Implement Purge undo, cleanup

docs/UserGuide.md

@@ -231,6 +231,14 @@ Deletes a specified task from the tasks list by a given index.
 
 `task delete 2`
 
+### Undo previous command : `undo`
+
+Undos the previous command, returning the user back to the previous state, up to a maximum of 15 previous commands.
+
+Format: `undo`
+
+- Setting a filter is not considered a command that can be undone.
+
 ### Purge all visible tasks : `task purge`
 
 Clears all visible (filtered) tasks from the address book.

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

@@ -32,11 +32,8 @@ public CommandResult execute(Model model) throws CommandException {
 
     @Override
     public CommandResult undo(Model model) throws CommandException {
-        if (this.canExecute) {
-            throw new CommandException(Messages.MESSAGE_UNABLE_TO_UNDO);
-        }
+        super.canUndo();
         model.setAddressBook(this.oldAddressBook);
-        this.canExecute = true;
         return new CommandResult(MESSAGE_SUCCESS);
     }
 }

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

@@ -42,7 +42,6 @@ public CommandResult execute(Model model) throws CommandException {
         super.canExecute();
         this.previousPredicate = model.getFilteredPersonPredicate();
         model.updateFilteredPersonList(predicate);
-        this.canExecute = false;
         return new CommandResult(
                 String.format(Messages.MESSAGE_PERSONS_LISTED_OVERVIEW, model.getFilteredPersonList().size()));
     }
@@ -58,7 +57,6 @@ public boolean equals(Object other) {
     public CommandResult undo(Model model) throws CommandException {
         super.canUndo();
         model.updateFilteredPersonList(this.previousPredicate);
-        this.canExecute = true;
         return new CommandResult(
                 String.format(Messages.MESSAGE_PERSONS_LISTED_OVERVIEW, model.getFilteredPersonList().size()));
     }

src/main/java/seedu/address/logic/commands/task/DeleteTaskCommand.java

@@ -73,7 +73,6 @@ public CommandResult undo(Model model) throws CommandException {
         super.canUndo();
         Predicate<? super Task> predicate = model.getFilteredTaskPredicate();
         model.insertTask(deletedTask, targetIndex.getZeroBased());
-        this.canExecute = true;
         return new CommandResult(String.format(MESSAGE_SUCCESS, deletedTask));
     }
 }

src/main/java/seedu/address/logic/commands/task/DoneTaskCommand.java

@@ -64,7 +64,6 @@ public boolean equals(Object o) {
     public CommandResult undo(Model model) throws CommandException {
         super.canUndo();
         this.execute(model);
-        this.canExecute = true;
         return new CommandResult(String.format(MESSAGE_SUCCESS,
                 this.completedTask));
     }

src/main/java/seedu/address/logic/commands/task/EditTaskCommand.java

@@ -118,7 +118,6 @@ public CommandResult undo(Model model) throws CommandException {
                 oldTaskDescriptor);
         model.setTask(taskToEdit,
                 previousEditTask);
-        this.canExecute = true;
         return new CommandResult(String.format(MESSAGE_EDIT_TASK_SUCCESS,
                 taskToEdit));
     }

src/main/java/seedu/address/logic/commands/task/PurgeTaskCommand.java

@@ -2,13 +2,16 @@
 
 import static java.util.Objects.requireNonNull;
 
+import java.util.ArrayList;
 import java.util.List;
+import java.util.TreeMap;
 
 import seedu.address.logic.commands.CommandResult;
 import seedu.address.logic.commands.TaskCommand;
 import seedu.address.logic.commands.exceptions.CommandException;
 import seedu.address.model.Model;
 import seedu.address.model.task.Task;
+import seedu.address.model.task.filters.TaskFilter;
 
 /**
  * Purges all tasks currently in the task list
@@ -22,6 +25,9 @@ public class PurgeTaskCommand extends TaskCommand {
             + ": Purges all tasks in the displayed task list.\n"
             + "Example: " + FULL_COMMAND_WORD;
 
+    private TreeMap<Integer, Task> deletedTasks;
+    private ArrayList<TaskFilter> deletedFilters;
+
     /**
      * Executes the command and returns the result message.
      *
@@ -38,9 +44,19 @@ public CommandResult execute(Model model) throws CommandException {
             throw new CommandException(MESSAGE_NO_TASK_TO_PURGE);
         }
 
-        // Create a copy of the list and deletes all tasks from the original
-        Task[] tasksToDelete = taskList.toArray(new Task[0]);
-        model.deleteAllInFilteredTaskList(tasksToDelete);
+        // Create a copy of the list for undo with their respective indexes
+        deletedTasks = new TreeMap<>();
+        for (Task deletedTask : taskList) {
+            int index = model.indexOf(deletedTask);
+            deletedTasks.put(index, deletedTask);
+        }
+
+        deletedFilters = new ArrayList<>();
+        deletedFilters.addAll(model.getSelectedTaskFilters());
+
+        super.canExecute();
+
+        model.deleteAllInFilteredTaskList();
         return new CommandResult(MESSAGE_SUCCESS);
     }
 
@@ -54,4 +70,18 @@ public boolean equals(Object other) {
         // instanceof handles nulls
         return other instanceof PurgeTaskCommand;
     }
+
+    @Override
+    public CommandResult undo(Model model) throws CommandException {
+        super.canUndo();
+
+        model.setTaskFilters(deletedFilters);
+        for (int index : deletedTasks.keySet()) {
+            Task task = deletedTasks.get(index);
+            model.insertTask(task, index);
+        }
+
+        return new CommandResult(MESSAGE_SUCCESS);
+
+    }
 }

src/main/java/seedu/address/model/Model.java

@@ -104,10 +104,9 @@ public interface Model {
     void deleteTask(Task deletedTask);
 
     /**
-     * Deletes a list of given tasks. The tasks must exist in the task list.
-     * @param tasksToDelete List of tasks to delete.
+     * Deletes the list of Filtered Tasks and their filters.
      */
-    void deleteAllInFilteredTaskList(Task... tasksToDelete);
+    void deleteAllInFilteredTaskList();
 
     /**
      * Adds the given task to the task list.
@@ -122,6 +121,13 @@ public interface Model {
      */
     void insertTask(Task task, int index);
 
+    /**
+     * Checks the index of the given task in the task list.
+     * @param task Task to check the index of.
+     * @return The 0-based index of the task.
+     */
+    int indexOf(Task task);
+
     /** Returns an unmodifiable view of the task list */
     ObservableList<Task> getFilteredTaskList();
 

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

@@ -4,6 +4,7 @@
 import static seedu.address.commons.util.CollectionUtil.requireAllNonNull;
 
 import java.nio.file.Path;
+import java.util.ArrayList;
 import java.util.Comparator;
 import java.util.List;
 import java.util.Optional;
@@ -180,6 +181,11 @@ public void addTask(Task task) {
         recomputeAvailableTaskFilters();
     }
 
+    @Override
+    public int indexOf(Task task) {
+        return taskList.indexOf(task);
+    }
+
     @Override
     public void insertTask(Task task, int index) {
         taskList.addTaskAtIndex(task, index);
@@ -273,13 +279,13 @@ public void deleteTask(Task deletedTask) {
     }
 
     /**
-     * Deletes a list of given tasks.
+     * Deletes the filtered list and their filters from the task list.
      * This method does not {@code updateTaskFilters} so as to show distinct changes to the task list, if any.
      * Instead, it removes all currently selected task filters from {@code availableTaskFilters}
-     * @param tasksToDelete List of tasks in the filtered list to delete.
      */
     @Override
-    public void deleteAllInFilteredTaskList(Task... tasksToDelete) {
+    public void deleteAllInFilteredTaskList() {
+        List<Task> tasksToDelete = new ArrayList<>(filteredTasks);
         for (Task task : tasksToDelete) {
             taskList.removeTask(task);
         }

src/main/java/seedu/address/model/TaskList.java

@@ -38,6 +38,10 @@ public void setTask(Task oldTask, Task newTask) {
         tasks.set(tasks.indexOf(oldTask), newTask);
     }
 
+    public int indexOf(Task task) {
+        return tasks.indexOf(task);
+    }
+
     @Override
     public boolean equals(Object other) {
         return other == this // short circuit if same object

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

@@ -241,7 +241,12 @@ public CommandHistory getCommandHistory() {
         }
 
         @Override
-        public void deleteAllInFilteredTaskList(Task... tasksToDelete) {
+        public void deleteAllInFilteredTaskList() {
+            throw new AssertionError("This method should not be called.");
+        }
+
+        @Override
+        public int indexOf(Task task) {
             throw new AssertionError("This method should not be called.");
         }
     }