/**
 *
 */
package de.intevation.gnv.geobackend.base.query;

import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import de.intevation.gnv.geobackend.base.DefaultResult;
import de.intevation.gnv.geobackend.base.DefaultResultDescriptor;
import de.intevation.gnv.geobackend.base.Result;
import de.intevation.gnv.geobackend.base.ResultDescriptor;

/**
 * This is an abstract Basicimplementation of the Interface
 * QueryExecutor providing several Helpermethods.
 * @author Tim Englich <tim.englich@intevation.de>
 *
 */
public abstract class QueryExecutorBase implements QueryExecutor {

    /**
     * Constructor
     */
    public QueryExecutorBase() {
        super();
    }
    
    /**
     * This Method puts the Filtervalues into the Querystring
     * @param queryString the Query which should be manipulated
     * @param filter the values which should be put into the Query
     * @return the manipulated Query
     */
    protected String setFilterValues(String queryString, String[] filter){
        String returnValue = queryString;
        for (int i = 0; i < filter.length; i++){
            returnValue = returnValue.replaceFirst("[?]", filter[i]);
        }
        return returnValue;
    }
    
    /**
     * This Methods converts the ResultSet into an Collection of Result-objects
     * @param resultSet the ResultSet which should be converted
     * @return an Collection containing Result-Objects
     * @throws SQLException
     */
    protected Collection<Result> createResultCollection(ResultSet resultSet) throws SQLException{
        Collection<Result> returnValue =  new ArrayList<Result>();
        
        ResultDescriptor resultDescriptor = null;
        int columns = -1;
        List<String> columnNames = null;
        while (resultSet.next()){
            if (resultDescriptor == null){
                resultDescriptor = new DefaultResultDescriptor();
                ResultSetMetaData rsmd = resultSet.getMetaData();
                columns = rsmd.getColumnCount();
                columnNames = new ArrayList<String>(columns);
                for (int i = 1; i <= columns; i++){
                    resultDescriptor.addColumn(rsmd.getColumnName(i), rsmd.getColumnClassName(i));
                    columnNames.add(rsmd.getColumnName(i));
                }
            }
            
            Result result = convertResult(resultSet, resultDescriptor,columnNames);
            
            returnValue.add(result);
        }
        return returnValue;
    }

    /**
     * This Method converts one Singel ResultSetEntry into an Result-Object
     * @param resultSet the ResultSet where the Entry should be took from.
     * @param resultDescriptor the ResultsetDescriptor which describes the Entry
     * @param columnNames the Name of the Columns which Values should be fetched.
     * @return an new Result-Objects containing the Values of the ResultSet-Entry
     * @throws SQLException
     */
    private Result convertResult(ResultSet resultSet,
            ResultDescriptor resultDescriptor, List<String> columnNames)
            throws SQLException {
        Result result = new DefaultResult(resultDescriptor);
        for (int i = 0; i < columnNames.size(); i++){
            String columnName = columnNames.get(i);
            result.addColumnValue(columnName, resultSet.getObject(columnName));
        }
        return result;
    }

}