summer_code_jam_solution.py

"""
Use this file to write your solution for the Summer Code Jam 2020 Qualifier.

Important notes for submission:

- Do not change the names of the two classes included below. The test suite we
  will use to test your submission relies on existence these two classes.

- You can leave the `ArticleField` class as-is if you do not wish to tackle the
  advanced requirements.

- Do not include "debug"-code in your submission. This means that you should
  remove all debug prints and other debug statements before you submit your
  solution.
"""
import collections
import datetime
import typing
import re
import textwrap
import weakref


class ArticleField:
    """The `ArticleField` class for the Advanced Requirements."""

    def __init__(self, field_type: typing.Type[typing.Any]):
        self.field_type = field_type
        self.instances = weakref.WeakKeyDictionary()
        self.name = None

    def __get__(self, instance, owner=None):
        if instance is None:
            return self

        try:
            return self.instances[instance]

        except KeyError:
            raise AttributeError(f"article field '{self.name}' is not set") from None

    def __set__(self, instance, value):
        msg = " ".join((
            f"expected an instance of type '{self.field_type.__qualname__}'",
            f"for attribute '{self.name}', got '{type(value).__qualname__}'",
            "instead.",
        ))

        if not isinstance(value, self.field_type):
            raise TypeError(msg)

        self.instances[instance] = value

    def __set_name__(self, owner, name):
        self.name = name


class Article:
    """The `Article` class you need to write for the qualifier."""

    current_article_idx = 0

    def __init__(self, title: str, author: str, publication_date: datetime.datetime, content: str):
        self.title = title
        self.author = author

        self.publication_date = publication_date
        self.id = self._new_article_id()

        self._content = content
        self.last_edited = None

    @classmethod
    def _new_article_id(cls):
        article_id = cls.current_article_idx
        cls.current_article_idx += 1
        return article_id

    @property
    def content(self):
        return self._content

    @content.setter
    def content(self, content):
        self._content = content
        self.last_edited = datetime.datetime.now()
         
    def __repr__(self):
        title = self.title
        author = self.author
        publication_date = self.publication_date.isoformat()

        return f"<Article {title=} {author=} {publication_date=}>"
    
    def __len__(self):
        return len(self.content)

    def __lt__(self, other):
        return self.publication_date < other.publication_date

    def __gt__(self, other):
        return self.publication_date > other.publication_date

    def short_introduction(self, n_characters: int):
        return textwrap.shorten(self.content, n_characters, placeholder="")
        
    def most_common_words(self, n_words: int):
        word_list = re.findall("\w+", self.content.lower())
        return dict(collections.Counter(word_list).most_common(n_words))