Implement command history feature

src/main/java/seedu/address/logic/CommandHistory.java

@@ -0,0 +1,65 @@
+package seedu.address.logic;
+
+import java.util.ArrayList;
+
+/**
+ * Represents an abstraction for a command history data structure.
+ */
+public class CommandHistory {
+
+    private final ArrayList<String> commandHistory = new ArrayList<>();
+    private int index = 0;
+
+    /**
+     * Get the previous command text.
+     *
+     * @return the previous command text.
+     */
+    public String getPrevious() {
+        assert -1 <= index && index <= commandHistory.size();
+
+        if (index < 0) {
+            return "";
+        }
+
+        index -= 1;
+
+        if (index < 0) {
+            return "";
+        }
+
+        return commandHistory.get(index);
+    }
+
+    /**
+     * Get the next command text.
+     *
+     * @return the next command text.
+     */
+    public String getNext() {
+        assert -1 <= index && index <= commandHistory.size();
+
+        if (index >= commandHistory.size()) {
+            return "";
+        }
+
+        index += 1;
+
+        if (index >= commandHistory.size()) {
+            return "";
+        }
+
+        return commandHistory.get(index);
+    }
+
+    /**
+     * Add a valid command text to the command history.
+     *
+     * @param commandText the command text string.
+     */
+    public void add(String commandText) {
+        commandHistory.add(commandText);
+        index = commandHistory.size();
+    }
+
+}

src/main/java/seedu/address/logic/Logic.java

@@ -13,16 +13,30 @@
  * API of the Logic component
  */
 public interface Logic {
+
     /**
      * Executes the command and returns the result.
      * @param commandText The command as entered by the user.
      * @return the result of the command execution.
      * @throws CommandException If an error occurs during command execution.
      * @throws ParseException If an error occurs during parsing.
      */
-
     String execute(String commandText) throws CommandException, ParseException, StorageException;
 
+    /**
+     * Gets the previous command's text.
+     *
+     * @return the previous command's text.
+     */
+    String getPreviousCommandText();
+
+    /**
+     * Gets the next command's text.
+     *
+     * @return the next command's text.
+     */
+    String getNextCommandText();
+
     /** Returns an unmodifiable view of the filtered list of persons */
     ObservableList<Person> getFilteredPersonList();
 
@@ -40,4 +54,5 @@ public interface Logic {
      * Set the user prefs' GUI settings.
      */
     void setGuiSettings(GuiSettings guiSettings);
+
 }

src/main/java/seedu/address/logic/LogicManager.java

@@ -25,6 +25,8 @@
     private final Model model;
     private final Storage storage;
 
+    private final CommandHistory commandHistory = new CommandHistory();
+
     /**
      * Constructs a {@code LogicManager} with the given {@code Model} and {@code Storage}.
      */
@@ -41,9 +43,23 @@
         String commandResult = command.execute(model);
         storage.saveAddressBook(model.getAddressBook());
 
+        // keep track of valid commands
+        commandHistory.add(commandText);
+        logger.info("\"" + commandText + "\" pushed to stack, commandTextFuture stack cleared");
+
         return commandResult;
     }
 
+    @Override
+    public String getPreviousCommandText() {
+        return commandHistory.getPrevious();
+    }
+
+    @Override
+    public String getNextCommandText() {
+        return commandHistory.getNext();
+    }
+
     @Override
     public ObservableList<Person> getFilteredPersonList() {
         return model.getFilteredPersonList();

src/main/java/seedu/address/ui/CommandBox.java

@@ -1,9 +1,14 @@
 package seedu.address.ui;
 
+import java.util.logging.Logger;
+
 import javafx.collections.ObservableList;
 import javafx.fxml.FXML;
 import javafx.scene.control.TextField;
+import javafx.scene.input.KeyCode;
+import javafx.scene.input.KeyEvent;
 import javafx.scene.layout.Region;
+import seedu.address.commons.core.LogsCenter;
 import seedu.address.logic.commands.exceptions.CommandException;
 import seedu.address.logic.util.exceptions.ParseException;
 import seedu.address.storage.exceptions.StorageException;
@@ -13,7 +18,9 @@
  */
 public class CommandBox extends UiPart<Region> {
 
-    public static final String ERROR_STYLE_CLASS = "error";
+    private static final Logger logger = LogsCenter.getLogger(CommandBox.class);
+
+    private static final String ERROR_STYLE_CLASS = "error";
     private static final String FXML = "CommandBox.fxml";
 
     private final CommandExecutor commandExecutor;
@@ -27,8 +34,12 @@
     public CommandBox(CommandExecutor commandExecutor) {
         super(FXML);
         this.commandExecutor = commandExecutor;
+
         // calls #setStyleToDefault() whenever there is a change to the text of the command box.
         commandTextField.textProperty().addListener((unused1, unused2, unused3) -> setStyleToDefault());
+
+        // add listener for key presses
+        commandTextField.setOnKeyPressed(this::handleKeyPressed);
     }
 
     /**
@@ -70,16 +81,29 @@
     }
 
     /**
-     * Represents a function that can execute commands.
+     * Handle the event when a key is pressed.
+     *
+     * @param event the KeyEvent when a key is pressed.
      */
-    @FunctionalInterface
-    public interface CommandExecutor {
-        /**
-         * Executes the command and returns the result.
-         *
-         * @see seedu.address.logic.Logic#execute(String)
-         */
-        String execute(String commandText) throws CommandException, ParseException, StorageException;
+    private void handleKeyPressed(KeyEvent event) {
+        String commandText = null;
+        if (event.getCode() == KeyCode.UP) {
+            // go up the command history
+            logger.info("UP key pressed");
+            commandText = commandExecutor.getPreviousCommandText();
+        } else if (event.getCode() == KeyCode.DOWN) {
+            // go down the command history
+            logger.info("DOWN key pressed");
+            commandText = commandExecutor.getNextCommandText();
+        }
+
+        if (commandText != null) {
+            commandTextField.setText(commandText);
+            commandTextField.positionCaret(commandTextField.getLength());
+            logger.info("commandTextField set to \"" + commandText + "\"");
+        }
+
+        event.consume();
     }
 
 }

src/main/java/seedu/address/ui/CommandExecutor.java

@@ -0,0 +1,33 @@
+package seedu.address.ui;
+
+import seedu.address.logic.commands.exceptions.CommandException;
+import seedu.address.logic.util.exceptions.ParseException;
+import seedu.address.storage.exceptions.StorageException;
+
+/**
+ * Represents an API which supports command execution and history tracking.
+ */
+public interface CommandExecutor {
+
+    /**
+     * Executes the command and returns the result.
+     *
+     * @see seedu.address.logic.Logic#execute(String)
+     */
+    String execute(String commandText) throws CommandException, ParseException, StorageException;
+
+    /**
+     * Gets the previous command's text.
+     *
+     * @return the previous command's text.
+     */
+    String getPreviousCommandText();
+
+    /**
+     * Gets the next command's text.
+     *
+     * @return the next command's text.
+     */
+    String getNextCommandText();
+
+}

src/main/java/seedu/address/ui/MainWindow.java

@@ -123,7 +123,7 @@
         StatusBarFooter statusBarFooter = new StatusBarFooter(logic.getAddressBookFilePath());
         statusbarPlaceholder.getChildren().add(statusBarFooter.getRoot());
 
-        CommandBox commandBox = new CommandBox(this::executeCommand);
+        CommandBox commandBox = new CommandBox(new CommandExecutorInator());
         commandBoxPlaceholder.getChildren().add(commandBox.getRoot());
     }
 
@@ -174,39 +174,50 @@
         clipboard.setContent(content);
     }
 
-    /**
-     * Executes the command and returns the result.
-     *
-     * @see seedu.address.logic.Logic#execute(String)
-     */
-    private String executeCommand(String commandText) throws CommandException, ParseException, StorageException {
-        String commandResult;
-        try {
-            commandResult = logic.execute(commandText);
-            logger.info("Result: " + commandResult);
-            showMessage(commandResult);
-        } catch (CommandException | ParseException | StorageException e) {
-            logger.info("An error occurred while executing command: " + commandText);
-            showMessage(e.getMessage());
-            throw e;
-        }
+    public void showMessage(String msg) {
+        resultDisplay.setFeedbackToUser(msg);
+    }
+
+    private class CommandExecutorInator implements CommandExecutor {
+
+        @Override
+        public String execute(String commandText) throws CommandException, ParseException, StorageException {
+            String commandResult;
+            try {
+                commandResult = logic.execute(commandText);
+                logger.info("Result: " + commandResult);
+                showMessage(commandResult);
+            } catch (CommandException | ParseException | StorageException e) {
+                logger.info("An error occurred while executing command: " + commandText);
+                showMessage(e.getMessage());
+                throw e;
+            }
 
-        // == used to prevent an edge case where a command may somehow return this exact string,
-        // but is not actually a help or exit command.
-        if (commandResult == Messages.MESSAGE_SHOWING_HELP) {
-            handleHelp();
+            // == used to prevent an edge case where a command may somehow return this exact string,
+            // but is not actually a help or exit command.
+            if (commandResult == Messages.MESSAGE_SHOWING_HELP) {
+                handleHelp();
+            }
+            if (commandResult == Messages.MESSAGE_EXITING) {
+                handleExit();
+            }
+            if (commandResult.startsWith(Messages.MESSAGE_COPIED.substring(0, Messages.MESSAGE_COPIED_LEN + 1))) {
+                handleCopy(commandResult.substring(Messages.MESSAGE_COPIED_LEN).trim());
+            }
+
+            return commandResult;
         }
-        if (commandResult == Messages.MESSAGE_EXITING) {
-            handleExit();
+
+        @Override
+        public String getPreviousCommandText() {
+            return logic.getPreviousCommandText();
         }
-        if (commandResult.startsWith(Messages.MESSAGE_COPIED.substring(0, Messages.MESSAGE_COPIED_LEN + 1))) {
-            handleCopy(commandResult.substring(Messages.MESSAGE_COPIED_LEN).trim());
+
+        @Override
+        public String getNextCommandText() {
+            return logic.getNextCommandText();
         }
-        return commandResult;
-    }
 
-    public void showMessage(String msg) {
-        resultDisplay.setFeedbackToUser(msg);
     }
 
 }

src/main/java/seedu/address/ui/UiManager.java

@@ -41,7 +41,6 @@ public void start(Stage primaryStage) {
 
         try {
             mainWindow = new MainWindow(primaryStage, logic);
-
         } catch (Throwable e) {
             logger.severe(StringUtil.getDetails(e));
             showFatalErrorDialogAndShutdown("Fatal error during initializing", e);