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SQL support for querydsl
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/*
 * Copyright 2011, Mysema Ltd
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.mysema.query.sql;

import static com.google.common.collect.ImmutableList.copyOf;

import java.util.Collection;
import java.util.List;
import java.util.Map;

import javax.annotation.Nullable;

import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.mysema.query.types.FactoryExpression;
import com.mysema.query.types.Ops;
import com.mysema.query.types.Path;
import com.mysema.query.types.PathMetadata;
import com.mysema.query.types.PathMetadataFactory;
import com.mysema.query.types.expr.NumberExpression;
import com.mysema.query.types.expr.NumberOperation;
import com.mysema.query.types.path.BeanPath;

/**
 * RelationalPathBase is a base class for {@link RelationalPath} implementations
 *
 * @author tiwe
 *
 * @param 
 *            entity type
 */
public class RelationalPathBase extends BeanPath implements RelationalPath {

    private static final long serialVersionUID = -7031357250283629202L;

    @Nullable
    private PrimaryKey primaryKey;

    private final List> columns = Lists.newArrayList();

    private final Map, ColumnMetadata> columnMetadata = Maps.newHashMap();

    private final List> foreignKeys = Lists.newArrayList();

    private final List> inverseForeignKeys = Lists.newArrayList();

    private final String schema, table;

    private transient FactoryExpression projection;

    private transient NumberExpression count, countDistinct;

    public RelationalPathBase(Class type, String variable, String schema, String table) {
        this(type, PathMetadataFactory.forVariable(variable), schema, table);
    }

    public RelationalPathBase(Class type, PathMetadata metadata, String schema,
            String table) {
        super(type, metadata);
        this.schema = schema;
        this.table = table;
    }

    protected PrimaryKey createPrimaryKey(Path... columns) {
        primaryKey = new PrimaryKey(this, columns);
        return primaryKey;
    }

    protected  ForeignKey createForeignKey(Path local, String foreign) {
        ForeignKey foreignKey = new ForeignKey(this, local, foreign);
        foreignKeys.add(foreignKey);
        return foreignKey;
    }

    protected  ForeignKey createForeignKey(List> local, List foreign) {
        ForeignKey foreignKey = new ForeignKey(this, copyOf(local), copyOf(foreign));
        foreignKeys.add(foreignKey);
        return foreignKey;
    }

    protected  ForeignKey createInvForeignKey(Path local, String foreign) {
        ForeignKey foreignKey = new ForeignKey(this, local, foreign);
        inverseForeignKeys.add(foreignKey);
        return foreignKey;
    }

    protected  ForeignKey createInvForeignKey(List> local,
            List foreign) {
        ForeignKey foreignKey = new ForeignKey(this, copyOf(local), copyOf(foreign));
        inverseForeignKeys.add(foreignKey);
        return foreignKey;
    }

    protected > P addMetadata(P path, ColumnMetadata metadata) {
        columnMetadata.put(path, metadata);
        return path;
    }

    @Override
    public NumberExpression count() {
        if (count == null) {
            if (primaryKey != null) {
                count = NumberOperation.create(Long.class, Ops.AggOps.COUNT_AGG,
                        primaryKey.getLocalColumns().get(0));
            } else {
                throw new IllegalStateException("No count expression can be created");
            }
        }
        return count;
    }

    @Override
    public NumberExpression countDistinct() {
        if (countDistinct == null) {
            if (primaryKey != null) {
                // TODO handle multiple column primary keys properly
                countDistinct = NumberOperation.create(Long.class, Ops.AggOps.COUNT_DISTINCT_AGG,
                        primaryKey.getLocalColumns().get(0));
            } else {
                throw new IllegalStateException("No count distinct expression can be created");
            }
        }
        return countDistinct;
    }

    @Override
    public FactoryExpression getProjection() {
        if (projection == null) {
            projection = RelationalPathUtils.createProjection(this);
        }
        return projection;
    }

    public Path[] all() {
        Path[] all = new Path[columns.size()];
        columns.toArray(all);
        return all;
    }

    @Override
    protected > P add(P path) {
        columns.add(path);
        return path;
    }

    @Override
    public List> getColumns() {
        return columns;
    }

    @Override
    public Collection> getForeignKeys() {
        return foreignKeys;
    }

    @Override
    public Collection> getInverseForeignKeys() {
        return inverseForeignKeys;
    }

    @Override
    public PrimaryKey getPrimaryKey() {
        return primaryKey;
    }

    @Override
    public String getSchemaName() {
        return schema;
    }

    @Override
    public String getTableName() {
        return table;
    }

    @Override
    public ColumnMetadata getMetadata(Path column) {
        return columnMetadata.get(column);
    }

}