# -*- coding: utf-8 -*-
# MegEngine is Licensed under the Apache License, Version 2.0 (the "License")
#
# Copyright (c) 2014-2020 Megvii Inc. All rights reserved.
#
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT ARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

import argparse
import getpass
import json
import os
import shelve

from .logconf import get_logger
from .mgb import _PersistentCache


class _FakeRedisConn:
    def __init__(self):
        try:
            from ..hub.hub import _get_megengine_home

            cache_dir = os.path.expanduser(
                os.path.join(_get_megengine_home(), "persistent_cache")
            )
            os.makedirs(cache_dir, exist_ok=True)
            cache_file = os.path.join(cache_dir, "cache")
            self._dict = shelve.open(cache_file)
            self._is_shelve = True
        except:
            self._dict = {}
            self._is_shelve = False

    def get(self, key):
        if self._is_shelve and isinstance(key, bytes):
            key = key.decode("utf-8")

        return self._dict.get(key)

    def set(self, key, val):
        if self._is_shelve and isinstance(key, bytes):
            key = key.decode("utf-8")

        self._dict[key] = val

    def __del__(self):
        if self._is_shelve:
            self._dict.close()


class PersistentCacheOnServer(_PersistentCache):
    _cached_conn = None
    _prefix = None
    _prev_get_refkeep = None

    @property
    def _conn(self):
        """get redis connection"""
        if self._cached_conn is None:
            try:
                self._cached_conn = self.make_redis_conn()
            except Exception as exc:
                get_logger().error(
                    "failed to connect to cache server: {!r}; fallback to "
                    "in-memory cache".format(exc)
                )
                self._cached_conn = _FakeRedisConn()
            self._prefix = self.make_user_prefix()

        return self._cached_conn

    @classmethod
    def make_user_prefix(cls):
        return "mgbcache:{}".format(getpass.getuser())

    @classmethod
    def make_redis_conn(cls):
        import redis

        conn = redis.StrictRedis(
            'localhost', 6381,
            socket_connect_timeout=2, socket_timeout=1)
        return conn

    def _make_key(self, category, key):
        return b"@".join((self._prefix.encode("ascii"), category.encode("ascii"), key))

    def put(self, category, key, value):
        conn = self._conn
        key = self._make_key(category, key)
        conn.set(key, value)

    def get(self, category, key):
        conn = self._conn
        key = self._make_key(category, key)
        self._prev_get_refkeep = conn.get(key)
        return self._prev_get_refkeep


def _clean():
    match = PersistentCacheOnServer.make_user_prefix() + "*"
    conn = PersistentCacheOnServer.make_redis_conn()
    cursor = 0
    nr_del = 0
    while True:
        cursor, values = conn.scan(cursor, match)
        if values:
            conn.delete(*values)
            nr_del += len(values)
        if not cursor:
            break

    print("{} cache entries deleted".format(nr_del))


def main():
    parser = argparse.ArgumentParser(description="manage persistent cache")
    subp = parser.add_subparsers(description="action to be performed", dest="cmd")
    subp.required = True
    subp_clean = subp.add_parser("clean", help="clean all the cache of current user")
    subp_clean.set_defaults(action=_clean)
    args = parser.parse_args()
    args.action()


if __name__ == "__main__":
    main()