# Enthought library imports.
from pyface.action.api import StatusBarManager
from traits.api import Callable, HasTraits, Instance, List, Str, \
     Unicode

# Local imports.
from action.schema import MenuBarSchema, ToolBarSchema
from action.schema_addition import SchemaAddition
from pyface.tasks.task_layout import TaskLayout


class Task(HasTraits):
    """ A collection of pane, menu, tool bar, and status bar factories.

    The central class in the Tasks plugin, a Task is responsible for
    describing a set of user interface elements, as well as mediating between
    its view (a TaskWindow) and an application-specific model.
    """

    # The task's identifier.
    id = Str

    # The task's user-visible name.
    name = Unicode

    # The default layout to use for the task. If not overridden, only the
    # central pane is displayed.
    default_layout = Instance(TaskLayout, ())

    # A list of extra IDockPane factories for the task. These dock panes are
    # used in conjunction with the dock panes returned by create_dock_panes().
    extra_dock_pane_factories = List(Callable)

    # The window to which the task is attached. Set by the framework.
    window = Instance('pyface.tasks.task_window.TaskWindow')

    #### Actions ##############################################################

    # The menu bar for the task.
    menu_bar = Instance(MenuBarSchema)

    # The (optional) status bar for the task.
    status_bar = Instance(StatusBarManager)

    # The list of tool bars for the tasks.
    tool_bars = List(ToolBarSchema)

    # A list of extra actions, groups, and menus that are inserted into menu
    # bars and tool bars constructed from the above schemas.
    extra_actions = List(SchemaAddition)

    ###########################################################################
    # 'Task' interface.
    ###########################################################################

    def activated(self):
        """ Called after the task has been activated in a TaskWindow.
        """
        pass

    def create_central_pane(self):
        """ Create and return the central pane, which must implement ITaskPane.
        """
        raise NotImplementedError

    def create_dock_panes(self):
        """ Create and return the task's dock panes (IDockPane instances).

        This method is called *after* create_central_pane() when the task is
        added to a TaskWindow.
        """
        return []

    def initialized(self):
        """ Called when the task is about to be activated in a TaskWindow for
        the first time.

        Override this method to perform any initialization that requires the
        Task's panes to be instantiated. Note that this method, when called, is
        called before activated().
        """
        pass

    def prepare_destroy(self):
        """ Called when the task is about to be removed from its TaskWindow.

        Override this method to perform any cleanup before the task's controls
        are destroyed.
        """
        pass
