# Source code for scrapy.http.response.text

    """
    This module implements the TextResponse class which adds encoding handling and
    discovering (through HTTP headers) to base Response class.

    See documentation in docs/topics/request-response.rst
    """

    import json
    import warnings
    from contextlib import suppress
    from typing import Generator
    from urllib.parse import urljoin

    import parsel
    from w3lib.encoding import (html_body_declared_encoding, html_to_unicode,
                                http_content_type_encoding, resolve_encoding)
    from w3lib.html import strip_html5_whitespace

    from scrapy.exceptions import ScrapyDeprecationWarning
    from scrapy.http import Request
    from scrapy.http.response import Response
    from scrapy.utils.python import memoizemethod_noargs, to_unicode
    from scrapy.utils.response import get_base_url

    _NONE = object()

    class TextResponse(Response):

        _DEFAULT_ENCODING = 'ascii'
        _cached_decoded_json = _NONE

        def __init__(self, *args, **kwargs):
            self._encoding = kwargs.pop('encoding', None)
            self._cached_benc = None
            self._cached_ubody = None
            self._cached_selector = None
            super().__init__(*args, **kwargs)

        def _set_url(self, url):
            if isinstance(url, str):
                self._url = to_unicode(url, self.encoding)
            else:
                super()._set_url(url)

        def _set_body(self, body):
            self._body = b''  # used by encoding detection
            if isinstance(body, str):
                if self._encoding is None:
                    raise TypeError('Cannot convert unicode body - '
                                    f'{type(self).__name__} has no encoding')
                self._body = body.encode(self._encoding)
            else:
                super()._set_body(body)

        def replace(self, *args, **kwargs):
            kwargs.setdefault('encoding', self.encoding)
            return Response.replace(self, *args, **kwargs)

        @property
        def encoding(self):
            return self._declared_encoding() or self._body_inferred_encoding()

        def _declared_encoding(self):
            return (
                self._encoding
                or self._headers_encoding()
                or self._body_declared_encoding()
            )

        def body_as_unicode(self):
            """Return body as unicode"""
            warnings.warn('Response.body_as_unicode() is deprecated, '
                          'please use Response.text instead.',
                          ScrapyDeprecationWarning, stacklevel=2)
            return self.text

        def json(self):
            """
            .. versionadded:: 2.2

            Deserialize a JSON document to a Python object.
            """
            if self._cached_decoded_json is _NONE:
                self._cached_decoded_json = json.loads(self.text)
            return self._cached_decoded_json

        @property
        def text(self):
            """ Body as unicode """
            # access self.encoding before _cached_ubody to make sure
            # _body_inferred_encoding is called
            benc = self.encoding
            if self._cached_ubody is None:
                charset = f'charset={benc}'
                self._cached_ubody = html_to_unicode(charset, self.body)[1]
            return self._cached_ubody

        def urljoin(self, url):
            """Join this Response's url with a possible relative url to form an
            absolute interpretation of the latter."""
            return urljoin(get_base_url(self), url)

        @memoizemethod_noargs
        def _headers_encoding(self):
            content_type = self.headers.get(b'Content-Type', b'')
            return http_content_type_encoding(to_unicode(content_type))

        def _body_inferred_encoding(self):
            if self._cached_benc is None:
                content_type = to_unicode(self.headers.get(b'Content-Type', b''))
                benc, ubody = html_to_unicode(content_type, self.body,
                                              auto_detect_fun=self._auto_detect_fun,
                                              default_encoding=self._DEFAULT_ENCODING)
                self._cached_benc = benc
                self._cached_ubody = ubody
            return self._cached_benc

        def _auto_detect_fun(self, text):
            for enc in (self._DEFAULT_ENCODING, 'utf-8', 'cp1252'):
                try:
                    text.decode(enc)
                except UnicodeError:
                    continue
                return resolve_encoding(enc)

        @memoizemethod_noargs
        def _body_declared_encoding(self):
            return html_body_declared_encoding(self.body)

        @property
        def selector(self):
            from scrapy.selector import Selector
            if self._cached_selector is None:
                self._cached_selector = Selector(self)
            return self._cached_selector

        def xpath(self, query, **kwargs):
            return self.selector.xpath(query, **kwargs)

        def css(self, query):
            return self.selector.css(query)

        def follow(self, url, callback=None, method='GET', headers=None, body=None,
                   cookies=None, meta=None, encoding=None, priority=0,
                   dont_filter=False, errback=None, cb_kwargs=None, flags=None):
            # type: (...) -> Request
            """
            Return a :class:`~.Request` instance to follow a link ``url``.
            It accepts the same arguments as ``Request.__init__`` method,
            but ``url`` can be not only an absolute URL, but also

            * a relative URL
            * a :class:`~scrapy.link.Link` object, e.g. the result of
              :ref:`topics-link-extractors`
            * a :class:`~scrapy.selector.Selector` object for a ``<link>`` or ``<a>`` element, e.g.
              ``response.css('a.my_link')[0]``
            * an attribute :class:`~scrapy.selector.Selector` (not SelectorList), e.g.
              ``response.css('a::attr(href)')[0]`` or
              ``response.xpath('//img/@src')[0]``

            See :ref:`response-follow-example` for usage examples.
            """
            if isinstance(url, parsel.Selector):
                url = _url_from_selector(url)
            elif isinstance(url, parsel.SelectorList):
                raise ValueError("SelectorList is not supported")
            encoding = self.encoding if encoding is None else encoding
            return super().follow(
                url=url,
                callback=callback,
                method=method,
                headers=headers,
                body=body,
                cookies=cookies,
                meta=meta,
                encoding=encoding,
                priority=priority,
                dont_filter=dont_filter,
                errback=errback,
                cb_kwargs=cb_kwargs,
                flags=flags,
            )

        def follow_all(self, urls=None, callback=None, method='GET', headers=None, body=None,
                       cookies=None, meta=None, encoding=None, priority=0,
                       dont_filter=False, errback=None, cb_kwargs=None, flags=None,
                       css=None, xpath=None):
            # type: (...) -> Generator[Request, None, None]
            """
            A generator that produces :class:`~.Request` instances to follow all
            links in ``urls``. It accepts the same arguments as the :class:`~.Request`'s
            ``__init__`` method, except that each ``urls`` element does not need to be
            an absolute URL, it can be any of the following:

            * a relative URL
            * a :class:`~scrapy.link.Link` object, e.g. the result of
              :ref:`topics-link-extractors`
            * a :class:`~scrapy.selector.Selector` object for a ``<link>`` or ``<a>`` element, e.g.
              ``response.css('a.my_link')[0]``
            * an attribute :class:`~scrapy.selector.Selector` (not SelectorList), e.g.
              ``response.css('a::attr(href)')[0]`` or
              ``response.xpath('//img/@src')[0]``

            In addition, ``css`` and ``xpath`` arguments are accepted to perform the link extraction
            within the ``follow_all`` method (only one of ``urls``, ``css`` and ``xpath`` is accepted).

            Note that when passing a ``SelectorList`` as argument for the ``urls`` parameter or
            using the ``css`` or ``xpath`` parameters, this method will not produce requests for
            selectors from which links cannot be obtained (for instance, anchor tags without an
            ``href`` attribute)
            """
            arguments = [x for x in (urls, css, xpath) if x is not None]
            if len(arguments) != 1:
                raise ValueError(
                    "Please supply exactly one of the following arguments: urls, css, xpath"
                )
            if not urls:
                if css:
                    urls = self.css(css)
                if xpath:
                    urls = self.xpath(xpath)
            if isinstance(urls, parsel.SelectorList):
                selectors = urls
                urls = []
                for sel in selectors:
                    with suppress(_InvalidSelector):
                        urls.append(_url_from_selector(sel))
            return super().follow_all(
                urls=urls,
                callback=callback,
                method=method,
                headers=headers,
                body=body,
                cookies=cookies,
                meta=meta,
                encoding=encoding,
                priority=priority,
                dont_filter=dont_filter,
                errback=errback,
                cb_kwargs=cb_kwargs,
                flags=flags,
            )

    class _InvalidSelector(ValueError):
        """
        Raised when a URL cannot be obtained from a Selector
        """

    def _url_from_selector(sel):
        # type: (parsel.Selector) -> str
        if isinstance(sel.root, str):
            # e.g. ::attr(href) result
            return strip_html5_whitespace(sel.root)
        if not hasattr(sel.root, 'tag'):
            raise _InvalidSelector(f"Unsupported selector: {sel}")
        if sel.root.tag not in ('a', 'link'):
            raise _InvalidSelector("Only <a> and <link> elements are supported; "
                                   f"got <{sel.root.tag}>")
        href = sel.root.get('href')
        if href is None:
            raise _InvalidSelector(f"<{sel.root.tag}> element has no href attribute: {sel}")
        return strip_html5_whitespace(href)