# -*- coding: utf-8 -*-
"""
 werkzeug.urls
 ~~~~~~~~~~~~~

 ``werkzeug.urls`` used to provide several wrapper functions for Python 2
 urlparse, whose main purpose were to work around the behavior of the Py2
 stdlib and its lack of unicode support. While this was already a somewhat
 inconvenient situation, it got even more complicated because Python 3's
 ``urllib.parse`` actually does handle unicode properly. In other words,
 this module would wrap two libraries with completely different behavior. So
 now this module contains a 2-and-3-compatible backport of Python 3's
 ``urllib.parse``, which is mostly API-compatible.

 :copyright: 2007 Pallets
 :license: BSD-3-Clause
"""
import codecs
import os
import re
from collections import namedtuple

from ._compat import fix_tuple_repr
from ._compat import implements_to_string
from ._compat import make_literal_wrapper
from ._compat import normalize_string_tuple
from ._compat import PY2
from ._compat import text_type
from ._compat import to_native
from ._compat import to_unicode
from ._compat import try_coerce_native
from ._internal import _decode_idna
from ._internal import _encode_idna

# A regular expression for what a valid schema looks like
_scheme_re = re.compile(r"^[a-zA-Z0-9+-.]+$")

# Characters that are safe in any part of an URL.
_always_safe = frozenset(
 bytearray(
 b"abcdefghijklmnopqrstuvwxyz"
 b"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
 b"0123456789"
 b"-._~"
 )
)

_hexdigits = "0123456789ABCDEFabcdef"
_hextobyte = dict(
 ((a + b).encode(), int(a + b, 16)) for a in _hexdigits for b in _hexdigits
)
_bytetohex = [("%%%02X" % char).encode("ascii") for char in range(256)]


_URLTuple = fix_tuple_repr(
 namedtuple("_URLTuple", ["scheme", "netloc", "path", "query", "fragment"])
)


class BaseURL(_URLTuple):
 """Superclass of :py:class:`URL` and :py:class:`BytesURL`."""

 __slots__ = ()

 def replace(self, **kwargs):
 """Return an URL with the same values, except for those parameters
 given new values by whichever keyword arguments are specified."""
 return self._replace(**kwargs)

 @property
 def host(self):
 """The host part of the URL if available, otherwise `None`. The
 host is either the hostname or the IP address mentioned in the
 URL. It will not contain the port.
 """
 return self._split_host()[0]

 @property
 def ascii_host(self):
 """Works exactly like :attr:`host` but will return a result that
 is restricted to ASCII. If it finds a netloc that is not ASCII
 it will attempt to idna decode it. This is useful for socket
 operations when the URL might include internationalized characters.
 """
 rv = self.host
 if rv is not None and isinstance(rv, text_type):
 try:
 rv = _encode_idna(rv)
 except UnicodeError:
 rv = rv.encode("ascii", "ignore")
 return to_native(rv, "ascii", "ignore")

 @property
 def port(self):
 """The port in the URL as an integer if it was present, `None`
 otherwise. This does not fill in default ports.
 """
 try:
 rv = int(to_native(self._split_host()[1]))
 if 0 <= rv <= 65535:
 return rv
 except (ValueError, TypeError):
 pass

 @property
 def auth(self):
 """The authentication part in the URL if available, `None`
 otherwise.
 """
 return self._split_netloc()[0]

 @property
 def username(self):
 """The username if it was part of the URL, `None` otherwise.
 This undergoes URL decoding and will always be a unicode string.
 """
 rv = self._split_auth()[0]
 if rv is not None:
 return _url_unquote_legacy(rv)

 @property
 def raw_username(self):
 """The username if it was part of the URL, `None` otherwise.
 Unlike :attr:`username` this one is not being decoded.
 """
 return self._split_auth()[0]

 @property
 def password(self):
 """The password if it was part of the URL, `None` otherwise.
 This undergoes URL decoding and will always be a unicode string.
 """
 rv = self._split_auth()[1]
 if rv is not None:
 return _url_unquote_legacy(rv)

 @property
 def raw_password(self):
 """The password if it was part of the URL, `None` otherwise.
 Unlike :attr:`password` this one is not being decoded.
 """
 return self._split_auth()[1]

 def decode_query(self, *args, **kwargs):
 """Decodes the query part of the URL. Ths is a shortcut for
 calling :func:`url_decode` on the query argument. The arguments and
 keyword arguments are forwarded to :func:`url_decode` unchanged.
 """
 return url_decode(self.query, *args, **kwargs)

 def join(self, *args, **kwargs):
 """Joins this URL with another one. This is just a convenience
 function for calling into :meth:`url_join` and then parsing the
 return value again.
 """
 return url_parse(url_join(self, *args, **kwargs))

 def to_url(self):
 """Returns a URL string or bytes depending on the type of the
 information stored. This is just a convenience function
 for calling :meth:`url_unparse` for this URL.
 """
 return url_unparse(self)

 def decode_netloc(self):
 """Decodes the netloc part into a string."""
 rv = _decode_idna(self.host or "")

 if ":" in rv:
 rv = "[%s]" % rv
 port = self.port
 if port is not None:
 rv = "%s:%d" % (rv, port)
 auth = ":".join(
 filter(
 None,
 [
 _url_unquote_legacy(self.raw_username or "", "/:%@"),
 _url_unquote_legacy(self.raw_password or "", "/:%@"),
 ],
 )
 )
 if auth:
 rv = "%s@%s" % (auth, rv)
 return rv

 def to_uri_tuple(self):
 """Returns a :class:`BytesURL` tuple that holds a URI. This will
 encode all the information in the URL properly to ASCII using the
 rules a web browser would follow.

 It's usually more interesting to directly call :meth:`iri_to_uri` which
 will return a string.
 """
 return url_parse(iri_to_uri(self).encode("ascii"))

 def to_iri_tuple(self):
 """Returns a :class:`URL` tuple that holds a IRI. This will try
 to decode as much information as possible in the URL without
 losing information similar to how a web browser does it for the
 URL bar.

 It's usually more interesting to directly call :meth:`uri_to_iri` which
 will return a string.
 """
 return url_parse(uri_to_iri(self))

 def get_file_location(self, pathformat=None):
 """Returns a tuple with the location of the file in the form
 ``(server, location)``. If the netloc is empty in the URL or
 points to localhost, it's represented as ``None``.

 The `pathformat` by default is autodetection but needs to be set
 when working with URLs of a specific system. The supported values
 are ``'windows'`` when working with Windows or DOS paths and
 ``'posix'`` when working with posix paths.

 If the URL does not point to a local file, the server and location
 are both represented as ``None``.

 :param pathformat: The expected format of the path component.
 Currently ``'windows'`` and ``'posix'`` are
 supported. Defaults to ``None`` which is
 autodetect.
 """
 if self.scheme != "file":
 return None, None

 path = url_unquote(self.path)
 host = self.netloc or None

 if pathformat is None:
 if os.name == "nt":
 pathformat = "windows"
 else:
 pathformat = "posix"

 if pathformat == "windows":
 if path[:1] == "/" and path[1:2].isalpha() and path[2:3] in "|:":
 path = path[1:2] + ":" + path[3:]
 windows_share = path[:3] in ("\\" * 3, "/" * 3)
 import ntpath

 path = ntpath.normpath(path)
 # Windows shared drives are represented as ``\\host\\directory``.
 # That results in a URL like ``file://///host/directory``, and a
 # path like ``///host/directory``. We need to special-case this
 # because the path contains the hostname.
 if windows_share and host is None:
 parts = path.lstrip("\\").split("\\", 1)
 if len(parts) == 2:
 host, path = parts
 else:
 host = parts[0]
 path = ""
 elif pathformat == "posix":
 import posixpath

 path = posixpath.normpath(path)
 else:
 raise TypeError("Invalid path format %s" % repr(pathformat))

 if host in ("127.0.0.1", "::1", "localhost"):
 host = None

 return host, path

 def _split_netloc(self):
 if self._at in self.netloc:
 return self.netloc.split(self._at, 1)
 return None, self.netloc

 def _split_auth(self):
 auth = self._split_netloc()[0]
 if not auth:
 return None, None
 if self._colon not in auth:
 return auth, None
 return auth.split(self._colon, 1)

 def _split_host(self):
 rv = self._split_netloc()[1]
 if not rv:
 return None, None

 if not rv.startswith(self._lbracket):
 if self._colon in rv:
 return rv.split(self._colon, 1)
 return rv, None

 idx = rv.find(self._rbracket)
 if idx < 0:
 return rv, None

 host = rv[1:idx]
 rest = rv[idx + 1 :]
 if rest.startswith(self._colon):
 return host, rest[1:]
 return host, None


@implements_to_string
class URL(BaseURL):
 """Represents a parsed URL. This behaves like a regular tuple but
 also has some extra attributes that give further insight into the
 URL.
 """

 __slots__ = ()
 _at = "@"
 _colon = ":"
 _lbracket = "["
 _rbracket = "]"

 def __str__(self):
 return self.to_url()

 def encode_netloc(self):
 """Encodes the netloc part to an ASCII safe URL as bytes."""
 rv = self.ascii_host or ""
 if ":" in rv:
 rv = "[%s]" % rv
 port = self.port
 if port is not None:
 rv = "%s:%d" % (rv, port)
 auth = ":".join(
 filter(
 None,
 [
 url_quote(self.raw_username or "", "utf-8", "strict", "/:%"),
 url_quote(self.raw_password or "", "utf-8", "strict", "/:%"),
 ],
 )
 )
 if auth:
 rv = "%s@%s" % (auth, rv)
 return to_native(rv)

 def encode(self, charset="utf-8", errors="replace"):
 """Encodes the URL to a tuple made out of bytes. The charset is
 only being used for the path, query and fragment.
 """
 return BytesURL(
 self.scheme.encode("ascii"),
 self.encode_netloc(),
 self.path.encode(charset, errors),
 self.query.encode(charset, errors),
 self.fragment.encode(charset, errors),
 )


class BytesURL(BaseURL):
 """Represents a parsed URL in bytes."""

 __slots__ = ()
 _at = b"@"
 _colon = b":"
 _lbracket = b"["
 _rbracket = b"]"

 def __str__(self):
 return self.to_url().decode("utf-8", "replace")

 def encode_netloc(self):
 """Returns the netloc unchanged as bytes."""
 return self.netloc

 def decode(self, charset="utf-8", errors="replace"):
 """Decodes the URL to a tuple made out of strings. The charset is
 only being used for the path, query and fragment.
 """
 return URL(
 self.scheme.decode("ascii"),
 self.decode_netloc(),
 self.path.decode(charset, errors),
 self.query.decode(charset, errors),
 self.fragment.decode(charset, errors),
 )


_unquote_maps = {frozenset(): _hextobyte}


def _unquote_to_bytes(string, unsafe=""):
 if isinstance(string, text_type):
 string = string.encode("utf-8")

 if isinstance(unsafe, text_type):
 unsafe = unsafe.encode("utf-8")

 unsafe = frozenset(bytearray(unsafe))
 groups = iter(string.split(b"%"))
 result = bytearray(next(groups, b""))

 try:
 hex_to_byte = _unquote_maps[unsafe]
 except KeyError:
 hex_to_byte = _unquote_maps[unsafe] = {
 h: b for h, b in _hextobyte.items() if b not in unsafe
 }

 for group in groups:
 code = group[:2]

 if code in hex_to_byte:
 result.append(hex_to_byte[code])
 result.extend(group[2:])
 else:
 result.append(37) # %
 result.extend(group)

 return bytes(result)


def _url_encode_impl(obj, charset, encode_keys, sort, key):
 from .datastructures import iter_multi_items

 iterable = iter_multi_items(obj)
 if sort:
 iterable = sorted(iterable, key=key)
 for key, value in iterable:
 if value is None:
 continue
 if not isinstance(key, bytes):
 key = text_type(key).encode(charset)
 if not isinstance(value, bytes):
 value = text_type(value).encode(charset)
 yield _fast_url_quote_plus(key) + "=" + _fast_url_quote_plus(value)


def _url_unquote_legacy(value, unsafe=""):
 try:
 return url_unquote(value, charset="utf-8", errors="strict", unsafe=unsafe)
 except UnicodeError:
 return url_unquote(value, charset="latin1", unsafe=unsafe)


def url_parse(url, scheme=None, allow_fragments=True):
 """Parses a URL from a string into a :class:`URL` tuple. If the URL
 is lacking a scheme it can be provided as second argument. Otherwise,
 it is ignored. Optionally fragments can be stripped from the URL
 by setting `allow_fragments` to `False`.

 The inverse of this function is :func:`url_unparse`.

 :param url: the URL to parse.
 :param scheme: the default schema to use if the URL is schemaless.
 :param allow_fragments: if set to `False` a fragment will be removed
 from the URL.
 """
 s = make_literal_wrapper(url)
 is_text_based = isinstance(url, text_type)

 if scheme is None:
 scheme = s("")
 netloc = query = fragment = s("")
 i = url.find(s(":"))
 if i > 0 and _scheme_re.match(to_native(url[:i], errors="replace")):
 # make sure "iri" is not actually a port number (in which case
 # "scheme" is really part of the path)
 rest = url[i + 1 :]
 if not rest or any(c not in s("0123456789") for c in rest):
 # not a port number
 scheme, url = url[:i].lower(), rest

 if url[:2] == s("//"):
 delim = len(url)
 for c in s("/?#"):
 wdelim = url.find(c, 2)
 if wdelim >= 0:
 delim = min(delim, wdelim)
 netloc, url = url[2:delim], url[delim:]
 if (s("[") in netloc and s("]") not in netloc) or (
 s("]") in netloc and s("[") not in netloc
 ):
 raise ValueError("Invalid IPv6 URL")

 if allow_fragments and s("#") in url:
 url, fragment = url.split(s("#"), 1)
 if s("?") in url:
 url, query = url.split(s("?"), 1)

 result_type = URL if is_text_based else BytesURL
 return result_type(scheme, netloc, url, query, fragment)


def _make_fast_url_quote(charset="utf-8", errors="strict", safe="/:", unsafe=""):
 """Precompile the translation table for a URL encoding function.

 Unlike :func:`url_quote`, the generated function only takes the
 string to quote.

 :param charset: The charset to encode the result with.
 :param errors: How to handle encoding errors.
 :param safe: An optional sequence of safe characters to never encode.
 :param unsafe: An optional sequence of unsafe characters to always encode.
 """
 if isinstance(safe, text_type):
 safe = safe.encode(charset, errors)

 if isinstance(unsafe, text_type):
 unsafe = unsafe.encode(charset, errors)

 safe = (frozenset(bytearray(safe)) | _always_safe) - frozenset(bytearray(unsafe))
 table = [chr(c) if c in safe else "%%%02X" % c for c in range(256)]

 if not PY2:

 def quote(string):
 return "".join([table[c] for c in string])

 else:

 def quote(string):
 return "".join([table[c] for c in bytearray(string)])

 return quote


_fast_url_quote = _make_fast_url_quote()
_fast_quote_plus = _make_fast_url_quote(safe=" ", unsafe="+")


def _fast_url_quote_plus(string):
 return _fast_quote_plus(string).replace(" ", "+")


def url_quote(string, charset="utf-8", errors="strict", safe="/:", unsafe=""):
 """URL encode a single string with a given encoding.

 :param s: the string to quote.
 :param charset: the charset to be used.
 :param safe: an optional sequence of safe characters.
 :param unsafe: an optional sequence of unsafe characters.

 .. versionadded:: 0.9.2
 The `unsafe` parameter was added.
 """
 if not isinstance(string, (text_type, bytes, bytearray)):
 string = text_type(string)
 if isinstance(string, text_type):
 string = string.encode(charset, errors)
 if isinstance(safe, text_type):
 safe = safe.encode(charset, errors)
 if isinstance(unsafe, text_type):
 unsafe = unsafe.encode(charset, errors)
 safe = (frozenset(bytearray(safe)) | _always_safe) - frozenset(bytearray(unsafe))
 rv = bytearray()
 for char in bytearray(string):
 if char in safe:
 rv.append(char)
 else:
 rv.extend(_bytetohex[char])
 return to_native(bytes(rv))


def url_quote_plus(string, charset="utf-8", errors="strict", safe=""):
 """URL encode a single string with the given encoding and convert
 whitespace to "+".

 :param s: The string to quote.
 :param charset: The charset to be used.
 :param safe: An optional sequence of safe characters.
 """
 return url_quote(string, charset, errors, safe + " ", "+").replace(" ", "+")


def url_unparse(components):
 """The reverse operation to :meth:`url_parse`. This accepts arbitrary
 as well as :class:`URL` tuples and returns a URL as a string.

 :param components: the parsed URL as tuple which should be converted
 into a URL string.
 """
 scheme, netloc, path, query, fragment = normalize_string_tuple(components)
 s = make_literal_wrapper(scheme)
 url = s("")

 # We generally treat file:///x and file:/x the same which is also
 # what browsers seem to do. This also allows us to ignore a schema
 # register for netloc utilization or having to differentiate between
 # empty and missing netloc.
 if netloc or (scheme and path.startswith(s("/"))):
 if path and path[:1] != s("/"):
 path = s("/") + path
 url = s("//") + (netloc or s("")) + path
 elif path:
 url += path
 if scheme:
 url = scheme + s(":") + url
 if query:
 url = url + s("?") + query
 if fragment:
 url = url + s("#") + fragment
 return url


def url_unquote(string, charset="utf-8", errors="replace", unsafe=""):
 """URL decode a single string with a given encoding. If the charset
 is set to `None` no unicode decoding is performed and raw bytes
 are returned.

 :param s: the string to unquote.
 :param charset: the charset of the query string. If set to `None`
 no unicode decoding will take place.
 :param errors: the error handling for the charset decoding.
 """
 rv = _unquote_to_bytes(string, unsafe)
 if charset is not None:
 rv = rv.decode(charset, errors)
 return rv


def url_unquote_plus(s, charset="utf-8", errors="replace"):
 """URL decode a single string with the given `charset` and decode "+" to
 whitespace.

 Per default encoding errors are ignored. If you want a different behavior
 you can set `errors` to ``'replace'`` or ``'strict'``. In strict mode a
 :exc:`HTTPUnicodeError` is raised.

 :param s: The string to unquote.
 :param charset: the charset of the query string. If set to `None`
 no unicode decoding will take place.
 :param errors: The error handling for the `charset` decoding.
 """
 if isinstance(s, text_type):
 s = s.replace(u"+", u" ")
 else:
 s = s.replace(b"+", b" ")
 return url_unquote(s, charset, errors)


def url_fix(s, charset="utf-8"):
 r"""Sometimes you get an URL by a user that just isn't a real URL because
 it contains unsafe characters like ' ' and so on. This function can fix
 some of the problems in a similar way browsers handle data entered by the
 user:

 >>> url_fix(u'http://de.wikipedia.org/wiki/Elf (Begriffskl\xe4rung)')
 'http://de.wikipedia.org/wiki/Elf%20(Begriffskl%C3%A4rung)'

 :param s: the string with the URL to fix.
 :param charset: The target charset for the URL if the url was given as
 unicode string.
 """
 # First step is to switch to unicode processing and to convert
 # backslashes (which are invalid in URLs anyways) to slashes. This is
 # consistent with what Chrome does.
 s = to_unicode(s, charset, "replace").replace("\\", "/")

 # For the specific case that we look like a malformed windows URL
 # we want to fix this up manually:
 if s.startswith("file://") and s[7:8].isalpha() and s[8:10] in (":/", "|/"):
 s = "file:///" + s[7:]

 url = url_parse(s)
 path = url_quote(url.path, charset, safe="/%+$!*'(),")
 qs = url_quote_plus(url.query, charset, safe=":&%=+$!*'(),")
 anchor = url_quote_plus(url.fragment, charset, safe=":&%=+$!*'(),")
 return to_native(url_unparse((url.scheme, url.encode_netloc(), path, qs, anchor)))


# not-unreserved characters remain quoted when unquoting to IRI
_to_iri_unsafe = "".join([chr(c) for c in range(128) if c not in _always_safe])


def _codec_error_url_quote(e):
 """Used in :func:`uri_to_iri` after unquoting to re-quote any
 invalid bytes.
 """
 out = _fast_url_quote(e.object[e.start : e.end])

 if PY2:
 out = out.decode("utf-8")

 return out, e.end


codecs.register_error("werkzeug.url_quote", _codec_error_url_quote)


def uri_to_iri(uri, charset="utf-8", errors="werkzeug.url_quote"):
 """Convert a URI to an IRI. All valid UTF-8 characters are unquoted,
 leaving all reserved and invalid characters quoted. If the URL has
 a domain, it is decoded from Punycode.

 >>> uri_to_iri("http://xn--n3h.net/p%C3%A5th?q=%C3%A8ry%DF")
 'http://\\u2603.net/p\\xe5th?q=\\xe8ry%DF'

 :param uri: The URI to convert.
 :param charset: The encoding to encode unquoted bytes with.
 :param errors: Error handler to use during ``bytes.encode``. By
 default, invalid bytes are left quoted.

 .. versionchanged:: 0.15
 All reserved and invalid characters remain quoted. Previously,
 only some reserved characters were preserved, and invalid bytes
 were replaced instead of left quoted.

 .. versionadded:: 0.6
 """
 if isinstance(uri, tuple):
 uri = url_unparse(uri)

 uri = url_parse(to_unicode(uri, charset))
 path = url_unquote(uri.path, charset, errors, _to_iri_unsafe)
 query = url_unquote(uri.query, charset, errors, _to_iri_unsafe)
 fragment = url_unquote(uri.fragment, charset, errors, _to_iri_unsafe)
 return url_unparse((uri.scheme, uri.decode_netloc(), path, query, fragment))


# reserved characters remain unquoted when quoting to URI
_to_uri_safe = ":/?#[]@!$&'()*+,;=%"


def iri_to_uri(iri, charset="utf-8", errors="strict", safe_conversion=False):
 """Convert an IRI to a URI. All non-ASCII and unsafe characters are
 quoted. If the URL has a domain, it is encoded to Punycode.

 >>> iri_to_uri('http://\\u2603.net/p\\xe5th?q=\\xe8ry%DF')
 'http://xn--n3h.net/p%C3%A5th?q=%C3%A8ry%DF'

 :param iri: The IRI to convert.
 :param charset: The encoding of the IRI.
 :param errors: Error handler to use during ``bytes.encode``.
 :param safe_conversion: Return the URL unchanged if it only contains
 ASCII characters and no whitespace. See the explanation below.

 There is a general problem with IRI conversion with some protocols
 that are in violation of the URI specification. Consider the
 following two IRIs::

 magnet:?xt=uri:whatever
 itms-services://?action=download-manifest

 After parsing, we don't know if the scheme requires the ``//``,
 which is dropped if empty, but conveys different meanings in the
 final URL if it's present or not. In this case, you can use
 ``safe_conversion``, which will return the URL unchanged if it only
 contains ASCII characters and no whitespace. This can result in a
 URI with unquoted characters if it was not already quoted correctly,
 but preserves the URL's semantics. Werkzeug uses this for the
 ``Location`` header for redirects.

 .. versionchanged:: 0.15
 All reserved characters remain unquoted. Previously, only some
 reserved characters were left unquoted.

 .. versionchanged:: 0.9.6
 The ``safe_conversion`` parameter was added.

 .. versionadded:: 0.6
 """
 if isinstance(iri, tuple):
 iri = url_unparse(iri)

 if safe_conversion:
 # If we're not sure if it's safe to convert the URL, and it only
 # contains ASCII characters, return it unconverted.
 try:
 native_iri = to_native(iri)
 ascii_iri = native_iri.encode("ascii")

 # Only return if it doesn't have whitespace. (Why?)
 if len(ascii_iri.split()) == 1:
 return native_iri
 except UnicodeError:
 pass

 iri = url_parse(to_unicode(iri, charset, errors))
 path = url_quote(iri.path, charset, errors, _to_uri_safe)
 query = url_quote(iri.query, charset, errors, _to_uri_safe)
 fragment = url_quote(iri.fragment, charset, errors, _to_uri_safe)
 return to_native(
 url_unparse((iri.scheme, iri.encode_netloc(), path, query, fragment))
 )


def url_decode(
 s,
 charset="utf-8",
 decode_keys=False,
 include_empty=True,
 errors="replace",
 separator="&",
 cls=None,
):
 """
 Parse a querystring and return it as :class:`MultiDict`. There is a
 difference in key decoding on different Python versions. On Python 3
 keys will always be fully decoded whereas on Python 2, keys will
 remain bytestrings if they fit into ASCII. On 2.x keys can be forced
 to be unicode by setting `decode_keys` to `True`.

 If the charset is set to `None` no unicode decoding will happen and
 raw bytes will be returned.

 Per default a missing value for a key will default to an empty key. If
 you don't want that behavior you can set `include_empty` to `False`.

 Per default encoding errors are ignored. If you want a different behavior
 you can set `errors` to ``'replace'`` or ``'strict'``. In strict mode a
 `HTTPUnicodeError` is raised.

 .. versionchanged:: 0.5
 In previous versions ";" and "&" could be used for url decoding.
 This changed in 0.5 where only "&" is supported. If you want to
 use ";" instead a different `separator` can be provided.

 The `cls` parameter was added.

 :param s: a string with the query string to decode.
 :param charset: the charset of the query string. If set to `None`
 no unicode decoding will take place.
 :param decode_keys: Used on Python 2.x to control whether keys should
 be forced to be unicode objects. If set to `True`
 then keys will be unicode in all cases. Otherwise,
 they remain `str` if they fit into ASCII.
 :param include_empty: Set to `False` if you don't want empty values to
 appear in the dict.
 :param errors: the decoding error behavior.
 :param separator: the pair separator to be used, defaults to ``&``
 :param cls: an optional dict class to use. If this is not specified
 or `None` the default :class:`MultiDict` is used.
 """
 if cls is None:
 from .datastructures import MultiDict

 cls = MultiDict
 if isinstance(s, text_type) and not isinstance(separator, text_type):
 separator = separator.decode(charset or "ascii")
 elif isinstance(s, bytes) and not isinstance(separator, bytes):
 separator = separator.encode(charset or "ascii")
 return cls(
 _url_decode_impl(
 s.split(separator), charset, decode_keys, include_empty, errors
 )
 )


def url_decode_stream(
 stream,
 charset="utf-8",
 decode_keys=False,
 include_empty=True,
 errors="replace",
 separator="&",
 cls=None,
 limit=None,
 return_iterator=False,
):
 """Works like :func:`url_decode` but decodes a stream. The behavior
 of stream and limit follows functions like
 :func:`~werkzeug.wsgi.make_line_iter`. The generator of pairs is
 directly fed to the `cls` so you can consume the data while it's
 parsed.

 .. versionadded:: 0.8

 :param stream: a stream with the encoded querystring
 :param charset: the charset of the query string. If set to `None`
 no unicode decoding will take place.
 :param decode_keys: Used on Python 2.x to control whether keys should
 be forced to be unicode objects. If set to `True`,
 keys will be unicode in all cases. Otherwise, they
 remain `str` if they fit into ASCII.
 :param include_empty: Set to `False` if you don't want empty values to
 appear in the dict.
 :param errors: the decoding error behavior.
 :param separator: the pair separator to be used, defaults to ``&``
 :param cls: an optional dict class to use. If this is not specified
 or `None` the default :class:`MultiDict` is used.
 :param limit: the content length of the URL data. Not necessary if
 a limited stream is provided.
 :param return_iterator: if set to `True` the `cls` argument is ignored
 and an iterator over all decoded pairs is
 returned
 """
 from .wsgi import make_chunk_iter

 pair_iter = make_chunk_iter(stream, separator, limit)
 decoder = _url_decode_impl(pair_iter, charset, decode_keys, include_empty, errors)

 if return_iterator:
 return decoder

 if cls is None:
 from .datastructures import MultiDict

 cls = MultiDict

 return cls(decoder)


def _url_decode_impl(pair_iter, charset, decode_keys, include_empty, errors):
 for pair in pair_iter:
 if not pair:
 continue
 s = make_literal_wrapper(pair)
 equal = s("=")
 if equal in pair:
 key, value = pair.split(equal, 1)
 else:
 if not include_empty:
 continue
 key = pair
 value = s("")
 key = url_unquote_plus(key, charset, errors)
 if charset is not None and PY2 and not decode_keys:
 key = try_coerce_native(key)
 yield key, url_unquote_plus(value, charset, errors)


def url_encode(
 obj, charset="utf-8", encode_keys=False, sort=False, key=None, separator=b"&"
):
 """URL encode a dict/`MultiDict`. If a value is `None` it will not appear
 in the result string. Per default only values are encoded into the target
 charset strings. If `encode_keys` is set to ``True`` unicode keys are
 supported too.

 If `sort` is set to `True` the items are sorted by `key` or the default
 sorting algorithm.

 .. versionadded:: 0.5
 `sort`, `key`, and `separator` were added.

 :param obj: the object to encode into a query string.
 :param charset: the charset of the query string.
 :param encode_keys: set to `True` if you have unicode keys. (Ignored on
 Python 3.x)
 :param sort: set to `True` if you want parameters to be sorted by `key`.
 :param separator: the separator to be used for the pairs.
 :param key: an optional function to be used for sorting. For more details
 check out the :func:`sorted` documentation.
 """
 separator = to_native(separator, "ascii")
 return separator.join(_url_encode_impl(obj, charset, encode_keys, sort, key))


def url_encode_stream(
 obj,
 stream=None,
 charset="utf-8",
 encode_keys=False,
 sort=False,
 key=None,
 separator=b"&",
):
 """Like :meth:`url_encode` but writes the results to a stream
 object. If the stream is `None` a generator over all encoded
 pairs is returned.

 .. versionadded:: 0.8

 :param obj: the object to encode into a query string.
 :param stream: a stream to write the encoded object into or `None` if
 an iterator over the encoded pairs should be returned. In
 that case the separator argument is ignored.
 :param charset: the charset of the query string.
 :param encode_keys: set to `True` if you have unicode keys. (Ignored on
 Python 3.x)
 :param sort: set to `True` if you want parameters to be sorted by `key`.
 :param separator: the separator to be used for the pairs.
 :param key: an optional function to be used for sorting. For more details
 check out the :func:`sorted` documentation.
 """
 separator = to_native(separator, "ascii")
 gen = _url_encode_impl(obj, charset, encode_keys, sort, key)
 if stream is None:
 return gen
 for idx, chunk in enumerate(gen):
 if idx:
 stream.write(separator)
 stream.write(chunk)


def url_join(base, url, allow_fragments=True):
 """Join a base URL and a possibly relative URL to form an absolute
 interpretation of the latter.

 :param base: the base URL for the join operation.
 :param url: the URL to join.
 :param allow_fragments: indicates whether fragments should be allowed.
 """
 if isinstance(base, tuple):
 base = url_unparse(base)
 if isinstance(url, tuple):
 url = url_unparse(url)

 base, url = normalize_string_tuple((base, url))
 s = make_literal_wrapper(base)

 if not base:
 return url
 if not url:
 return base

 bscheme, bnetloc, bpath, bquery, bfragment = url_parse(
 base, allow_fragments=allow_fragments
 )
 scheme, netloc, path, query, fragment = url_parse(url, bscheme, allow_fragments)
 if scheme != bscheme:
 return url
 if netloc:
 return url_unparse((scheme, netloc, path, query, fragment))
 netloc = bnetloc

 if path[:1] == s("/"):
 segments = path.split(s("/"))
 elif not path:
 segments = bpath.split(s("/"))
 if not query:
 query = bquery
 else:
 segments = bpath.split(s("/"))[:-1] + path.split(s("/"))

 # If the rightmost part is "./" we want to keep the slash but
 # remove the dot.
 if segments[-1] == s("."):
 segments[-1] = s("")

 # Resolve ".." and "."
 segments = [segment for segment in segments if segment != s(".")]
 while 1:
 i = 1
 n = len(segments) - 1
 while i < n:
 if segments[i] == s("..") and segments[i - 1] not in (s(""), s("..")):
 del segments[i - 1 : i + 1]
 break
 i += 1
 else:
 break

 # Remove trailing ".." if the URL is absolute
 unwanted_marker = [s(""), s("..")]
 while segments[:2] == unwanted_marker:
 del segments[1]

 path = s("/").join(segments)
 return url_unparse((scheme, netloc, path, query, fragment))


class Href(object):
 """Implements a callable that constructs URLs with the given base. The
 function can be called with any number of positional and keyword
 arguments which than are used to assemble the URL. Works with URLs
 and posix paths.

 Positional arguments are appended as individual segments to
 the path of the URL:

 >>> href = Href('/foo')
 >>> href('bar', 23)
 '/foo/bar/23'
 >>> href('foo', bar=23)
 '/foo/foo?bar=23'

 If any of the arguments (positional or keyword) evaluates to `None` it
 will be skipped. If no keyword arguments are given the last argument
 can be a :class:`dict` or :class:`MultiDict` (or any other dict subclass),
 otherwise the keyword arguments are used for the query parameters, cutting
 off the first trailing underscore of the parameter name:

 >>> href(is_=42)
 '/foo?is=42'
 >>> href({'foo': 'bar'})
 '/foo?foo=bar'

 Combining of both methods is not allowed:

 >>> href({'foo': 'bar'}, bar=42)
 Traceback (most recent call last):
 ...
 TypeError: keyword arguments and query-dicts can't be combined

 Accessing attributes on the href object creates a new href object with
 the attribute name as prefix:

 >>> bar_href = href.bar
 >>> bar_href("blub")
 '/foo/bar/blub'

 If `sort` is set to `True` the items are sorted by `key` or the default
 sorting algorithm:

 >>> href = Href("/", sort=True)
 >>> href(a=1, b=2, c=3)
 '/?a=1&b=2&c=3'

 .. versionadded:: 0.5
 `sort` and `key` were added.
 """

 def __init__(self, base="./", charset="utf-8", sort=False, key=None):
 if not base:
 base = "./"
 self.base = base
 self.charset = charset
 self.sort = sort
 self.key = key

 def __getattr__(self, name):
 if name[:2] == "__":
 raise AttributeError(name)
 base = self.base
 if base[-1:] != "/":
 base += "/"
 return Href(url_join(base, name), self.charset, self.sort, self.key)

 def __call__(self, *path, **query):
 if path and isinstance(path[-1], dict):
 if query:
 raise TypeError("keyword arguments and query-dicts can't be combined")
 query, path = path[-1], path[:-1]
 elif query:
 query = dict(
 [(k.endswith("_") and k[:-1] or k, v) for k, v in query.items()]
 )
 path = "/".join(
 [
 to_unicode(url_quote(x, self.charset), "ascii")
 for x in path
 if x is not None
 ]
 ).lstrip("/")
 rv = self.base
 if path:
 if not rv.endswith("/"):
 rv += "/"
 rv = url_join(rv, "./" + path)
 if query:
 rv += "?" + to_unicode(
 url_encode(query, self.charset, sort=self.sort, key=self.key), "ascii"
 )
 return to_native(rv)