AddressBook: remove master tag list

We keep track of a master tag list which holds all the tags in
AddressBook.

As the master tag list was deemed unnecessary and may be too complex
for new developers to grasp, as discussed in
se-edu/addressbook-level4#753 and se-edu/addressbook-level4#794,
the master tag list has already been removed in addressbook-level4
in se-edu/addressbook-level4#824. As such, the master tag list
should also be removed here for consistency.

Let's remove the master tag list in AddressBook.

src/seedu/addressbook/data/AddressBook.java

@@ -1,8 +1,6 @@
 package seedu.addressbook.data;
 
-import java.util.HashMap;
 import java.util.HashSet;
-import java.util.Map;
 import java.util.Set;
 
 import seedu.addressbook.data.person.Person;
@@ -15,72 +13,34 @@
 
 /**
  * Represents the entire address book. Contains the data of the address book.
- *
- * Guarantees:
- *  - Every tag found in every person will also be found in the tag list.
- *  - The tags in each person point to tag objects in the master list. (== equality)
  */
 public class AddressBook {
 
     private final UniquePersonList allPersons;
-    private final UniqueTagList allTags; // can contain tags not attached to any person
 
     /**
      * Creates an empty address book.
      */
     public AddressBook() {
         allPersons = new UniquePersonList();
-        allTags = new UniqueTagList();
     }
 
     /**
      * Constructs an address book with the given data.
-     * Also updates the tag list with any missing tags found in any person.
      *
      * @param persons external changes to this will not affect this address book
-     * @param tags external changes to this will not affect this address book
      */
-    public AddressBook(UniquePersonList persons, UniqueTagList tags) {
+    public AddressBook(UniquePersonList persons) {
         this.allPersons = new UniquePersonList(persons);
-        this.allTags = new UniqueTagList(tags);
-        for (Person p : allPersons) {
-            syncTagsWithMasterList(p);
-        }
-    }
-
-    /**
-     * Ensures that every tag in this person:
-     *  - exists in the master list {@link #allTags}
-     *  - points to a Tag object in the master list
-     */
-    private void syncTagsWithMasterList(Person person) {
-        final UniqueTagList personTags = person.getTags();
-        allTags.mergeFrom(personTags);
-
-        // Create map with values = tag object references in the master list
-        final Map<Tag, Tag> masterTagObjects = new HashMap<>();
-        for (Tag tag : allTags) {
-            masterTagObjects.put(tag, tag);
-        }
-
-        // Rebuild the list of person tags using references from the master list
-        final Set<Tag> commonTagReferences = new HashSet<>();
-        for (Tag tag : personTags) {
-            commonTagReferences.add(masterTagObjects.get(tag));
-        }
-        person.setTags(new UniqueTagList(commonTagReferences));
     }
 
     /**
      * Adds a person to the address book.
-     * Also checks the new person's tags and updates {@link #allTags} with any new tags found,
-     * and updates the Tag objects in the person to point to those in {@link #allTags}.
      *
      * @throws DuplicatePersonException if an equivalent person already exists.
      */
     public void addPerson(Person toAdd) throws DuplicatePersonException {
         allPersons.add(toAdd);
-        syncTagsWithMasterList(toAdd);
     }
 
     /**
@@ -104,7 +64,6 @@ public void removePerson(ReadOnlyPerson toRemove) throws PersonNotFoundException
      */
     public void clear() {
         allPersons.clear();
-        allTags.clear();
     }
 
     /**
@@ -115,17 +74,21 @@ public UniquePersonList getAllPersons() {
     }
 
     /**
-     * Returns a new UniqueTagList of all tags in the address book at the time of the call.
+     * Returns a new UniqueTagList of all tags in all persons in the address book at the time of the call.
      */
     public UniqueTagList getAllTags() {
-        return new UniqueTagList(allTags);
+        Set<Tag> tagSet = new HashSet<>();
+        for (Person person : allPersons) {
+            tagSet.addAll(person.getTags().toSet());
+        }
+
+        return new UniqueTagList(tagSet);
     }
 
     @Override
     public boolean equals(Object other) {
         return other == this // short circuit if same object
                 || (other instanceof AddressBook // instanceof handles nulls
-                        && this.allPersons.equals(((AddressBook) other).allPersons)
-                        && this.allTags.equals(((AddressBook) other).allTags));
+                        && this.allPersons.equals(((AddressBook) other).allPersons));
     }
 }

src/seedu/addressbook/storage/jaxb/AdaptedAddressBook.java

@@ -3,7 +3,6 @@
 import seedu.addressbook.data.AddressBook;
 import seedu.addressbook.data.exception.IllegalValueException;
 import seedu.addressbook.data.tag.Tag;
-import seedu.addressbook.data.tag.UniqueTagList;
 import seedu.addressbook.data.person.Person;
 import seedu.addressbook.data.person.ReadOnlyPerson;
 import seedu.addressbook.data.person.UniquePersonList;
@@ -74,14 +73,10 @@ public boolean isAnyRequiredFieldMissing() {
      * @throws IllegalValueException if there were any data constraints violated in the adapted person
      */
     public AddressBook toModelType() throws IllegalValueException {
-        final List<Tag> tagList = new ArrayList<>();
         final List<Person> personList = new ArrayList<>();
-        for (AdaptedTag tag : tags) {
-            tagList.add(tag.toModelType());
-        }
         for (AdaptedPerson person : persons) {
             personList.add(person.toModelType());
         }
-        return new AddressBook(new UniquePersonList(personList), new UniqueTagList(tagList));
+        return new AddressBook(new UniquePersonList(personList));
     }
 }

test/java/seedu/addressbook/data/AddressBookTest.java

@@ -69,8 +69,7 @@ public void setUp() throws Exception {
                                     new UniqueTagList(tagEconomist, tagPrizeWinner));
 
         emptyAddressBook = new AddressBook();
-        defaultAddressBook = new AddressBook(new UniquePersonList(aliceBetsy, bobChaplin),
-                                             new UniqueTagList(tagMathematician, tagScientist));
+        defaultAddressBook = new AddressBook(new UniquePersonList(aliceBetsy, bobChaplin));
     }
 
     @Rule
@@ -81,12 +80,8 @@ public void addPerson_emptyAddressBook() throws Exception {
         emptyAddressBook.addPerson(bobChaplin);
         emptyAddressBook.addPerson(charlieDouglas);
 
-        UniqueTagList expectedTagList = new UniqueTagList(tagMathematician, tagScientist);
-        assertTrue(isIdentical(expectedTagList, emptyAddressBook.getAllTags()));
-
         assertTrue(isTagObjectInAddressBookList(tagMathematician, emptyAddressBook));
         assertTrue(isTagObjectInAddressBookList(tagScientist, emptyAddressBook));
-
     }
 
     @Test
@@ -104,19 +99,6 @@ public void addPerson_personAlreadyInList_throwsDuplicatePersonException() throw
         defaultAddressBook.addPerson(aliceBetsy);
     }
 
-    @Test
-    public void addPerson_personAlreadyInListButHasTagNotInList_tagNotAdded() throws Exception {
-        aliceBetsy.setTags(new UniqueTagList(tagMathematician, tagPrizeWinner));
-
-        try {
-            defaultAddressBook.addPerson(aliceBetsy);
-        } catch (DuplicatePersonException e) {
-            // ignore expected exception
-        }
-
-        assertFalse(isTagObjectInAddressBookList(tagPrizeWinner, defaultAddressBook));
-    }
-
     @Test
     public void containsPerson() throws Exception {
         UniquePersonList personsWhoShouldBeIn = new UniquePersonList(aliceBetsy, bobChaplin);
@@ -173,9 +155,8 @@ public void getAllPersons() throws Exception {
     @Test
     public void getAllTags() throws Exception {
         UniqueTagList allTags = defaultAddressBook.getAllTags();
-        UniqueTagList tagsToCheck = new UniqueTagList(tagMathematician, tagScientist);
 
-        assertTrue(isIdentical(allTags, tagsToCheck));
+        assertTrue(allTags.contains(tagMathematician));
     }
 
     /**

test/java/seedu/addressbook/util/TestUtil.java

@@ -64,7 +64,7 @@ public static List<ReadOnlyPerson> createList(Person...persons) {
      * of Persons and Tags. The Persons and Tags are not cloned.
      */
     public static AddressBook clone(AddressBook addressBook) {
-        return new AddressBook(addressBook.getAllPersons(), addressBook.getAllTags());
+        return new AddressBook(addressBook.getAllPersons());
     }
 
     /**