/*******************************************************************************
 * Copyright 2013 SAP AG
 * 
 * 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.sap.core.odata.processor.core.jpa.jpql;

import java.util.Iterator;
import java.util.Map.Entry;

import com.sap.core.odata.processor.api.jpa.exception.ODataJPARuntimeException;
import com.sap.core.odata.processor.api.jpa.jpql.JPQLContextType;
import com.sap.core.odata.processor.api.jpa.jpql.JPQLContextView;
import com.sap.core.odata.processor.api.jpa.jpql.JPQLSelectContextView;
import com.sap.core.odata.processor.api.jpa.jpql.JPQLStatement;
import com.sap.core.odata.processor.api.jpa.jpql.JPQLStatement.JPQLStatementBuilder;

public class JPQLSelectStatementBuilder extends JPQLStatementBuilder {

  JPQLStatement jpqlStatement;
  private JPQLSelectContextView context;

  public JPQLSelectStatementBuilder(final JPQLContextView context) {
    this.context = (JPQLSelectContextView) context;
  }

  @Override
  public JPQLStatement build() throws ODataJPARuntimeException {
    jpqlStatement = createStatement(createJPQLQuery());
    return jpqlStatement;

  }

  private String createJPQLQuery() throws ODataJPARuntimeException {

    StringBuilder jpqlQuery = new StringBuilder();
    String tableAlias = context.getJPAEntityAlias();
    String fromClause = context.getJPAEntityName() + JPQLStatement.DELIMITER.SPACE + tableAlias;

    jpqlQuery.append(JPQLStatement.KEYWORD.SELECT).append(JPQLStatement.DELIMITER.SPACE);
    if (context.getType().equals(JPQLContextType.SELECT_COUNT)) { //$COUNT
      jpqlQuery.append(JPQLStatement.KEYWORD.COUNT).append(JPQLStatement.DELIMITER.SPACE);
      jpqlQuery.append(JPQLStatement.DELIMITER.PARENTHESIS_LEFT).append(JPQLStatement.DELIMITER.SPACE);
      jpqlQuery.append(context.getSelectExpression()).append(JPQLStatement.DELIMITER.SPACE);
      jpqlQuery.append(JPQLStatement.DELIMITER.PARENTHESIS_RIGHT).append(JPQLStatement.DELIMITER.SPACE);
    } else {//Normal
      jpqlQuery.append(context.getSelectExpression()).append(JPQLStatement.DELIMITER.SPACE);
    }

    jpqlQuery.append(JPQLStatement.KEYWORD.FROM).append(JPQLStatement.DELIMITER.SPACE);
    jpqlQuery.append(fromClause);

    if (context.getWhereExpression() != null) {
      jpqlQuery.append(JPQLStatement.DELIMITER.SPACE);
      jpqlQuery.append(JPQLStatement.KEYWORD.WHERE).append(JPQLStatement.DELIMITER.SPACE);
      jpqlQuery.append(context.getWhereExpression());
    }

    if (context.getOrderByCollection() != null
        && context.getOrderByCollection().size() > 0) {

      StringBuilder orderByBuilder = new StringBuilder();
      Iterator<Entry<String, String>> orderItr = context
          .getOrderByCollection().entrySet().iterator();

      int i = 0;

      while (orderItr.hasNext()) {
        if (i != 0) {
          orderByBuilder.append(JPQLStatement.DELIMITER.SPACE).append(JPQLStatement.DELIMITER.COMMA).append(JPQLStatement.DELIMITER.SPACE);
        }
        Entry<String, String> entry = orderItr.next();
        orderByBuilder.append(entry.getKey()).append(JPQLStatement.DELIMITER.SPACE);
        orderByBuilder.append(entry.getValue());
        i++;
      }
      jpqlQuery.append(JPQLStatement.DELIMITER.SPACE);
      jpqlQuery.append(JPQLStatement.KEYWORD.ORDERBY).append(JPQLStatement.DELIMITER.SPACE);
      jpqlQuery.append(orderByBuilder);
    }

    return jpqlQuery.toString();

  }

}