from __future__ import absolute_import
import datetime
import logging
import os
import sys
import socket
from socket import error as SocketError, timeout as SocketTimeout
import warnings
import six
from six.moves.http_client import HTTPConnection as _HTTPConnection
from six.moves.http_client import HTTPException  # noqa: F401

try:  # Compiled with SSL?
    import ssl
    BaseSSLError = ssl.SSLError
except (ImportError, AttributeError):  # Platform-specific: No SSL.
    ssl = None

    class BaseSSLError(BaseException):
        pass


try:  # Python 3:
    # Not a no-op, we're adding this to the namespace so it can be imported.
    ConnectionError = ConnectionError
except NameError:  # Python 2:
    class ConnectionError(Exception):
        pass


from .exceptions import (
    NewConnectionError,
    ConnectTimeoutError,
    SubjectAltNameWarning,
    SystemTimeWarning,
)
from .packages.ssl_match_hostname import match_hostname, CertificateError

from .util.ssl_ import (
    resolve_cert_reqs,
    resolve_ssl_version,
    assert_fingerprint,
    create_urllib3_context,
    ssl_wrap_socket
)


from .util import connection

from ._collections import HTTPHeaderDict

log = logging.getLogger(__name__)

port_by_scheme = {
    'http': 80,
    'https': 443,
}

# When updating RECENT_DATE, move it to
# within two years of the current date, and no
# earlier than 6 months ago.
RECENT_DATE = datetime.date(2016, 1, 1)


class DummyConnection(object):
    """Used to detect a failed ConnectionCls import."""
    pass


class HTTPConnection(_HTTPConnection, object):
    """
    Based on httplib.HTTPConnection but provides an extra constructor
    backwards-compatibility layer between older and newer Pythons.

    Additional keyword parameters are used to configure attributes of the connection.
    Accepted parameters include:

      - ``strict``: See the documentation on :class:`urllib3.connectionpool.HTTPConnectionPool`
      - ``source_address``: Set the source address for the current connection.

        .. note:: This is ignored for Python 2.6. It is only applied for 2.7 and 3.x

      - ``socket_options``: Set specific options on the underlying socket. If not specified, then
        defaults are loaded from ``HTTPConnection.default_socket_options`` which includes disabling
        Nagle's algorithm (sets TCP_NODELAY to 1) unless the connection is behind a proxy.

        For example, if you wish to enable TCP Keep Alive in addition to the defaults,
        you might pass::

            HTTPConnection.default_socket_options + [
                (socket.SOL_SOCKET, socket.SO_KEEPALIVE, 1),
            ]

        Or you may want to disable the defaults by passing an empty list (e.g., ``[]``).
    """

    default_port = port_by_scheme['http']

    #: Disable Nagle's algorithm by default.
    #: ``[(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)]``
    default_socket_options = [(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)]

    #: Whether this connection verifies the host's certificate.
    is_verified = False

    def __init__(self, *args, **kw):
        if six.PY3:  # Python 3
            kw.pop('strict', None)

        # Pre-set source_address in case we have an older Python like 2.6.
        self.source_address = kw.get('source_address')

        if sys.version_info < (2, 7):  # Python 2.6
            # _HTTPConnection on Python 2.6 will balk at this keyword arg, but
            # not newer versions. We can still use it when creating a
            # connection though, so we pop it *after* we have saved it as
            # self.source_address.
            kw.pop('source_address', None)

        #: The socket options provided by the user. If no options are
        #: provided, we use the default options.
        self.socket_options = kw.pop('socket_options', self.default_socket_options)

        # Superclass also sets self.source_address in Python 2.7+.
        _HTTPConnection.__init__(self, *args, **kw)

    def _new_conn(self):
        """ Establish a socket connection and set nodelay settings on it.

        :return: New socket connection.
        """
        extra_kw = {}
        if self.source_address:
            extra_kw['source_address'] = self.source_address

        if self.socket_options:
            extra_kw['socket_options'] = self.socket_options

        try:
            conn = connection.create_connection(
                (self.host, self.port), self.timeout, **extra_kw)

        except SocketTimeout:
            raise ConnectTimeoutError(
                self, "Connection to %s timed out. (connect timeout=%s)" %
                (self.host, self.timeout))

        except SocketError as e:
            raise NewConnectionError(
                self, "Failed to establish a new connection: %s" % e)

        return conn

    def _prepare_conn(self, conn):
        self.sock = conn
        # the _tunnel_host attribute was added in python 2.6.3 (via
        # http://hg.python.org/cpython/rev/0f57b30a152f) so pythons 2.6(0-2) do
        # not have them.
        if getattr(self, '_tunnel_host', None):
            # TODO: Fix tunnel so it doesn't depend on self.sock state.
            self._tunnel()
            # Mark this connection as not reusable
            self.auto_open = 0

    def connect(self):
        conn = self._new_conn()
        self._prepare_conn(conn)

    def request_chunked(self, method, url, body=None, headers=None):
        """
        Alternative to the common request method, which sends the
        body with chunked encoding and not as one block
        """
        headers = HTTPHeaderDict(headers if headers is not None else {})
        skip_accept_encoding = 'accept-encoding' in headers
        skip_host = 'host' in headers
        self.putrequest(
            method,
            url,
            skip_accept_encoding=skip_accept_encoding,
            skip_host=skip_host
        )
        for header, value in headers.items():
            self.putheader(header, value)
        if 'transfer-encoding' not in headers:
            self.putheader('Transfer-Encoding', 'chunked')
        self.endheaders()

        if body is not None:
            stringish_types = six.string_types + (six.binary_type,)
            if isinstance(body, stringish_types):
                body = (body,)
            for chunk in body:
                if not chunk:
                    continue
                if not isinstance(chunk, six.binary_type):
                    chunk = chunk.encode('utf8')
                len_str = hex(len(chunk))[2:]
                self.send(len_str.encode('utf-8'))
                self.send(b'\r\n')
                self.send(chunk)
                self.send(b'\r\n')

        # After the if clause, to always have a closed body
        self.send(b'0\r\n\r\n')


class HTTPSConnection(HTTPConnection):
    default_port = port_by_scheme['https']

    ssl_version = None

    def __init__(self, host, port=None, key_file=None, cert_file=None,
                 strict=None, timeout=socket._GLOBAL_DEFAULT_TIMEOUT,
                 ssl_context=None, **kw):

        HTTPConnection.__init__(self, host, port, strict=strict,
                                timeout=timeout, **kw)

        self.key_file = key_file
        self.cert_file = cert_file
        self.ssl_context = ssl_context

        # Required property for Google AppEngine 1.9.0 which otherwise causes
        # HTTPS requests to go out as HTTP. (See Issue #356)
        self._protocol = 'https'

    def connect(self):
        conn = self._new_conn()
        self._prepare_conn(conn)

        if self.ssl_context is None:
            self.ssl_context = create_urllib3_context(
                ssl_version=resolve_ssl_version(None),
                cert_reqs=resolve_cert_reqs(None),
            )

        self.sock = ssl_wrap_socket(
            sock=conn,
            keyfile=self.key_file,
            certfile=self.cert_file,
            ssl_context=self.ssl_context,
        )


class VerifiedHTTPSConnection(HTTPSConnection):
    """
    Based on httplib.HTTPSConnection but wraps the socket with
    SSL certification.
    """
    cert_reqs = None
    ca_certs = None
    ca_cert_dir = None
    ssl_version = None
    assert_fingerprint = None

    def set_cert(self, key_file=None, cert_file=None,
                 cert_reqs=None, ca_certs=None,
                 assert_hostname=None, assert_fingerprint=None,
                 ca_cert_dir=None):
        """
        This method should only be called once, before the connection is used.
        """
        # If cert_reqs is not provided, we can try to guess. If the user gave
        # us a cert database, we assume they want to use it: otherwise, if
        # they gave us an SSL Context object we should use whatever is set for
        # it.
        if cert_reqs is None:
            if ca_certs or ca_cert_dir:
                cert_reqs = 'CERT_REQUIRED'
            elif self.ssl_context is not None:
                cert_reqs = self.ssl_context.verify_mode

        self.key_file = key_file
        self.cert_file = cert_file
        self.cert_reqs = cert_reqs
        self.assert_hostname = assert_hostname
        self.assert_fingerprint = assert_fingerprint
        self.ca_certs = ca_certs and os.path.expanduser(ca_certs)
        self.ca_cert_dir = ca_cert_dir and os.path.expanduser(ca_cert_dir)

    def connect(self):
        # Add certificate verification
        conn = self._new_conn()

        hostname = self.host
        if getattr(self, '_tunnel_host', None):
            # _tunnel_host was added in Python 2.6.3
            # (See: http://hg.python.org/cpython/rev/0f57b30a152f)

            self.sock = conn
            # Calls self._set_hostport(), so self.host is
            # self._tunnel_host below.
            self._tunnel()
            # Mark this connection as not reusable
            self.auto_open = 0

            # Override the host with the one we're requesting data from.
            hostname = self._tunnel_host

        is_time_off = datetime.date.today() < RECENT_DATE
        if is_time_off:
            warnings.warn((
                'System time is way off (before {0}). This will probably '
                'lead to SSL verification errors').format(RECENT_DATE),
                SystemTimeWarning
            )

        # Wrap socket using verification with the root certs in
        # trusted_root_certs
        if self.ssl_context is None:
            self.ssl_context = create_urllib3_context(
                ssl_version=resolve_ssl_version(self.ssl_version),
                cert_reqs=resolve_cert_reqs(self.cert_reqs),
            )

        context = self.ssl_context
        context.verify_mode = resolve_cert_reqs(self.cert_reqs)
        self.sock = ssl_wrap_socket(
            sock=conn,
            keyfile=self.key_file,
            certfile=self.cert_file,
            ca_certs=self.ca_certs,
            ca_cert_dir=self.ca_cert_dir,
            server_hostname=hostname,
            ssl_context=context)

        if self.assert_fingerprint:
            assert_fingerprint(self.sock.getpeercert(binary_form=True),
                               self.assert_fingerprint)
        elif context.verify_mode != ssl.CERT_NONE \
                and not getattr(context, 'check_hostname', False) \
                and self.assert_hostname is not False:
            # While urllib3 attempts to always turn off hostname matching from
            # the TLS library, this cannot always be done. So we check whether
            # the TLS Library still thinks it's matching hostnames.
            cert = self.sock.getpeercert()
            if not cert.get('subjectAltName', ()):
                warnings.warn((
                    'Certificate for {0} has no `subjectAltName`, falling back to check for a '
                    '`commonName` for now. This feature is being removed by major browsers and '
                    'deprecated by RFC 2818. (See https://github.com/shazow/urllib3/issues/497 '
                    'for details.)'.format(hostname)),
                    SubjectAltNameWarning
                )
            _match_hostname(cert, self.assert_hostname or hostname)

        self.is_verified = (
            context.verify_mode == ssl.CERT_REQUIRED or
            self.assert_fingerprint is not None
        )


def _match_hostname(cert, asserted_hostname):
    try:
        match_hostname(cert, asserted_hostname)
    except CertificateError as e:
        log.error(
            'Certificate did not match expected hostname: %s. '
            'Certificate: %s', asserted_hostname, cert
        )
        # Add cert to exception and reraise so client code can inspect
        # the cert when catching the exception, if they want to
        e._peer_cert = cert
        raise


if ssl:
    # Make a copy for testing.
    UnverifiedHTTPSConnection = HTTPSConnection
    HTTPSConnection = VerifiedHTTPSConnection
else:
    HTTPSConnection = DummyConnection
