Erasing stacks when empty. Also moved some event-related code to the keyboard object.

lib/keyboard.c

@@ -1,6 +1,22 @@
 #include <stdio.h>
+#include "display.h"
 #include "keyboard.h"
 
+void handle_stock_event() {
+  if (!empty(deck->stock)) {
+    /* erase the stack before emptying it */
+    if (length(deck->stock) == 1) {
+      erase_stack(deck->stock);
+    }
+    move_card(&(deck->stock), &(deck->waste_pile));
+    expose_card(deck->waste_pile->card);
+    draw_stack(deck->stock);
+    draw_stack(deck->waste_pile);
+  }
+
+  return;
+}
+
 int key_event() {
   int pressed_key;