[se-edu#534] HistoryCommand: Returns previous commands in reverse chr…

…onological order (se-edu#537)

The HistoryCommand returns the previous commands in chronological
order.

This goes against the intuition that history ought to be viewed in
reverse chronological order. We are expecting that the user will want
to see what he has typed most recently, just like how Google Chrome
History works.

Let’s update HistoryCommand to return previous commands in reverse
chronological order.

docs/UserGuide.adoc

@@ -152,7 +152,7 @@ Selects the 1st person in the results of the `find` command.
 
 === Listing entered commands : `history`
 
-Lists all the commands that you have entered in chronological order. +
+Lists all the commands that you have entered in reverse chronological order. +
 Format: `history`
 
 === Clearing all entries : `clear`

src/main/java/seedu/address/logic/commands/HistoryCommand.java

@@ -2,6 +2,7 @@
 
 import static java.util.Objects.requireNonNull;
 
+import java.util.Collections;
 import java.util.List;
 
 import seedu.address.logic.CommandHistory;
@@ -13,7 +14,7 @@
 public class HistoryCommand extends Command {
 
     public static final String COMMAND_WORD = "history";
-    public static final String MESSAGE_SUCCESS = "Entered commands (from earliest to most recent):\n%1$s";
+    public static final String MESSAGE_SUCCESS = "Entered commands (from most recent to earliest):\n%1$s";
     public static final String MESSAGE_NO_HISTORY = "You have not yet entered any commands.";
 
     @Override
@@ -24,6 +25,7 @@ public CommandResult execute() {
             return new CommandResult(MESSAGE_NO_HISTORY);
         }
 
+        Collections.reverse(previousCommands);
         return new CommandResult(String.format(MESSAGE_SUCCESS, String.join("\n", previousCommands)));
     }
 

src/test/java/seedu/address/logic/commands/HistoryCommandTest.java

@@ -35,7 +35,7 @@ public void execute() {
         history.add(command3);
 
         String expectedMessage = String.format(HistoryCommand.MESSAGE_SUCCESS,
-                String.join("\n", command1, command2, command3));
+                String.join("\n", command3, command2, command1));
 
         assertCommandResult(historyCommand, expectedMessage);
     }