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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.
 * 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 org.dashbuilder.dataprovider.sql.dialect;

import java.util.HashMap;
import java.util.Map;

import org.dashbuilder.dataprovider.sql.model.Column;
import org.dashbuilder.dataprovider.sql.model.DynamicDateColumn;
import org.dashbuilder.dataprovider.sql.model.Select;
import org.dashbuilder.dataset.group.DateIntervalType;

public class DB2Dialect extends DefaultDialect {

    public static final String PATTERN_YEAR = "YYYY";
    public static final String PATTERN_MONTH = "YYYY-MM";
    public static final String PATTERN_DAY = "YYYY-MM-DD";
    public static final String PATTERN_HOUR = "YYYY-MM-DD HH24";
    public static final String PATTERN_MINUTE = "YYYY-MM-DD HH24:MI";
    public static final String PATTERN_SECOND = "YYYY-MM-DD HH24:MI:SS";

    private static Map datePatternMap = new HashMap();
    static {
        datePatternMap.put(DateIntervalType.SECOND, PATTERN_SECOND);
        datePatternMap.put(DateIntervalType.MINUTE, PATTERN_MINUTE);
        datePatternMap.put(DateIntervalType.HOUR, PATTERN_HOUR);
        datePatternMap.put(DateIntervalType.DAY, PATTERN_DAY);
        datePatternMap.put(DateIntervalType.WEEK, PATTERN_DAY);
        datePatternMap.put(DateIntervalType.MONTH, PATTERN_MONTH);
        datePatternMap.put(DateIntervalType.QUARTER, PATTERN_MONTH);
        datePatternMap.put(DateIntervalType.YEAR, PATTERN_YEAR);
        datePatternMap.put(DateIntervalType.DECADE, PATTERN_YEAR);
        datePatternMap.put(DateIntervalType.CENTURY, PATTERN_YEAR);
        datePatternMap.put(DateIntervalType.MILLENIUM, PATTERN_YEAR);
    }

    @Override
    public String getConcatFunctionSQL(Column[] columns) {
        return super.getConcatFunctionSQL(columns, "CONCAT(", ")", ",");
    }

    @Override
    public String getDynamicDateColumnSQL(DynamicDateColumn column) {
        DateIntervalType type = column.getDateType();
        if (!datePatternMap.containsKey(type)) {
            throw new IllegalArgumentException("Group '" + column.getName() +
                    "' by the given date interval type is not supported: " + type);
        }
        String datePattern = datePatternMap.get(type);
        String columnName = getColumnNameSQL(column.getName());
        return "VARCHAR_FORMAT(" + columnName + ", '" + datePattern + "')";
    }

    @Override
    public String getSQL(Select select) {

        String sql = super.getSQL(select);

        int offset = select.getOffset();
        int limit = select.getLimit();

        if (limit > 0) {
            sql += " FETCH FIRST " + (limit + (offset > 0 ? offset : 0)) + " ROWS ONLY";
        }

        if (offset > 0) {
            return "SELECT * FROM (SELECT Q.*, ROWNUMBER() OVER(ORDER BY ORDER OF Q) AS RN FROM (" + sql + ") AS Q)  WHERE RN > " + offset + " ORDER BY RN";
        }
        else {
            return sql;
        }
    }

    @Override
    public String getOffsetLimitSQL(Select select) {
        return null;
    }
}