# -*- coding: utf-8 -*-
from __future__ import absolute_import
from __future__ import division

from typing import Any, Callable, Optional, Sequence, TypeVar, Iterable, Tuple
from six import text_type, binary_type
import base64
import errno
import hashlib
import heapq
import itertools
import os
from time import sleep

from django.conf import settings
from six.moves import range
from zerver.lib.str_utils import force_text

T = TypeVar('T')

def statsd_key(val, clean_periods=False):
    # type: (Any, bool) -> str
    if not isinstance(val, str):
        val = str(val)

    if ':' in val:
        val = val.split(':')[0]
    val = val.replace('-', "_")
    if clean_periods:
        val = val.replace('.', '_')

    return val

class StatsDWrapper(object):
    """Transparently either submit metrics to statsd
    or do nothing without erroring out"""

    # Backported support for gauge deltas
    # as our statsd server supports them but supporting
    # pystatsd is not released yet
    def _our_gauge(self, stat, value, rate=1, delta=False):
            # type: (str, float, float, bool) -> str
            """Set a gauge value."""
            from django_statsd.clients import statsd
            if delta:
                value_str = '%+g|g' % (value,)
            else:
                value_str = '%g|g' % (value,)
            statsd._send(stat, value_str, rate)

    def __getattr__(self, name):
        # type: (str) -> Any
        # Hand off to statsd if we have it enabled
        # otherwise do nothing
        if name in ['timer', 'timing', 'incr', 'decr', 'gauge']:
            if settings.STATSD_HOST != '':
                from django_statsd.clients import statsd
                if name == 'gauge':
                    return self._our_gauge
                else:
                    return getattr(statsd, name)
            else:
                return lambda *args, **kwargs: None

        raise AttributeError

statsd = StatsDWrapper()

# Runs the callback with slices of all_list of a given batch_size
def run_in_batches(all_list, batch_size, callback, sleep_time = 0, logger = None):
    # type: (Sequence[T], int, Callable[[Sequence[T]], None], int, Optional[Callable[[str], None]]) ->  None
    if len(all_list) == 0:
        return

    limit = (len(all_list) // batch_size) + 1;
    for i in range(limit):
        start = i*batch_size
        end = (i+1) * batch_size
        if end >= len(all_list):
            end = len(all_list)
        batch = all_list[start:end]

        if logger:
            logger("Executing %s in batch %s of %s" % (end-start, i+1, limit))

        callback(batch)

        if i != limit - 1:
            sleep(sleep_time)

def make_safe_digest(string, hash_func=hashlib.sha1):
    # type: (text_type, Callable[[binary_type], Any]) -> text_type
    """
    return a hex digest of `string`.
    """
    # hashlib.sha1, md5, etc. expect bytes, so non-ASCII strings must
    # be encoded.
    return force_text(hash_func(string.encode('utf-8')).hexdigest())


def log_statsd_event(name):
    # type: (str) -> None
    """
    Sends a single event to statsd with the desired name and the current timestamp

    This can be used to provide vertical lines in generated graphs,
    for example when doing a prod deploy, bankruptcy request, or
    other one-off events

    Note that to draw this event as a vertical line in graphite
    you can use the drawAsInfinite() command
    """
    event_name = "events.%s" % (name,)
    statsd.incr(event_name)

def generate_random_token(length):
    # type: (int) -> text_type
    return base64.b16encode(os.urandom(length // 2)).decode('utf-8').lower()

def mkdir_p(path):
    # type: (str) -> None
    # Python doesn't have an analog to `mkdir -p` < Python 3.2.
    try:
        os.makedirs(path)
    except OSError as e:
        if e.errno == errno.EEXIST and os.path.isdir(path):
            pass
        else:
            raise

def query_chunker(queries, id_collector=None, chunk_size=1000, db_chunk_size=None):
    # type: (List[Any], Set[int], int, int) -> Iterable[Any]

    '''
    This merges one or more Django ascending-id queries into
    a generator that returns chunks of chunk_size row objects
    during each yield, preserving id order across all results..

    Queries should satisfy these conditions:
        - They should be Django filters.
        - They should return Django objects with "id" attributes.
        - They should be disjoint.

    The generator also populates id_collector, which we use
    internally to enforce unique ids, but which the caller
    can pass in to us if they want the side effect of collecting
    all ids.
    '''
    if db_chunk_size is None:
        db_chunk_size = chunk_size // len(queries)

    assert db_chunk_size >= 2
    assert chunk_size >= 2

    if id_collector is not None:
        assert(len(id_collector) == 0)
    else:
        id_collector = set()

    def chunkify(q, i):
        # type: (Any, int) -> Iterable[Tuple[int, int, Any]]
        q = q.order_by('id')
        min_id = -1
        while True:
            rows = list(q.filter(id__gt=min_id)[0:db_chunk_size])
            if len(rows) == 0:
                break
            for row in rows:
                yield (row.id, i, row)
            min_id = rows[-1].id

    iterators = [chunkify(q, i) for i, q in enumerate(queries)]
    merged_query = heapq.merge(*iterators)

    while True:
        tup_chunk = list(itertools.islice(merged_query, 0, chunk_size))
        if len(tup_chunk) == 0:
            break

        # Do duplicate-id management here.
        tup_ids = set([tup[0] for tup in tup_chunk])
        assert len(tup_ids) == len(tup_chunk)
        assert len(tup_ids.intersection(id_collector)) == 0
        id_collector.update(tup_ids)

        yield [row for row_id, i, row in tup_chunk]