Supporting a button library.

libraries/button/src/button_digital.h

@@ -0,0 +1,57 @@
+#ifndef BUTTON_DIGITAL_H
+#define BUTTON_DIGITAL_H
+
+#include "button.h"
+#include "hal.h"
+
+/*
+ * Button -- Real hardware implementation (digital read).
+ *
+ * Reads a physical pushbutton connected to a digital pin.
+ * Supports both wiring configurations:
+ *
+ *   Active-low (most common, use INPUT_PULLUP):
+ *     Pin -> Button -> GND
+ *     Reads LOW when pressed, HIGH when released.
+ *     Set active_low = true (default).
+ *
+ *   Active-high (external pull-down resistor):
+ *     Pin -> Button -> VCC, with pull-down to GND
+ *     Reads HIGH when pressed, LOW when released.
+ *     Set active_low = false.
+ *
+ * Wiring (active-low, no external resistor needed):
+ *   Digital pin  -> one leg of button
+ *   GND          -> other leg of button
+ *   Set pin mode to INPUT_PULLUP in your sketch.
+ *
+ * Note: This implementation does NOT debounce. If your application
+ * needs debounce (most do), implement it in your app logic -- that
+ * way you can test it with the mock and simulator.
+ */
+class ButtonDigital : public Button {
+public:
+    /// Create a button on the given digital pin.
+    /// active_low: true if pressed reads LOW (default, use with INPUT_PULLUP).
+    ButtonDigital(Hal* hal, uint8_t pin, bool active_low = true)
+        : hal_(hal)
+        , pin_(pin)
+        , active_low_(active_low)
+    {}
+
+    bool isPressed() override {
+        int state = hal_->digitalRead(pin_);
+        return active_low_ ? (state == LOW) : (state == HIGH);
+    }
+
+    int readState() override {
+        return hal_->digitalRead(pin_);
+    }
+
+private:
+    Hal* hal_;
+    uint8_t pin_;
+    bool active_low_;
+};
+
+#endif // BUTTON_DIGITAL_H