import copy
import re
from io import BytesIO
from itertools import chain
from urllib.parse import quote, urlencode, urljoin, urlsplit

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.datastructures import ImmutableList, MultiValueDict
from django.utils.encoding import escape_uri_path, force_bytes, iri_to_uri
from django.utils.http import is_same_domain, limited_parse_qsl

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:
    """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 '<%s>' % self.__class__.__name__
        return '<%s: %s %r>' % (self.__class__.__name__, self.method, 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):
        """
        Attempt to return a signed cookie. If the signature fails or the
        cookie has expired, raise an exception, unless the `default` argument
        is provided,  in which case return that value.
        """
        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):
        """
        Build an absolute URI from the location and the variables available in
        this request. If no ``location`` is specified, bulid the absolute URI
        using request.get_full_path(). If the location is absolute, convert it
        to an RFC 3987 compliant URI and return it. If location is relative or
        is scheme-relative (i.e., ``//example.com/``), urljoin() it 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. Return '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):
        """
        Set the encoding used for GET/POST accesses. If the GET or POST
        dictionary has already been created, remove and recreate it 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):
        """Return 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:
                raise UnreadablePostError(*e.args) from e
            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:
            raise UnreadablePostError(*e.args) from e

    def readline(self, *args, **kwargs):
        self._read_started = True
        try:
            return self._stream.readline(*args, **kwargs)
        except IOError as e:
            raise UnreadablePostError(*e.args) from e

    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 str.
    """

    # 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().__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 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)
        self._mutable = mutable

    @classmethod
    def fromkeys(cls, iterable, value='', mutable=False, encoding=None):
        """
        Return a new QueryDict with keys (may be repeated) from an iterable and
        values from value.
        """
        q = cls('', mutable=True, encoding=encoding)
        for key in iterable:
            q.appendlist(key, value)
        if not mutable:
            q._mutable = False
        return q

    @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().__setitem__(key, value)

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

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

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

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

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

    def clear(self):
        self._assert_mutable()
        super().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().setdefault(key, default)

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

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

        `safe` specifies characters which don't 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.force_text for parsing URLs and form inputs. Thus,
# this slightly more restricted function, used by QueryDict.
def bytes_to_text(s, encoding):
    """
    Convert bytes objects to strings, using the given encoding. Illegally
    encoded input characters are replaced with Unicode "unknown" codepoint
    (\ufffd).

    Return any non-bytes objects without change.
    """
    if isinstance(s, bytes):
        return str(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)
    domain, port = bits if len(bits) == 2 else (bits[0], '')
    # Remove a trailing dot (if present) from the domain.
    domain = domain[:-1] if domain.endswith('.') else domain
    return domain, port


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

    return False
