#include <stdlib.h>
#include <time.h>
#include <gtk/gtk.h>

#define ROWS 4
#define COLS 4

const double pi = 3.141592653589793;

const int diameter = 40;

int board[ROWS][COLS];
GtkWidget *drawing_area;


void turn(int r, int c) {
  board[r][c] = !board[r][c];
  if (c > 0)        board[r][c - 1] = !board[r][c - 1];
  if (c < COLS - 1) board[r][c + 1] = !board[r][c + 1];
  if (r > 0)        board[r - 1][c] = !board[r - 1][c];
  if (r < ROWS - 1) board[r + 1][c] = !board[r + 1][c];
  gtk_widget_queue_draw(drawing_area);
}

gboolean draw(GtkWidget *widget, cairo_t *cr, gpointer data) {
  cairo_set_source_rgba(cr, 0.9, 0.9, 0.9, 1);
  cairo_paint(cr);
  for(int r = 0; r < ROWS; ++r) {
    for(int c = 0; c < COLS; ++c) {
      if (board[r][c]) {
        cairo_set_source_rgba(cr, 0.0, 0.0, 1.0, 1.0);
      } else {
        cairo_set_source_rgba(cr, 1.0, 1.0, 0.0, 1.0);
      }
      cairo_arc(cr, (c + 0.5)*diameter, (r + 0.5)*diameter, 0.5*diameter, 0.0, 2.0*pi);
      cairo_fill_preserve(cr);
      cairo_set_source_rgba(cr, 0.0, 0.0, 0.0, 1.0);
      cairo_stroke(cr);
    }
  }
  return TRUE;
}

gboolean button_press(GtkWidget *widget, GdkEventButton *event, gpointer data) {
  int c = (int)(event->x)/diameter;
  int r = (int)(event->y)/diameter;
  if (r >= 0 && c >= 0 && r < ROWS && c < COLS)
    turn(r, c);
  return TRUE;
}

void clicked(GtkButton *button, gpointer data) {
  for(int i = 0; i < ROWS*COLS*10; ++i) {
    int r = rand() % ROWS;
    int c = rand() % COLS;
    turn(r, c);
  }
}

void activate(GtkApplication* app, gpointer data) {
  srand(time(NULL));

  GtkWidget *window = gtk_application_window_new (app);

  GtkWidget *hbox = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 10);
  gtk_container_add(GTK_CONTAINER(window), hbox);
  
  drawing_area = gtk_drawing_area_new();
  gtk_widget_set_size_request(GTK_WIDGET(drawing_area), COLS*diameter, ROWS*diameter);
  gtk_widget_set_hexpand(drawing_area, TRUE);
  gtk_widget_add_events(drawing_area, GDK_BUTTON_PRESS_MASK);
  g_signal_connect(drawing_area, "draw", G_CALLBACK(draw), NULL);
  g_signal_connect(drawing_area, "button-press-event", G_CALLBACK(button_press), NULL);
  gtk_container_add(GTK_CONTAINER(hbox), drawing_area);

  GtkWidget *button = gtk_button_new_with_label("Randomize");
  gtk_widget_set_valign(button, GTK_ALIGN_START);
  g_signal_connect(button, "clicked", G_CALLBACK(clicked), NULL);
  gtk_container_add(GTK_CONTAINER(hbox), button);
  
  gtk_widget_show_all(window);
}

int main(int argc, char **argv) {
  GtkApplication *application = gtk_application_new(NULL, 0);
  g_signal_connect(application, "activate", G_CALLBACK(activate), NULL);
  int status = g_application_run(G_APPLICATION(application), argc, argv);
  g_object_unref(application);
  return status;
}