from pybtex.style.sorting.author_year_title import (SortingStyle as
                                                    AuthorYearSortingStyle)
from dateutil import parser
from datetime import datetime

[docs]def extract_month(month_str):
    '''Get the first thing which parses as a month. Will only find months at the
    beginning of the string.'''
    if len(month_str) < 3:
        return None
    for l in range(3, len(month_str)):
        try:
            month = parser.parse(month_str[:l+1]).month
            return month
        except ValueError:
            continue

[docs]class SortingStyle(AuthorYearSortingStyle):
    '''A sorting style that prioritizes the publication date over title and
    author. Sorting is in descending order. More specific dates (i.e. with month
    as opposed to year only) are given precedence.'''

[docs]    def sorting_key(self, entry):
        year = 2017
        month = 1
        day = 1
        if 'year' in entry.fields:
            year = int(entry.fields['year'])
        if 'month' in entry.fields:
            month = extract_month(entry.fields['month']) or 1

        date_key = datetime(year=year, month=month, day=day)

        # this part is simply the same functionality as in the builtin
        # author_year_title style; at the end we inject the year at the
        # beginning
        if entry.type in ('book', 'inbook'):
            author_key = self.author_editor_key(entry)
        elif 'author' in entry.persons:
            author_key = self.persons_key(entry.persons['author'])
        else:
            author_key = ''

        return (date_key, author_key, entry.fields.get('title', ''))

[docs]    def sort(self, entries):
        keys_entries = [(self.sorting_key(entry), entry) for entry in entries]
        # disambiguate
        entry_dict = {}
        for key, entry in keys_entries:
            c = 1
            newkey = list(key)
            title_field = key[-1] + '*'
            while tuple(newkey) in entry_dict:
                title_field += '%d' % c     # append something while not unique
                newkey[-1] = title_field
                c += 1
            entry_dict[tuple(newkey)] = entry
        sorted_keys = reversed(sorted(entry_dict))
        sorted_entries = [entry_dict[key] for key in sorted_keys]
        return sorted_entries