start refactoring pong entities to use classes

src/ball.cpp

@@ -0,0 +1,51 @@
+#include <Arduino.h>
+#include <stdint.h>
+#include "config.h"
+
+class Ball {
+
+  private:
+
+    uint8_t _x, _y;
+    int8_t _direction_x, _direction_y;
+
+    void _init_directions(int8_t &_direction) {
+      if (random(2) == 0) _direction= 1;
+      else _direction= -1;
+    }
+
+  public:
+
+    void move() {
+      if (!_direction_x) _init_directions(_direction_x);
+      if (!_direction_y) _init_directions(_direction_y);
+
+      if (_x + _direction_x >= 0 && _x + _direction_x < MATRIX_WIDTH)
+        _x+= _direction_x;
+      if (_y + _direction_y >= 0 && _y + _direction_y < MATRIX_HEIGHT)
+        _y+= _direction_y;
+    }
+
+    void bounce_on_pad() {
+      _direction_x *= -1;
+    }
+
+    void bounce_on_sides() {
+      _direction_y *= -1;
+    }
+
+    void reset_position () {
+      _x= BALL_RESET_X;
+      _y= BALL_RESET_Y;
+      _init_directions(_direction_x);
+      _init_directions(_direction_y);
+    }
+
+    uint8_t get_x() {
+      return _x;
+    }
+
+    uint8_t get_y() {
+      return _y;
+    }
+};