from __future__ import absolute_import
from contextlib import contextmanager
import zlib
import io
import logging
from socket import timeout as SocketTimeout
from socket import error as SocketError

from ._collections import HTTPHeaderDict
from .exceptions import (
    BodyNotHttplibCompatible, ProtocolError, DecodeError, ReadTimeoutError,
    ResponseNotChunked, IncompleteRead, InvalidHeader
)
from .packages.six import string_types as basestring, binary_type, PY3
from .packages.six.moves import http_client as httplib
from .connection import HTTPException, BaseSSLError
from .util.response import is_fp_closed, is_response_to_head

log = logging.getLogger(__name__)


class DeflateDecoder(object):

    def __init__(self):
        self._first_try = True
        self._data = binary_type()
        self._obj = zlib.decompressobj()

    def __getattr__(self, name):
        return getattr(self._obj, name)

    def decompress(self, data):
        if not data:
            return data

        if not self._first_try:
            return self._obj.decompress(data)

        self._data += data
        try:
            decompressed = self._obj.decompress(data)
            if decompressed:
                self._first_try = False
                self._data = None
            return decompressed
        except zlib.error:
            self._first_try = False
            self._obj = zlib.decompressobj(-zlib.MAX_WBITS)
            try:
                return self.decompress(self._data)
            finally:
                self._data = None


class GzipDecoderState(object):

    FIRST_MEMBER = 0
    OTHER_MEMBERS = 1
    SWALLOW_DATA = 2


class GzipDecoder(object):

    def __init__(self):
        self._obj = zlib.decompressobj(16 + zlib.MAX_WBITS)
        self._state = GzipDecoderState.FIRST_MEMBER

    def __getattr__(self, name):
        return getattr(self._obj, name)

    def decompress(self, data):
        ret = binary_type()
        if self._state == GzipDecoderState.SWALLOW_DATA or not data:
            return ret
        while True:
            try:
                ret += self._obj.decompress(data)
            except zlib.error:
                previous_state = self._state
                # Ignore data after the first error
                self._state = GzipDecoderState.SWALLOW_DATA
                if previous_state == GzipDecoderState.OTHER_MEMBERS:
                    # Allow trailing garbage acceptable in other gzip clients
                    return ret
                raise
            data = self._obj.unused_data
            if not data:
                return ret
            self._state = GzipDecoderState.OTHER_MEMBERS
            self._obj = zlib.decompressobj(16 + zlib.MAX_WBITS)


def _get_decoder(mode):
    if mode == 'gzip':
        return GzipDecoder()

    return DeflateDecoder()


class HTTPResponse(io.IOBase):
    """
    HTTP Response container.

    Backwards-compatible to httplib's HTTPResponse but the response ``body`` is
    loaded and decoded on-demand when the ``data`` property is accessed.  This
    class is also compatible with the Python standard library's :mod:`io`
    module, and can hence be treated as a readable object in the context of that
    framework.

    Extra parameters for behaviour not present in httplib.HTTPResponse:

    :param preload_content:
        If True, the response's body will be preloaded during construction.

    :param decode_content:
        If True, will attempt to decode the body based on the
        'content-encoding' header.

    :param original_response:
        When this HTTPResponse wrapper is generated from an httplib.HTTPResponse
        object, it's convenient to include the original for debug purposes. It's
        otherwise unused.

    :param retries:
        The retries contains the last :class:`~urllib3.util.retry.Retry` that
        was used during the request.

    :param enforce_content_length:
        Enforce content length checking. Body returned by server must match
        value of Content-Length header, if present. Otherwise, raise error.
    """

    CONTENT_DECODERS = ['gzip', 'deflate']
    REDIRECT_STATUSES = [301, 302, 303, 307, 308]

    def __init__(self, body='', headers=None, status=0, version=0, reason=None,
                 strict=0, preload_content=True, decode_content=True,
                 original_response=None, pool=None, connection=None, msg=None,
                 retries=None, enforce_content_length=False,
                 request_method=None, request_url=None):

        if isinstance(headers, HTTPHeaderDict):
            self.headers = headers
        else:
            self.headers = HTTPHeaderDict(headers)
        self.status = status
        self.version = version
        self.reason = reason
        self.strict = strict
        self.decode_content = decode_content
        self.retries = retries
        self.enforce_content_length = enforce_content_length

        self._decoder = None
        self._body = None
        self._fp = None
        self._original_response = original_response
        self._fp_bytes_read = 0
        self.msg = msg
        self._request_url = request_url

        if body and isinstance(body, (basestring, binary_type)):
            self._body = body

        self._pool = pool
        self._connection = connection

        if hasattr(body, 'read'):
            self._fp = body

        # Are we using the chunked-style of transfer encoding?
        self.chunked = False
        self.chunk_left = None
        tr_enc = self.headers.get('transfer-encoding', '').lower()
        # Don't incur the penalty of creating a list and then discarding it
        encodings = (enc.strip() for enc in tr_enc.split(","))
        if "chunked" in encodings:
            self.chunked = True

        # Determine length of response
        self.length_remaining = self._init_length(request_method)

        # If requested, preload the body.
        if preload_content and not self._body:
            self._body = self.read(decode_content=decode_content)

    def get_redirect_location(self):
        """
        Should we redirect and where to?

        :returns: Truthy redirect location string if we got a redirect status
            code and valid location. ``None`` if redirect status and no
            location. ``False`` if not a redirect status code.
        """
        if self.status in self.REDIRECT_STATUSES:
            return self.headers.get('location')

        return False

    def release_conn(self):
        if not self._pool or not self._connection:
            return

        self._pool._put_conn(self._connection)
        self._connection = None

    @property
    def data(self):
        # For backwords-compat with earlier urllib3 0.4 and earlier.
        if self._body:
            return self._body

        if self._fp:
            return self.read(cache_content=True)

    @property
    def connection(self):
        return self._connection

    def isclosed(self):
        return is_fp_closed(self._fp)

    def tell(self):
        """
        Obtain the number of bytes pulled over the wire so far. May differ from
        the amount of content returned by :meth:``HTTPResponse.read`` if bytes
        are encoded on the wire (e.g, compressed).
        """
        return self._fp_bytes_read

    def _init_length(self, request_method):
        """
        Set initial length value for Response content if available.
        """
        length = self.headers.get('content-length')

        if length is not None:
            if self.chunked:
                # This Response will fail with an IncompleteRead if it can't be
                # received as chunked. This method falls back to attempt reading
                # the response before raising an exception.
                log.warning("Received response with both Content-Length and "
                            "Transfer-Encoding set. This is expressly forbidden "
                            "by RFC 7230 sec 3.3.2. Ignoring Content-Length and "
                            "attempting to process response as Transfer-Encoding: "
                            "chunked.")
                return None

            try:
                # RFC 7230 section 3.3.2 specifies multiple content lengths can
                # be sent in a single Content-Length header
                # (e.g. Content-Length: 42, 42). This line ensures the values
                # are all valid ints and that as long as the `set` length is 1,
                # all values are the same. Otherwise, the header is invalid.
                lengths = set([int(val) for val in length.split(',')])
                if len(lengths) > 1:
                    raise InvalidHeader("Content-Length contained multiple "
                                        "unmatching values (%s)" % length)
                length = lengths.pop()
            except ValueError:
                length = None
            else:
                if length < 0:
                    length = None

        # Convert status to int for comparison
        # In some cases, httplib returns a status of "_UNKNOWN"
        try:
            status = int(self.status)
        except ValueError:
            status = 0

        # Check for responses that shouldn't include a body
        if status in (204, 304) or 100 <= status < 200 or request_method == 'HEAD':
            length = 0

        return length

    def _init_decoder(self):
        """
        Set-up the _decoder attribute if necessary.
        """
        # Note: content-encoding value should be case-insensitive, per RFC 7230
        # Section 3.2
        content_encoding = self.headers.get('content-encoding', '').lower()
        if self._decoder is None and content_encoding in self.CONTENT_DECODERS:
            self._decoder = _get_decoder(content_encoding)

    def _decode(self, data, decode_content, flush_decoder):
        """
        Decode the data passed in and potentially flush the decoder.
        """
        try:
            if decode_content and self._decoder:
                data = self._decoder.decompress(data)
        except (IOError, zlib.error) as e:
            content_encoding = self.headers.get('content-encoding', '').lower()
            raise DecodeError(
                "Received response with content-encoding: %s, but "
                "failed to decode it." % content_encoding, e)

        if flush_decoder and decode_content:
            data += self._flush_decoder()

        return data

    def _flush_decoder(self):
        """
        Flushes the decoder. Should only be called if the decoder is actually
        being used.
        """
        if self._decoder:
            buf = self._decoder.decompress(b'')
            return buf + self._decoder.flush()

        return b''

    @contextmanager
    def _error_catcher(self):
        """
        Catch low-level python exceptions, instead re-raising urllib3
        variants, so that low-level exceptions are not leaked in the
        high-level api.

        On exit, release the connection back to the pool.
        """
        clean_exit = False

        try:
            try:
                yield

            except SocketTimeout:
                # FIXME: Ideally we'd like to include the url in the ReadTimeoutError but
                # there is yet no clean way to get at it from this context.
                raise ReadTimeoutError(self._pool, None, 'Read timed out.')

            except BaseSSLError as e:
                # FIXME: Is there a better way to differentiate between SSLErrors?
                if 'read operation timed out' not in str(e):  # Defensive:
                    # This shouldn't happen but just in case we're missing an edge
                    # case, let's avoid swallowing SSL errors.
                    raise

                raise ReadTimeoutError(self._pool, None, 'Read timed out.')