[wpimath] Move debouncer to filters (#3838)

wpimath/src/main/native/include/frc/filter/Debouncer.h

@@ -0,0 +1,51 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#pragma once
+
+#include <wpi/timestamp.h>
+
+#include "units/time.h"
+
+namespace frc {
+/**
+ * A simple debounce filter for boolean streams.  Requires that the boolean
+ * change value from baseline for a specified period of time before the filtered
+ * value changes.
+ */
+class WPILIB_DLLEXPORT Debouncer {
+ public:
+  enum DebounceType { kRising, kFalling, kBoth };
+
+  /**
+   * Creates a new Debouncer.
+   *
+   * @param debounceTime The number of seconds the value must change from
+   *                     baseline for the filtered value to change.
+   * @param type         Which type of state change the debouncing will be
+   *                     performed on.
+   */
+  explicit Debouncer(units::second_t debounceTime,
+                     DebounceType type = DebounceType::kRising);
+
+  /**
+   * Applies the debouncer to the input stream.
+   *
+   * @param input The current value of the input stream.
+   * @return The debounced value of the input stream.
+   */
+  bool Calculate(bool input);
+
+ private:
+  units::second_t m_debounceTime;
+  bool m_baseline;
+  DebounceType m_debounceType;
+
+  units::second_t m_prevTime;
+
+  void ResetTimer();
+
+  bool HasElapsed() const;
+};
+}  // namespace frc