# (C) Copyright 2005-2020 Enthought, Inc., Austin, TX
# All rights reserved.
#
# This software is provided without warranty under the terms of the BSD
# license included in LICENSE.txt and may be redistributed only under
# the conditions described in the aforementioned license. The license
# is also available online at http://www.enthought.com/licenses/BSD.txt
#
# Thanks for using Enthought open source!
""" A UI that allows the user to choose a view. """


from pyface.workbench.api import IView, WorkbenchWindow
from traits.api import Any, HasTraits, Instance, List, Str
from traits.api import TraitError, Undefined
from traitsui.api import Item, TreeEditor, TreeNode, View
from traitsui.menu import Action  # fixme: Non-api import!


class Category(HasTraits):
    """ A view category. """

    # The name of the category.
    name = Str()

    # The views in the category.
    views = List()


class WorkbenchWindowTreeNode(TreeNode):
    """ A tree node for workbench windows that displays the window's views.

    The views are grouped by their category.

    """

    # 'TreeNode' interface -------------------------------------------------

    # List of object classes that the node applies to.
    node_for = [WorkbenchWindow]

    # ------------------------------------------------------------------------
    # 'TreeNode' interface.
    # ------------------------------------------------------------------------

    def get_children(self, object):
        """ Get the object's children. """

        # Collate the window's views into categories.
        categories_by_name = self._get_categories_by_name(object)

        categories = list(categories_by_name.values())
        categories.sort(key=lambda category: category.name)

        return categories

    # ------------------------------------------------------------------------
    # Private interface.
    # ------------------------------------------------------------------------

    def _get_categories_by_name(self, window):
        """ Return a dictionary containing all categories keyed by name. """

        categories_by_name = {}
        for view in window.views:
            category = categories_by_name.get(view.category)
            if category is None:
                category = Category(name=view.category)
                categories_by_name[view.category] = category

            category.views.append(view)

        return categories_by_name


class IViewTreeNode(TreeNode):
    """ A tree node for objects that implement the 'IView' interface.

    This node does *not* recognise objects that can be *adapted* to the 'IView'
    interface, only those that actually implement it. If we wanted to allow
    for adaptation we would have to work out a way for the rest of the
    'TreeNode' code to access the adapter, not the original object. We could,
    of course override every method, but that seems a little, errr, tedious.
    We could probably do with something like in the Pyface tree where there
    is a method that returns the actual object that we want to manipulate.

    """

    def is_node_for(self, obj):
        """ Returns whether this is the node that handles a specified object.

        """

        # By checking for 'is obj' here, we are *not* allowing adaptation (if
        # we were allowing adaptation it would be 'is not None'). See the class
        # doc string for details.
        return IView(obj, Undefined) is obj

    def get_icon(self, obj, is_expanded):
        """ Returns the icon for a specified object. """

        if obj.image is not None:
            icon = obj.image

        else:
            # fixme: A bit of magic here! Is there a better way to say 'use
            # the default leaf icon'?
            icon = "<item>"

        return icon


class ViewChooser(HasTraits):
    """ Allow the user to choose a view.

    This implementation shows views in a tree grouped by category.

    """

    # The window that contains the views to choose from.
    window = Instance("pyface.workbench.api.WorkbenchWindow")

    # The currently selected tree item (at any point in time this might be
    # either None, a view category, or a view).
    selected = Any()

    # The selected view (None if the selected item is not a view).
    view = Instance(IView)

    # Traits UI views -----------------------------------------------------#

    traits_ui_view = View(
        Item(
            name="window",
            editor=TreeEditor(
                nodes=[
                    WorkbenchWindowTreeNode(
                        auto_open=True,
                        label="=Views",
                        rename=False,
                        copy=False,
                        delete=False,
                        insert=False,
                        menu=None,
                    ),
                    TreeNode(
                        node_for=[Category],
                        auto_open=True,
                        children="views",
                        label="name",
                        rename=False,
                        copy=False,
                        delete=False,
                        insert=False,
                        menu=None,
                    ),
                    IViewTreeNode(
                        auto_open=False,
                        label="name",
                        rename=False,
                        copy=False,
                        delete=False,
                        insert=False,
                        menu=None,
                    ),
                ],
                editable=False,
                hide_root=True,
                selected="selected",
                show_icons=True,
            ),
            show_label=False,
        ),
        buttons=[Action(name="OK", enabled_when="view is not None"), "Cancel"],
        resizable=True,
        style="custom",
        title="Show View",
        width=0.2,
        height=0.4,
    )

    # ------------------------------------------------------------------------
    # 'ViewChooser' interface.
    # ------------------------------------------------------------------------

    def _selected_changed(self, old, new):
        """ Static trait change handler. """

        # If the assignment fails then the selected object does *not* implement
        # the 'IView' interface.
        try:
            self.view = new

        except TraitError:
            self.view = None

        return
