Archive/Unarchive

Several other improvements

model.go

@@ -16,7 +16,7 @@ func (a *AppState) addTask(taskString string) error {
 		t.CreatedDate = time.Now()
 	}
 	a.TaskList.AddTask(t)
-	return nil
+	return a.WriteList()
 }
 
 func (a *AppState) toggleTaskComplete(id int) error {
@@ -30,7 +30,7 @@ func (a *AppState) toggleTaskComplete(id int) error {
 	} else {
 		task.Complete()
 	}
-	return nil
+	return a.WriteList()
 }
 
 func (a *AppState) archiveTask(id int) error {
@@ -39,12 +39,25 @@ func (a *AppState) archiveTask(id int) error {
 	if task, err = a.TaskList.GetTask(id); err != nil {
 		return err
 	}
-	task.Completed = true
 	if err := a.TaskList.ArchiveTaskToFile(*task, app.getDoneFile()); err != nil {
 		return err
 	}
 	a.TaskList.RemoveTask(*task)
-	return nil
+	return a.WriteList()
+}
+
+func (a *AppState) unarchiveTask(id int) error {
+	var err error
+	var task *todotxt.Task
+	if task, err = a.DoneList.GetTask(id); err != nil {
+		return err
+	}
+	a.TaskList.AddTask(task)
+	if err = a.WriteList(); err != nil {
+		return err
+	}
+	a.DoneList.RemoveTask(*task)
+	return a.WriteDoneList()
 }
 
 func (a *AppState) getFilterPredicate(filter string) func(todotxt.Task) bool {