import cgi

import io

import urllib.request

import urllib.parse

class OXRAPIRequest:

    DEFAULT_API_ROOT = 'https://openexchangerates.org/api/'

    DEFAULT_RESPONSE_ENCODING = 'utf-8'

    def __init__(self, app_id, api_root=None, *, open_func=urllib.request.urlopen):

        self.api_root = self.DEFAULT_API_ROOT if api_root is None else api_root

        self.app_id = app_id

        self.open_url = open_func

    def _get_response_encoding(self, response, default=None):

        try:

            content_type = response.getheader('Content-Type', 'application/json')

            _, ct_options = cgi.parse_header(content_type)

            encoding = ct_options['charset']

        except (KeyError, ValueError):

            encoding = self.DEFAULT_RESPONSE_ENCODING if default is None else default

        return encoding

    def _raw_query(self, url_tail, params):

        url = '{}?{}'.format(

            urllib.parse.urljoin(self.api_root, url_tail),

            urllib.parse.urlencode(params),

        )

        response = self.open_url(url)

        status_code = response.status

        encoding = self._get_response_encoding(response)

        response_body = io.TextIOWrapper(response, encoding=encoding)

        if 200 <= status_code < 203:

            return response_body

        elif status_code == 404 or status_code == 410:

            exc_class = LoaderNoDataError

        elif status_code >= 500:

            exc_class = LoaderSourceError

        else:

            exc_class = LoaderBadRequestError

        with response_body:

            raise exc_class(url, response_body.read(64 * 1024))

    def historical(self, date, base):

        return self._raw_query(

            'historical/{}.json'.format(date.isoformat()),

            {'app_id': self.app_id, 'base': base},

        )