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from __future__ import unicode_literals

import base64
import calendar
import datetime
import re
import sys

from binascii import Error as BinasciiError
from email.utils import formatdate

from django.utils.datastructures import MultiValueDict
from django.utils.encoding import force_str, force_text
from django.utils.functional import allow_lazy
from django.utils import six
from django.utils.six.moves.urllib.parse import (
    quote, quote_plus, unquote, unquote_plus, urlparse,
    urlencode as original_urlencode)

ETAG_MATCH = re.compile(r'(?:W/)?"((?:\\.|[^"])*)"')

MONTHS = 'jan feb mar apr may jun jul aug sep oct nov dec'.split()
__D = r'(?P<day>\d{2})'
__D2 = r'(?P<day>[ \d]\d)'
__M = r'(?P<mon>\w{3})'
__Y = r'(?P<year>\d{4})'
__Y2 = r'(?P<year>\d{2})'
__T = r'(?P<hour>\d{2}):(?P<min>\d{2}):(?P<sec>\d{2})'
RFC1123_DATE = re.compile(r'^\w{3}, %s %s %s %s GMT$' % (__D, __M, __Y, __T))
RFC850_DATE = re.compile(r'^\w{6,9}, %s-%s-%s %s GMT$' % (__D, __M, __Y2, __T))
ASCTIME_DATE = re.compile(r'^\w{3} %s %s %s %s$' % (__M, __D2, __T, __Y))


def urlquote(url, safe='/'):
    """
A version of Python's urllib.quote() function that can operate on unicode
strings. The url is first UTF-8 encoded before quoting. The returned string
can safely be used as part of an argument to a subsequent iri_to_uri() call
without double-quoting occurring.
"""
    return force_text(quote(force_str(url), force_str(safe)))
urlquote = allow_lazy(urlquote, six.text_type)


def urlquote_plus(url, safe=''):
    """
A version of Python's urllib.quote_plus() function that can operate on
unicode strings. The url is first UTF-8 encoded before quoting. The
returned string can safely be used as part of an argument to a subsequent
iri_to_uri() call without double-quoting occurring.
"""
    return force_text(quote_plus(force_str(url), force_str(safe)))
urlquote_plus = allow_lazy(urlquote_plus, six.text_type)


def urlunquote(quoted_url):
    """
A wrapper for Python's urllib.unquote() function that can operate on
the result of django.utils.http.urlquote().
"""
    return force_text(unquote(force_str(quoted_url)))
urlunquote = allow_lazy(urlunquote, six.text_type)


def urlunquote_plus(quoted_url):
    """
A wrapper for Python's urllib.unquote_plus() function that can operate on
the result of django.utils.http.urlquote_plus().
"""
    return force_text(unquote_plus(force_str(quoted_url)))
urlunquote_plus = allow_lazy(urlunquote_plus, six.text_type)


def urlencode(query, doseq=0):
    """
A version of Python's urllib.urlencode() function that can operate on
unicode strings. The parameters are first cast to UTF-8 encoded strings and
then encoded as per normal.
"""
    if isinstance(query, MultiValueDict):
        query = query.lists()
    elif hasattr(query, 'items'):
        query = query.items()
    return original_urlencode(
        [(force_str(k),
         [force_str(i) for i in v] if isinstance(v, (list, tuple)) else force_str(v))
            for k, v in query],
        doseq)


def cookie_date(epoch_seconds=None):
    """
Formats the time to ensure compatibility with Netscape's cookie standard.

Accepts a floating point number expressed in seconds since the epoch, in
UTC - such as that outputted by time.time(). If set to None, defaults to
the current time.

Outputs a string in the format 'Wdy, DD-Mon-YYYY HH:MM:SS GMT'.
"""
    rfcdate = formatdate(epoch_seconds)
    return '%s-%s-%s GMT' % (rfcdate[:7], rfcdate[8:11], rfcdate[12:25])


def http_date(epoch_seconds=None):
    """
Formats the time to match the RFC1123 date format as specified by HTTP
RFC2616 section 3.3.1.

Accepts a floating point number expressed in seconds since the epoch, in
UTC - such as that outputted by time.time(). If set to None, defaults to
the current time.

Outputs a string in the format 'Wdy, DD Mon YYYY HH:MM:SS GMT'.
"""
    return formatdate(epoch_seconds, usegmt=True)


def parse_http_date(date):
    """
Parses a date format as specified by HTTP RFC2616 section 3.3.1.

The three formats allowed by the RFC are accepted, even if only the first
one is still in widespread use.

Returns an integer expressed in seconds since the epoch, in UTC.
"""
    # emails.Util.parsedate does the job for RFC1123 dates; unfortunately
    # RFC2616 makes it mandatory to support RFC850 dates too. So we roll
    # our own RFC-compliant parsing.
    for regex in RFC1123_DATE, RFC850_DATE, ASCTIME_DATE:
        m = regex.match(date)
        if m is not None:
            break
    else:
        raise ValueError("%r is not in a valid HTTP date format" % date)
    try:
        year = int(m.group('year'))
        if year < 100:
            if year < 70:
                year += 2000
            else:
                year += 1900
        month = MONTHS.index(m.group('mon').lower()) + 1
        day = int(m.group('day'))
        hour = int(m.group('hour'))
        min = int(m.group('min'))
        sec = int(m.group('sec'))
        result = datetime.datetime(year, month, day, hour, min, sec)
        return calendar.timegm(result.utctimetuple())
    except Exception:
        six.reraise(ValueError, ValueError("%r is not a valid date" % date), sys.exc_info()[2])


def parse_http_date_safe(date):
    """
Same as parse_http_date, but returns None if the input is invalid.
"""
    try:
        return parse_http_date(date)
    except Exception:
        pass


# Base 36 functions: useful for generating compact URLs

def base36_to_int(s):
    """
Converts a base 36 string to an ``int``. Raises ``ValueError` if the
input won't fit into an int.
"""
    # To prevent overconsumption of server resources, reject any
    # base36 string that is long than 13 base36 digits (13 digits
    # is sufficient to base36-encode any 64-bit integer)
    if len(s) > 13:
        raise ValueError("Base36 input too large")
    value = int(s, 36)
    # ... then do a final check that the value will fit into an int to avoid
    # returning a long (#15067). The long type was removed in Python 3.
    if six.PY2 and value > sys.maxint:
        raise ValueError("Base36 input too large")
    return value


def int_to_base36(i):
    """
Converts an integer to a base36 string
"""
    digits = "0123456789abcdefghijklmnopqrstuvwxyz"
    factor = 0
    if i < 0:
        raise ValueError("Negative base36 conversion input.")
    if six.PY2:
        if not isinstance(i, six.integer_types):
            raise TypeError("Non-integer base36 conversion input.")
        if i > sys.maxint:
            raise ValueError("Base36 conversion input too large.")
    # Find starting factor
    while True:
        factor += 1
        if i < 36 ** factor:
            factor -= 1
            break
    base36 = []
    # Construct base36 representation
    while factor >= 0:
        j = 36 ** factor
        base36.append(digits[i // j])
        i = i % j
        factor -= 1
    return ''.join(base36)


def urlsafe_base64_encode(s):
    """
Encodes a bytestring in base64 for use in URLs, stripping any trailing
equal signs.
"""
    return base64.urlsafe_b64encode(s).rstrip(b'\n=')


def urlsafe_base64_decode(s):
    """
Decodes a base64 encoded string, adding back any trailing equal signs that
might have been stripped.
"""
    s = s.encode('utf-8') # base64encode should only return ASCII.
    try:
        return base64.urlsafe_b64decode(s.ljust(len(s) + len(s) % 4, b'='))
    except (LookupError, BinasciiError) as e:
        raise ValueError(e)


def parse_etags(etag_str):
    """
Parses a string with one or several etags passed in If-None-Match and
If-Match headers by the rules in RFC 2616. Returns a list of etags
without surrounding double quotes (") and unescaped from \<CHAR>.
"""
    etags = ETAG_MATCH.findall(etag_str)
    if not etags:
        # etag_str has wrong format, treat it as an opaque string then
        return [etag_str]
    etags = [e.encode('ascii').decode('unicode_escape') for e in etags]
    return etags


def quote_etag(etag):
    """
Wraps a string in double quotes escaping contents as necessary.
"""
    return '"%s"' % etag.replace('\\', '\\\\').replace('"', '\\"')


def same_origin(url1, url2):
    """
Checks if two URLs are 'same-origin'
"""
    p1, p2 = urlparse(url1), urlparse(url2)
    try:
        return (p1.scheme, p1.hostname, p1.port) == (p2.scheme, p2.hostname, p2.port)
    except ValueError:
        return False


def is_safe_url(url, host=None):
    """
Return ``True`` if the url is a safe redirection (i.e. it doesn't point to
a different host and uses a safe scheme).

Always returns ``False`` on an empty url.
"""
    if not url:
        return False
    url_info = urlparse(url)
    return ((not url_info.netloc or url_info.netloc == host) and
            (not url_info.scheme or url_info.scheme in ['http', 'https']))
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