/*
 * 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.transform;

import java.util.Arrays;

import org.hibernate.HibernateException;
import org.hibernate.property.access.internal.PropertyAccessStrategyBasicImpl;
import org.hibernate.property.access.internal.PropertyAccessStrategyChainedImpl;
import org.hibernate.property.access.internal.PropertyAccessStrategyFieldImpl;
import org.hibernate.property.access.internal.PropertyAccessStrategyMapImpl;
import org.hibernate.property.access.spi.Setter;

/**
 * Result transformer that allows to transform a result to
 * a user specified class which will be populated via setter
 * methods or fields matching the alias names.
 * <p/>
 * <pre>
 * List resultWithAliasedBean = s.createCriteria(Enrolment.class)
 * 			.createAlias("student", "st")
 * 			.createAlias("course", "co")
 * 			.setProjection( Projections.projectionList()
 * 					.add( Projections.property("co.description"), "courseDescription" )
 * 			)
 * 			.setResultTransformer( new AliasToBeanResultTransformer(StudentDTO.class) )
 * 			.list();
 * <p/>
 *  StudentDTO dto = (StudentDTO)resultWithAliasedBean.get(0);
 * 	</pre>
 *
 * @author max
 */
public class AliasToBeanResultTransformer extends AliasedTupleSubsetResultTransformer {

	// IMPL NOTE : due to the delayed population of setters (setters cached
	// 		for performance), we really cannot properly define equality for
	// 		this transformer

	private final Class resultClass;
	private boolean isInitialized;
	private String[] aliases;
	private Setter[] setters;

	public AliasToBeanResultTransformer(Class resultClass) {
		if ( resultClass == null ) {
			throw new IllegalArgumentException( "resultClass cannot be null" );
		}
		isInitialized = false;
		this.resultClass = resultClass;
	}

	@Override
	public boolean isTransformedValueATupleElement(String[] aliases, int tupleLength) {
		return false;
	}

	@Override
	public Object transformTuple(Object[] tuple, String[] aliases) {
		Object result;

		try {
			if ( ! isInitialized ) {
				initialize( aliases );
			}
			else {
				check( aliases );
			}
			
			result = resultClass.newInstance();

			for ( int i = 0; i < aliases.length; i++ ) {
				if ( setters[i] != null ) {
					setters[i].set( result, tuple[i], null );
				}
			}
		}
		catch ( InstantiationException e ) {
			throw new HibernateException( "Could not instantiate resultclass: " + resultClass.getName() );
		}
		catch ( IllegalAccessException e ) {
			throw new HibernateException( "Could not instantiate resultclass: " + resultClass.getName() );
		}

		return result;
	}

	private void initialize(String[] aliases) {
		PropertyAccessStrategyChainedImpl propertyAccessStrategy = new PropertyAccessStrategyChainedImpl(
				PropertyAccessStrategyBasicImpl.INSTANCE,
				PropertyAccessStrategyFieldImpl.INSTANCE,
				PropertyAccessStrategyMapImpl.INSTANCE
		);
		this.aliases = new String[ aliases.length ];
		setters = new Setter[ aliases.length ];
		for ( int i = 0; i < aliases.length; i++ ) {
			String alias = aliases[ i ];
			if ( alias != null ) {
				this.aliases[ i ] = alias;
				setters[ i ] = propertyAccessStrategy.buildPropertyAccess( resultClass, alias ).getSetter();
			}
		}
		isInitialized = true;
	}

	private void check(String[] aliases) {
		if ( ! Arrays.equals( aliases, this.aliases ) ) {
			throw new IllegalStateException(
					"aliases are different from what is cached; aliases=" + Arrays.asList( aliases ) +
							" cached=" + Arrays.asList( this.aliases ) );
		}
	}

	@Override
	public boolean equals(Object o) {
		if ( this == o ) {
			return true;
		}
		if ( o == null || getClass() != o.getClass() ) {
			return false;
		}

		AliasToBeanResultTransformer that = ( AliasToBeanResultTransformer ) o;

		if ( ! resultClass.equals( that.resultClass ) ) {
			return false;
		}
		if ( ! Arrays.equals( aliases, that.aliases ) ) {
			return false;
		}

		return true;
	}

	@Override
	public int hashCode() {
		int result = resultClass.hashCode();
		result = 31 * result + ( aliases != null ? Arrays.hashCode( aliases ) : 0 );
		return result;
	}
}