# -*- coding: utf-8; -*-
################################################################################
#
#  Rattail -- Retail Software Framework
#  Copyright © 2010-2019 Lance Edgar
#
#  This file is part of Rattail.
#
#  Rattail is free software: you can redistribute it and/or modify it under the
#  terms of the GNU General Public License as published by the Free Software
#  Foundation, either version 3 of the License, or (at your option) any later
#  version.
#
#  Rattail is distributed in the hope that it will be useful, but WITHOUT ANY
#  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
#  FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
#  details.
#
#  You should have received a copy of the GNU General Public License along with
#  Rattail.  If not, see <http://www.gnu.org/licenses/>.
#
################################################################################
"""
Tools for displaying data diffs
"""

from __future__ import unicode_literals, absolute_import

from pyramid.renderers import render
from webhelpers2.html import HTML


class Diff(object):
    """
    Core diff class.  In sore need of documentation.
    """

    def __init__(self, old_data, new_data, columns=None, fields=None,
                 render_field=None, render_value=None,
                 monospace=False, extra_row_attrs=None):
        """
        Constructor.  You must provide the old and new data sets, and
        the set of relevant fields as well, if they cannot be easily
        introspected.

        :param old_data: Dict of "old" data values.

        :param new_data: Dict of "old" data values.

        :param fields: Sequence of relevant field names.  Note that
           both data dicts are expected to have keys which match these
           field names.  If you do not specify the fields then they
           will (hopefully) be introspected from the old or new data
           sets; however this will not work if they are both empty.

        :param monospace: If true, this flag will cause the value
           columns to be rendered in monospace font.  This is assumed
           to be helpful when comparing "raw" data values which are
           shown as e.g. ``repr(val)``.
        """
        self.old_data = old_data
        self.new_data = new_data
        self.columns = columns or ["field name", "old value", "new value"]
        self.fields = fields or self.make_fields()
        self._render_field = render_field or self.render_field_default
        self.render_value = render_value or self.render_value_default
        self.monospace = monospace
        self.extra_row_attrs = extra_row_attrs

    def make_fields(self):
        return sorted(set(self.old_data) | set(self.new_data), key=lambda x: x.lower())

    def old_value(self, field):
        return self.old_data.get(field)

    def new_value(self, field):
        return self.new_data.get(field)

    def values_differ(self, field):
        return self.new_value(field) != self.old_value(field)

    def render_html(self, template='/diff.mako', **kwargs):
        context = kwargs
        context['diff'] = self
        return HTML.literal(render(template, context))

    def get_row_attrs(self, field):
        """
        Returns a *rendered* set of extra attributes for the ``<tr>`` element
        for the given field.  May be an empty string, or a snippet of HTML
        attribute syntax, e.g.:

        .. code-highlight:: none

           class="diff" foo="bar"

        If you wish to supply additional attributes, please define
        :attr:`extra_row_attrs`, which can be either a static dict, or a
        callable returning a dict.
        """
        attrs = {}
        if self.values_differ(field):
            attrs['class'] = 'diff'

        if self.extra_row_attrs:
            if callable(self.extra_row_attrs):
                attrs.update(self.extra_row_attrs(field, attrs))
            else:
                attrs.update(self.extra_row_attrs)

        return HTML.render_attrs(attrs)

    def render_field(self, field):
        return self._render_field(field, self)

    def render_field_default(self, field, diff):
        return field

    def render_value_default(self, field, value):
        return repr(value)

    def render_old_value(self, field):
        value = self.old_value(field)
        return self.render_value(field, value)

    def render_new_value(self, field):
        value = self.new_value(field)
        return self.render_value(field, value)