/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
 * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
 */
package org.hibernate.id.enhanced;

import java.io.Serializable;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import org.hibernate.HibernateException;
import org.hibernate.id.IntegralDataTypeHolder;
import org.hibernate.internal.CoreMessageLogger;
import org.jboss.logging.Logger;

/**
 * Variation of {@link PooledOptimizer} which interprets the incoming database value as the lo value, rather than
 * the hi value.
 *
 * @author Steve Ebersole
 *
 * @see PooledOptimizer
 */
public class PooledLoOptimizer extends AbstractOptimizer {
	private static final CoreMessageLogger LOG = Logger.getMessageLogger(
			CoreMessageLogger.class,
			PooledLoOptimizer.class.getName()
	);

	private static class GenerationState {
		// last value read from db source
		private IntegralDataTypeHolder lastSourceValue;
		// the current generator value
		private IntegralDataTypeHolder value;
		// the value at which we'll hit the db again
		private IntegralDataTypeHolder upperLimitValue;
	}

	/**
	 * Constructs a PooledLoOptimizer.
	 *
	 * @param returnClass The Java type of the values to be generated
	 * @param incrementSize The increment size.
	 */
	public PooledLoOptimizer(Class returnClass, int incrementSize) {
		super( returnClass, incrementSize );
		if ( incrementSize < 1 ) {
			throw new HibernateException( "increment size cannot be less than 1" );
		}
		LOG.creatingPooledLoOptimizer( incrementSize, returnClass.getName() );
	}

	@Override
	public synchronized Serializable generate(AccessCallback callback) {
		final GenerationState generationState = locateGenerationState( callback.getTenantIdentifier() );

		if ( generationState.lastSourceValue == null
				|| ! generationState.value.lt( generationState.upperLimitValue ) ) {
			generationState.lastSourceValue = callback.getNextValue();
			generationState.upperLimitValue = generationState.lastSourceValue.copy().add( incrementSize );
			generationState.value = generationState.lastSourceValue.copy();
			// handle cases where initial-value is less that one (hsqldb for instance).
			while ( generationState.value.lt( 1 ) ) {
				generationState.value.increment();
			}
		}
		return generationState.value.makeValueThenIncrement();
	}

	private GenerationState noTenantState;
	private Map<String,GenerationState> tenantSpecificState;

	private GenerationState locateGenerationState(String tenantIdentifier) {
		if ( tenantIdentifier == null ) {
			if ( noTenantState == null ) {
				noTenantState = new GenerationState();
			}
			return noTenantState;
		}
		else {
			GenerationState state;
			if ( tenantSpecificState == null ) {
				tenantSpecificState = new ConcurrentHashMap<String, GenerationState>();
				state = new GenerationState();
				tenantSpecificState.put( tenantIdentifier, state );
			}
			else {
				state = tenantSpecificState.get( tenantIdentifier );
				if ( state == null ) {
					state = new GenerationState();
					tenantSpecificState.put( tenantIdentifier, state );
				}
			}
			return state;
		}
	}

	private GenerationState noTenantGenerationState() {
		if ( noTenantState == null ) {
			throw new IllegalStateException( "Could not locate previous generation state for no-tenant" );
		}
		return noTenantState;
	}

	@Override
	public IntegralDataTypeHolder getLastSourceValue() {
		return noTenantGenerationState().lastSourceValue;
	}

	@Override
	public boolean applyIncrementSizeToSourceValues() {
		return true;
	}
}