnostic pop
#endif

USAGE("");


static GtkWidget *window;
static GtkWidget *status;
static GtkAccelGroup *accelgroup;
static int timer;
static const char *statustext = "";
static atomic_flag lock = ATOMIC_FLAG_INIT;
static volatile int statusdefered = 0;

#define DELAY {.tv_sec = 0, .tv_nsec = 500000000L}
static const struct itimerspec delay = {.it_interval = {0, 0}, .it_value = DELAY};


#if defined(__GNUC__)
__attribute__((__pure__))
#endif
static int
check_luhn(const char *s)
{
	unsigned sum = 0;

	switch (strlen(s) & 1U) {
		for (;;) {
		case 0:
			if ('0' <= *s && *s <= '4')
				sum += 2U * (unsigned)(*s - '0');
			else if ('5' <= *s && *s <= '9')
				sum += 2U * (unsigned)(*s - '0') - 9U;
			else if (!*s)
				break;
			s++;

			/* fall through */

		case 1:
			if ('0' <= *s && *s <= '9')
				sum += (unsigned)(*s - '0');
			else if (!*s)
				break;
			s++;

			sum %= 10U;
		}
	}

	return (sum % 10U) == 0U;
}


static int
set_status_text(void *user_data)
{
	(void) user_data;

	while (atomic_flag_test_and_set_explicit(&lock, memory_order_acquire));

	gtk_label_set_text(GTK_LABEL(status), statustext);
	statusdefered = 0;

	atomic_flag_clear(&lock);

	return 0; /* remove from idle */
}


static void *
defer_set_status_text(void *user_data)
{
	read(timer, &(uint64_t){0}, sizeof(uint64_t));
	g_idle_add(&set_status_text, user_data);
	return NULL;
}


static void
number_changed(GtkEditable *editable, GtkWidget *button)
{
	const char *text = gtk_entry_get_text(GTK_ENTRY(editable));
	int add_idle = 0;
	int ok = *text && check_luhn(text);
	const char *display;

	while (atomic_flag_test_and_set_explicit(&lock, memory_order_acquire));

	if (!text) {
		display = statustext = "";
	} else if (ok) {
		display = statustext = "Valid number";
	} else {
		statustext = "Invalid number";
		display = timer >= 0 ? "" : statustext;
		if (!statusdefered && timer >= 0) {
			statusdefered = 1;
			add_idle = 1;
		}
	}

	if (timerfd_settime(timer, 0, &delay, NULL))
		display = statustext;

	gtk_label_set_text(GTK_LABEL(status), display);
	gtk_widget_set_sensitive(button, ok);

	atomic_flag_clear(&lock);

	if (add_idle)
		g_thread_unref(g_thread_new("deferred validity update", &defer_set_status_text, NULL));
}


static void
copybutton_clicked(GtkWidget *button, GtkEditable *editable)
{
	const char *text = gtk_entry_get_text(GTK_ENTRY(editable));
	(void) button;
	gtk_clipboard_set_text(gtk_clipboard_get(GDK_SELECTION_CLIPBOARD), text, -1);
	gtk_clipboard_set_text(gtk_clipboard_get(GDK_SELECTION_PRIMARY), text, -1);
	gtk_clipboard_store(gtk_clipboard_get(GDK_SELECTION_CLIPBOARD));
}


static void
on_insert_text(GtkEditable *editable, const char *text, int length, int *position, void *user_data)
{
	size_t i, j, n = (size_t)length;
	char *result = n >= 1024U ? malloc(n + 1U) : alloca(n + 1U);

	(void) user_data;

	j = 0;
	for (i = 0; i < n; i++)
		if ('0' <= text[i] && text[i] <= '9')
			result[j++] = text[i];
	result[j] = '\0';

	if (j < n) {
		g_signal_stop_emission_by_name(editable, "insert-text");
		if (j)
			gtk_editable_insert_text(editable, result, (int)j, position);
	}

	if (n >= 1024U)
		free(result);
}


static void
close_window(GtkWidget *menu_item, void *user_data)
{
	(void) menu_item;
	(void) user_data;
	gtk_main_quit();
}


static GtkWidget *
add_menu(GtkWidget *parent, const char *label)
{
	GtkWidget *menu = gtk_menu_new();
	GtkWidget *item = gtk_menu_item_new_with_mnemonic(label);
	gtk_menu_item_set_submenu(GTK_MENU_ITEM(item), menu);
	gtk_menu_shell_append(GTK_MENU_SHELL(parent), item);
	return menu;
}


static GtkWidget *
add_menu_item(GtkWidget *parent, const char *label, const char *icon, unsigned int key,
              GdkModifierType mods, void (*action)(GtkWidget *menu_item, void *user_data))
{
	GtkWidget *item, *image;
	if (icon) {
		item = gtk_image_menu_item_new_with_mnemonic(label);
		image = gtk_image_new_from_icon_name(icon, GTK_ICON_SIZE_MENU);
		gtk_image_menu_item_set_image(GTK_IMAGE_MENU_ITEM(item), image);
		gtk_image_menu_item_set_always_show_image(GTK_IMAGE_MENU_ITEM(item), TRUE);
	} else {
		item = gtk_menu_item_new_with_mnemonic(label);
	}
	gtk_menu_shell_append(GTK_MENU_SHELL(parent), item);
	if (key)
		gtk_widget_add_accelerator(item, "activate", accelgroup, key, mods, GTK_ACCEL_VISIBLE);
	if (action)
		g_signal_connect(item, "activate", G_CALLBACK(action), NULL);
	return item;
}


static void
create_window(void)
{
	GtkWidget *outer_vbox, *vbox, *hbox, *label, *number, *copybutton;
	GtkWidget *menubar, *menu;

	window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
	g_signal_connect(window, "destroy", G_CALLBACK(&gtk_main_quit), NULL);
	gtk_window_set_title(GTK_WINDOW(window), "gluhncheck");

	accelgroup = gtk_accel_group_new();
	gtk_window_add_accel_group(GTK_WINDOW(window), accelgroup);

	outer_vbox = gtk_vbox_new(FALSE, 0);
	gtk_container_add(GTK_CONTAINER(window), outer_vbox);

	menubar = gtk_menu_bar_new();
	gtk_box_pack_start(GTK_BOX(outer_vbox), menubar, FALSE, FALSE, 0);

	menu = add_menu(menubar, "_File");
	add_menu_item(menu, "_Close", "window-close", GDK_w, GDK_CONTROL_MASK, &close_window);

	vbox = gtk_vbox_new(FALSE, 0);
	gtk_container_set_border_width(GTK_CONTAINER(vbox), 8);
	gtk_container_add(GTK_CONTAINER(outer_vbox), vbox);

	label = gtk_label_new_with_mnemonic("Enter _number:");
	gtk_misc_set_alignment(GTK_MISC(label), 0.0f, 0.5f);
	gtk_box_pack_start(GTK_BOX(vbox), label, FALSE, FALSE, 2);

	number = gtk_entry_new();
	gtk_entry_set_activates_default(GTK_ENTRY(number), TRUE);
	gtk_box_pack_start(GTK_BOX(vbox), number, FALSE, FALSE, 0);

	label = gtk_label_new(NULL);
	gtk_widget_set_size_request(label, 8, 8);
	gtk_box_pack_start(GTK_BOX(vbox), label, FALSE, FALSE, 0);

	gtk_label_set_mnemonic_widget(GTK_LABEL(label), number);

	status = gtk_label_new("");
	gtk_misc_set_alignment(GTK_MISC(status), 0.5f, 0.0f);
	gtk_box_pack_start(GTK_BOX(vbox), status, TRUE, TRUE, 0);

	hbox = gtk_hbox_new(FALSE, 0);
	gtk_box_pack_start(GTK_BOX(vbox), hbox, FALSE, FALSE, 0);

	label = gtk_label_new(NULL);
	gtk_box_pack_start(GTK_BOX(hbox), label, TRUE, TRUE, 0);

	copybutton = gtk_button_new_from_stock(GTK_STOCK_COPY);
	gtk_widget_set_tooltip_text(copybutton, "Copy to the clipboard");
	gtk_widget_set_sensitive(copybutton, FALSE);
	gtk_box_pack_start(GTK_BOX(hbox), copybutton, FALSE, FALSE, 0);

	g_signal_connect(G_OBJECT(copybutton), "clicked", G_CALLBACK(&copybutton_clicked), number);
	g_signal_connect(G_OBJECT(number), "changed", G_CALLBACK(&number_changed), copybutton);
	g_signal_connect(G_OBJECT(number), "insert-text", G_CALLBACK(&on_insert_text), NULL);
}


int
main(int argc, char *argv[])
{
	GtkIconTheme *theme;
	const char *icon;
	int xargc = 1;
	char *xargva[] = {argv[0], NULL};
	char **xargv = xargva;

	ARGBEGIN {
	default:
		usage();
	} ARGEND;

	if (argc)
		usage();

	timer = timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC);

	g_set_prgname(argv0);
	g_set_application_name("gluhncheck");

	gtk_init(&xargc, &xargv);
	theme = gtk_icon_theme_get_default();
	if (!gtk_icon_theme_has_icon(theme, icon = "apps/gluhncheck") &&
	    !gtk_icon_theme_has_icon(theme, icon = "gluhncheck") &&
	    !gtk_icon_theme_has_icon(theme, icon = "actions/dialog-apply") &&
	    !gtk_icon_theme_has_icon(theme, icon = "dialog-apply"))
		icon = "gluhncheck";
	gtk_window_set_default_icon_name(icon);

	create_window();
	gtk_window_set_icon_name(GTK_WINDOW(window), icon);
	gtk_window_set_wmclass(GTK_WINDOW(window), "gluhncheck", "gluhncheck");
	gtk_window_set_role(GTK_WINDOW(window), "gluhncheck");
	gtk_widget_show_all(window);
	gtk_window_present(GTK_WINDOW(window));

	gtk_main();
}