from urllib.request import urlopen
from pathlib import Path
import base64

FILE_CACHE_DIR = "wiki_cache"

class Internet:
    DISALLOWED = [":", "#", "/", "?"]
    """
    This class represents the Internet. Feel free to look,
    but do NOT edit this file. Also, do NOT access the
    Internet in any way except through this class,
    or you will see unexpected results.

    get_page(page) will return the HTML code from a given page.
    page should be formatted as "/wiki/Something", which will
    give the HTML for the page https://en.wikipedia.org/wiki/Something.

    get_random() is a function you can use if you desire. It will return the HTML
    of a random page on Wikipedia.


    Usage of Internet:
    internet = Internet()
    html = internet.get_page("/wiki/Computer_science")
    print(html)

    """

    def __init__(self):
        self.requests = []

    def get_page(self, page):
        if page[:6] != "/wiki/":
            raise ValueError(f"Links must start with /wiki/. {page} is not valid.")
        if any(i in page[6:] for i in Internet.DISALLOWED):
            raise ValueError(f"Link cannot contain disallowed character. {page} is not valid.")
        self.requests.append(page)
        return Internet.__get_page_internal(page)

    # You may find this useful in your wikiracer implementation.
    def get_random(self):
        return urlopen(f"https://en.wikipedia.org/wiki/Special:Random").read().decode('utf-8')

    @staticmethod
    def __get_page_internal(page):
        # First see if we have it in the local cache, to reduce the number of spam requests to Wikipedia
        file_cache_dir_path = Path(FILE_CACHE_DIR)
        if not file_cache_dir_path.is_dir():
            file_cache_dir_path.mkdir()

        # Convert page to a filesystem safe name
        safe_name = base64.urlsafe_b64encode(page.encode("utf-8")).decode("utf-8")

        local_path = file_cache_dir_path / safe_name

        if local_path.is_file():
            return local_path.read_text(encoding="utf-8")

        html = urlopen(f"https://en.wikipedia.org{page}").read().decode('utf-8')

        # write to file cache
        local_path.write_text(html, encoding="utf-8")

        return html