Add serial monitor command history

app/src/processing/app/CommandHistory.java

@@ -0,0 +1,167 @@
+package processing.app;
+
+import java.util.LinkedList;
+import java.util.ListIterator;
+
+/**
+ * Keeps track of command history in console-like applications.
+ * @author P.J.S. Kools
+ */
+public class CommandHistory {
+
+  private final LinkedList<String> commandHistory = new LinkedList<String>();
+  private final int maxHistorySize;
+  private ListIterator<String> iterator = null;
+  private boolean iteratorAsc;
+
+  /**
+   * Create a new {@link CommandHistory}.
+   * @param maxHistorySize - The max command history size.
+   */
+  public CommandHistory(int maxHistorySize) {
+    this.maxHistorySize = (maxHistorySize < 0 ? 0 : maxHistorySize);
+    this.commandHistory.addLast(""); // Current command placeholder.
+  }
+
+  /**
+   * Adds the given command to the history and resets the history traversal
+   * position to the latest command. If the latest command in the history is
+   * equal to the given command, it will not be added to the history.
+   * If the max history size is exceeded, the oldest command will be removed
+   * from the history.
+   * @param command - The command to add.
+   */
+  public void addCommand(String command) {
+    if (this.maxHistorySize == 0) {
+      return;
+    }
+
+    // Remove 'current' command.
+    this.commandHistory.removeLast();
+
+    // Add new command if it differs from the latest command.
+    if (this.commandHistory.isEmpty()
+        || !this.commandHistory.getLast().equals(command)) {
+
+      // Remove oldest command if max history size is exceeded.
+      if (this.commandHistory.size() >= this.maxHistorySize) {
+        this.commandHistory.removeFirst();
+      }
+
+      // Add new command and reset 'current' command.
+      this.commandHistory.addLast(command);
+    }
+
+    // Re-add 'current' command and reset command iterator.
+    this.commandHistory.addLast(""); // Current command placeholder.
+    this.iterator = null;
+  }
+
+  /**
+   * Gets whether a next (more recent) command is available in the history.
+   * @return {@code true} if a next command is available,
+   * returns {@code false} otherwise.
+   */
+  public boolean hasNextCommand() {
+    if (this.iterator == null) {
+      return false;
+    }
+    if (!this.iteratorAsc) {
+      this.iterator.next(); // Current command, ascending.
+      this.iteratorAsc = true;
+    }
+    return this.iterator.hasNext();
+  }
+
+  /**
+   * Gets the next (more recent) command from the history.
+   * @return The next command or {@code null} if no next command is available.
+   */
+  public String getNextCommand() {
+
+    // Return null if there is no next command available.
+    if (!this.hasNextCommand()) {
+      return null;
+    }
+
+    // Get next command.
+    String next = this.iterator.next();
+
+    // Reset 'current' command when at the end of the list.
+    if (this.iterator.nextIndex() == this.commandHistory.size()) {
+      this.iterator.set(""); // Reset 'current' command.
+    }
+    return next;
+  }
+
+  /**
+   * Gets whether a previous (older) command is available in the history.
+   * @return {@code true} if a previous command is available,
+   * returns {@code false} otherwise.
+   */
+  public boolean hasPreviousCommand() {
+    if (this.iterator == null) {
+      return this.commandHistory.size() > 1;
+    }
+    if (this.iteratorAsc) {
+      this.iterator.previous(); // Current command, descending.
+      this.iteratorAsc = false;
+    }
+    return this.iterator.hasPrevious();
+  }
+
+  /**
+   * Gets the previous (older) command from the history.
+   * When this method is called while the most recent command in the history is
+   * selected, this will store the current command as temporary latest command
+   * so that {@link #getNextCommand()} will return it once. This temporary
+   * latest command gets reset when this case occurs again or when
+   * {@link #addCommand(String)} is invoked.
+   * @param currentCommand - The current unexecuted command.
+   * @return The previous command or {@code null} if no previous command is
+   * available.
+   */
+  public String getPreviousCommand(String currentCommand) {
+
+    // Return null if there is no previous command available.
+    if (!this.hasPreviousCommand()) {
+      return null;
+    }
+
+    // Store current unexecuted command and create iterator if not traversing.
+    if (this.iterator == null) {
+      this.iterator =
+          this.commandHistory.listIterator(this.commandHistory.size());
+      this.iterator.previous(); // Last element, descending.
+      this.iteratorAsc = false;
+    }
+
+    // Store current unexecuted command if on 'current' index.
+    if (this.iterator.nextIndex() == this.commandHistory.size() - 1) {
+      this.iterator.set(currentCommand == null ? "" : currentCommand);
+    }
+
+    // Return the previous command.
+    return this.iterator.previous();
+  }
+
+  /**
+   * Resets the history location to the most recent command.
+   * @returns The latest unexecuted command as stored by
+   * {@link #getPreviousCommand(String)} or an empty string if no such command
+   * was set.
+   */
+  public String resetHistoryLocation() {
+    this.iterator = null;
+    return this.commandHistory.set(this.commandHistory.size() - 1, "");
+  }
+
+  /**
+   * Clears the command history.
+   */
+  public void clear() {
+    this.iterator = null;
+    this.commandHistory.clear();
+    this.commandHistory.addLast(""); // Current command placeholder.
+  }
+}

app/src/processing/app/SerialMonitor.java

@@ -23,6 +23,9 @@
 
 import java.awt.Color;
 import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import java.awt.event.KeyAdapter;
+import java.awt.event.KeyEvent;
 
 import static processing.app.I18n.tr;
 
@@ -32,6 +35,10 @@ public class SerialMonitor extends AbstractTextMonitor {
   private Serial serial;
   private int serialRate;
 
+  private static final int COMMAND_HISTORY_SIZE = 100;
+  private final CommandHistory commandHistory =
+      new CommandHistory(COMMAND_HISTORY_SIZE);
+
   public SerialMonitor(Base base, BoardPort port) {
     super(base, port);
 
@@ -54,11 +61,42 @@ public SerialMonitor(Base base, BoardPort port) {
     });
 
     onSendCommand((ActionEvent event) -> {
-      send(textField.getText());
+      String command = textField.getText();
+      send(command);
+      commandHistory.addCommand(command);
       textField.setText("");
     });
-    
+
     onClearCommand((ActionEvent event) -> textArea.setText(""));
+
+    // Add key listener to UP, DOWN, ESC keys for command history traversal.
+    textField.addKeyListener(new KeyAdapter() {
+      @Override
+      public void keyPressed(KeyEvent e) {
+        switch (e.getKeyCode()) {
+
+          // Select previous command.
+          case KeyEvent.VK_UP:
+            if (commandHistory.hasPreviousCommand()) {
+              textField.setText(
+                  commandHistory.getPreviousCommand(textField.getText()));
+            }
+            break;
+
+          // Select next command.
+          case KeyEvent.VK_DOWN:
+            if (commandHistory.hasNextCommand()) {
+              textField.setText(commandHistory.getNextCommand());
+            }
+            break;
+
+          // Reset history location, restoring the last unexecuted command.
+          case KeyEvent.VK_ESCAPE:
+            textField.setText(commandHistory.resetHistoryLocation());
+            break;
+        }
+      }
+    });
   }
 
   private void send(String s) {