Modify change to

docs/DeveloperGuide.md

@@ -545,7 +545,7 @@ Use case ends.
 **MSS**
 
 1. User requests to change storage file location
-2. MESS changes storage file location and saves in that location
+2. MESS changes storage file location and saves in that location/loads from that location if file already contains data
 
 **Extensions**
 2a. The file path may not be valid

docs/UserGuide.md

@@ -256,7 +256,9 @@ There is no need to save manually.
 <!-- @@author A0144939R -->
 
 #### Change storage location : `change-to`
-Shows a list of tasks and events in the todo list.<br>
+Changes to a new storage location and saves task manager data there<br>
+Note: If new file already has data, then the taskmanager will load that data.
+
 Format: `change-to NEWFILEPATH`
 Example:
 * `change-to data/taskmanager.xml`

src/main/java/seedu/task/commons/events/model/ReloadFromNewFileEvent.java

@@ -0,0 +1,25 @@
+//@@author A0144939R
+package seedu.task.commons.events.model;
+
+import java.util.Optional;
+import seedu.task.commons.events.BaseEvent;
+import seedu.task.model.ReadOnlyTaskManager;
+import seedu.task.model.TaskManager;
+
+/** Indicates that the user wishes to load from an existing file*/
+public class ReloadFromNewFileEvent extends BaseEvent {
+
+    public final String filePath;
+    public final ReadOnlyTaskManager taskManager;
+
+    public ReloadFromNewFileEvent(String newFilePath, Optional<ReadOnlyTaskManager> newTaskManager) {
+        this.filePath = newFilePath;
+        this.taskManager = newTaskManager.orElse(new TaskManager());
+    }
+
+    @Override
+    public String toString() {
+        return "The new file path is "+filePath;
+    }
+
+}

src/main/java/seedu/task/commons/events/storage/FilePathChangedEvent.java

@@ -2,6 +2,7 @@
 package seedu.task.commons.events.storage;
 
 import seedu.task.commons.events.BaseEvent;
+
 import seedu.task.model.ReadOnlyTaskManager;
 
 /** Indicates that the user has specified a new file path*/

src/main/java/seedu/task/model/ModelManager.java

@@ -3,23 +3,33 @@
 import javafx.collections.transformation.FilteredList;
 import javafx.collections.transformation.SortedList;
 import seedu.task.commons.core.ComponentManager;
+import seedu.task.commons.core.Config;
 import seedu.task.commons.core.EventsCenter;
 import seedu.task.commons.core.LogsCenter;
 import seedu.task.commons.core.UnmodifiableObservableList;
+import seedu.task.commons.events.model.ReloadFromNewFileEvent;
 import seedu.task.commons.events.model.TaskManagerChangedEvent;
+import seedu.task.commons.events.storage.ConfigFilePathChangedEvent;
+import seedu.task.commons.events.storage.FilePathChangedEvent;
+import seedu.task.commons.exceptions.DataConversionException;
 import seedu.task.commons.events.ui.JumpToListRequestEvent;
 import seedu.task.commons.logic.CommandKeys.Commands;
+import seedu.task.commons.util.ConfigUtil;
 import seedu.task.commons.util.StringUtil;
 import seedu.task.model.tag.Tag;
 import seedu.task.model.task.DateTime;
 import seedu.task.model.task.ReadOnlyTask;
 import seedu.task.model.task.Task;
 import seedu.task.model.task.UniqueTaskList;
+import seedu.task.storage.Storage;
 
+import java.io.IOException;
 import java.util.HashMap;
 import java.util.Set;
 import java.util.logging.Logger;
 
+import com.google.common.eventbus.Subscribe;
+
 /**
  * Represents the in-memory model of the task list data. All changes to any
  * model should be synchronized.
@@ -349,4 +359,11 @@ public boolean run(ReadOnlyTask task) {
             return (task.getComplete() == this.isCompleted);
         }
     }
+
+    //@@author A0144939R
+    @Subscribe
+    public void handleReloadFromNewFileEvent(ReloadFromNewFileEvent event) throws DataConversionException {
+        logger.info(LogsCenter.getEventHandlingLogMessage(event, "Load from new file path requested"));
+        resetData(event.taskManager);
+    }
 }

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

@@ -5,16 +5,20 @@
 import seedu.task.commons.core.ComponentManager;
 import seedu.task.commons.core.Config;
 import seedu.task.commons.core.LogsCenter;
+import seedu.task.commons.events.model.ReloadFromNewFileEvent;
 import seedu.task.commons.events.model.TaskManagerChangedEvent;
 import seedu.task.commons.events.storage.ConfigFilePathChangedEvent;
 import seedu.task.commons.events.storage.DataSavingExceptionEvent;
 import seedu.task.commons.events.storage.FilePathChangedEvent;
 import seedu.task.commons.exceptions.DataConversionException;
 import seedu.task.commons.util.ConfigUtil;
+import seedu.task.model.Model;
 import seedu.task.model.ReadOnlyTaskManager;
 import seedu.task.model.UserPrefs;
 
+import java.io.File;
 import java.io.IOException;
+import java.nio.file.FileAlreadyExistsException;
 import java.util.Optional;
 import java.util.logging.Logger;
 
@@ -107,17 +111,51 @@ public void handleTaskManagerChangedEvent(TaskManagerChangedEvent event) {
     //@@author A0144939R
     @Subscribe
     public void handleFilePathChangedEvent(FilePathChangedEvent event) throws DataConversionException {
-        //ReadOnlyTaskManager taskManager
+        logger.info(LogsCenter.getEventHandlingLogMessage(event, "File path change requested, attempting to update file path"));
+        String newFilePath = event.newFilePath;
+        String oldFilePath = getTaskManagerFilePath();
         try {
-            logger.info(LogsCenter.getEventHandlingLogMessage(event, "File path change requested, updating file path"));
-            setTaskManagerFilePath(event.newFilePath);
+            //save data
             saveTaskManager(event.taskManager);
+
+            //change file path
+            setTaskManagerFilePath(newFilePath);
+
+            if(!isFileAlreadyPresent(newFilePath)) { 
+                //save to new location
+                saveTaskManager(event.taskManager);                
+            } else {
+                //load from pre existing file                
+                Optional<ReadOnlyTaskManager> newTaskManager = readTaskManager(newFilePath); 
+                raise(new ReloadFromNewFileEvent(newFilePath, newTaskManager));
+            }
+
             config.setTaskManagerFilePath(event.newFilePath);
             ConfigUtil.saveConfig(config, config.getFilePath());
             raise(new ConfigFilePathChangedEvent(event.newFilePath));
-        } catch (IOException e) {
-            e.printStackTrace();
+
+        } catch (IOException e)  {
+
+            logger.info(LogsCenter.getEventHandlingLogMessage(event, "Error occured on saving/loading"));
+            raise(new DataSavingExceptionEvent(e));
+            //clean up
+            setTaskManagerFilePath(oldFilePath);
+
+        } catch(DataConversionException e) {
+
+            logger.info(LogsCenter.getEventHandlingLogMessage(event, "Error occured on loading from new file"));
+            //clean up
+            setTaskManagerFilePath(oldFilePath);
         }
     }
-
+
+    /**
+     * Returns true if the file already exists
+     * @param filePath
+     * @return boolean value indicating whether file already exists
+     */
+    private boolean isFileAlreadyPresent(String filePath) {
+        File newFile = new File(filePath);
+        return newFile.exists() && !newFile.isDirectory();
+    }
 }