import socket
try:
    from select import poll, POLLIN
except ImportError:  # `poll` doesn't exist on OSX and other platforms
    poll = False
    try:
        from select import select
    except ImportError:  # `select` doesn't exist on AppEngine.
        select = False


def is_connection_dropped(conn):  # Platform-specific
    """
    Returns True if the connection is dropped and should be closed.

    :param conn:
        :class:`httplib.HTTPConnection` object.

    Note: For platforms like AppEngine, this will always return ``False`` to
    let the platform handle connection recycling transparently for us.
    """
    sock = getattr(conn, 'sock', False)
    if sock is False:  # Platform-specific: AppEngine
        return False
    if sock is None:  # Connection already closed (such as by httplib).
        return True

    if not poll:
        if not select:  # Platform-specific: AppEngine
            return False

        try:
            return select([sock], [], [], 0.0)[0]
        except socket.error:
            return True

    # This version is better on platforms that support it.
    p = poll()
    p.register(sock, POLLIN)
    for (fno, ev) in p.poll(0.0):
        if fno == sock.fileno():
            # Either data is buffered (bad), or the connection is dropped.
            return True


# This function is copied from socket.py in the Python 2.7 standard
# library test suite. Added to its signature is only `socket_options`.
def create_connection(address, timeout=socket._GLOBAL_DEFAULT_TIMEOUT,
                      source_address=None, socket_options=None):
    """Connect to *address* and return the socket object.

    Convenience function.  Connect to *address* (a 2-tuple ``(host,
    port)``) and return the socket object.  Passing the optional
    *timeout* parameter will set the timeout on the socket instance
    before attempting to connect.  If no *timeout* is supplied, the
    global default timeout setting returned by :func:`getdefaulttimeout`
    is used.  If *source_address* is set it must be a tuple of (host, port)
    for the socket to bind as a source address before making the connection.
    An host of '' or port 0 tells the OS to use the default.
    """

    host, port = address
    if host.startswith('['):
        host = host.strip('[]')
    err = None
    for res in socket.getaddrinfo(host, port, 0, socket.SOCK_STREAM):
        af, socktype, proto, canonname, sa = res
        sock = None
        try:
            sock = socket.socket(af, socktype, proto)

            # If provided, set socket level options before connecting.
            # This is the only addition urllib3 makes to this function.
            _set_socket_options(sock, socket_options)

            if timeout is not socket._GLOBAL_DEFAULT_TIMEOUT:
                sock.settimeout(timeout)
            if source_address:
                sock.bind(source_address)
            sock.connect(sa)
            return sock

        except socket.error as e:
            err = e
            if sock is not None:
                sock.close()
                sock = None

    if err is not None:
        raise err

    raise socket.error("getaddrinfo returns an empty list")


def _set_socket_options(sock, options):
    if options is None:
        return

    for opt in options:
        sock.setsockopt(*opt)
