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/*
 Licensed to Diennea S.r.l. under one
 or more contributor license agreements. See the NOTICE file
 distributed with this work for additional information
 regarding copyright ownership. Diennea S.r.l. licenses this file
 to you 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 blazingcache.client.impl;

import blazingcache.utils.RawString;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.locks.ReentrantLock;

/**
 * Manages running fetches
 *
 * @author enrico.olivelli
 */
public class PendingFetchesManager {

    private final Map> pendingFetchesByKey = new HashMap<>();
    private final AtomicLong idgenerator = new AtomicLong();
    private final ReentrantLock lock = new ReentrantLock();

    /**
     * Register a new fetch request for a key
     * @param key key to fetch
     * @return fetch id
     */
    public long registerFetchForKey(RawString key) {
        long id = idgenerator.incrementAndGet();
        lock.lock();
        try {
            Set actual = pendingFetchesByKey.get(key);
            if (actual == null) {
                actual = new HashSet<>();
                pendingFetchesByKey.put(key, actual);
            }
            actual.add(id);
        } finally {
            lock.unlock();
        }
        return id;
    }

    /**
     * Validates that a fetch is still running and removes it from the running list.
     * @param key
     * @param fetchId
     * @return true if the fetch was running and was successfully removed
     */
    public boolean consumeAndValidateFetchForKey(RawString key, long fetchId) {
        lock.lock();
        try {
            Set actual = pendingFetchesByKey.get(key);
            if (actual == null) {
                return false;
            } else {
                boolean removed = actual.remove(fetchId);
                if (actual.isEmpty()) {
                    pendingFetchesByKey.remove(key);
                }
                return removed;
            }
        } finally {
            lock.unlock();
        }
    }

    /**
     * Cancels every running fetch for the given key
     * @param key
     */
    public void cancelFetchesForKey(RawString key) {
        lock.lock();
        try {
            pendingFetchesByKey.remove(key);
        } finally {
            lock.unlock();
        }

    }

    /**
     * Cancels every running fetch
     */
    public void clear() {
        lock.lock();
        try {
            pendingFetchesByKey.clear();
        } finally {
            lock.unlock();
        }
    }
    
    protected Map> getPendingFetchesForTest() {
        return pendingFetchesByKey;
    }
}