Stroage: Add backupAddressBook(ReadOnlyAddressBook)

src/main/java/seedu/address/storage/AddressBookStorage.java

@@ -17,6 +17,11 @@ public interface AddressBookStorage {
      */
     Path getAddressBookFilePath();
 
+    /**
+     * Returns the file path of the backup data file.
+     */
+    Path getAddressBookBackupFilePath();
+
     /**
      * Returns AddressBook data as a {@link ReadOnlyAddressBook}.
      *   Returns {@code Optional.empty()} if storage file is not found.
@@ -42,4 +47,10 @@ public interface AddressBookStorage {
      */
     void saveAddressBook(ReadOnlyAddressBook addressBook, Path filePath) throws IOException;
 
+    /**
+     * Backup the given {@link ReadOnlyAddressBook} to the storage.
+     * @param addressBook
+     * @throws IOException
+     */
+    void backupAddressBook(ReadOnlyAddressBook addressBook) throws IOException;
 }

src/main/java/seedu/address/storage/JsonAddressBookStorage.java

@@ -1,9 +1,11 @@
 package seedu.address.storage;
 
+import static java.util.Objects.isNull;
 import static java.util.Objects.requireNonNull;
 
 import java.io.IOException;
 import java.nio.file.Path;
+import java.nio.file.Paths;
 import java.util.Optional;
 import java.util.logging.Logger;
 
@@ -22,15 +24,25 @@ public class JsonAddressBookStorage implements AddressBookStorage {
     private static final Logger logger = LogsCenter.getLogger(JsonAddressBookStorage.class);
 
     private Path filePath;
+    private Path backupFilePath;
 
     public JsonAddressBookStorage(Path filePath) {
         this.filePath = filePath;
+        if (isNull(filePath.getParent())) {
+            this.backupFilePath = Paths.get("backup.json");
+        } else {
+            this.backupFilePath = filePath.getParent().resolve("backup.json");
+        }
     }
 
     public Path getAddressBookFilePath() {
         return filePath;
     }
 
+    public Path getAddressBookBackupFilePath() {
+        return backupFilePath;
+    }
+
     @Override
     public Optional<ReadOnlyAddressBook> readAddressBook() throws DataConversionException {
         return readAddressBook(filePath);
@@ -77,4 +89,8 @@ public void saveAddressBook(ReadOnlyAddressBook addressBook, Path filePath) thro
         JsonUtil.saveJsonFile(new JsonSerializableAddressBook(addressBook), filePath);
     }
 
+    @Override
+    public void backupAddressBook(ReadOnlyAddressBook addressBook) throws IOException {
+        saveAddressBook(addressBook, backupFilePath);
+    }
 }

src/main/java/seedu/address/storage/Storage.java

@@ -23,10 +23,16 @@ public interface Storage extends AddressBookStorage, UserPrefsStorage {
     @Override
     Path getAddressBookFilePath();
 
+    @Override
+    Path getAddressBookBackupFilePath();
+
     @Override
     Optional<ReadOnlyAddressBook> readAddressBook() throws DataConversionException, IOException;
 
     @Override
     void saveAddressBook(ReadOnlyAddressBook addressBook) throws IOException;
 
+    @Override
+    void backupAddressBook(ReadOnlyAddressBook addressBook) throws IOException;
+
 }

src/main/java/seedu/address/storage/StorageManager.java

@@ -52,6 +52,11 @@ public Path getAddressBookFilePath() {
         return addressBookStorage.getAddressBookFilePath();
     }
 
+    @Override
+    public Path getAddressBookBackupFilePath() {
+        return addressBookStorage.getAddressBookBackupFilePath();
+    }
+
     @Override
     public Optional<ReadOnlyAddressBook> readAddressBook() throws DataConversionException, IOException {
         return readAddressBook(addressBookStorage.getAddressBookFilePath());
@@ -74,4 +79,10 @@ public void saveAddressBook(ReadOnlyAddressBook addressBook, Path filePath) thro
         addressBookStorage.saveAddressBook(addressBook, filePath);
     }
 
+    @Override
+    public void backupAddressBook(ReadOnlyAddressBook addressBook) throws IOException {
+        logger.fine("Attempting to write to backup data file: " + addressBookStorage.getAddressBookBackupFilePath());
+        addressBookStorage.backupAddressBook(addressBook);
+    }
+
 }

src/test/java/seedu/address/storage/JsonAddressBookStorageTest.java

@@ -98,6 +98,27 @@ public void readAndSaveAddressBook_allInOrder_success() throws Exception {
 
     }
 
+    @Test
+    public void readAndBackupAddressBook_allInOrder_success() throws Exception {
+        Path filePath = testFolder.getRoot().toPath().resolve("TempAddressBook.json");
+        AddressBook original = getTypicalAddressBook();
+        JsonAddressBookStorage jsonAddressBookStorage = new JsonAddressBookStorage(filePath);
+
+        // Backup in new file and read back
+        jsonAddressBookStorage.backupAddressBook(original);
+        ReadOnlyAddressBook readBack = jsonAddressBookStorage.readAddressBook(
+                jsonAddressBookStorage.getAddressBookBackupFilePath()).get();
+        assertEquals(original, new AddressBook(readBack));
+
+        // Modify data, overwrite backup file, and read back
+        original.addPerson(HOON);
+        original.removePerson(ALICE);
+        jsonAddressBookStorage.backupAddressBook(original);
+        readBack = jsonAddressBookStorage.readAddressBook(
+                jsonAddressBookStorage.getAddressBookBackupFilePath()).get();
+        assertEquals(original, new AddressBook(readBack));
+    }
+
     @Test
     public void saveAddressBook_nullAddressBook_throwsNullPointerException() {
         thrown.expect(NullPointerException.class);

src/test/java/seedu/address/storage/StorageManagerTest.java

@@ -62,9 +62,28 @@ public void addressBookReadSave() throws Exception {
         assertEquals(original, new AddressBook(retrieved));
     }
 
+    @Test
+    public void addressBookReadBackup() throws Exception {
+        /*
+         * Note: This is an integration test that verifies the StorageManager is properly wired to the
+         * {@link JsonAddressBookStorage} class.
+         * More extensive testing of UserPref saving/reading is done in {@link JsonAddressBookStorageTest} class.
+         */
+        AddressBook original = getTypicalAddressBook();
+        storageManager.backupAddressBook(original);
+        ReadOnlyAddressBook retrieved = storageManager.readAddressBook(
+                storageManager.getAddressBookBackupFilePath()).get();
+        assertEquals(original, new AddressBook(retrieved));
+    }
+
     @Test
     public void getAddressBookFilePath() {
         assertNotNull(storageManager.getAddressBookFilePath());
     }
 
+    @Test
+    public void getAddressBookBackupFilePath() {
+        assertNotNull(storageManager.getAddressBookBackupFilePath());
+    }
+
 }