[commands] Extract common trigger binding logic (#7550)

This makes the logic clearer in the actual binding methods and will hopefully make it less annoying to make changes such as allowing control over initial edges.

Also changes Java to use previous and current to match C++.

Author: KangarooKoala

wpilibNewCommands/src/main/java/edu/wpi/first/wpilibj2/command/button/Trigger.java

@@ -24,6 +24,18 @@
  * <p>This class is provided by the NewCommands VendorDep
  */
 public class Trigger implements BooleanSupplier {
+  /** Functional interface for the body of a trigger binding. */
+  @FunctionalInterface
+  private interface BindingBody {
+    /**
+     * Executes the body of the binding.
+     *
+     * @param previous The previous state of the condition.
+     * @param current The current state of the condition.
+     */
+    void run(boolean previous, boolean current);
+  }
+
   private final BooleanSupplier m_condition;
   private final EventLoop m_loop;
 
@@ -50,26 +62,38 @@ public Trigger(BooleanSupplier condition) {
   }
 
   /**
-   * Starts the command when the condition changes.
+   * Adds a binding to the EventLoop.
    *
-   * @param command the command to start
-   * @return this trigger, so calls can be chained
+   * @param body The body of the binding to add.
    */
-  public Trigger onChange(Command command) {
-    requireNonNullParam(command, "command", "onChange");
+  private void addBinding(BindingBody body) {
     m_loop.bind(
         new Runnable() {
-          private boolean m_pressedLast = m_condition.getAsBoolean();
+          private boolean m_previous = m_condition.getAsBoolean();
 
           @Override
           public void run() {
-            boolean pressed = m_condition.getAsBoolean();
+            boolean current = m_condition.getAsBoolean();
 
-            if (m_pressedLast != pressed) {
-              command.schedule();
-            }
+            body.run(m_previous, current);
 
-            m_pressedLast = pressed;
+            m_previous = current;
+          }
+        });
+  }
+
+  /**
+   * Starts the command when the condition changes.
+   *
+   * @param command the command to start
+   * @return this trigger, so calls can be chained
+   */
+  public Trigger onChange(Command command) {
+    requireNonNullParam(command, "command", "onChange");
+    addBinding(
+        (previous, current) -> {
+          if (previous != current) {
+            command.schedule();
           }
         });
     return this;
@@ -83,19 +107,10 @@ public void run() {
    */
   public Trigger onTrue(Command command) {
     requireNonNullParam(command, "command", "onTrue");
-    m_loop.bind(
-        new Runnable() {
-          private boolean m_pressedLast = m_condition.getAsBoolean();
-
-          @Override
-          public void run() {
-            boolean pressed = m_condition.getAsBoolean();
-
-            if (!m_pressedLast && pressed) {
-              command.schedule();
-            }
-
-            m_pressedLast = pressed;
+    addBinding(
+        (previous, current) -> {
+          if (!previous && current) {
+            command.schedule();
           }
         });
     return this;
@@ -109,19 +124,10 @@ public void run() {
    */
   public Trigger onFalse(Command command) {
     requireNonNullParam(command, "command", "onFalse");
-    m_loop.bind(
-        new Runnable() {
-          private boolean m_pressedLast = m_condition.getAsBoolean();
-
-          @Override
-          public void run() {
-            boolean pressed = m_condition.getAsBoolean();
-
-            if (m_pressedLast && !pressed) {
-              command.schedule();
-            }
-
-            m_pressedLast = pressed;
+    addBinding(
+        (previous, current) -> {
+          if (previous && !current) {
+            command.schedule();
           }
         });
     return this;
@@ -139,21 +145,12 @@ public void run() {
    */
   public Trigger whileTrue(Command command) {
     requireNonNullParam(command, "command", "whileTrue");
-    m_loop.bind(
-        new Runnable() {
-          private boolean m_pressedLast = m_condition.getAsBoolean();
-
-          @Override
-          public void run() {
-            boolean pressed = m_condition.getAsBoolean();
-
-            if (!m_pressedLast && pressed) {
-              command.schedule();
-            } else if (m_pressedLast && !pressed) {
-              command.cancel();
-            }
-
-            m_pressedLast = pressed;
+    addBinding(
+        (previous, current) -> {
+          if (!previous && current) {
+            command.schedule();
+          } else if (previous && !current) {
+            command.cancel();
           }
         });
     return this;
@@ -171,21 +168,12 @@ public void run() {
    */
   public Trigger whileFalse(Command command) {
     requireNonNullParam(command, "command", "whileFalse");
-    m_loop.bind(
-        new Runnable() {
-          private boolean m_pressedLast = m_condition.getAsBoolean();
-
-          @Override
-          public void run() {
-            boolean pressed = m_condition.getAsBoolean();
-
-            if (m_pressedLast && !pressed) {
-              command.schedule();
-            } else if (!m_pressedLast && pressed) {
-              command.cancel();
-            }
-
-            m_pressedLast = pressed;
+    addBinding(
+        (previous, current) -> {
+          if (previous && !current) {
+            command.schedule();
+          } else if (!previous && current) {
+            command.cancel();
           }
         });
     return this;
@@ -199,23 +187,14 @@ public void run() {
    */
   public Trigger toggleOnTrue(Command command) {
     requireNonNullParam(command, "command", "toggleOnTrue");
-    m_loop.bind(
-        new Runnable() {
-          private boolean m_pressedLast = m_condition.getAsBoolean();
-
-          @Override
-          public void run() {
-            boolean pressed = m_condition.getAsBoolean();
-
-            if (!m_pressedLast && pressed) {
-              if (command.isScheduled()) {
-                command.cancel();
-              } else {
-                command.schedule();
-              }
+    addBinding(
+        (previous, current) -> {
+          if (!previous && current) {
+            if (command.isScheduled()) {
+              command.cancel();
+            } else {
+              command.schedule();
             }
-
-            m_pressedLast = pressed;
           }
         });
     return this;
@@ -229,23 +208,14 @@ public void run() {
    */
   public Trigger toggleOnFalse(Command command) {
     requireNonNullParam(command, "command", "toggleOnFalse");
-    m_loop.bind(
-        new Runnable() {
-          private boolean m_pressedLast = m_condition.getAsBoolean();
-
-          @Override
-          public void run() {
-            boolean pressed = m_condition.getAsBoolean();
-
-            if (m_pressedLast && !pressed) {
-              if (command.isScheduled()) {
-                command.cancel();
-              } else {
-                command.schedule();
-              }
+    addBinding(
+        (previous, current) -> {
+          if (previous && !current) {
+            if (command.isScheduled()) {
+              command.cancel();
+            } else {
+              command.schedule();
             }
-
-            m_pressedLast = pressed;
           }
         });
     return this;