"""
Copyright 2023-2024 SGLang Team
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.
"""

"""Base cache class."""

import time


class BaseCache:
    def __init__(self, enable=True):
        self.enable = enable
        self.reset()

    def reset(self):
        self.cache = {}
        self.metrics = {"total": 0, "hit": 0, "avg_init_time": 0}

    def query(self, key):
        def _init_with_timer(key):
            start = time.monotonic()
            val = self.init_value(key)
            init_time = time.monotonic() - start
            curr_total = self.metrics["total"]
            new_total = curr_total + 1

            # Update average init time without old_avg * old_total to avoid overflow.
            self.metrics["avg_init_time"] = (init_time / new_total) + (
                curr_total / new_total
            ) * self.metrics["avg_init_time"]
            return val

        if key in self.cache:
            self.metrics["hit"] += 1
            val = self.cache[key]
        else:
            # Cache miss or disabled.
            val = _init_with_timer(key)

        if self.enable:
            self.metrics["total"] += 1
            self.cache[key] = val
        return val

    def init_value(self, key):
        raise NotImplementedError

    def get_cache_hit_rate(self):
        if self.metrics["total"] == 0:
            return 0
        return self.metrics["hit"] / self.metrics["total"]

    def get_avg_init_time(self):
        return self.metrics["avg_init_time"]
