# -*- coding: utf-8 -*-
# Copyright 2015, 2016 OpenMarket Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import synapse.metrics
from lrucache import LruCache
import os

CACHE_SIZE_FACTOR = float(os.environ.get("SYNAPSE_CACHE_FACTOR", 0.1))

DEBUG_CACHES = False

metrics = synapse.metrics.get_metrics_for("synapse.util.caches")

caches_by_name = {}
cache_counter = metrics.register_cache(
    "cache",
    lambda: {(name,): len(caches_by_name[name]) for name in caches_by_name.keys()},
    labels=["name"],
)

_string_cache = LruCache(int(5000 * CACHE_SIZE_FACTOR))
caches_by_name["string_cache"] = _string_cache


KNOWN_KEYS = {
    key: key for key in
    (
        "auth_events",
        "content",
        "depth",
        "event_id",
        "hashes",
        "origin",
        "origin_server_ts",
        "prev_events",
        "room_id",
        "sender",
        "signatures",
        "state_key",
        "type",
        "unsigned",
        "user_id",
    )
}


def intern_string(string):
    """Takes a (potentially) unicode string and interns using custom cache
    """
    return _string_cache.setdefault(string, string)


def intern_dict(dictionary):
    """Takes a dictionary and interns well known keys and their values
    """
    return {
        KNOWN_KEYS.get(key, key): _intern_known_values(key, value)
        for key, value in dictionary.items()
    }


def _intern_known_values(key, value):
    intern_str_keys = ("event_id", "room_id")
    intern_unicode_keys = ("sender", "user_id", "type", "state_key")

    if key in intern_str_keys:
        return intern(value.encode('ascii'))

    if key in intern_unicode_keys:
        return intern_string(value)

    return value