/*
    * Copyright (C) 2018, David Pursehouse <david.pursehouse@gmail.com> and others
    *
    * This program and the accompanying materials are made available under the
    * terms of the Eclipse Distribution License v. 1.0 which is available at
    * https://www.eclipse.org/org/documents/edl-v10.php.
    *
    * SPDX-License-Identifier: BSD-3-Clause
    */
  package org.eclipse.jgit.storage.file;
  
  import java.util.Map;
  
  import javax.management.MXBean;
  
  import org.eclipse.jgit.internal.storage.file.WindowCache;
  
  /**
   * Cache statistics for {@link WindowCache}.
   *
   * @since 4.11
   */
  @MXBean
  public interface WindowCacheStats {
  	/**
  	 * @return the number of open files.
  	 * @deprecated use {@link #getOpenFileCount()} instead
  	 */
  	@Deprecated
  	public static int getOpenFiles() {
  		return (int) WindowCache.getInstance().getStats().getOpenFileCount();
  	}
  
  	/**
  	 * @return the number of open bytes.
  	 * @deprecated use {@link #getOpenByteCount()} instead
  	 */
  	@Deprecated
  	public static long getOpenBytes() {
  		return WindowCache.getInstance().getStats().getOpenByteCount();
  	}
  
  	/**
  	 * @return cache statistics for the WindowCache
  	 * @since 5.1.13
  	 */
  	public static WindowCacheStats getStats() {
  		return WindowCache.getInstance().getStats();
  	}
  
  	/**
  	 * Number of cache hits
  	 *
  	 * @return number of cache hits
  	 */
  	long getHitCount();
  
  	/**
  	 * Ratio of cache requests which were hits defined as
  	 * {@code hitCount / requestCount}, or {@code 1.0} when
  	 * {@code requestCount == 0}. Note that {@code hitRate + missRate =~ 1.0}.
  	 *
  	 * @return the ratio of cache requests which were hits
  	 */
  	default double getHitRatio() {
  		long requestCount = getRequestCount();
  		return (requestCount == 0) ? 1.0
  				: (double) getHitCount() / requestCount;
  	}
  
  	/**
  	 * Number of cache misses.
  	 *
  	 * @return number of cash misses
  	 */
  	long getMissCount();
  
  	/**
  	 * Ratio of cache requests which were misses defined as
  	 * {@code missCount / requestCount}, or {@code 0.0} when
  	 * {@code requestCount == 0}. Note that {@code hitRate + missRate =~ 1.0}.
  	 * Cache misses include all requests which weren't cache hits, including
  	 * requests which resulted in either successful or failed loading attempts.
  	 *
  	 * @return the ratio of cache requests which were misses
  	 */
  	default double getMissRatio() {
  		long requestCount = getRequestCount();
  		return (requestCount == 0) ? 0.0
  				: (double) getMissCount() / requestCount;
  	}
  
  	/**
  	 * Number of successful loads
  	 *
  	 * @return number of successful loads
  	 */
  	long getLoadSuccessCount();
  
 	/**
 	 * Number of failed loads
 	 *
 	 * @return number of failed loads
 	 */
 	long getLoadFailureCount();
 
 	/**
 	 * Ratio of cache load attempts which threw exceptions. This is defined as
 	 * {@code loadFailureCount / (loadSuccessCount + loadFailureCount)}, or
 	 * {@code 0.0} when {@code loadSuccessCount + loadFailureCount == 0}.
 	 *
 	 * @return the ratio of cache loading attempts which threw exceptions
 	 */
 	default double getLoadFailureRatio() {
 		long loadFailureCount = getLoadFailureCount();
 		long totalLoadCount = getLoadSuccessCount() + loadFailureCount;
 		return (totalLoadCount == 0) ? 0.0
 				: (double) loadFailureCount / totalLoadCount;
 	}
 
 	/**
 	 * Total number of times that the cache attempted to load new values. This
 	 * includes both successful load operations, as well as failed loads. This
 	 * is defined as {@code loadSuccessCount + loadFailureCount}.
 	 *
 	 * @return the {@code loadSuccessCount + loadFailureCount}
 	 */
 	default long getLoadCount() {
 		return getLoadSuccessCount() + getLoadFailureCount();
 	}
 
 	/**
 	 * Number of cache evictions
 	 *
 	 * @return number of evictions
 	 */
 	long getEvictionCount();
 
 	/**
 	 * Ratio of cache evictions. This is defined as
 	 * {@code evictionCount / requestCount}, or {@code 0.0} when
 	 * {@code requestCount == 0}.
 	 *
 	 * @return the ratio of cache loading attempts which threw exceptions
 	 */
 	default double getEvictionRatio() {
 		long evictionCount = getEvictionCount();
 		long requestCount = getRequestCount();
 		return (requestCount == 0) ? 0.0
 				: (double) evictionCount / requestCount;
 	}
 
 	/**
 	 * Number of times the cache returned either a cached or uncached value.
 	 * This is defined as {@code hitCount + missCount}.
 	 *
 	 * @return the {@code hitCount + missCount}
 	 */
 	default long getRequestCount() {
 		return getHitCount() + getMissCount();
 	}
 
 	/**
 	 * Average time in nanoseconds for loading new values. This is
 	 * {@code totalLoadTime / (loadSuccessCount + loadFailureCount)}.
 	 *
 	 * @return the average time spent loading new values
 	 */
 	default double getAverageLoadTime() {
 		long totalLoadCount = getLoadSuccessCount() + getLoadFailureCount();
 		return (totalLoadCount == 0) ? 0.0
 				: (double) getTotalLoadTime() / totalLoadCount;
 	}
 
 	/**
 	 * Total time in nanoseconds the cache spent loading new values.
 	 *
 	 * @return the total number of nanoseconds the cache has spent loading new
 	 *         values
 	 */
 	long getTotalLoadTime();
 
 	/**
 	 * Number of pack files kept open by the cache
 	 *
 	 * @return number of files kept open by cache
 	 */
 	long getOpenFileCount();
 
 	/**
 	 * Number of bytes cached
 	 *
 	 * @return number of bytes cached
 	 */
 	long getOpenByteCount();
 
 	/**
 	 * Number of bytes cached per repository
 	 *
 	 * @return number of bytes cached per repository
 	 */
 	Map<String, Long> getOpenByteCountPerRepository();
 
 	/**
 	 * Reset counters. Does not reset open bytes and open files counters.
 	 */
 	void resetCounters();
 }