/*
 * Hibernate OGM, Domain model persistence for NoSQL datastores
 *
 * 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.ogm.datastore.mongodb.dialect.impl;

import static org.hibernate.ogm.datastore.mongodb.dialect.impl.MongoHelpers.getValueOrNull;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;

import org.hibernate.ogm.datastore.document.association.impl.DocumentHelpers;
import org.hibernate.ogm.datastore.document.association.spi.AssociationRows;
import org.hibernate.ogm.datastore.mongodb.MongoDBDialect;
import org.hibernate.ogm.model.key.spi.AssociationKey;
import org.hibernate.ogm.model.key.spi.AssociationType;

import org.bson.Document;

/**
 * An association snapshot based on a {@link Document} retrieved from MongoDB.
 *
 * @author Alan Fitton <alan at eth0.org.uk>
 * @author Emmanuel Bernard <emmanuel@hibernate.org>
 * @author Gunnar Morling
 */
public class MongoDBAssociationSnapshot extends AssociationRows {

	private static final String EMBEDDABLE_COLUMN_PREFIX = ".value.";

	private final Document dbObject;

	public MongoDBAssociationSnapshot(Document document, AssociationKey associationKey, AssociationStorageStrategy storageStrategy) {
		super( associationKey, getRows( document, associationKey, storageStrategy ), MongoDBAssociationRowFactory.INSTANCE );
		this.dbObject = document;
	}

	//not for embedded
	public Document getQueryObject() {
		Document query = new Document();
		query.put( MongoDBDialect.ID_FIELDNAME, dbObject.get( MongoDBDialect.ID_FIELDNAME ) );
		return query;
	}

	private static Collection<?> getRows(Document document, AssociationKey associationKey, AssociationStorageStrategy storageStrategy) {
		Collection<?> rows = null;

		if ( associationKey.getMetadata().getAssociationType() == AssociationType.ONE_TO_ONE ) {
			Object oneToOneValue = getValueOrNull( document, associationKey.getMetadata().getCollectionRole(), Object.class );
			if ( oneToOneValue != null ) {
				rows = Collections.singletonList( oneToOneValue );
			}
		}
		else {
			Object toManyValue;

			if ( storageStrategy == AssociationStorageStrategy.IN_ENTITY ) {
				toManyValue = getValueOrNull( document, associationKey.getMetadata().getCollectionRole() );
			}
			else {
				toManyValue = document.get( MongoDBDialect.ROWS_FIELDNAME );
			}

			// list of rows
			if ( toManyValue instanceof Collection ) {
				rows = (Collection<?>) toManyValue;
			}
			// a map-typed association, rows are organized by row key
			else if ( toManyValue instanceof Document ) {
				rows = getRowsFromMapAssociation( associationKey, (Document) toManyValue );
			}
		}

		return rows != null ? rows : Collections.emptyList();
	}

	/**
	 * Restores the list representation of the given map-typed association. E.g. { 'home' : 123, 'work' : 456 } will be
	 * transformed into [{ 'addressType='home', 'address_id'=123}, { 'addressType='work', 'address_id'=456} ]) as
	 * expected by the row accessor.
	 */
	private static Collection<?> getRowsFromMapAssociation(AssociationKey associationKey, Document value) {
		String rowKeyIndexColumn = associationKey.getMetadata().getRowKeyIndexColumnNames()[0];
		List<Document> rows = new ArrayList<Document>();

		String[] associationKeyColumns = associationKey.getMetadata()
				.getAssociatedEntityKeyMetadata()
				.getAssociationKeyColumns();

		// Omit shared prefix of compound ids, will be handled in the row accessor
		String prefix = DocumentHelpers.getColumnSharedPrefix( associationKeyColumns );
		prefix = prefix == null ? "" : prefix + ".";

		String embeddedValueColumnPrefix = associationKey.getMetadata().getCollectionRole() + EMBEDDABLE_COLUMN_PREFIX;

		// restore the list representation
		for ( String rowKey : value.keySet() ) {
			Object mapRow = value.get( rowKey );

			// include the row key index column
			Document row = new Document();
			row.put( rowKeyIndexColumn, rowKey );

			// several value columns, copy them all
			if ( mapRow instanceof Document ) {
				for ( String column : associationKey.getMetadata().getAssociatedEntityKeyMetadata().getAssociationKeyColumns() ) {
					// The column is part of an element collection; Restore the "value" node in the hierarchy
					if ( column.startsWith( embeddedValueColumnPrefix ) ) {
						MongoHelpers.setValue(
								row,
								column.substring( associationKey.getMetadata().getCollectionRole().length() + 1 ),
								( (Document) mapRow ).get( column.substring( embeddedValueColumnPrefix.length() ) )
						);
					}
					else {
						row.put(
								column.substring( prefix.length() ),
								( (Document) mapRow ).get( column.substring( prefix.length() ) )
						);
					}
				}
			}
			// single value column
			else {
				row.put( associationKey.getMetadata().getAssociatedEntityKeyMetadata().getAssociationKeyColumns()[0], mapRow );
			}

			rows.add( row );
		}

		return rows;
	}

	// TODO This only is used for tests; Can we get rid of it?
	public Document getDocument() {
		return this.dbObject;
	}

	@Override
	public String toString() {
		final StringBuilder sb = new StringBuilder();
		sb.append( "MongoDBAssociationSnapshot(" );
		sb.append( size() );
		sb.append( ") RowKey entries)." );
		return sb.toString();
	}
}