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/*
 * RED5 Open Source Media Server - https://github.com/Red5/ Copyright 2006-2016 by respective authors (see below). All rights reserved. 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 org.red5.io;

import java.io.File;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import java.util.Random;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

import org.red5.io.flv.IKeyFrameDataAnalyzer.KeyFrameMeta;

public class CachingFileKeyFrameMetaCache extends FileKeyFrameMetaCache {

    private Map inMemoryMetaCache = new HashMap();

    private ReadWriteLock rwLock = new ReentrantReadWriteLock();

    private int maxCacheEntry = 500;

    private Random random = new Random();

    private void freeCachingMetadata() {
        int cacheSize = inMemoryMetaCache.size();
        int randomIndex = random.nextInt(cacheSize);
        Map.Entry entryToRemove = null;
        for (Map.Entry cacheEntry : inMemoryMetaCache.entrySet()) {
            if (randomIndex == 0) {
                entryToRemove = cacheEntry;
                break;
            }
            randomIndex--;
        }
        if (entryToRemove != null) {
            inMemoryMetaCache.remove(entryToRemove.getKey());
        }
    }

    @Override
    public KeyFrameMeta loadKeyFrameMeta(File file) {
        rwLock.readLock().lock();
        try {
            String canonicalPath = file.getCanonicalPath();
            if (!inMemoryMetaCache.containsKey(canonicalPath)) {
                rwLock.readLock().unlock();
                rwLock.writeLock().lock();
                try {
                    if (inMemoryMetaCache.size() >= maxCacheEntry) {
                        freeCachingMetadata();
                    }
                    KeyFrameMeta keyFrameMeta = super.loadKeyFrameMeta(file);
                    if (keyFrameMeta != null) {
                        inMemoryMetaCache.put(canonicalPath, keyFrameMeta);
                    } else {
                        return null;
                    }
                } finally {
                    rwLock.writeLock().unlock();
                    rwLock.readLock().lock();
                }
            }
            return inMemoryMetaCache.get(canonicalPath);
        } catch (IOException e) {
            return null;
        } finally {
            rwLock.readLock().unlock();
        }
    }

    @Override
    public void removeKeyFrameMeta(File file) {
        rwLock.writeLock().lock();
        try {
            String canonicalPath = file.getCanonicalPath();
            inMemoryMetaCache.remove(canonicalPath);
        } catch (IOException e) {
        } finally {
            rwLock.writeLock().unlock();
        }
        super.removeKeyFrameMeta(file);
    }

    @Override
    public void saveKeyFrameMeta(File file, KeyFrameMeta meta) {
        rwLock.writeLock().lock();
        try {
            String canonicalPath = file.getCanonicalPath();
            if (inMemoryMetaCache.containsKey(canonicalPath)) {
                inMemoryMetaCache.remove(canonicalPath);
            }
        } catch (IOException e) {
            // ignore the exception here, let super class to handle it.
        } finally {
            rwLock.writeLock().unlock();
        }
        super.saveKeyFrameMeta(file, meta);
    }

    public void setMaxCacheEntry(int maxCacheEntry) {
        this.maxCacheEntry = maxCacheEntry;
    }
}