#  Copyright (c) 2007, Enthought, Inc.
#  License: BSD Style.

#--(Extended Traits UI Item and Editor References)------------------------
"""
Extended Traits UI Item and Editor References
=============================================

In Traits 3.0, the Traits UI **Item** class and various *editor* classes
have been extended to use the new extended trait name support provided by the
*on_trait_change* method.

In previous Traits versions, for example, **Item** objects could only refer to
traits defined directly on a UI context object. For example::

    view = View(
        Item( 'name' ),
        Item( 'object.age' ),
        Item( 'handler.status' )
    )

In Traits 3.0 this restriction has been lifted, and now **Items** can reference
(i.e. edit) any trait reachable from a UI context object::

    view = View(
        Item( 'object.mother.name' ),
        Item( 'object.axel.chassis.serial_number', style = 'readonly' )
    )

Similarly, any Traits UI *editor* classes that previously accepted a trait name
now accept an extended trait name::

    view = View(
        Item( 'address' ),
        Item( 'state', editor = EnumEditor( name = 'handler.country.states' )
    )

Because **Items** and *editors* only refer to a single trait, you should not use
extended trait references that refer to multiple traits, such as
*'foo.[bar,baz]'* or *'foo.+editable'*, since the behavior of such references
is not defined.

Look at the code tabs for this lesson for a complete example of a Traits UI
using extended **Item** and editor references. In particular, the
**LeagueModelView Class** tab contains a **View** definition containing
extended references.

Code Incompatibilities
----------------------

Note that the editor enhancement may cause some incompatibities with editors
that previously supported both an *object* and *name* trait, with the *object*
trait containing the context object name, and the *name* trait containing the
name of  the trait on the specified context object. Using the new extended trait
references, these have been combined into a single *name* trait.

If you encounter such an occurrence in existing code, simply combine the
context object name and trait name into a single extended name of the form::

    context_object_name.trait_name

Warning
-------

Avoid extended **Item** references that contain intermediate links that could
be *None*. For example, in the following code::

    view = View(
        ...
        Item( 'object.team.players', ... )
        ...
    )

an exception will be raised if *object.team* is *None*, or is set to *None*,
while the view is active, since there is no obvious way to obtain a valid value
for *object.team.players* for the associated **Item** *editor* to display.

Note that the above example is borrowed from this lesson's demo code, which has
additional code written to ensure that *object.team* is not *None*. See the
*_model_changed* method in the **LeagueModelView Class** tab, which makes sure
that the *team* trait is intialized to a valid value when a new **League**
model is set up.
"""

#--<Imports>--------------------------------------------------------------

from traits.api \
    import *

from traitsui.api \
    import *

from traitsui.table_column \
    import *
from functools import reduce

#--[Player Class]---------------------------------------------------------

# Define a baseball player:


class Player(HasTraits):

    # The name of the player:
    name = Str('<new player>')

    # The number of hits the player made this season:
    hits = Int()

#--[Team Class]-----------------------------------------------------------

# Define a baseball team:


class Team(HasTraits):

    # The name of the team:
    name = Str('<new team>')

    # The players on the team:
    players = List(Player)

    # The number of players on the team:
    num_players = Property(depends_on='players')

    def _get_num_players(self):
        """ Implementation of the 'num_players' property.
        """
        return len(self.players)

#--[League Class]---------------------------------------------------------

# Define a baseball league model:


class League(HasTraits):

    # The name of the league:
    name = Str('<new league>')

    # The teams in the league:
    teams = List(Team)

#--[LeagueModelView Class]-----------------------------------------------------

# Define a ModelView for a League model:


class LeagueModelView(ModelView):

    # The currently selected team:
    team = Instance(Team)

    # The currently selected player:
    player = Instance(Player)

    # Button to add a hit to the current player:
    got_hit = Button('Got a Hit')

    # The total number of hits
    total_hits = Property(depends_on='model.teams.players.hits')

    @cached_property
    def _get_total_hits(self):
        """ Returns the total number of hits across all teams and players.
        """
        return 0
        return reduce(add, [reduce(add, [p.hits for p in t.players], 0)
                            for t in self.model.teams], 0)

    view = View(
        VGroup(
            HGroup(
                Item('total_hits', style='readonly'),
                label='League Statistics',
                show_border=True
            ),
            VGroup(
                Item('model.teams',
                     show_label=False,
                     editor=TableEditor(
                         columns=[ObjectColumn(name='name',
                                               width=0.70),
                                  ObjectColumn(name='num_players',
                                               label='# Players',
                                               editable=False,
                                               width=0.29)],
                         selected='object.team',
                         auto_add=True,
                         row_factory=Team,
                         configurable=False,
                         sortable=False)
                     ),
                label='League Teams',
                show_border=True
            ),
            VGroup(
                Item('object.team.players',  # <-- Extended Item name
                     show_label=False,
                     editor=TableEditor(
                         columns=[ObjectColumn(name='name',
                                               width=0.70),
                                  ObjectColumn(name='hits',
                                               editable=False,
                                               width=0.29)],
                         selected='object.player',
                         auto_add=True,
                         row_factory=Player,
                         configurable=False,
                         sortable=False)
                     ),
                '_',
                HGroup(
                    Item('got_hit',
                         show_label=False,
                         enabled_when='player is not None'
                         )
                ),
                label='Team Players',
                show_labels=False,
                show_border=True
            )
        ),
        resizable=True
    )

    def _model_changed(self, model):
        """ Handles the 'league' model being initialized.
        """
        if len(model.teams) > 0:
            self.team = model.teams[0]

    def _got_hit_changed(self):
        """ Handles the currently selected player making a hit.
        """
        self.player.hits += 1

    def _team_changed(self, team):
        """ Handles a new team being selected.
        """
        if len(team.players) > 0:
            self.player = team.players[0]
        else:
            self.player = None

# Function to add two numbers (used with 'reduce'):
add = lambda a, b: a + b

#--[Example*]-------------------------------------------------------------

# Define some sample teams and players:
blue_birds = Team(name='Blue Birds', players=[
    Player(name='Mike Scott', hits=25),
    Player(name='Willy Shofield', hits=37),
    Player(name='Tony Barucci', hits=19)])

chicken_hawks = Team(name='Chicken Hawks', players=[
    Player(name='Jimmy Domore', hits=34),
    Player(name='Bill Janks', hits=16),
    Player(name='Tim Saunders', hits=27)])

eagles = Team(name='Eagles', players=[
    Player(name='Joe Peppers', hits=33),
    Player(name='Sam Alone', hits=12),
    Player(name='Roger Clemson', hits=23)])

# Create a league and its corresponding model view:
demo = LeagueModelView(
    League(name='National Baseball Conference',
           teams=[blue_birds, chicken_hawks, eagles])
)


if __name__ == '__main__':
    demo.configure_traits()
