Implement search feature for help command

docs/UserGuide.adoc

@@ -30,7 +30,7 @@ AlgoBase (AB) is for those who prefer to use a desktop app for managing algorith
 image::Ui.png[width="790"]
 +
 .  Type the command in the command box and press kbd:[Enter] to execute it. +
-e.g. typing *`help`* and pressing kbd:[Enter] will open the help window.
+e.g. typing *`help`* and pressing kbd:[Enter] will list all possible commands in the result window and open the help window.
 .  Some example commands you can try:
 
 * *`list`* : lists all problems
@@ -297,7 +297,13 @@ Switches to the tab at index 1.
 
 ==== Viewing help : `help`
 
-Format: `help`
+List all possible commands or find command usage using the command word. +
+Format: `help [COMMAND_WORD]`
+
+* `help`
+Shows all possible commands.
+* `help add`
+Shows command usage for `add` command.
 
 ==== Clearing all entries : `clear`
 

src/main/java/seedu/algobase/commons/core/Messages.java

@@ -14,4 +14,5 @@ public class Messages {
     public static final String MESSAGE_INVALID_TAG_FORMAT = "Invalid tag format! \n";
     public static final String MESSAGE_INVALID_TAG_DISPLAYED_INDEX = "The Tag index provided is invalid";
     public static final String MESSAGE_PLANS_LISTED_OVERVIEW = "%1$d plans listed!";
+    public static final String MESSAGE_INVALID_COMMAND_NAME = "Command %1$s not found!";
 }

src/main/java/seedu/algobase/commons/util/AppUtil.java

@@ -36,4 +36,17 @@ public static void checkArgument(Boolean condition, String errorMessage) {
             throw new IllegalArgumentException(errorMessage);
         }
     }
+
+    public static String getClassStringField(Class targetClass, String fieldName) {
+        try {
+            String result = (String) targetClass.getField(fieldName).get("");
+            return result;
+        } catch (NoSuchFieldException e) {
+            throw new AssertionError("Class " + targetClass.getName()
+                + "doesn't have " + fieldName + " field.");
+        } catch (IllegalAccessException e) {
+            throw new AssertionError("Class " + targetClass.getName()
+                + "has non-public " + fieldName + ".");
+        }
+    }
 }

src/main/java/seedu/algobase/logic/commands/Command.java

@@ -8,6 +8,31 @@
  */
 public abstract class Command {
 
+    public static final Class[] COMMAND_LIST = {
+        AddCommand.class,
+        AddPlanCommand.class,
+        AddTagCommand.class,
+        ClearCommand.class,
+        DeleteCommand.class,
+        DeletePlanCommand.class,
+        DeleteTagCommand.class,
+        DeleteTaskCommand.class,
+        DoneTaskCommand.class,
+        EditCommand.class,
+        EditPlanCommand.class,
+        EditTagCommand.class,
+        ExitCommand.class,
+        FindCommand.class,
+        FindPlanCommand.class,
+        HelpCommand.class,
+        ListCommand.class,
+        ListPlanCommand.class,
+        ListTagCommand.class,
+        SortCommand.class,
+        SwitchCommand.class,
+        UndoneTaskCommand.class
+    };
+
     /**
      * Executes the command and returns the result message.
      *

src/main/java/seedu/algobase/logic/commands/CommandResult.java

@@ -68,4 +68,8 @@ public int hashCode() {
         return Objects.hash(feedbackToUser, showHelp, exit);
     }
 
+    @Override
+    public String toString() {
+        return "[CommandResult]: " + feedbackToUser;
+    }
 }

src/main/java/seedu/algobase/logic/commands/HelpCommand.java

@@ -1,5 +1,11 @@
 package seedu.algobase.logic.commands;
 
+import static java.util.Objects.requireNonNull;
+import static seedu.algobase.commons.util.AppUtil.getClassStringField;
+
+import java.util.ArrayList;
+import java.util.List;
+
 import seedu.algobase.model.Model;
 
 /**
@@ -8,15 +14,64 @@
 public class HelpCommand extends Command {
 
     public static final String COMMAND_WORD = "help";
-
     public static final String MESSAGE_USAGE = COMMAND_WORD
-            + ": Shows program usage instructions.\n"
-            + "Example: " + COMMAND_WORD;
+        + ": Shows program usage instructions.\n"
+        + "Parameter:\n"
+        + "COMMAND_NAME (can be empty if you want a list of possible commands)\n"
+        + "Example: " + COMMAND_WORD + " find";
+
+    private final boolean isListAllCommands;
+    private final Class commandClass;
+
+    public HelpCommand(Class commandClass, boolean isListAllCommands) {
+        this.isListAllCommands = isListAllCommands;
+        if (!isListAllCommands) {
+            requireNonNull(commandClass);
+            this.commandClass = commandClass;
+        } else {
+            this.commandClass = commandClass;
+        }
+    }
+
+    public boolean isListAllCommands() {
+        return isListAllCommands;
+    }
 
-    public static final String SHOWING_HELP_MESSAGE = "Opened help window.";
+    public Class getCommandClass() {
+        return commandClass;
+    }
 
     @Override
     public CommandResult execute(Model model) {
-        return new CommandResult(SHOWING_HELP_MESSAGE, true, false);
+        if (isListAllCommands) {
+            List<String> commandWords = new ArrayList<>();
+            for (Class command : Command.COMMAND_LIST) {
+                commandWords.add(getClassStringField(command, "COMMAND_WORD"));
+            }
+            String commandPrompt = "Available commands are: " + commandWords.toString() + "\n"
+                + "More information can be found in the popup window.";
+            return new CommandResult(commandPrompt, true, false);
+        } else {
+            String commandUsage = getClassStringField(commandClass, "MESSAGE_USAGE");
+            return new CommandResult(commandUsage, false, false);
+        }
+    }
+
+    @Override
+    public boolean equals(Object other) {
+        // short circuit if same object
+        if (other == this) {
+            return true;
+        }
+
+        // instanceof handles nulls
+        if (!(other instanceof HelpCommand)) {
+            return false;
+        }
+
+        // state check
+        HelpCommand h = (HelpCommand) other;
+        return isListAllCommands == h.isListAllCommands()
+            && commandClass.equals(h.getCommandClass());
     }
 }

src/main/java/seedu/algobase/logic/parser/AlgoBaseParser.java

@@ -115,7 +115,7 @@ public Command parseCommand(String userInput) throws ParseException {
             return new ExitCommand();
 
         case HelpCommand.COMMAND_WORD:
-            return new HelpCommand();
+            return new HelpCommandParser().parse(arguments);
 
         case AddTagCommand.COMMAND_WORD:
             return new AddTagCommandParser().parse(arguments);

src/main/java/seedu/algobase/logic/parser/HelpCommandParser.java

@@ -0,0 +1,30 @@
+package seedu.algobase.logic.parser;
+
+import static seedu.algobase.commons.core.Messages.MESSAGE_INVALID_COMMAND_NAME;
+import static seedu.algobase.commons.util.AppUtil.getClassStringField;
+
+import seedu.algobase.logic.commands.Command;
+import seedu.algobase.logic.commands.HelpCommand;
+import seedu.algobase.logic.parser.exceptions.ParseException;
+
+/**
+ * Parses input arguments and creates a new HelpCommand object
+ */
+public class HelpCommandParser implements Parser<HelpCommand> {
+
+    @Override
+    public HelpCommand parse(String userInput) throws ParseException {
+        String trimmedArgs = userInput.trim();
+        if (trimmedArgs.isEmpty()) {
+            return new HelpCommand(null, true);
+        } else {
+            for (Class command : Command.COMMAND_LIST) {
+                String commandWord = getClassStringField(command, "COMMAND_WORD");
+                if (commandWord.equals(trimmedArgs)) {
+                    return new HelpCommand(command, false);
+                }
+            }
+            throw new ParseException(String.format(MESSAGE_INVALID_COMMAND_NAME, trimmedArgs));
+        }
+    }
+}

src/main/resources/view/ResultDisplay.fxml

@@ -2,7 +2,6 @@
 
 <?import javafx.scene.control.TextArea?>
 <?import javafx.scene.layout.StackPane?>
-<StackPane fx:id="placeHolder" styleClass="pane-with-border" xmlns="http://javafx.com/javafx/8"
-           xmlns:fx="http://javafx.com/fxml/1">
-  <TextArea fx:id="resultDisplay" editable="false" styleClass="result-display"/>
+<StackPane fx:id="placeHolder" styleClass="pane-with-border" xmlns="http://javafx.com/javafx/11.0.1" xmlns:fx="http://javafx.com/fxml/1">
+  <TextArea fx:id="resultDisplay" editable="false" styleClass="result-display" wrapText="true" />
 </StackPane>

src/test/java/seedu/algobase/logic/commands/AddCommandTest.java

@@ -23,7 +23,7 @@ public void constructor_nullProblem_throwsNullPointerException() {
     }
 
     @Test
-    public void execute_problemAcceptedByModel_addSuccessful() throws Exception {
+    public void execute_problemAcceptedByModel_addsSuccessful() throws Exception {
         ModelStubAcceptingProblemAdded modelStub = new ModelStubAcceptingProblemAdded();
         Problem validProblem = new ProblemBuilder().build();
 

src/test/java/seedu/algobase/logic/commands/HelpCommandTest.java

@@ -0,0 +1,39 @@
+package seedu.algobase.logic.commands;
+
+import static seedu.algobase.logic.commands.CommandTestUtil.assertCommandSuccess;
+import static seedu.algobase.testutil.Assert.assertThrows;
+import static seedu.algobase.testutil.TypicalProblems.getTypicalAlgoBase;
+
+import org.junit.jupiter.api.Test;
+
+import seedu.algobase.model.Model;
+import seedu.algobase.model.ModelManager;
+import seedu.algobase.model.UserPrefs;
+
+class HelpCommandTest {
+
+    private static final String EXPECTED_COMMAND_LIST = "Available commands are: [add, addplan, addtag, "
+        + "clear, delete, deleteplan, deletetag, deletetask, donetask, edit, editplan, edittag, exit, "
+        + "find, findplan, help, list, listplan, listtag, sort, switch, undonetask]\n"
+        + "More information can be found in the popup window.";
+    private Model model = new ModelManager(getTypicalAlgoBase(), new UserPrefs());
+    private Model expectedModel = new ModelManager(getTypicalAlgoBase(), new UserPrefs());
+
+    @Test
+    void constructor_nullCommandClassWithoutListingAllCommands_throwsNullPointerException() {
+        assertThrows(NullPointerException.class, () -> new HelpCommand(null, false));
+    }
+
+    @Test
+    void constructor_nullCommandClassWithListingAllCommands_success() {
+        HelpCommand command = new HelpCommand(null, true);
+        assertCommandSuccess(command, model,
+            new CommandResult(EXPECTED_COMMAND_LIST, true, false), expectedModel);
+    }
+
+    @Test
+    void execute_correctCommandWord_showsMessageUsage() {
+        HelpCommand command = new HelpCommand(AddCommand.class, false);
+        assertCommandSuccess(command, model, AddCommand.MESSAGE_USAGE, expectedModel);
+    }
+}

src/test/java/seedu/algobase/logic/parser/CommandParserTestUtil.java

@@ -0,0 +1,38 @@
+package seedu.algobase.logic.parser;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import seedu.algobase.logic.commands.Command;
+import seedu.algobase.logic.parser.exceptions.ParseException;
+
+/**
+ * Contains helper methods for testing command parsers.
+ */
+public class CommandParserTestUtil {
+
+    /**
+     * Asserts that the parsing of {@code userInput} by {@code parser} is successful and the command created
+     * equals to {@code expectedCommand}.
+     */
+    public static void assertParseSuccess(Parser parser, String userInput, Command expectedCommand) {
+        try {
+            Command command = parser.parse(userInput);
+            assertEquals(expectedCommand, command);
+        } catch (ParseException pe) {
+            throw new IllegalArgumentException("Invalid userInput.", pe);
+        }
+    }
+
+    /**
+     * Asserts that the parsing of {@code userInput} by {@code parser} is unsuccessful and the error message
+     * equals to {@code expectedMessage}.
+     */
+    public static void assertParseFailure(Parser parser, String userInput, String expectedMessage) {
+        try {
+            parser.parse(userInput);
+            throw new AssertionError("The expected ParseException was not thrown.");
+        } catch (ParseException pe) {
+            assertEquals(expectedMessage, pe.getMessage());
+        }
+    }
+}

src/test/java/seedu/algobase/logic/parser/HelpCommandParserTest.java

@@ -0,0 +1,37 @@
+package seedu.algobase.logic.parser;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static seedu.algobase.commons.core.Messages.MESSAGE_INVALID_COMMAND_NAME;
+import static seedu.algobase.logic.parser.CommandParserTestUtil.assertParseFailure;
+import static seedu.algobase.logic.parser.CommandParserTestUtil.assertParseSuccess;
+
+import org.junit.jupiter.api.Test;
+
+import seedu.algobase.logic.commands.AddCommand;
+import seedu.algobase.logic.commands.HelpCommand;
+import seedu.algobase.logic.parser.exceptions.ParseException;
+
+class HelpCommandParserTest {
+    private static final String INVALID_COMMAND_WORD = "1nval1dC0mmand";
+    private static final String VALID_COMMAND_WORD = AddCommand.COMMAND_WORD;
+    private static final Class VALID_COMMAND_CLASS = AddCommand.class;
+    private HelpCommandParser helpCommandParser = new HelpCommandParser();
+
+    @Test
+    void parse_emptyInput_returnsListAllHelpCommand() throws ParseException {
+        HelpCommand helpCommand = helpCommandParser.parse("");
+        assertTrue(helpCommand.isListAllCommands());
+    }
+
+    @Test
+    void parse_wrongCommandWord_throwsInvalidCommandWordException() {
+        String expectedMessage = String.format(MESSAGE_INVALID_COMMAND_NAME, INVALID_COMMAND_WORD);
+        assertParseFailure(helpCommandParser, INVALID_COMMAND_WORD, expectedMessage);
+    }
+
+    @Test
+    void parse_correctCommandWord_returnsHelpCommandForTheCommand() {
+        assertParseSuccess(helpCommandParser, VALID_COMMAND_WORD,
+            new HelpCommand(VALID_COMMAND_CLASS, false));
+    }
+}

src/test/java/seedu/algobase/model/problem/DescriptionContainsKeywordsPredicateTest.java

@@ -9,7 +9,7 @@
 
 class DescriptionContainsKeywordsPredicateTest {
 
-    private static String KEYWORD_NOT_IN_QUICK_SORT_DESCRIPTION = "1mP0ss1ble";
+    private static final String KEYWORD_NOT_IN_QUICK_SORT_DESCRIPTION = "1mP0ss1ble";
 
     @Test
     public void test_problemDescriptionContainsKeywords_returnTrue() {

src/test/java/seedu/algobase/model/problem/NameContainsKeywordsPredicateTest.java

@@ -9,7 +9,7 @@
 
 class NameContainsKeywordsPredicateTest {
 
-    private static String KEYWORD_NOT_IN_QUICK_SORT_NAME = "1mP0ss1ble";
+    private static final String KEYWORD_NOT_IN_QUICK_SORT_NAME = "1mP0ss1ble";
 
     @Test
     public void test_problemNameContainsKeywords_returnTrue() {