Ui: remove Earl specific behaviour

Moved welcome and goodbye message definitions into the Earl class
instead.

Add HelpHandler

A help command is invoked when the user types "help", or an invalid
input, enumerating the list of available commands.

src/main/java/earl/Earl.java

@@ -1,7 +1,6 @@
 package earl;
 
 import earl.exceptions.EarlException;
-import earl.exceptions.ParserException;
 import earl.exceptions.StorageException;
 import earl.logic.Handler;
 import earl.util.Storage;
@@ -15,6 +14,15 @@
  */
 public class Earl {
 
+    private static final String[] GREETING_MESSAGE = {
+        "Greetings, I, Earl, extend my esteemed salutations.",
+        "Pray, how may I be of service to you on this auspicious day?"
+    };
+    private static final String[] GOODBYE_MESSAGE = {
+        "Farewell, dear interlocutor!",
+        "Until our paths intertwine again, I bid you adieu."
+    };
+
     private final Storage storage;
     private final TaskList tasks;
     private final Ui ui;
@@ -25,14 +33,14 @@ public class Earl {
      * @param filePath  a path to the text file storing past data
      */
     public Earl(String filePath) {
-        ui = new Ui();
+        ui = new Ui(GREETING_MESSAGE);
         storage = new Storage(filePath);
         tasks = new TaskList(storage.load(TaskStorageParser::parse));
         if (!storage.wasLoadSuccessful()) {
             ui.buildResponse("Storage hath succumb to corruption... ",
                     "initiating an unfortunate state of emptiness.");
         }
-        ui.showGreeting();
+        ui.completeResponse();
     }
 
     /** Main function for TUI mode. */
@@ -81,15 +89,13 @@ private void processUserInput(String input) {
             handler.handle(tasks, ui);
         } catch (EarlException e) {
             ui.makeResponse(e.getMessage());
-        } catch (ParserException e) {
-            ui.makeResponse("Input defies parsing: " + e.getMessage());
         }
     }
 
     private void saveAndExit() {
         try {
             storage.save(tasks.getAsStorageStringStream());
-            ui.showGoodbye();
+            ui.makeResponse(GOODBYE_MESSAGE);
         } catch (StorageException e) {
             ui.makeResponse("Alas, a grievous misfortune occurred "
                     + "during the endeavour to save.");

src/main/java/earl/exceptions/ParserException.java

@@ -8,7 +8,4 @@ public class ParserException extends Exception {
     public ParserException() {
         super();
     }
-    public ParserException(String message) {
-        super(message);
-    }
 }

src/main/java/earl/logic/HandlerType.java

@@ -52,6 +52,12 @@ public Handler createHandler(String args) {
         public Handler createHandler(String args) {
             return new FindHandler(args);
         }
+    },
+    HELP {
+        @Override
+        public Handler createHandler(String args) {
+            return new HelpHandler(args);
+        }
     };
 
     public abstract Handler createHandler(String args);

src/main/java/earl/logic/HelpHandler.java

@@ -0,0 +1,27 @@
+package earl.logic;
+
+import earl.util.TaskList;
+import earl.util.Ui;
+
+/**
+ * Class responsible for displaying list of available commands.
+ */
+public class HelpHandler extends Handler {
+
+    public HelpHandler(String args) {
+        super(args);
+    }
+
+    @Override
+    public void handle(TaskList tasks, Ui ui) {
+        if (!args.isEmpty()) {
+            ui.buildResponse("Input defies parsing: " + args);
+        }
+        ui.buildResponse("Pray, issue a command forthwith.");
+        ui.buildResponse("The sanctioned commands unfold:");
+        for (HandlerType type : HandlerType.values()) {
+            ui.buildResponse("-" + type.name().toLowerCase());
+        }
+        ui.completeResponse();
+    }
+}

src/main/java/earl/logic/TaskHandler.java

@@ -21,13 +21,12 @@ protected String[] addTask(TaskList tasks, TaskType type, String... data)
         try {
             Task newTask = type.createTask(data);
             tasks.add(newTask);
-
-            String first = "A new " + type.name() + " " + newTask.toString();
-            String second = "hath been appended to the "
-                    + "roster of responsibilities.";
-            String third = "The ledger of tasks bears witness to "
-                    + tasks.getSize() + " endeavour(s).";
-            return new String[]{first, second, third};
+            return new String[]{
+                "A new " + type.name() + " " + newTask.toString(),
+                "hath been appended to the roster of responsibilities.",
+                "The ledger of tasks bears witness to "
+                        + tasks.getSize() + " endeavour(s)."
+            };
         } catch (IndexOutOfBoundsException e) {
             throw new EarlException("An error befalls.");
         } catch (TimeException e) {

src/main/java/earl/util/Ui.java

@@ -12,24 +12,17 @@ public class Ui {
     private static final String PADDING = " ".repeat(4);
     private static final String DIVIDER = "_".repeat(60);
     private static final String NEWLINE = System.lineSeparator();
-    private static final String GREETING_MESSAGE =
-            "Greetings, I, Earl, extend my esteemed salutations." + NEWLINE
-            + PADDING + "Pray, how may I be of service to you"
-                    + " on this auspicious day?";
-    private static final String GOODBYE_MESSAGE =
-            "Farewell, dear interlocutor!" + NEWLINE
-            + PADDING + "Until our paths intertwine again, I bid you adieu.";
 
     private final Scanner sc;
     private final List<String> delayedResponse;
+
     private String[] response; // the lines of the previous response
 
     /** Class constructor. */
-    public Ui() {
+    public Ui(String... initialMessage) {
         sc = new Scanner(System.in);
-        response = new String[1];
-        response[0] = GREETING_MESSAGE;
-        delayedResponse = new ArrayList<>();
+        response = initialMessage;
+        delayedResponse = new ArrayList<>(List.of(initialMessage));
     }
 
     private void setPrevResponse(String... arr) {
@@ -88,17 +81,6 @@ public String appendNewline(String line) {
         return line + NEWLINE;
     }
 
-    /** Displays the initial greeting. */
-    public void showGreeting() {
-        // response is built in case of any preceding error messages
-        buildResponse(GREETING_MESSAGE);
-        completeResponse();
-    }
-
-    public void showGoodbye() {
-        makeResponse(GOODBYE_MESSAGE);
-    }
-
     /**
      * Returns the previous response made for GUI interactions.
      *

src/main/java/earl/util/parsers/InputParser.java

@@ -1,6 +1,5 @@
 package earl.util.parsers;
 
-import earl.exceptions.ParserException;
 import earl.logic.Handler;
 import earl.logic.HandlerType;
 
@@ -14,19 +13,22 @@ public class InputParser implements Parser<Handler> {
      *
      * @param input             text input by the user
      * @return                  a {@code Handler} object of the relevant type
-     * @throws ParserException  if user input is of unexpected format
      */
-    public static Handler parse(String input) throws ParserException {
+    public static Handler parse(String input) {
         try {
             // all valid input is expected to be of the format
             // <command> [<arg1>, <arg2>, ...]
             String[] data = input.split("\\s+", 2);
+            assert data.length > 0;
             String command = data[0].toUpperCase();
+            if (command.isEmpty()) {
+                return HandlerType.HELP.createHandler(input);
+            }
             String args = (data.length > 1) ? data[1] : "";
             HandlerType handlerType = HandlerType.valueOf(command);
             return handlerType.createHandler(args);
         } catch (Exception e) {
-            throw new ParserException(input);
+            return HandlerType.HELP.createHandler(input);
         }
     }
 }

src/test/java/earl/util/parsers/InputParserTest.java

@@ -1,14 +1,12 @@
 package earl.util.parsers;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertInstanceOf;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
-import static org.junit.jupiter.api.Assertions.fail;
 
 import org.junit.jupiter.api.Test;
 
-import earl.exceptions.ParserException;
 import earl.logic.Handler;
+import earl.logic.HelpHandler;
 import earl.logic.TodoHandler;
 
 class InputParserTest {
@@ -21,12 +19,8 @@ void parse_normalInput_handlerReturnedSuccess() throws Exception {
     }
 
     @Test
-    void parse_invalidInput_exceptionThrown() {
-        try {
-            InputParser.parse("no ip");
-            fail();
-        } catch (ParserException e) {
-            assertEquals("no ip", e.getMessage());
-        }
+    void parse_invalidInput_returnHelpHandler() {
+        Handler handler = InputParser.parse("no ip");
+        assertInstanceOf(HelpHandler.class, handler);
     }
 }