Add functionality to return the list of commands available if the user requires help

Author: jingxueguo

src/main/java/duke/Duke.java

@@ -4,6 +4,17 @@ public class Duke {
     private Storage storage;
     private TaskList taskList;
 
+    private enum Commands {
+        LIST,
+        TODO,
+        DEADLINE,
+        EVENT,
+        BYE,
+        FIND,
+        DONE,
+        DELETE
+    }
+
 
     /**
      * This constructor create a duke class after loading the tasks from a given file path
@@ -19,11 +30,21 @@ public Duke(String filePath) {
             taskList = new TaskList();
         }
     }
+    public static String getHelp() {
+        return "You have entered invalid commands! " +
+                "Type 'help' if you are unsure of which commands I can understand:>";
+    }
 
 
 
     public String getResponse(String string) {
         switch (string.toLowerCase()) {
+        case "help":
+            String commandsList = "The commands that I can understand are: \n";
+            for (Commands command : Commands.values()) {
+                commandsList += command.toString() + "\n";
+            }
+            return commandsList;
         case "bye":
             try {
                 storage.writeToFile(taskList, "./data/duke.txt");

src/main/java/duke/Parser.java

@@ -33,7 +33,7 @@ public static Task parseFile(String data) throws DukeException {
     public static Pair parseInput(String input, TaskList tasks) {
         String[] inputSplit = input.split(" ");
         if (inputSplit.length < 2) {
-            return new Pair(tasks, "You have entered invalid command!");
+            return new Pair(tasks, Duke.getHelp());
         }
         Task task;
         String message;
@@ -44,7 +44,7 @@ public static Pair parseInput(String input, TaskList tasks) {
             TaskList result = tasks.findTask(keyword);
             message = "Here are the matching tasks in your list: \n";
             for (int i = 0; i < result.getSize(); i++) {
-                message += result.getTask(i).toString();
+                message += i+1 + ". " + result.getTask(i).toString();
             }
             break;
         case "done":
@@ -76,7 +76,7 @@ public static Pair parseInput(String input, TaskList tasks) {
             message = "Got it. I have added this task: \n" + task.toString();
             break;
         default:
-            message = "You have entered invalid commands!";
+            message = Duke.getHelp();
         }
 
         return new Pair(tasks, message);

src/main/resources/view/DialogBox.fxml

@@ -5,7 +5,9 @@
 <?import javafx.scene.image.ImageView?>
 <?import javafx.scene.layout.HBox?>
 
-<fx:root alignment="TOP_RIGHT" maxHeight="1.7976931348623157E308" maxWidth="1.7976931348623157E308" prefWidth="400.0" type="javafx.scene.layout.HBox" xmlns="http://javafx.com/javafx/8.0.171" xmlns:fx="http://javafx.com/fxml/1">
+<fx:root alignment="TOP_RIGHT" maxHeight="1.7976931348623157E308"
+         maxWidth="1.7976931348623157E308" prefWidth="400.0" type="javafx.scene.layout.HBox"
+         xmlns="http://javafx.com/javafx/8.0.171" xmlns:fx="http://javafx.com/fxml/1">
     <children>
         <Label fx:id="dialog" text="Label" wrapText="true" />
         <ImageView fx:id="displayPicture" fitHeight="99.0" fitWidth="99.0" pickOnBounds="true" preserveRatio="true" />

src/main/resources/view/MainWindow.fxml

@@ -6,7 +6,9 @@
 <?import javafx.scene.layout.AnchorPane?>
 <?import javafx.scene.layout.VBox?>
 
-<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="600.0" prefWidth="400.0" xmlns="http://javafx.com/javafx/8.0.171" xmlns:fx="http://javafx.com/fxml/1" fx:controller="duke.MainWindow">
+<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity"
+            prefHeight="600.0" prefWidth="400.0" xmlns="http://javafx.com/javafx/8.0.171"
+            xmlns:fx="http://javafx.com/fxml/1" fx:controller="duke.MainWindow">
     <children>
         <TextField fx:id="userInput" layoutY="558.0" onAction="#handleUserInput" prefHeight="41.0" prefWidth="324.0" AnchorPane.bottomAnchor="1.0" />
         <Button fx:id="sendButton" layoutX="324.0" layoutY="558.0" mnemonicParsing="false" onAction="#handleUserInput" prefHeight="41.0" prefWidth="76.0" text="Send" />