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

#include <gtk gtk.h=""></gtk>

GtkWidget *entry_a;

GtkWidget *entry_b;

GtkWidget *entry_c;

GtkWidget *history;

char c_str[1024];

char history_str[1024];

void add_history(const char *str) {

  GtkTextIter iter;

  GtkTextBuffer *buffer = gtk_text_view_get_buffer(GTK_TEXT_VIEW(history));

  gtk_text_buffer_get_end_iter(buffer, &iter);

  gtk_text_buffer_insert(buffer, &iter, str, -1);

  gtk_text_buffer_insert(buffer, &iter, "\n", -1);

}

void clicked_add(GtkButton *button, gpointer data) {

  double a = atof(gtk_entry_get_text(GTK_ENTRY(entry_a)));

  double b = atof(gtk_entry_get_text(GTK_ENTRY(entry_b)));

  double c = a + b;

  sprintf(c_str, "%g", c);

  sprintf(history_str, "%g + %g = %g", a, b, c);

  gtk_entry_set_text(GTK_ENTRY(entry_c), c_str);

  add_history(history_str);

}

void clicked_sub(GtkButton *button, gpointer data) {

  double a = atof(gtk_entry_get_text(GTK_ENTRY(entry_a)));

  double b = atof(gtk_entry_get_text(GTK_ENTRY(entry_b)));

  double c = a - b;

  sprintf(c_str, "%g", c);

  sprintf(history_str, "%g - %g = %g", a, b, c);

  gtk_entry_set_text(GTK_ENTRY(entry_c), c_str);

  add_history(history_str);

}

void clicked_mul(GtkButton *button, gpointer data) {

  double a = atof(gtk_entry_get_text(GTK_ENTRY(entry_a)));

  double b = atof(gtk_entry_get_text(GTK_ENTRY(entry_b)));

  double c = a * b;

  sprintf(c_str, "%g", c);

  sprintf(history_str, "%g * %g = %g", a, b, c);

  gtk_entry_set_text(GTK_ENTRY(entry_c), c_str);

  add_history(history_str);

}

void clicked_div(GtkButton *button, gpointer data) {

  double a = atof(gtk_entry_get_text(GTK_ENTRY(entry_a)));

  double b = atof(gtk_entry_get_text(GTK_ENTRY(entry_b)));

  double c = a / b;

  sprintf(c_str, "%g", c);

  sprintf(history_str, "%g / %g = %g", a, b, c);

  gtk_entry_set_text(GTK_ENTRY(entry_c), c_str);

  add_history(history_str);

}

void activate(GtkApplication* app, gpointer data) {

  GtkWidget *window = gtk_application_window_new(app);

  gtk_window_set_default_size(GTK_WINDOW(window), 600, 400);

  gtk_container_set_border_width(GTK_CONTAINER(window), 10);  

  GtkWidget *hbox = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 5);

  gtk_container_add(GTK_CONTAINER(window), hbox);

  GtkWidget *vbox = gtk_box_new(GTK_ORIENTATION_VERTICAL, 5);

  gtk_container_add(GTK_CONTAINER(hbox), vbox);

  entry_a = gtk_entry_new();

  gtk_container_add(GTK_CONTAINER(vbox), entry_a);

  GtkWidget *buttons_box = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 5);

  gtk_box_set_homogeneous(GTK_BOX(buttons_box), TRUE);

  gtk_container_add(GTK_CONTAINER(vbox), buttons_box);

  GtkWidget *button_add = gtk_button_new_with_label("+");

  g_signal_connect(button_add, "clicked", G_CALLBACK(clicked_add), NULL);

  gtk_container_add(GTK_CONTAINER(buttons_box), button_add);

  GtkWidget *button_sub = gtk_button_new_with_label("-");

  g_signal_connect(button_sub, "clicked", G_CALLBACK(clicked_sub), NULL);

  gtk_container_add(GTK_CONTAINER(buttons_box), button_sub);

  GtkWidget *button_mul = gtk_button_new_with_label("*");

  g_signal_connect(button_mul, "clicked", G_CALLBACK(clicked_mul), NULL);

  gtk_container_add(GTK_CONTAINER(buttons_box), button_mul);

  GtkWidget *button_div = gtk_button_new_with_label("/");

  g_signal_connect(button_div, "clicked", G_CALLBACK(clicked_div), NULL);

  gtk_container_add(GTK_CONTAINER(buttons_box), button_div);

  entry_b = gtk_entry_new();

  gtk_container_add(GTK_CONTAINER(vbox), entry_b);

  GtkWidget *separator = gtk_separator_new(GTK_ORIENTATION_VERTICAL);

  gtk_container_add(GTK_CONTAINER(vbox), separator);

  entry_c = gtk_entry_new();

  gtk_container_add(GTK_CONTAINER(vbox), entry_c);

  GtkWidget *frame = gtk_frame_new(NULL);

  gtk_box_pack_end(GTK_BOX(hbox), frame, TRUE, TRUE, 0);

  GtkWidget *scroll = gtk_scrolled_window_new(NULL, NULL);

  gtk_container_add(GTK_CONTAINER(frame), scroll);

  history = gtk_text_view_new();

  gtk_text_view_set_left_margin(GTK_TEXT_VIEW(history), 5);

  gtk_text_view_set_right_margin(GTK_TEXT_VIEW(history), 5);

  gtk_text_view_set_top_margin(GTK_TEXT_VIEW(history), 5);

  gtk_text_view_set_bottom_margin(GTK_TEXT_VIEW(history), 5);

  gtk_container_add(GTK_CONTAINER(scroll), history);

  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;

}