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/cpp/Debouncer.cpp

@@ -0,0 +1,37 @@
+// 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.
+
+#include "frc/Debouncer.h"
+
+using namespace frc;
+
+Debouncer::Debouncer(units::second_t debounceTime, DebounceType type)
+    : m_debounceTime(debounceTime), m_debounceType(type) {
+  switch (type) {
+    case DebounceType::kBoth:  // fall-through
+    case DebounceType::kRising:
+      m_baseline = false;
+      break;
+    case DebounceType::kFalling:
+      m_baseline = true;
+      break;
+  }
+  m_timer.Start();
+}
+
+bool Debouncer::Calculate(bool input) {
+  if (input == m_baseline) {
+    m_timer.Reset();
+  }
+
+  if (m_timer.HasElapsed(m_debounceTime)) {
+    if (m_debounceType == DebounceType::kBoth) {
+      m_baseline = input;
+      m_timer.Reset();
+    }
+    return input;
+  } else {
+    return m_baseline;
+  }
+}