from __future__ import unicode_literals

import codecs
import logging
import sys
from io import BytesIO
from threading import Lock

from django import http
from django.core import signals
from django.core.handlers import base
from django.core.urlresolvers import set_script_prefix
from django.utils import datastructures
from django.utils.encoding import force_str, force_text, iri_to_uri

logger = logging.getLogger('django.request')


# See http://www.iana.org/assignments/http-status-codes
STATUS_CODE_TEXT = {
    100: 'CONTINUE',
    101: 'SWITCHING PROTOCOLS',
    102: 'PROCESSING',
    200: 'OK',
    201: 'CREATED',
    202: 'ACCEPTED',
    203: 'NON-AUTHORITATIVE INFORMATION',
    204: 'NO CONTENT',
    205: 'RESET CONTENT',
    206: 'PARTIAL CONTENT',
    207: 'MULTI-STATUS',
    208: 'ALREADY REPORTED',
    226: 'IM USED',
    300: 'MULTIPLE CHOICES',
    301: 'MOVED PERMANENTLY',
    302: 'FOUND',
    303: 'SEE OTHER',
    304: 'NOT MODIFIED',
    305: 'USE PROXY',
    306: 'RESERVED',
    307: 'TEMPORARY REDIRECT',
    400: 'BAD REQUEST',
    401: 'UNAUTHORIZED',
    402: 'PAYMENT REQUIRED',
    403: 'FORBIDDEN',
    404: 'NOT FOUND',
    405: 'METHOD NOT ALLOWED',
    406: 'NOT ACCEPTABLE',
    407: 'PROXY AUTHENTICATION REQUIRED',
    408: 'REQUEST TIMEOUT',
    409: 'CONFLICT',
    410: 'GONE',
    411: 'LENGTH REQUIRED',
    412: 'PRECONDITION FAILED',
    413: 'REQUEST ENTITY TOO LARGE',
    414: 'REQUEST-URI TOO LONG',
    415: 'UNSUPPORTED MEDIA TYPE',
    416: 'REQUESTED RANGE NOT SATISFIABLE',
    417: 'EXPECTATION FAILED',
    422: 'UNPROCESSABLE ENTITY',
    423: 'LOCKED',
    424: 'FAILED DEPENDENCY',
    426: 'UPGRADE REQUIRED',
    500: 'INTERNAL SERVER ERROR',
    501: 'NOT IMPLEMENTED',
    502: 'BAD GATEWAY',
    503: 'SERVICE UNAVAILABLE',
    504: 'GATEWAY TIMEOUT',
    505: 'HTTP VERSION NOT SUPPORTED',
    506: 'VARIANT ALSO NEGOTIATES',
    507: 'INSUFFICIENT STORAGE',
    508: 'LOOP DETECTED',
    510: 'NOT EXTENDED',
}

class LimitedStream(object):
    '''
    LimitedStream wraps another stream in order to not allow reading from it
    past specified amount of bytes.
    '''
    def __init__(self, stream, limit, buf_size=64 * 1024 * 1024):
        self.stream = stream
        self.remaining = limit
        self.buffer = b''
        self.buf_size = buf_size

    def _read_limited(self, size=None):
        if size is None or size > self.remaining:
            size = self.remaining
        if size == 0:
            return b''
        result = self.stream.read(size)
        self.remaining -= len(result)
        return result

    def read(self, size=None):
        if size is None:
            result = self.buffer + self._read_limited()
            self.buffer = b''
        elif size < len(self.buffer):
            result = self.buffer[:size]
            self.buffer = self.buffer[size:]
        else: # size >= len(self.buffer)
            result = self.buffer + self._read_limited(size - len(self.buffer))
            self.buffer = b''
        return result

    def readline(self, size=None):
        while b'\n' not in self.buffer and \
              (size is None or len(self.buffer) < size):
            if size:
                # since size is not None here, len(self.buffer) < size
                chunk = self._read_limited(size - len(self.buffer))
            else:
                chunk = self._read_limited()
            if not chunk:
                break
            self.buffer += chunk
        sio = BytesIO(self.buffer)
        if size:
            line = sio.readline(size)
        else:
            line = sio.readline()
        self.buffer = sio.read()
        return line


class WSGIRequest(http.HttpRequest):
    def __init__(self, environ):
        script_name = base.get_script_name(environ)
        path_info = base.get_path_info(environ)
        if not path_info:
            # Sometimes PATH_INFO exists, but is empty (e.g. accessing
            # the SCRIPT_NAME URL without a trailing slash). We really need to
            # operate as if they'd requested '/'. Not amazingly nice to force
            # the path like this, but should be harmless.
            path_info = '/'
        self.environ = environ
        self.path_info = path_info
        self.path = '%s%s' % (script_name, path_info)
        self.META = environ
        self.META['PATH_INFO'] = path_info
        self.META['SCRIPT_NAME'] = script_name
        self.method = environ['REQUEST_METHOD'].upper()
        _, content_params = self._parse_content_type(self.META.get('CONTENT_TYPE', ''))
        if 'charset' in content_params:
            try:
                codecs.lookup(content_params['charset'])
            except LookupError:
                pass
            else:
                self.encoding = content_params['charset']
        self._post_parse_error = False
        try:
            content_length = int(self.environ.get('CONTENT_LENGTH'))
        except (ValueError, TypeError):
            content_length = 0
        self._stream = LimitedStream(self.environ['wsgi.input'], content_length)
        self._read_started = False

    def _is_secure(self):
        return 'wsgi.url_scheme' in self.environ and self.environ['wsgi.url_scheme'] == 'https'

    def _parse_content_type(self, ctype):
        """
        Media Types parsing according to RFC 2616, section 3.7.

        Returns the data type and parameters. For example:
        Input: "text/plain; charset=iso-8859-1"
        Output: ('text/plain', {'charset': 'iso-8859-1'})
        """
        content_type, _, params = ctype.partition(';')
        content_params = {}
        for parameter in params.split(';'):
            k, _, v = parameter.strip().partition('=')
            content_params[k] = v
        return content_type, content_params

    def _get_request(self):
        if not hasattr(self, '_request'):
            self._request = datastructures.MergeDict(self.POST, self.GET)
        return self._request

    def _get_get(self):
        if not hasattr(self, '_get'):
            # The WSGI spec says 'QUERY_STRING' may be absent.
            self._get = http.QueryDict(self.environ.get('QUERY_STRING', ''), encoding=self._encoding)
        return self._get

    def _set_get(self, get):
        self._get = get

    def _get_post(self):
        if not hasattr(self, '_post'):
            self._load_post_and_files()
        return self._post

    def _set_post(self, post):
        self._post = post

    def _get_cookies(self):
        if not hasattr(self, '_cookies'):
            self._cookies = http.parse_cookie(self.environ.get('HTTP_COOKIE', ''))
        return self._cookies

    def _set_cookies(self, cookies):
        self._cookies = cookies

    def _get_files(self):
        if not hasattr(self, '_files'):
            self._load_post_and_files()
        return self._files

    GET = property(_get_get, _set_get)
    POST = property(_get_post, _set_post)
    COOKIES = property(_get_cookies, _set_cookies)
    FILES = property(_get_files)
    REQUEST = property(_get_request)


class WSGIHandler(base.BaseHandler):
    initLock = Lock()
    request_class = WSGIRequest

    def __call__(self, environ, start_response):
        # Set up middleware if needed. We couldn't do this earlier, because
        # settings weren't available.
        if self._request_middleware is None:
            with self.initLock:
                try:
                    # Check that middleware is still uninitialised.
                    if self._request_middleware is None:
                        self.load_middleware()
                except:
                    # Unload whatever middleware we got
                    self._request_middleware = None
                    raise

        set_script_prefix(base.get_script_name(environ))
        signals.request_started.send(sender=self.__class__)
        try:
            request = self.request_class(environ)
        except UnicodeDecodeError:
            logger.warning('Bad Request (UnicodeDecodeError)',
                exc_info=sys.exc_info(),
                extra={
                    'status_code': 400,
                }
            )
            response = http.HttpResponseBadRequest()
        else:
            response = self.get_response(request)

        response._handler_class = self.__class__

        try:
            status_text = STATUS_CODE_TEXT[response.status_code]
        except KeyError:
            status_text = 'UNKNOWN STATUS CODE'
        status = '%s %s' % (response.status_code, status_text)
        response_headers = [(str(k), str(v)) for k, v in response.items()]
        for c in response.cookies.values():
            response_headers.append((str('Set-Cookie'), str(c.output(header=''))))
        start_response(force_str(status), response_headers)
        return response