Add tag and untag function

src/main/java/seedu/duke/Duke.java

@@ -53,6 +53,19 @@ public static void main(String[] args) {
                     Ui.printLine();
                     break;
 
+                case "tag":
+                    Ui.printLine();
+                    Parser.tagCommand(command, list);
+                    Ui.printLine();
+                    break;
+
+                case "untag":
+                    Ui.printLine();
+                    Parser.removeTagCommand(command, list);
+                    Ui.printLine();
+                    break;
+
+
                 case "help":
                     Ui.printLine();
                     Ui.helpCommand();

src/main/java/seedu/duke/Parser.java

@@ -109,4 +109,40 @@ public static void uncheckCommand(String[] command, TravelActivityList list) thr
             throw new OmniException("Please specify which task to uncheck");
         }
     }
+
+    /**
+     * Handles the case where the tag command is given as input
+     *
+     * @param command Command array of input string without spaces
+     * @param list List of travel activities
+     * @throws OmniException if command.length == 2
+     * @throws OmniException if command.length == 1
+     */
+    public static void tagCommand(String[] command, TravelActivityList list) throws OmniException {
+        if (command.length == 3 && isNumeric(command[1])){
+            int listNumber = Integer.parseInt(command[1]);
+            String tag = command[2];
+            list.tagActivity(listNumber, tag);
+        } else if (command.length == 2) {
+            throw new OmniException("Please specify a tag name");
+        } else {
+            throw new OmniException("Please specify which task to tag");
+        }
+    }
+
+    /**
+     * Handles the case where the untag command is given as input
+     *
+     * @param command Command array of input string without spaces
+     * @param list List of travel activities
+     * @throws OmniException if command.length != 2 && command[1] is not numeric
+     */
+    public static void removeTagCommand(String[] command, TravelActivityList list) throws OmniException {
+        if (command.length == 2 && isNumeric(command[1])) {
+            int listNumber = Integer.parseInt(command[1]);
+            list.removeTag(listNumber);
+        } else {
+            throw new OmniException("Please specify which task to remove tag");
+        }
+    }
 }

src/main/java/seedu/duke/TravelActivity.java

@@ -5,6 +5,9 @@ public class TravelActivity {
     private String travelActivity;
     /** Travel activity status */
     private boolean taskIsDone = false;
+    /** Travel activity tag */
+    private String tag;
+
     public TravelActivity(String line){
         travelActivity = line;
     }
@@ -32,4 +35,20 @@ public String getPlan(){
 
     public boolean getTaskStatus() {return taskIsDone;}
 
+    /**
+     * Gets the tag of the travel activity
+     * @return The tag of the travel activity
+     */
+    public String getTag() {
+        return tag;
+    }
+
+    public void setTag(String tag) {
+        this.tag = tag;
+    }
+
+    public void removeTag() {
+        this.tag = "";
+    }
+
 }

src/main/java/seedu/duke/TravelActivityList.java

@@ -130,5 +130,36 @@ public void uncheckTravelActivity(int taskNumber) throws OmniException{
         System.out.println(markedTask);
     }
 
+    /**
+     * Adds a tag to travel activity
+     * @param taskNumber The travel activity number on the list
+     * @param tag The tag of travel activity
+     */
+    public void tagActivity(int taskNumber, String tag) throws OmniException{
+        assert taskNumber != 0 : "There is no tasks in the list";
+        if (taskNumber > travelActivities.size()) {
+            throw new OmniException("Travel activity cannot be found");
+        }
+        int indexOfTask = taskNumber - 1;
+        TravelActivity taggedTask  = travelActivities.get(indexOfTask);
+        taggedTask.setTag(tag);
+        System.out.println("I have tagged this task:");
+        System.out.println(taggedTask + "(" + tag + ")");
+    }
 
+    /**
+     * Removes the tag on a travel activity
+     * @param taskNumber The travel activity number on the list
+     */
+    public void removeTag(int taskNumber) throws OmniException {
+        assert taskNumber != 0 : "There is no task in the list";
+        if (taskNumber > travelActivities.size()) {
+            throw new OmniException("Travel activity cannot be found");
+        }
+        int indexOfTask = taskNumber - 1;
+        TravelActivity taggedTask = travelActivities.get(indexOfTask);
+        taggedTask.removeTag();
+        System.out.println("Tag removed from the task:");
+        System.out.println(taggedTask);
+    }
 }