# -*- 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 django.http import HttpRequest
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]

def get_subdomain(request):
    # type: (HttpRequest) -> text_type
    domain = request.get_host().lower()
    index = domain.find("." + settings.EXTERNAL_HOST)
    if index == -1:
        return ""
    subdomain = domain[0:index]
    if subdomain in settings.ROOT_SUBDOMAIN_ALIASES:
        return ""
    return subdomain

def check_subdomain(realm_subdomain, user_subdomain):
    # type: (text_type, text_type) -> bool
    if settings.REALMS_HAVE_SUBDOMAINS and realm_subdomain is not None:
        if (realm_subdomain == "" and user_subdomain is None):
            return True
        if realm_subdomain != user_subdomain:
            return False
    return True