from collections import defaultdict
import struct
from threading import Thread, Event
from time import sleep, time

from kafka.common import BufferUnderflowError


def write_int_string(s):
    if s is None:
        return struct.pack('>i', -1)
    else:
        return struct.pack('>i%ds' % len(s), len(s), s)


def write_short_string(s):
    if s is None:
        return struct.pack('>h', -1)
    else:
        return struct.pack('>h%ds' % len(s), len(s), s)


def read_short_string(data, cur):
    if len(data) < cur + 2:
        raise BufferUnderflowError("Not enough data left")

    (strlen,) = struct.unpack('>h', data[cur:cur + 2])
    if strlen == -1:
        return None, cur + 2

    cur += 2
    if len(data) < cur + strlen:
        raise BufferUnderflowError("Not enough data left")

    out = data[cur:cur + strlen]
    return out, cur + strlen


def read_int_string(data, cur):
    if len(data) < cur + 4:
        raise BufferUnderflowError(
            "Not enough data left to read string len (%d < %d)" %
            (len(data), cur + 4))

    (strlen,) = struct.unpack('>i', data[cur:cur + 4])
    if strlen == -1:
        return None, cur + 4

    cur += 4
    if len(data) < cur + strlen:
        raise BufferUnderflowError("Not enough data left")

    out = data[cur:cur + strlen]
    return out, cur + strlen


def relative_unpack(fmt, data, cur):
    size = struct.calcsize(fmt)
    if len(data) < cur + size:
        raise BufferUnderflowError("Not enough data left")

    out = struct.unpack(fmt, data[cur:cur + size])
    return out, cur + size


def group_by_topic_and_partition(tuples):
    out = defaultdict(dict)
    for t in tuples:
        out[t.topic][t.partition] = t
    return out


class ReentrantTimer(object):
    """
    A timer that can be restarted, unlike threading.Timer
    (although this uses threading.Timer)

    t: timer interval in milliseconds
    fn: a callable to invoke
    args: tuple of args to be passed to function
    kwargs: keyword arguments to be passed to function
    """
    def __init__(self, t, fn, *args, **kwargs):

        if t <= 0:
            raise ValueError('Invalid timeout value')

        if not callable(fn):
            raise ValueError('fn must be callable')

        self.thread = None
        self.t = t / 1000.0
        self.fn = fn
        self.args = args
        self.kwargs = kwargs
        self.active = None

    def _timer(self, active):
        while not active.wait(self.t):
            self.fn(*self.args, **self.kwargs)

    def start(self):
        if self.thread is not None:
            self.stop()

        self.active = Event()
        self.thread = Thread(target=self._timer, args=(self.active,))
        self.thread.daemon = True  # So the app exits when main thread exits
        self.thread.start()

    def stop(self):
        if self.thread is None:
            return

        self.active.set()
        self.thread.join(self.t + 1)
        self.timer = None

DEFAULT_TOPIC_CREATION_TIMEOUT_SECONDS = 30
def ensure_topic_creation(client, topic,
                          timeout=DEFAULT_TOPIC_CREATION_TIMEOUT_SECONDS):
    if timeout is not None:
        max_time = time() + timeout

    while timeout is None or timeout > 0:
        client.load_metadata_for_topics(topic)
        if client.has_metadata_for_topic(topic):
            return

        if timeout is not None:
            # If we have a timeout, reduce it to the appropriate value
            timeout = max_time - time()

        sleep(1)

    raise RuntimeError("Unable to create topic %s" % topic)