/**
 * Copyright (c) 2015, Intel Corporation
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 *     * Redistributions of source code must retain the above copyright notice,
 *       this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of Intel Corporation nor the names of its contributors
 *       may be used to endorse or promote products derived from this software
 *       without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package com.intel.stl.dbengine.impl;

import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.concurrent.ConcurrentHashMap;

import javax.persistence.EntityManager;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.intel.stl.api.DatabaseException;
import com.intel.stl.api.failure.FailureManager;
import com.intel.stl.api.failure.IFailureManagement;
import com.intel.stl.dbengine.DatabaseContext;
import com.intel.stl.dbengine.DatabaseEngine;
import com.intel.stl.dbengine.DatabaseServer;

public class DatabaseServerImpl implements DatabaseServer {

    private static Logger log = LoggerFactory.getLogger(DatabaseServerImpl.class);

    protected static final long UNUSED_THRESHOLD = 600000L;

    private final DatabaseEngine engine;

    private final Map<String, DatabaseContextImpl> dbContexts =
            new ConcurrentHashMap<String, DatabaseContextImpl>(8, 0.9f, 1);

    public DatabaseServerImpl(DatabaseEngine engine) {
        this.engine = engine;
    }

    @Override
    public DatabaseContext getDatabaseContext(String contextName) {
        DatabaseContextImpl ctx = dbContexts.get(contextName);
        if (ctx == null) {
            ctx = createDatabaseContext(contextName);
        }
        ctx.setLastUsed(System.currentTimeMillis());
        return ctx;
    }

    @Override
    public void addDatabaseContext(String contextName) {
        Iterator<Entry<String, DatabaseContextImpl>> iterator =
                dbContexts.entrySet().iterator();
        while (iterator.hasNext()) {
            Entry<String, DatabaseContextImpl> entry = iterator.next();
            if (entry.getKey().equals(contextName)) {
                entry.getValue().getEntityManager().close();
                iterator.remove();
            } else {
                long now = System.currentTimeMillis();
                long lastUsed = entry.getValue().getLastUsed();
                if ((now - lastUsed) > UNUSED_THRESHOLD) {
                    entry.getValue().getEntityManager().close();
                    iterator.remove();
                }
            }
        }
        createDatabaseContext(contextName);
    }

    private DatabaseContextImpl createDatabaseContext(String contextName) {
        EntityManager em = null;
        try {
            em = engine.getEntityManager();
        } catch (DatabaseException e) {
            log.error(e.getMessage(), e);
        }
        IFailureManagement failureMgr = FailureManager.getManager();
        DatabaseContextImpl ctx = new DatabaseContextImpl(em, failureMgr);
        ctx.setLastUsed(System.currentTimeMillis());
        dbContexts.put(contextName, ctx);
        return ctx;
    }

    protected Map<String, DatabaseContextImpl> getDbContexts() {
        return dbContexts;
    }
}
