# Τεκμηρίωση του Django - 1.10.7

# Πηγαίος κώδικας για το django.http.request

    from __future__ import unicode_literals

    import copy
    import re
    import sys
    from io import BytesIO
    from itertools import chain

    from django.conf import settings
    from django.core import signing
    from django.core.exceptions import (
        DisallowedHost, ImproperlyConfigured, RequestDataTooBig,
    )
    from django.core.files import uploadhandler
    from django.http.multipartparser import MultiPartParser, MultiPartParserError
    from django.utils import six
    from django.utils.datastructures import ImmutableList, MultiValueDict
    from django.utils.encoding import (
        escape_uri_path, force_bytes, force_str, force_text, iri_to_uri,
    )
    from django.utils.http import is_same_domain, limited_parse_qsl
    from django.utils.six.moves.urllib.parse import (
        quote, urlencode, urljoin, urlsplit,
    )

    RAISE_ERROR = object()
    host_validation_re = re.compile(r"^([a-z0-9.-]+|\[[a-f0-9]*:[a-f0-9:]+\])(:\d+)?$")

    class UnreadablePostError(IOError):
        pass

    class RawPostDataException(Exception):
        """
        You cannot access raw_post_data from a request that has
        multipart/* POST data if it has been accessed via POST,
        FILES, etc..
        """
        pass

    class HttpRequest(object):
        """A basic HTTP request."""

        # The encoding used in GET/POST dicts. None means use default setting.
        _encoding = None
        _upload_handlers = []

        def __init__(self):
            # WARNING: The `WSGIRequest` subclass doesn't call `super`.
            # Any variable assignment made here should also happen in
            # `WSGIRequest.__init__()`.

            self.GET = QueryDict(mutable=True)
            self.POST = QueryDict(mutable=True)
            self.COOKIES = {}
            self.META = {}
            self.FILES = MultiValueDict()

            self.path = ''
            self.path_info = ''
            self.method = None
            self.resolver_match = None
            self._post_parse_error = False
            self.content_type = None
            self.content_params = None

        def __repr__(self):
            if self.method is None or not self.get_full_path():
                return force_str('<%s>' % self.__class__.__name__)
            return force_str(
                '<%s: %s %r>' % (self.__class__.__name__, self.method, force_str(self.get_full_path()))
            )

        def _get_raw_host(self):
            """
            Return the HTTP host using the environment or request headers. Skip
            allowed hosts protection, so may return an insecure host.
            """
            # We try three options, in order of decreasing preference.
            if settings.USE_X_FORWARDED_HOST and (
                    'HTTP_X_FORWARDED_HOST' in self.META):
                host = self.META['HTTP_X_FORWARDED_HOST']
            elif 'HTTP_HOST' in self.META:
                host = self.META['HTTP_HOST']
            else:
                # Reconstruct the host using the algorithm from PEP 333.
                host = self.META['SERVER_NAME']
                server_port = self.get_port()
                if server_port != ('443' if self.is_secure() else '80'):
                    host = '%s:%s' % (host, server_port)
            return host

        def get_host(self):
            """Return the HTTP host using the environment or request headers."""
            host = self._get_raw_host()

            # Allow variants of localhost if ALLOWED_HOSTS is empty and DEBUG=True.
            allowed_hosts = settings.ALLOWED_HOSTS
            if settings.DEBUG and not allowed_hosts:
                allowed_hosts = ['localhost', '127.0.0.1', '[::1]']

            domain, port = split_domain_port(host)
            if domain and validate_host(domain, allowed_hosts):
                return host
            else:
                msg = "Invalid HTTP_HOST header: %r." % host
                if domain:
                    msg += " You may need to add %r to ALLOWED_HOSTS." % domain
                else:
                    msg += " The domain name provided is not valid according to RFC 1034/1035."
                raise DisallowedHost(msg)

        def get_port(self):
            """Return the port number for the request as a string."""
            if settings.USE_X_FORWARDED_PORT and 'HTTP_X_FORWARDED_PORT' in self.META:
                port = self.META['HTTP_X_FORWARDED_PORT']
            else:
                port = self.META['SERVER_PORT']
            return str(port)

        def get_full_path(self, force_append_slash=False):
            # RFC 3986 requires query string arguments to be in the ASCII range.
            # Rather than crash if this doesn't happen, we encode defensively.
            return '%s%s%s' % (
                escape_uri_path(self.path),
                '/' if force_append_slash and not self.path.endswith('/') else '',
                ('?' + iri_to_uri(self.META.get('QUERY_STRING', ''))) if self.META.get('QUERY_STRING', '') else ''
            )

        def get_signed_cookie(self, key, default=RAISE_ERROR, salt='', max_age=None):
            """
            Attempts to return a signed cookie. If the signature fails or the
            cookie has expired, raises an exception... unless you provide the
            default argument in which case that value will be returned instead.
            """
            try:
                cookie_value = self.COOKIES[key]
            except KeyError:
                if default is not RAISE_ERROR:
                    return default
                else:
                    raise
            try:
                value = signing.get_cookie_signer(salt=key + salt).unsign(
                    cookie_value, max_age=max_age)
            except signing.BadSignature:
                if default is not RAISE_ERROR:
                    return default
                else:
                    raise
            return value

        def get_raw_uri(self):
            """
            Return an absolute URI from variables available in this request. Skip
            allowed hosts protection, so may return insecure URI.
            """
            return '{scheme}://{host}{path}'.format(
                scheme=self.scheme,
                host=self._get_raw_host(),
                path=self.get_full_path(),
            )

        def build_absolute_uri(self, location=None):
            """
            Builds an absolute URI from the location and the variables available in
            this request. If no ``location`` is specified, the absolute URI is
            built on ``request.get_full_path()``. Anyway, if the location is
            absolute, it is simply converted to an RFC 3987 compliant URI and
            returned and if location is relative or is scheme-relative (i.e.,
            ``//example.com/``), it is urljoined to a base URL constructed from the
            request variables.
            """
            if location is None:
                # Make it an absolute url (but schemeless and domainless) for the
                # edge case that the path starts with '//'.
                location = '//%s' % self.get_full_path()
            bits = urlsplit(location)
            if not (bits.scheme and bits.netloc):
                current_uri = '{scheme}://{host}{path}'.format(scheme=self.scheme,
                                                               host=self.get_host(),
                                                               path=self.path)
                # Join the constructed URL with the provided location, which will
                # allow the provided ``location`` to apply query strings to the
                # base path as well as override the host, if it begins with //
                location = urljoin(current_uri, location)
            return iri_to_uri(location)

        def _get_scheme(self):
            """
            Hook for subclasses like WSGIRequest to implement. Returns 'http' by
            default.
            """
            return 'http'

        @property
        def scheme(self):
            if settings.SECURE_PROXY_SSL_HEADER:
                try:
                    header, value = settings.SECURE_PROXY_SSL_HEADER
                except ValueError:
                    raise ImproperlyConfigured(
                        'The SECURE_PROXY_SSL_HEADER setting must be a tuple containing two values.'
                    )
                if self.META.get(header) == value:
                    return 'https'
            return self._get_scheme()

        def is_secure(self):
            return self.scheme == 'https'

        def is_ajax(self):
            return self.META.get('HTTP_X_REQUESTED_WITH') == 'XMLHttpRequest'

        @property
        def encoding(self):
            return self._encoding

        @encoding.setter
        def encoding(self, val):
            """
            Sets the encoding used for GET/POST accesses. If the GET or POST
            dictionary has already been created, it is removed and recreated on the
            next access (so that it is decoded correctly).
            """
            self._encoding = val
            if hasattr(self, '_get'):
                del self._get
            if hasattr(self, '_post'):
                del self._post

        def _initialize_handlers(self):
            self._upload_handlers = [uploadhandler.load_handler(handler, self)
                                     for handler in settings.FILE_UPLOAD_HANDLERS]

        @property
        def upload_handlers(self):
            if not self._upload_handlers:
                # If there are no upload handlers defined, initialize them from settings.
                self._initialize_handlers()
            return self._upload_handlers

        @upload_handlers.setter
        def upload_handlers(self, upload_handlers):
            if hasattr(self, '_files'):
                raise AttributeError("You cannot set the upload handlers after the upload has been processed.")
            self._upload_handlers = upload_handlers

        def parse_file_upload(self, META, post_data):
            """Returns a tuple of (POST QueryDict, FILES MultiValueDict)."""
            self.upload_handlers = ImmutableList(
                self.upload_handlers,
                warning="You cannot alter upload handlers after the upload has been processed."
            )
            parser = MultiPartParser(META, post_data, self.upload_handlers, self.encoding)
            return parser.parse()

        @property
        def body(self):
            if not hasattr(self, '_body'):
                if self._read_started:
                    raise RawPostDataException("You cannot access body after reading from request's data stream")

                # Limit the maximum request data size that will be handled in-memory.
                if (settings.DATA_UPLOAD_MAX_MEMORY_SIZE is not None and
                        int(self.META.get('CONTENT_LENGTH') or 0) > settings.DATA_UPLOAD_MAX_MEMORY_SIZE):
                    raise RequestDataTooBig('Request body exceeded settings.DATA_UPLOAD_MAX_MEMORY_SIZE.')

                try:
                    self._body = self.read()
                except IOError as e:
                    six.reraise(UnreadablePostError, UnreadablePostError(*e.args), sys.exc_info()[2])
                self._stream = BytesIO(self._body)
            return self._body

        def _mark_post_parse_error(self):
            self._post = QueryDict()
            self._files = MultiValueDict()
            self._post_parse_error = True

        def _load_post_and_files(self):
            """Populate self._post and self._files if the content-type is a form type"""
            if self.method != 'POST':
                self._post, self._files = QueryDict(encoding=self._encoding), MultiValueDict()
                return
            if self._read_started and not hasattr(self, '_body'):
                self._mark_post_parse_error()
                return

            if self.content_type == 'multipart/form-data':
                if hasattr(self, '_body'):
                    # Use already read data
                    data = BytesIO(self._body)
                else:
                    data = self
                try:
                    self._post, self._files = self.parse_file_upload(self.META, data)
                except MultiPartParserError:
                    # An error occurred while parsing POST data. Since when
                    # formatting the error the request handler might access
                    # self.POST, set self._post and self._file to prevent
                    # attempts to parse POST data again.
                    # Mark that an error occurred. This allows self.__repr__ to
                    # be explicit about it instead of simply representing an
                    # empty POST
                    self._mark_post_parse_error()
                    raise
            elif self.content_type == 'application/x-www-form-urlencoded':
                self._post, self._files = QueryDict(self.body, encoding=self._encoding), MultiValueDict()
            else:
                self._post, self._files = QueryDict(encoding=self._encoding), MultiValueDict()

        def close(self):
            if hasattr(self, '_files'):
                for f in chain.from_iterable(l[1] for l in self._files.lists()):
                    f.close()

        # File-like and iterator interface.
        #
        # Expects self._stream to be set to an appropriate source of bytes by
        # a corresponding request subclass (e.g. WSGIRequest).
        # Also when request data has already been read by request.POST or
        # request.body, self._stream points to a BytesIO instance
        # containing that data.

        def read(self, *args, **kwargs):
            self._read_started = True
            try:
                return self._stream.read(*args, **kwargs)
            except IOError as e:
                six.reraise(UnreadablePostError, UnreadablePostError(*e.args), sys.exc_info()[2])

        def readline(self, *args, **kwargs):
            self._read_started = True
            try:
                return self._stream.readline(*args, **kwargs)
            except IOError as e:
                six.reraise(UnreadablePostError, UnreadablePostError(*e.args), sys.exc_info()[2])

        def xreadlines(self):
            while True:
                buf = self.readline()
                if not buf:
                    break
                yield buf

        __iter__ = xreadlines

        def readlines(self):
            return list(iter(self))

    class QueryDict(MultiValueDict):
        """
        A specialized MultiValueDict which represents a query string.

        A QueryDict can be used to represent GET or POST data. It subclasses
        MultiValueDict since keys in such data can be repeated, for instance
        in the data from a form with a <select multiple> field.

        By default QueryDicts are immutable, though the copy() method
        will always return a mutable copy.

        Both keys and values set on this class are converted from the given encoding
        (DEFAULT_CHARSET by default) to unicode.
        """

        # These are both reset in __init__, but is specified here at the class
        # level so that unpickling will have valid values
        _mutable = True
        _encoding = None

        def __init__(self, query_string=None, mutable=False, encoding=None):
            super(QueryDict, self).__init__()
            if not encoding:
                encoding = settings.DEFAULT_CHARSET
            self.encoding = encoding
            query_string = query_string or ''
            parse_qsl_kwargs = {
                'keep_blank_values': True,
                'fields_limit': settings.DATA_UPLOAD_MAX_NUMBER_FIELDS,
                'encoding': encoding,
            }
            if six.PY3:
                if isinstance(query_string, bytes):
                    # query_string normally contains URL-encoded data, a subset of ASCII.
                    try:
                        query_string = query_string.decode(encoding)
                    except UnicodeDecodeError:
                        # ... but some user agents are misbehaving :-(
                        query_string = query_string.decode('iso-8859-1')
                for key, value in limited_parse_qsl(query_string, **parse_qsl_kwargs):
                    self.appendlist(key, value)
            else:
                for key, value in limited_parse_qsl(query_string, **parse_qsl_kwargs):
                    try:
                        value = value.decode(encoding)
                    except UnicodeDecodeError:
                        value = value.decode('iso-8859-1')
                    self.appendlist(force_text(key, encoding, errors='replace'),
                                    value)
            self._mutable = mutable

        @property
        def encoding(self):
            if self._encoding is None:
                self._encoding = settings.DEFAULT_CHARSET
            return self._encoding

        @encoding.setter
        def encoding(self, value):
            self._encoding = value

        def _assert_mutable(self):
            if not self._mutable:
                raise AttributeError("This QueryDict instance is immutable")

        def __setitem__(self, key, value):
            self._assert_mutable()
            key = bytes_to_text(key, self.encoding)
            value = bytes_to_text(value, self.encoding)
            super(QueryDict, self).__setitem__(key, value)

        def __delitem__(self, key):
            self._assert_mutable()
            super(QueryDict, self).__delitem__(key)

        def __copy__(self):
            result = self.__class__('', mutable=True, encoding=self.encoding)
            for key, value in six.iterlists(self):
                result.setlist(key, value)
            return result

        def __deepcopy__(self, memo):
            result = self.__class__('', mutable=True, encoding=self.encoding)
            memo[id(self)] = result
            for key, value in six.iterlists(self):
                result.setlist(copy.deepcopy(key, memo), copy.deepcopy(value, memo))
            return result

        def setlist(self, key, list_):
            self._assert_mutable()
            key = bytes_to_text(key, self.encoding)
            list_ = [bytes_to_text(elt, self.encoding) for elt in list_]
            super(QueryDict, self).setlist(key, list_)

        def setlistdefault(self, key, default_list=None):
            self._assert_mutable()
            return super(QueryDict, self).setlistdefault(key, default_list)

        def appendlist(self, key, value):
            self._assert_mutable()
            key = bytes_to_text(key, self.encoding)
            value = bytes_to_text(value, self.encoding)
            super(QueryDict, self).appendlist(key, value)

        def pop(self, key, *args):
            self._assert_mutable()
            return super(QueryDict, self).pop(key, *args)

        def popitem(self):
            self._assert_mutable()
            return super(QueryDict, self).popitem()

        def clear(self):
            self._assert_mutable()
            super(QueryDict, self).clear()

        def setdefault(self, key, default=None):
            self._assert_mutable()
            key = bytes_to_text(key, self.encoding)
            default = bytes_to_text(default, self.encoding)
            return super(QueryDict, self).setdefault(key, default)

        def copy(self):
            """Returns a mutable copy of this object."""
            return self.__deepcopy__({})

        def urlencode(self, safe=None):
            """
            Returns an encoded string of all query string arguments.

            :arg safe: Used to specify characters which do not require quoting, for
                example::

                    >>> q = QueryDict(mutable=True)
                    >>> q['next'] = '/a&b/'
                    >>> q.urlencode()
                    'next=%2Fa%26b%2F'
                    >>> q.urlencode(safe='/')
                    'next=/a%26b/'
            """
            output = []
            if safe:
                safe = force_bytes(safe, self.encoding)

                def encode(k, v):
                    return '%s=%s' % ((quote(k, safe), quote(v, safe)))
            else:
                def encode(k, v):
                    return urlencode({k: v})
            for k, list_ in self.lists():
                k = force_bytes(k, self.encoding)
                output.extend(encode(k, force_bytes(v, self.encoding))
                              for v in list_)
            return '&'.join(output)

    # It's neither necessary nor appropriate to use
    # django.utils.encoding.smart_text for parsing URLs and form inputs. Thus,
    # this slightly more restricted function, used by QueryDict.
    def bytes_to_text(s, encoding):
        """
        Converts basestring objects to unicode, using the given encoding. Illegally
        encoded input characters are replaced with Unicode "unknown" codepoint
        (\ufffd).

        Returns any non-basestring objects without change.
        """
        if isinstance(s, bytes):
            return six.text_type(s, encoding, 'replace')
        else:
            return s

    def split_domain_port(host):
        """
        Return a (domain, port) tuple from a given host.

        Returned domain is lower-cased. If the host is invalid, the domain will be
        empty.
        """
        host = host.lower()

        if not host_validation_re.match(host):
            return '', ''

        if host[-1] == ']':
            # It's an IPv6 address without a port.
            return host, ''
        bits = host.rsplit(':', 1)
        if len(bits) == 2:
            return tuple(bits)
        return bits[0], ''

    def validate_host(host, allowed_hosts):
        """
        Validate the given host for this site.

        Check that the host looks valid and matches a host or host pattern in the
        given list of ``allowed_hosts``. Any pattern beginning with a period
        matches a domain and all its subdomains (e.g. ``.example.com`` matches
        ``example.com`` and any subdomain), ``*`` matches anything, and anything
        else must match exactly.

        Note: This function assumes that the given host is lower-cased and has
        already had the port, if any, stripped off.

        Return ``True`` for a valid host, ``False`` otherwise.
        """
        host = host[:-1] if host.endswith('.') else host

        for pattern in allowed_hosts:
            if pattern == '*' or is_same_domain(host, pattern):
                return True

        return False