Add Debouncer (#3590)

Supersedes #2358 with updates and cleanups.

Closes #2482 and closes #2487 because we shouldn't support both
time-based and count-based debouncing approaches.

Co-authored-by: oblarg <emichaelbarnett@gmail.com>

wpilibc/src/main/native/include/frc/Debouncer.h

@@ -0,0 +1,46 @@
+// 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 <units/time.h>
+
+#include "frc/Timer.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 Debouncer {
+ public:
+  enum DebounceType { kRising, kFalling, kBoth };
+
+  /**
+   * Creates a new Debouncer.
+   *
+   * @param debounce 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:
+  frc::Timer m_timer;
+  units::second_t m_debounceTime;
+  bool m_baseline;
+  DebounceType m_debounceType;
+};
+}  // namespace frc