/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF 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 org.apache.camel.impl;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Map;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;

import org.apache.camel.spi.ServicePool;
import org.apache.camel.support.ServiceSupport;
import org.apache.camel.util.LRUCache;
import org.apache.camel.util.ServiceHelper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Default implementation to inherit for a basic service pool.
 *
 * @version 
 */
public abstract class DefaultServicePool<Key, Service> extends ServiceSupport implements ServicePool<Key, Service> {
    protected final Logger log = LoggerFactory.getLogger(getClass());
    protected final Map<Key, BlockingQueue<Service>> pool;
    protected int capacity = 100;

    protected DefaultServicePool() {
        this.pool = new LRUCache(capacity);
    }

    public DefaultServicePool(int capacity) {
        this.capacity = capacity;
        this.pool = new LRUCache(capacity);
    }

    public int getCapacity() {
        return capacity;
    }

    public void setCapacity(int capacity) {
        this.capacity = capacity;
    }

    public synchronized int size() {
        int size = 0;
        for (BlockingQueue<Service> entry : pool.values()) {
            size += entry.size();
        }
        return size;
    }

    public synchronized Service addAndAcquire(Key key, Service service) {
        BlockingQueue<Service> entry = pool.get(key);
        if (entry == null) {
            entry = new ArrayBlockingQueue<Service>(capacity);
            pool.put(key, entry);
        }
        log.trace("AddAndAcquire key: {} service: {}", key, service);

        // test if queue will be full
        if (entry.size() >= capacity) {
            throw new IllegalStateException("Queue full");
        }
        return service;
    }

    public synchronized Service acquire(Key key) {
        BlockingQueue<Service> services = pool.get(key);
        if (services == null || services.isEmpty()) {
            log.trace("No free services in pool to acquire for key: {}", key);
            return null;
        }

        Service answer = services.poll();
        log.trace("Acquire: {} service: {}", key, answer);
        return answer;
    }

    public synchronized void release(Key key, Service service) {
        log.trace("Release: {} service: {}", key, service);
        BlockingQueue<Service> services = pool.get(key);
        if (services != null) {
            services.add(service);
        }
    }

    public void purge() {
        pool.clear();
    }

    protected void doStart() throws Exception {
        log.debug("Starting service pool: {}", this);
    }

    protected void doStop() throws Exception {
        log.debug("Stopping service pool: {}", this);
        for (BlockingQueue<Service> entry : pool.values()) {
            Collection<Service> values = new ArrayList<Service>();
            entry.drainTo(values);
            ServiceHelper.stopServices(values);
            entry.clear();
        }
        pool.clear();
    }

}
