content: /*
   * Copyright (C) 2016 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.android.exoplayer2.upstream.cache;
  
  import com.google.android.exoplayer2.upstream.cache.Cache.CacheException;
  import java.util.Comparator;
  import java.util.TreeSet;
  
  /**
   * Evicts least recently used cache files first.
   */
  public final class LeastRecentlyUsedCacheEvictor implements CacheEvictor, Comparator<CacheSpan> {
  
    private final long maxBytes;
    private final TreeSet<CacheSpan> leastRecentlyUsed;
  
    private long currentSize;
  
    public LeastRecentlyUsedCacheEvictor(long maxBytes) {
      this.maxBytes = maxBytes;
      this.leastRecentlyUsed = new TreeSet<>(this);
    }
  
    @Override
    public void onCacheInitialized() {
      // Do nothing.
    }
  
    @Override
    public void onStartFile(Cache cache, String key, long position, long maxLength) {
      evictCache(cache, maxLength);
    }
  
    @Override
    public void onSpanAdded(Cache cache, CacheSpan span) {
      leastRecentlyUsed.add(span);
      currentSize += span.length;
      evictCache(cache, 0);
    }
  
    @Override
    public void onSpanRemoved(Cache cache, CacheSpan span) {
      leastRecentlyUsed.remove(span);
      currentSize -= span.length;
    }
  
    @Override
    public void onSpanTouched(Cache cache, CacheSpan oldSpan, CacheSpan newSpan) {
      onSpanRemoved(cache, oldSpan);
      onSpanAdded(cache, newSpan);
    }
  
    @Override
    public int compare(CacheSpan lhs, CacheSpan rhs) {
      long lastAccessTimestampDelta = lhs.lastAccessTimestamp - rhs.lastAccessTimestamp;
      if (lastAccessTimestampDelta == 0) {
        // Use the standard compareTo method as a tie-break.
        return lhs.compareTo(rhs);
      }
      return lhs.lastAccessTimestamp < rhs.lastAccessTimestamp ? -1 : 1;
    }
  
    private void evictCache(Cache cache, long requiredSpace) {
      while (currentSize + requiredSpace > maxBytes && !leastRecentlyUsed.isEmpty()) {
        try {
          cache.removeSpan(leastRecentlyUsed.first());
        } catch (CacheException e) {
          // do nothing.
        }
      }
    }
  
  }
  