#------------------------------------------------------------------------------
#
#  Copyright (c) 2005, Enthought, Inc.
#  All rights reserved.
#
#  This software is provided without warranty under the terms of the BSD
#  license included in enthought/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!
#
#  Author: David C. Morrill
#  Date:   10/18/2004
#
#------------------------------------------------------------------------------

""" Defines the abstract ViewElement class that all trait view template items
    (i.e., View, Group, Item, Include) derive from.
"""

#-------------------------------------------------------------------------------
#  Imports:
#-------------------------------------------------------------------------------

from __future__ import absolute_import

import re

from traits.api import HasPrivateTraits, Trait, Bool
import traits._py2to3 as _py2to3

from .ui_traits import (ATheme, AnObject, DockStyle, EditorStyle, ExportType,
    HelpId, Image)

#-------------------------------------------------------------------------------
#  Constants:
#-------------------------------------------------------------------------------

label_pat  = re.compile( r"^(.*)\[(.*)\](.*)$", re.MULTILINE | re.DOTALL )
label_pat2 = re.compile( r"^(.*){(.*)}(.*)$",   re.MULTILINE | re.DOTALL )

#-------------------------------------------------------------------------------
#  'ViewElement' class (abstract):
#-------------------------------------------------------------------------------

class ViewElement ( HasPrivateTraits ):
    """ An element of a view.
    """

    #---------------------------------------------------------------------------
    #  Replaces any items which have an 'id' with an Include object with the
    #  same 'id', and puts the object with the 'id' into the specified
    #  ViewElements object:
    #---------------------------------------------------------------------------

    def replace_include ( self, view_elements ):
        """ Searches the current object's **content** attribute for objects that
        have an **id** attribute, and replaces each one with an Include object
        with the same **id** value, and puts the replaced object into the
        specified ViewElements object.

        Parameters
        ----------
        view_elements : ViewElements object
            Object containing Group, Item, and Include objects
        """
        pass # Normally overridden in a subclass

    #---------------------------------------------------------------------------
    #  Returns whether or not the object is replacable by an Include object:
    #---------------------------------------------------------------------------

    def is_includable ( self ):
        """ Returns whether the object is replacable by an Include object.
        """
        return False # Normally overridden in a subclass

#-------------------------------------------------------------------------------
#  'DefaultViewElement' class:
#-------------------------------------------------------------------------------

class DefaultViewElement ( ViewElement ):
    """ A view element that can be used as a default value for traits whose
        value is a view element.
    """

    #---------------------------------------------------------------------------
    #  Trait definitions:
    #---------------------------------------------------------------------------

    # The default context object to edit:
    object = AnObject

    # The default editor style to use:
    style = EditorStyle

    # The default dock style to use:
    dock = DockStyle

    # The default notebook tab image to use:
    image = Image

    # The category of elements dragged out of the view:
    export = ExportType

    # Should labels be added to items in a group?
    show_labels = Bool( True )

    # The default theme to use for a contained item:
    item_theme = ATheme

    # The default theme to use for a contained item's label:
    label_theme = ATheme

#-------------------------------------------------------------------------------
#  Trait definitions:
#-------------------------------------------------------------------------------

# The container trait used by ViewSubElements:
Container = Trait( DefaultViewElement(), ViewElement )

#-------------------------------------------------------------------------------
#  'ViewSubElement' class (abstract):
#-------------------------------------------------------------------------------

class ViewSubElement ( ViewElement ):
    """ Abstract class representing elements that can be contained in a view.
    """

    #---------------------------------------------------------------------------
    #  Trait definitions:
    #---------------------------------------------------------------------------

    # The object this ViewSubElement is contained in; must be a ViewElement.
    container = Container

    # External help context identifier:
    help_id = HelpId

    #---------------------------------------------------------------------------
    #  Splits a string at a specified character:
    #---------------------------------------------------------------------------

    def _split ( self, name, value, char, finder, assign, result ):
        """ Splits a string at a specified character.
        """
        col = finder( value, char )
        if col < 0:
            return value

        items = ( value[:col].strip(), value[col+1:].strip() )
        if items[ assign ] != '':
            setattr( self, name, items[ assign ] )

        return items[ result ]

    #---------------------------------------------------------------------------
    #  Sets an object trait if a specified option string is found:
    #---------------------------------------------------------------------------

    def _option ( self, string, option, name, value ):
        """ Sets a object trait if a specified option string is found.
        """
        col = string.find( option )
        if col >= 0:
            string = string[ : col ] + string[ col + len( option ): ]
            setattr( self, name, value )

        return string

    #---------------------------------------------------------------------------
    #  Parses any of the one character forms of the 'style' trait:
    #---------------------------------------------------------------------------

    def _parse_style ( self, value ):
        """ Parses any of the one-character forms of the **style** trait.
        """
        value = self._option( value, '$', 'style', 'simple' )
        value = self._option( value, '@', 'style', 'custom' )
        value = self._option( value, '*', 'style', 'text' )
        value = self._option( value, '~', 'style', 'readonly' )
        value = self._split( 'style',  value, ';', _py2to3.str_rfind, 1, 0 )

        return value

    #---------------------------------------------------------------------------
    #  Parses a '[label]' value from the string definition:
    #---------------------------------------------------------------------------

    def _parse_label ( self, value ):
        """ Parses a '[label]' value from the string definition.
        """
        match = label_pat.match( value )
        if match is not None:
            self._parsed_label()
        else:
            match = label_pat2.match( value )

        empty = False
        if match is not None:
            self.label = match.group( 2 ).strip()
            empty      = (self.label == '')
            value      = match.group( 1 ) + match.group( 3 )

        return ( value, empty )

    #---------------------------------------------------------------------------
    #  Handles a label being found in the string definition:
    #---------------------------------------------------------------------------

    def _parsed_label ( self ):
        """ Handles a label being found in the string definition.
        """
        pass

    #---------------------------------------------------------------------------
    #  Returns a 'pretty print' version of a specified trait value:
    #---------------------------------------------------------------------------

    def _repr_value ( self, value, prefix = '', suffix = '', ignore = '' ):
        """ Returns a "pretty print" version of a specified Item trait value.
        """
        if value == ignore:
            return ''

        return '%s%s%s' % ( prefix, value, suffix )

    #---------------------------------------------------------------------------
    #  Returns a 'pretty print' version of a list of traits:
    #---------------------------------------------------------------------------

    def _repr_options ( self, *names ):
        """ Returns a 'pretty print' version of a list of traits.
        """
        result = []
        for name in names:
            value = getattr( self, name )
            if value != self.trait( name ).default_value_for( self, name ):
                result.append( ( name, repr( value ) ) )

        if len( result ) > 0:
            n = max( [ len( name ) for name, value in result ] )
            return ',\n'.join( [ '%s = %s' % ( name.ljust( n ), value )
                                 for name, value in result ] )

        return None

    #---------------------------------------------------------------------------
    #  Indents each line in a specified string by a specified number of spaces:
    #---------------------------------------------------------------------------

    def _indent ( self, string, indent = '    ' ):
        """ Indents each line in a specified string by 4 spaces.
        """
        return '\n'.join( [ indent + s for s in string.split( '\n' ) ] )

