from __future__ import absolute_import

import binascii
import re
import time
import weakref

from kafka.errors import KafkaTimeoutError
from kafka.vendor import six


if six.PY3:
    MAX_INT = 2 ** 31
    TO_SIGNED = 2 ** 32

    def crc32(data):
        crc = binascii.crc32(data)
        # py2 and py3 behave a little differently
        # CRC is encoded as a signed int in kafka protocol
        # so we'll convert the py3 unsigned result to signed
        if crc >= MAX_INT:
            crc -= TO_SIGNED
        return crc
else:
    from binascii import crc32 # noqa: F401


def timeout_ms_fn(timeout_ms, error_message):
    elapsed = 0.0 # noqa: F841
    begin = time.time()
    def inner_timeout_ms(fallback=None):
        if timeout_ms is None:
            return fallback
        elapsed = (time.time() - begin) * 1000
        if elapsed >= timeout_ms:
            if error_message is not None:
                raise KafkaTimeoutError(error_message)
            else:
                return 0
        ret = max(0, timeout_ms - elapsed)
        if fallback is not None:
            return min(ret, fallback)
        return ret
    return inner_timeout_ms


# Taken from: https://github.com/apache/kafka/blob/39eb31feaeebfb184d98cc5d94da9148c2319d81/clients/src/main/java/org/apache/kafka/common/internals/Topic.java#L29
TOPIC_MAX_LENGTH = 249
TOPIC_LEGAL_CHARS = re.compile('^[a-zA-Z0-9._-]+$')

def ensure_valid_topic_name(topic):
    """ Ensures that the topic name is valid according to the kafka source. """

    # See Kafka Source:
    # https://github.com/apache/kafka/blob/39eb31feaeebfb184d98cc5d94da9148c2319d81/clients/src/main/java/org/apache/kafka/common/internals/Topic.java
    if topic is None:
        raise TypeError('All topics must not be None')
    if not isinstance(topic, six.string_types):
        raise TypeError('All topics must be strings')
    if len(topic) == 0:
        raise ValueError('All topics must be non-empty strings')
    if topic == '.' or topic == '..':
        raise ValueError('Topic name cannot be "." or ".."')
    if len(topic) > TOPIC_MAX_LENGTH:
        raise ValueError('Topic name is illegal, it can\'t be longer than {0} characters, topic: "{1}"'.format(TOPIC_MAX_LENGTH, topic))
    if not TOPIC_LEGAL_CHARS.match(topic):
        raise ValueError('Topic name "{0}" is illegal, it contains a character other than ASCII alphanumerics, ".", "_" and "-"'.format(topic))


class WeakMethod(object):
    """
    Callable that weakly references a method and the object it is bound to. It
    is based on https://stackoverflow.com/a/24287465.

    Arguments:

        object_dot_method: A bound instance method (i.e. 'object.method').
    """
    def __init__(self, object_dot_method):
        try:
            self.target = weakref.ref(object_dot_method.__self__)
        except AttributeError:
            self.target = weakref.ref(object_dot_method.im_self)
        self._target_id = id(self.target())
        try:
            self.method = weakref.ref(object_dot_method.__func__)
        except AttributeError:
            self.method = weakref.ref(object_dot_method.im_func)
        self._method_id = id(self.method())

    def __call__(self, *args, **kwargs):
        """
        Calls the method on target with args and kwargs.
        """
        return self.method()(self.target(), *args, **kwargs)

    def __hash__(self):
        return hash(self.target) ^ hash(self.method)

    def __eq__(self, other):
        if not isinstance(other, WeakMethod):
            return False
        return self._target_id == other._target_id and self._method_id == other._method_id


class Dict(dict):
    """Utility class to support passing weakrefs to dicts

    See: https://docs.python.org/2/library/weakref.html
    """
    pass