Add help

build.gradle

@@ -57,4 +57,5 @@ checkstyle {
 
 run{
     standardInput = System.in
+    enableAssertions = true
 }

docs/README.md

@@ -26,7 +26,8 @@ chat interface also gives users a more personal feeling.
 1. Ensure that you have Java `11` or above installed on your computer.
 2. Download the latest Duke Jar from [here](https://github.com/dianneloh9/ip/releases/tag/A-Release).
 3. Copy the file to the folder you want to use as the *home folder* for your Duke program.
-4. Double click the file to start the app. You should see the below GUI after a few seconds:
+4. Double click the file to start the app for Windows, or run `java -jar duke.jar` for Mac.
+You should see the below GUI after a few seconds:
 ![landing page](/docs/landing.png)
 5. Type the command in the command box and press Enter to execute it.
 
@@ -173,7 +174,7 @@ Format: `find KEYWORD...`
 - The order of the keywords does not matter, that is, `read book` or 
 `book read` will show the same result.
 - Only the task description is searched.
-- Only full words will be matched (eg `boo` will not match `book`);
+- Partial words can be matched (eg `boo` will match `book`);
 - Only tasks matching all keywords will be returned.
 
 Examples:  

src/main/java/duke/commands/HelpCommand.java

@@ -0,0 +1,12 @@
+package duke.commands;
+
+import static duke.utils.Messages.MESSAGE_HELP;
+
+import duke.tasklist.TaskList;
+
+public class HelpCommand extends Command {
+    @Override
+    public CommandResult execute(TaskList taskList) {
+        return new CommandResult(MESSAGE_HELP, false);
+    }
+}

src/main/java/duke/parsers/Parser.java

@@ -11,6 +11,7 @@
 import duke.commands.DeleteCommand;
 import duke.commands.DoneCommand;
 import duke.commands.FindCommand;
+import duke.commands.HelpCommand;
 import duke.commands.ListCommand;
 import duke.commands.TodayCommand;
 import duke.exceptions.DukeDateTimeParseException;
@@ -86,11 +87,17 @@ public static Command parse(String userInput) throws EmptyTaskDescriptionExcepti
                 throw new InvalidCommandFormatException();
             }
             return parseConfirm(splitByCommand[1].strip());
+        case "help":
+            return parseHelp();
         default:
             throw new InvalidCommandException();
         }
     }
 
+    private static Command parseHelp() {
+        return new HelpCommand();
+    }
+
     private static Command parseToday() {
         return new TodayCommand();
     }

src/main/java/duke/utils/Messages.java

@@ -8,7 +8,8 @@ public class Messages {
             + "| | | | | | | |/ / _ \\\n"
             + "| |_| | |_| |   <  __/\n"
             + "|____/ \\__,_|_|\\_\\___|\n";
-    public static final String MESSAGE_GREETING = "\t Hello! I'm Duke\n\t Here are the available commands:\n"
+    public static final String MESSAGE_BYE = "\t Bye. Hope to see you again soon!";
+    public static final String MESSAGE_HELP = "\t Here are the available commands:\n"
             + "\t \u2022 Create a todo (eg todo <task>)\n"
             + "\t \u2022 Create an event (eg event <eventName> /at <date/time(s)>)\n"
             + "\t \u2022 Create a deadline (eg deadline <deadlineName> /by <date/time>\n"
@@ -19,8 +20,7 @@ public class Messages {
             + "\t \u2022 List today's task (eg today)\n"
             + "\t \u2022 Confirm a date/time (eg confirm <task index> <date/time index>\n"
             + "\t \u2022 Exit the program (eg bye)\n";
-    public static final String MESSAGE_BYE = "\t Bye. Hope to see you again soon!";
-
+    public static final String MESSAGE_GREETING = "\t Hello! I'm Duke\n" + MESSAGE_HELP;
     public static final String MESSAGE_ADD_TASK = "\t Got it. I've added this task:\n";
     public static final String MESSAGE_DELETE_TASK = "\t Noted. I've removed this task:\n";
     public static final String MESSAGE_DONE_TASK = "\t Nice! I've marked this task as done:\n";