/*******************************************************************************
 * Copyright (c) 2011, 2014 Oracle and/or its affiliates. All rights reserved.
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
 * which accompanies this distribution.
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *     Oracle - initial API and implementation
 *
 ******************************************************************************/
package org.eclipse.persistence.jpa.jpql.tools.model.query;

import org.eclipse.persistence.jpa.jpql.parser.StateFieldPathExpression;
import org.eclipse.persistence.jpa.jpql.tools.TypeHelper;
import org.eclipse.persistence.jpa.jpql.tools.spi.IManagedType;
import org.eclipse.persistence.jpa.jpql.tools.spi.IManagedTypeProvider;
import org.eclipse.persistence.jpa.jpql.tools.spi.IManagedTypeVisitor;
import org.eclipse.persistence.jpa.jpql.tools.spi.IMapping;
import org.eclipse.persistence.jpa.jpql.tools.spi.IType;
import org.eclipse.persistence.jpa.jpql.tools.spi.ITypeDeclaration;
import org.eclipse.persistence.jpa.jpql.tools.utility.iterable.EmptyIterable;

/**
 * A single-valued association field is designated by the name of an association-field in a
 * one-to-one or many-to-one relationship. The type of a single-valued association field and thus a
 * single-valued association path expression is the abstract schema type of the related entity.
 *
 * <div><b>BNF:</b> <code>state_field_path_expression ::= {identification_variable | single_valued_association_path_expression}.state_field</code><p></div>
 *
 * <div><b>BNF:</b> <code>single_valued_association_path_expression ::= identification_variable.{single_valued_association_field.}*single_valued_association_field</code><p></div>
 *
 * @see StateFieldPathExpression
 *
 * @version 2.5
 * @since 2.4
 * @author Pascal Filion
 */
public class StateFieldPathExpressionStateObject extends AbstractPathExpressionStateObject {

	/**
	 * Creates a new <code>StateFieldPathExpressionStateObject</code>.
	 *
	 * @param parent The parent of this state object, which cannot be <code>null</code>
	 * @exception NullPointerException The given parent cannot be <code>null</code>
	 */
	public StateFieldPathExpressionStateObject(StateObject parent) {
		super(parent);
	}

	/**
	 * Creates a new <code>StateFieldPathExpressionStateObject</code>.
	 *
	 * @param parent The parent of this state object, which cannot be <code>null</code>
	 * @param path The state field path expression
	 * @exception NullPointerException The given parent cannot be <code>null</code>
	 */
	public StateFieldPathExpressionStateObject(StateObject parent, String path) {
		super(parent, path);
	}

	/**
	 * {@inheritDoc}
	 */
	public void accept(StateObjectVisitor visitor) {
		visitor.visit(this);
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	public StateFieldPathExpression getExpression() {
		return (StateFieldPathExpression) super.getExpression();
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	protected IManagedType resolveManagedType() {

		IMapping mapping = getMapping();

		if (mapping == null) {
			return null;
		}

		TypeHelper typeHelper = getTypeHelper();
		ITypeDeclaration typeDeclaration = mapping.getTypeDeclaration();
		IType type = typeDeclaration.getType();

		// Collection type cannot be traversed
		if (typeHelper.isCollectionType(type)) {

			ITypeDeclaration[] typeParameters = typeDeclaration.getTypeParameters();

			if (typeParameters.length == 0) {
				return null;
			}

			type = typeParameters[0].getType();
		}
		// Wrap the Map into a virtual IManagedType so it can be returned and the
		// IType for the Map can be used to retrieve the type of the key and value
		else if (typeHelper.isMapType(type)) {
			return new MapManagedType(getManagedTypeProvider(), type);
		}

		// Retrieve the corresponding managed type for the mapping's type
		return getManagedTypeProvider().getManagedType(type);
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	protected IType resolveType() {
		return getTypeHelper().convertPrimitive(getTypeDeclaration().getType());
	}

	/**
	 * Keeps a reference of the {@link StateFieldPathExpression parsed object} object, which
	 * should only be done when this object is instantiated during the conversion of a parsed JPQL
	 * query into {@link StateObject StateObjects}.
	 *
	 * @param expression The {@link StateFieldPathExpression parsed object} representing a state
	 * field path expression
	 */
	public void setExpression(StateFieldPathExpression expression) {
		super.setExpression(expression);
	}

	protected static class MapManagedType implements IManagedType {

		protected final IType mapType;
		protected final IManagedTypeProvider provider;

		protected MapManagedType(IManagedTypeProvider provider, IType mapType) {
			super();
			this.mapType  = mapType;
			this.provider = provider;
		}

		/**
		 * {@inheritDoc}
		 */
		public void accept(IManagedTypeVisitor visitor) {
		}

		/**
		 * {@inheritDoc}
		 */
		public int compareTo(IManagedType managedType) {
			return getType().getName().compareTo(managedType.getType().getName());
		}

		/**
		 * {@inheritDoc}
		 */
		public IMapping getMappingNamed(String name) {
			return null;
		}

		/**
		 * {@inheritDoc}
		 */
		public IManagedTypeProvider getProvider() {
			return provider;
		}

		/**
		 * {@inheritDoc}
		 */
		public IType getType() {
			return mapType;
		}

		/**
		 * {@inheritDoc}
		 */
		public Iterable<IMapping> mappings() {
			return EmptyIterable.instance();
		}

		/**
		 * {@inheritDoc}
		 */
		@Override
		public String toString() {
			return getType().getName();
		}
	}
}