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// Copyright (C) 2021 The Android Open Source Project
//
// 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.

package com.google.gerrit.server.cache;

import com.google.common.cache.Cache;
import com.google.common.cache.CacheStats;
import com.google.gerrit.common.Nullable;

public class CacheInfo {

  public String name;
  public CacheType type;
  public EntriesInfo entries;
  public String averageGet;
  public HitRatioInfo hitRatio;

  public CacheInfo(Cache cache) {
    this(null, cache);
  }

  public CacheInfo(String name, Cache cache) {
    this.name = name;

    CacheStats stat = cache.stats();

    entries = new EntriesInfo();
    entries.setMem(cache.size());

    averageGet = duration(stat.averageLoadPenalty());

    hitRatio = new HitRatioInfo();
    hitRatio.setMem(stat.hitCount(), stat.requestCount());

    if (cache instanceof PersistentCache) {
      type = CacheType.DISK;
      PersistentCache.DiskStats diskStats = ((PersistentCache) cache).diskStats();
      entries.setDisk(diskStats.size());
      entries.setSpace(diskStats.space());
      hitRatio.setDisk(diskStats.hitCount(), diskStats.requestCount());
    } else {
      type = CacheType.MEM;
    }
  }

  @Nullable
  private static String duration(double ns) {
    if (ns < 0.5) {
      return null;
    }
    String suffix = "ns";
    if (ns >= 1000.0) {
      ns /= 1000.0;
      suffix = "us";
    }
    if (ns >= 1000.0) {
      ns /= 1000.0;
      suffix = "ms";
    }
    if (ns >= 1000.0) {
      ns /= 1000.0;
      suffix = "s";
    }
    return String.format("%4.1f%s", ns, suffix).trim();
  }

  public static class EntriesInfo {
    public Long mem;
    public Long disk;
    public String space;

    public void setMem(long mem) {
      this.mem = mem != 0 ? mem : null;
    }

    public void setDisk(long disk) {
      this.disk = disk != 0 ? disk : null;
    }

    public void setSpace(double value) {
      space = bytes(value);
    }

    public static String bytes(double value) {
      value /= 1024;
      String suffix = "k";

      if (value > 1024) {
        value /= 1024;
        suffix = "m";
      }
      if (value > 1024) {
        value /= 1024;
        suffix = "g";
      }
      return String.format("%1$6.2f%2$s", value, suffix).trim();
    }
  }

  public static class HitRatioInfo {
    public Integer mem;
    public Integer disk;

    public void setMem(long value, long total) {
      mem = percent(value, total);
    }

    public void setDisk(long value, long total) {
      disk = percent(value, total);
    }

    @Nullable
    private static Integer percent(long value, long total) {
      if (total <= 0) {
        return null;
      }
      return (int) ((100 * value) / total);
    }
  }

  public enum CacheType {
    MEM,
    DISK
  }
}