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/*
 * Copyright 2015 Red Hat, Inc. and/or its affiliates.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * 
 *      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 org.drools.template.jdbc;

import org.drools.template.parser.DataListener;
import org.drools.template.parser.DefaultTemplateContainer;
import org.drools.template.parser.TemplateContainer;
import org.drools.template.parser.TemplateDataListener;

import java.io.InputStream;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

/**
 *  A Drools template compiler which takes a ResultSet and compiles it into
 * a template using DefaultTemplateContainer.
 * 
 * To use simply you need a JDBC ResultSet - with the field names mapping to the field names used in the template !
 */
public class ResultSetGenerator {

    /**
     * Generates DRL from a data provider for the spreadsheet data and templates.
     *
     * @param rs       the resultset for the table data
     * @param template the string containing the template resource name
     * @return the generated DRL text as a String
     */
    public String compile(final ResultSet rs,
                          final String template) {
        final InputStream templateStream = this.getClass().getResourceAsStream(template);
        return compile(rs,
                       templateStream);
    }

    /**
     * Generates DRL from a data provider for the spreadsheet data and templates.
     *
     * @param rs             the resultset for the table data
     * @param templateStream the InputStream for reading the templates
     * @return the generated DRL text as a String
     */
    public String compile(final ResultSet rs,
                          final InputStream templateStream) {
        TemplateContainer tc = new DefaultTemplateContainer(templateStream);
        closeStream(templateStream);
        return compile(rs,
                       new TemplateDataListener(tc));
    }

    /**
     * Generates DRL from a data provider for the spreadsheet data and templates.
     *
     * @param rs       the resultset for the table data
     * @param listener a template data listener
     * @return the generated DRL text as a String
     */
    public String compile(final ResultSet rs,
                          final TemplateDataListener listener) {
        List listeners = new ArrayList<>();
        listeners.add(listener);
        processData(rs,
                    listeners);
        return listener.renderDRL();
    }

    /**
     * Iterate through the resultset.
     *
     * @param rs        the resultset for the table data
     * @param listeners list of template data listener
     */
    private void processData(final ResultSet rs,
                             List listeners) {

        try {
            ResultSetMetaData rsmd = rs.getMetaData();
            int colCount = rsmd.getColumnCount();

            int i = 0;

            while (rs.next()) {
                newRow(listeners, i, colCount);
                for (int cellNum = 1; cellNum < colCount + 1; cellNum++) {
                    String cell;

                    int sqlType = rsmd.getColumnType(cellNum);
                    switch (sqlType) {
                        case java.sql.Types.DATE:
                            cell = rs.getDate(cellNum).toString();
                            break;
                        case java.sql.Types.INTEGER:
                        case java.sql.Types.DOUBLE:
                            cell = String.valueOf(rs.getInt(cellNum));
                            break;
                        default:
                            cell = rs.getString(cellNum);
                    }

                    newCell(listeners,
                            i,
                            cellNum - 1,
                            cell,
                            DataListener.NON_MERGED);
                }
                i++;
            }

        } catch (SQLException e) {
            //TODO: you need to throw or handle
        }

        finishData(listeners);
    }

    private void finishData(List listeners) {
        for (DataListener listener : listeners) {
            listener.finishSheet();
        }
    }

    private void newRow(List listeners,
                        int row,
                        int cols) {
        for (DataListener listener : listeners) {
            listener.newRow(row,
                            cols);
        }
    }

    public void newCell(List listeners,
                        int row,
                        int column,
                        String value,
                        int mergedColStart) {
        for (DataListener listener : listeners) {
            listener.newCell(row,
                             column,
                             value,
                             mergedColStart);
        }
    }

    protected void closeStream(final InputStream stream) {
        try {
            stream.close();
        } catch (final Exception e) {
            System.err.print("WARNING: Wasn't able to correctly close stream for rule template. " + e.getMessage());
        }
    }
}