from typing import List
from datetime import date, datetime

def find_category (categories, slug):
  for (category, articles) in categories:
    if category.slug == slug:
      return (category, articles)
  
  return (None, None)

def get_category_articles (categories, slug):
  category, articles = find_category(categories, slug)

  if category:
    return articles
  else:
    return []

def display_if_set (value, label):
  if value:
    if isinstance(value, (list, tuple)):
      value = ', '.join(value)

    if isinstance(value, (date)):
      value = date.strftime(value, '%d-%m-%Y')

    if isinstance(value, (datetime)):
      value = date.strftime(value, '%d-%m-%Y %H:%i')


    return '<dt>{}</dt><dd>{}</dd>'.format(label, value)
  else:
    return ''