package com.zhiqiyun.open.mybatis.paginator.dialect;

import com.zhiqiyun.open.mybatis.paginator.domain.PageBounds;
import org.apache.ibatis.mapping.MappedStatement;

/**
 * @author badqiu
 * @author miemiedev
 */
// Hibernate BUG: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2655
public class SQLServer2005Dialect extends Dialect {

    public SQLServer2005Dialect(MappedStatement mappedStatement, Object parameterObject, PageBounds pageBounds) {
        super(mappedStatement, parameterObject, pageBounds);
    }

    static String getOrderByPart(String sql) {
        String loweredString = sql.toLowerCase();
        int orderByIndex = loweredString.indexOf("order by");
        if (orderByIndex != -1) {
            // if we find a new "order by" then we need to ignore
            // the previous one since it was probably used for a subquery
            return sql.substring(orderByIndex);
        } else {
            return "";
        }
    }

    /**
     * Add a LIMIT clause to the given SQL SELECT
     * <p>
     * The LIMIT SQL will look like:
     * <p>
     * WITH query AS
     * (SELECT TOP 100 percent ROW_NUMBER() OVER (ORDER BY CURRENT_TIMESTAMP) as __row_number__, * from table_name)
     * SELECT *
     * FROM query
     * WHERE __row_number__ BETWEEN :offset and :lastRows
     * ORDER BY __row_number__
     *
     * @param sql    The SQL statement to base the limit query off of.
     * @param offset Offset of the first row to be returned by the query (zero-based)
     * @param limit  Maximum number of rows to be returned by the query
     * @return A new SQL statement with the LIMIT clause applied.
     */
    @Override
    protected String getLimitString(String sql, String offsetName, int offset, String limitName, int limit) {
        StringBuffer pagingBuilder = new StringBuffer();
        String orderby = getOrderByPart(sql);
        String distinctStr = "";

        String loweredString = sql.toLowerCase();
        String sqlPartString = sql;
        if (loweredString.trim().startsWith("select")) {
            int index = 6;
            if (loweredString.startsWith("select distinct")) {
                distinctStr = "DISTINCT ";
                index = 15;
            }
            sqlPartString = sqlPartString.substring(index);
        }
        pagingBuilder.append(sqlPartString);

        // if no ORDER BY is specified use fake ORDER BY field to avoid errors
        if (orderby == null || orderby.length() == 0) {
            orderby = "ORDER BY CURRENT_TIMESTAMP";
        }

        StringBuffer result = new StringBuffer();
        result.append("WITH query AS (SELECT ")
                .append(distinctStr)
                .append("TOP 100 PERCENT ")
                .append(" ROW_NUMBER() OVER (")
                .append(orderby)
                .append(") as __row_number__, ")
                .append(pagingBuilder)
                .append(") SELECT * FROM query WHERE __row_number__ > ? AND __row_number__ <= ?")
                .append(" ORDER BY __row_number__");
        setPageParameter(offsetName, offset, Integer.class);
        setPageParameter("__offsetEnd", offset + limit, Integer.class);
        return result.toString();
    }
}
