/*

   Derby - Class org.apache.derby.impl.sql.compile.OrderByColumn

   Licensed to the Apache Software Foundation (ASF) under one or more
   contributor license agreements.  See the NOTICE file distributed with
   this work for additional information regarding copyright ownership.
   The ASF licenses this file to you 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.apache.derby.impl.sql.compile;

import org.apache.derby.shared.common.error.StandardException;
import org.apache.derby.shared.common.reference.SQLState;
import org.apache.derby.iapi.services.context.ContextManager;
import org.apache.derby.shared.common.sanity.SanityManager;
import org.apache.derby.iapi.sql.compile.Visitor;

/**
 * An OrderByColumn is a column in the ORDER BY clause.  An OrderByColumn
 * can be ordered ascending or descending.
 *
 * We need to make sure that the named columns are
 * columns in that query, and that positions are within range.
 *
 */
class OrderByColumn extends OrderedColumn {

	private ResultColumn	resultCol;
	private boolean			ascending = true;
	private boolean			nullsOrderedLow = false;
	private ValueNode expression;
	private OrderByList     list;
    /**
     * If this sort key is added to the result column list then it is at result column position
     * 1 + resultColumnList.size() - resultColumnList.getOrderBySelect() + addedColumnOffset
     * If the sort key is already in the result column list then addedColumnOffset &lt; 0.
     */
    private int addedColumnOffset = -1;


   	/**
     * Constructor.
	 *
	 * @param expression            Expression of this column
     * @param cm                    The context manager
	 */
    OrderByColumn(ValueNode expression, ContextManager cm)
	{
        super(cm);
        this.expression = expression;
	}
	
	/**
	 * Convert this object to a String.  See comments in QueryTreeNode.java
	 * for how this should be done for tree printing.
	 *
	 * @return	This object as a String
	 */
    @Override
	public String toString() {
		if (SanityManager.DEBUG) {
			return
				"nullsOrderedLow: " + nullsOrderedLow + "\n" +
				"ascending; " + ascending + "\n" +
				"addedColumnOffset: " + addedColumnOffset + "\n" +
				super.toString();
		} else {
			return "";
		}
	}

	/**
	 * Prints the sub-nodes of this object.  See QueryTreeNode.java for
	 * how tree printing is supposed to work.
	 *
	 * @param depth		The depth of this node in the tree
	 */
    @Override
    void printSubNodes(int depth)
	{
		if (SanityManager.DEBUG)
		{
			super.printSubNodes(depth);

			if (expression != null) {
				printLabel(depth, "expression: ");
				expression.treePrint(depth + 1);
			}

			if (resultCol != null) {
				printLabel(depth, "resultCol: ");
				resultCol.treePrint(depth + 1);
			}
		}
	}

	/**
	 * Mark the column as descending order
	 */
    void setDescending() {
		ascending = false;
	}

	/**
	 * Get the column order.  Overrides 
	 * OrderedColumn.isAscending.
	 *
	 * @return true if ascending, false if descending
	 */
    @Override
    boolean isAscending() {
		return ascending;
	}

	/**
	 * Mark the column as ordered NULL values lower than non-NULL values.
	 */
    void setNullsOrderedLow() {
		nullsOrderedLow = true;
	}

	/**
	 * Get the column NULL ordering. Overrides
	 * OrderedColumn.getIsNullsOrderedLow.
	 *
	 * @return true if NULLs ordered low, false if NULLs ordered high
	 */
    @Override
    boolean isNullsOrderedLow() {
		return nullsOrderedLow;
	}

	/**
	 * Get the underlying ResultColumn.
	 *
	 * @return The underlying ResultColumn.
	 */
	ResultColumn getResultColumn()
	{
		return resultCol;
	}

	/**
	 * Get the underlying expression, skipping over ResultColumns that
	 * are marked redundant.
	 */
	ValueNode getNonRedundantExpression()
	{
		ResultColumn	rc;
		ValueNode		value;
		ColumnReference	colref = null;

		for (rc = resultCol; rc.isRedundant(); rc = colref.getSource())
		{
			value = rc.getExpression();

			if (value instanceof ColumnReference)
			{
				colref = (ColumnReference) value;
			}
			else
			{
				if (SanityManager.DEBUG)
				{
					SanityManager.THROWASSERT(
						"value should be a ColumnReference, but is a " +
						value.getClass().getName());
				}
			}
		}

		return rc.getExpression();
	}

	/**
	 * Bind this column.
	 *
	 * During binding, we may discover that this order by column was pulled
	 * up into the result column list, but is now a duplicate, because the
	 * actual result column was expanded into the result column list when "*"
	 * expressions were replaced with the list of the table's columns. In such
	 * a situation, we will end up calling back to the OrderByList to
	 * adjust the addedColumnOffset values of the columns; the "oblist"
	 * parameter exists to allow that callback to be performed.
	 *
	 * @param target	The result set being selected from
	 * @param oblist    OrderByList which contains this column
	 *
	 * @exception StandardException		Thrown on error
	 * @exception StandardException		Thrown when column not found
	 */
    void bindOrderByColumn(ResultSetNode target, OrderByList oblist)
				throws StandardException 
	{
		this.list = oblist;

		if(expression instanceof ColumnReference){
		
			ColumnReference cr = (ColumnReference) expression;
			
			resultCol = resolveColumnReference(target,
							   cr);
			
			columnPosition = resultCol.getColumnPosition();

			if (addedColumnOffset >= 0 &&
					target instanceof SelectNode &&
					( (SelectNode)target ).hasDistinct())
				throw StandardException.newException(SQLState.LANG_DISTINCT_ORDER_BY, cr.getColumnName());
		}else if(isReferedColByNum(expression)){
			
			ResultColumnList targetCols = target.getResultColumns();
			columnPosition = ((Integer)expression.getConstantValueAsObject()).intValue();
			resultCol = targetCols.getOrderByColumn(columnPosition);

			/* Column is out of range if either a) resultCol is null, OR
			 * b) resultCol points to a column that is not visible to the
			 * user (i.e. it was generated internally).
			 */
			if ((resultCol == null) ||
				(resultCol.getColumnPosition() > targetCols.visibleSize()))
			{
				throw StandardException.newException(SQLState.LANG_COLUMN_OUT_OF_RANGE, 
								     String.valueOf(columnPosition));
			}

		}else{
            if (list.isTableValueCtorOrdering()) {
                // For VALUES, we only allow ordering by column number,
                // SQL-92 style. This is a more general expression, so throw.
                throw StandardException.newException(
                        SQLState.LANG_TABLE_VALUE_CTOR_RESTRICTION);
            }

			/*checks for the conditions when using distinct*/
			if (addedColumnOffset >= 0 &&
					target instanceof SelectNode &&
					((SelectNode)target).hasDistinct() &&
					!expressionMatch(target))
			{
                CollectNodesVisitor<ColumnReference> collectNodesVisitor =
                    new CollectNodesVisitor<ColumnReference>(
                        ColumnReference.class);
				expression.accept(collectNodesVisitor);

                for (ColumnReference cr1 : collectNodesVisitor.getList())
				{//visits through the columns in this OrderByColumn
                    String col=cr1.getColumnName();
                    boolean match = columnMatchFound(target,cr1);
					/* breaks if a match not found, this is needed
					 * because all column references in this
					 * OrderByColumn should be there in the select
					 * clause.*/
					if(!match)
						throw StandardException.newException(
								SQLState.LANG_DISTINCT_ORDER_BY,
								col);
				}
			}

			if( SanityManager.DEBUG)
				SanityManager.ASSERT( addedColumnOffset >= 0,
				"Order by expression was not pulled into the result column list");
			resolveAddedColumn(target);
			if (resultCol == null)
				throw StandardException.newException(SQLState.LANG_UNION_ORDER_BY);
		}

		// Verify that the column is orderable
		resultCol.verifyOrderable();
	}

	/**
	 * Checks whether the whole expression (OrderByColumn) itself
	 * found in the select clause.
	 * @param target Result set
	 * @return boolean: whether any expression match found
	 * @throws StandardException
	 */
	private boolean expressionMatch(ResultSetNode target)
										throws StandardException{
		ResultColumnList rcl=target.getResultColumns();
		for (int i=1; i<=rcl.visibleSize();i++){
			//since RCs are 1 based
			if((rcl.getResultColumn(i)).isEquivalent(
					resultCol))
				return true;
		}
		return false;
	}

	/**
	 * This method checks a ColumnReference of this OrderByColumn
	 * against the ColumnReferences of the select clause of the query.
	 * @param target result set
	 * @param crOfExpression the CR to be checked
	 * @return whether a match found or not
	 * @throws StandardException
	 */
	private boolean columnMatchFound(ResultSetNode target,
			ColumnReference crOfExpression) throws StandardException{
		ResultColumnList rcl=target.getResultColumns();
		for (int i=1; i<=rcl.visibleSize();
		i++){//grab the RCs related to select clause
			ValueNode exp=rcl.getResultColumn(i).getExpression();
			if(exp instanceof ColumnReference)
			{//visits through the columns in the select clause
				ColumnReference cr2 =
					(ColumnReference) (exp);
				if(crOfExpression.isEquivalent(cr2))
					return true;
			}
		}
		return false;
	}

    /**
     * Assuming this OrderByColumn was "pulled" into the received target's
     * ResultColumnList (because it wasn't there to begin with), use
     * this.addedColumnOffset to figure out which of the target's result
     * columns is the one corresponding to "this".
     *
     * The desired position is w.r.t. the original, user-specified result
     * column list--which is what "visibleSize()" gives us.  I.e. To get
     * this OrderByColumn's position in target's RCL, first subtract out
     * all columns which were "pulled" into the RCL for GROUP BY or ORDER
     * BY, then add "this.addedColumnOffset". As an example, if the query
     * was:
     *
     *   select sum(j) as s from t1 group by i, k order by k, sum(k)
     *
     * then we will internally add columns "K" and "SUM(K)" to the RCL for
     * ORDER BY, *AND* we will add a generated column "I" to the RCL for
     * GROUP BY.  Thus we end up with four result columns:
     *
     *          (1)        (2)  (3)   (4)
     *  select sum(j) as s, K, SUM(K), I from t1 ...
     *
     * So when we get here and we want to find out which column "this"
     * corresponds to, we begin by taking the total number of VISIBLE
     * columns, which is 1 (i.e. 4 total columns minus 1 GROUP BY column
     * minus 2 ORDER BY columns).  Then we add this.addedColumnOffset in
     * order to find the target column position.  Since addedColumnOffset
     * is 0-based, an addedColumnOffset value of "0" means we want the
     * the first ORDER BY column added to target's RCL, "1" means we want
     * the second ORDER BY column added, etc.  So if we assume that
     * this.addedColumnOffset is "1" in this example then we add that
     * to the RCL's "visible size". And finally, we add 1 more to account
     * for fact that addedColumnOffset is 0-based while column positions
     * are 1-based. This gives:
     *
     *  position = 1 + 1 + 1 = 3
     *
     * which points to SUM(K) in the RCL.  Thus an addedColumnOffset
     * value of "1" resolves to column SUM(K) in target's RCL; similarly,
     * an addedColumnOffset value of "0" resolves to "K". DERBY-3303.
     */
    private void resolveAddedColumn(ResultSetNode target)
    {
        ResultColumnList targetCols = target.getResultColumns();
        columnPosition = targetCols.visibleSize() + addedColumnOffset + 1;
        resultCol = targetCols.getResultColumn( columnPosition);
    }

	/**
	 * Pull up this orderby column if it doesn't appear in the resultset
	 *
	 * @param target	The result set being selected from
	 *
	 */
    void pullUpOrderByColumn(ResultSetNode target)
				throws StandardException 
	{
        ResultColumnList targetCols = target.getResultColumns();

        if(expression instanceof ColumnReference){

			ColumnReference cr = (ColumnReference) expression;

			resultCol = targetCols.findResultColumnForOrderBy(
                    cr.getColumnName(), cr.getQualifiedTableName());

			if(resultCol == null){
               resultCol = new ResultColumn(
                        cr.getColumnName(), cr, getContextManager());
				targetCols.addResultColumn(resultCol);
                addedColumnOffset = targetCols.getOrderBySelect();
				targetCols.incOrderBySelect();
			}
			
		}else if(!isReferedColByNum(expression)){
           resultCol = new ResultColumn(
                    (String)null, expression, getContextManager());
			targetCols.addResultColumn(resultCol);
            addedColumnOffset = targetCols.getOrderBySelect();
			targetCols.incOrderBySelect();
		}
	}

	/**
	 * Order by columns now point to the PRN above the node of interest.
	 * We need them to point to the RCL under that one.  This is useful
	 * when combining sorts where we need to reorder the sorting
	 * columns.
	 */
	void resetToSourceRC()
	{
		if (SanityManager.DEBUG)
		{
			if (! (resultCol.getExpression() instanceof VirtualColumnNode))
			{
				SanityManager.THROWASSERT(
					"resultCol.getExpression() expected to be instanceof VirtualColumnNode " +
					", not " + resultCol.getExpression().getClass().getName());
			}
		}

		resultCol = resultCol.getExpression().getSourceResultColumn();
	}

	/**
	 * Is this OrderByColumn constant, according to the given predicate list?
	 * A constant column is one where all the column references it uses are
	 * compared equal to constants.
	 */
	boolean constantColumn(PredicateList whereClause)
	{
		ValueNode sourceExpr = resultCol.getExpression();

		return sourceExpr.constantExpression(whereClause);
	}

	/**
	 * Remap all the column references under this OrderByColumn to their
	 * expressions.
	 *
	 * @exception StandardException		Thrown on error
	 */
	void remapColumnReferencesToExpressions() throws StandardException
	{
		resultCol.setExpression(
			resultCol.getExpression().remapColumnReferencesToExpressions());
	}

	private static boolean isReferedColByNum(ValueNode expression) 
	throws StandardException{
		
       return expression instanceof NumericConstantNode &&
               expression.getConstantValueAsObject() instanceof Integer;
	}

	
	private ResultColumn resolveColumnReference(ResultSetNode target,
							   ColumnReference cr)
            throws StandardException {
		int					sourceTableNumber = -1;
		
		//bug 5716 - for db2 compatibility - no qualified names allowed in order by clause when union/union all operator is used 

		if (target instanceof SetOperatorNode && cr.getTableName() != null){
			String fullName = cr.getSQLColumnName();
			throw StandardException.newException(SQLState.LANG_QUALIFIED_COLUMN_NAME_NOT_ALLOWED, fullName);
		}

		if(cr.getQualifiedTableName() != null){
			TableName tableNameNode = cr.getQualifiedTableName();

			FromTable fromTable = target.getFromTableByName(tableNameNode.getTableName(),
									(tableNameNode.hasSchema() ?
									 tableNameNode.getSchemaName():null),
									true);
			if(fromTable == null){
				fromTable = target.getFromTableByName(tableNameNode.getTableName(),
								      (tableNameNode.hasSchema() ?
								       tableNameNode.getSchemaName():null),
								      false);
				if(fromTable == null){
					String fullName = cr.getQualifiedTableName().toString();
					throw StandardException.newException(SQLState.LANG_EXPOSED_NAME_NOT_FOUND, fullName);
				}
			}

			/* HACK - if the target is a UnionNode, then we have to
			 * have special code to get the sourceTableNumber.  This is
			 * because of the gyrations we go to with building the RCLs
			 * for a UnionNode.
			 */
			if (target instanceof SetOperatorNode)
			{
				sourceTableNumber = ((FromTable) target).getTableNumber();
			}
			else
			{
				sourceTableNumber = fromTable.getTableNumber();
			}
			
		}

		ResultColumnList	targetCols = target.getResultColumns();

        ResultColumn resCol = targetCols.getOrderByColumnToBind(
                            cr.getColumnName(),
							cr.getQualifiedTableName(),
							sourceTableNumber,
							this);
        /* Search targetCols before using addedColumnOffset because select list wildcards, '*',
         * are expanded after pullUpOrderByColumn is called. A simple column reference in the
         * order by clause may be found in the user specified select list now even though it was
         * not found when pullUpOrderByColumn was called.
         */
        if( resCol == null && addedColumnOffset >= 0)
            resolveAddedColumn(target);
							
        if (resCol == null || resCol.isNameGenerated()){
			String errString = cr.getColumnName();
			throw StandardException.newException(SQLState.LANG_ORDER_BY_COLUMN_NOT_FOUND, errString);
		}

        return resCol;

	}

	/**
	 * Reset addedColumnOffset to indicate that column is no longer added
	 *
	 * An added column is one which was artificially added to the result
	 * column list due to its presence in the ORDER BY clause, as opposed to
	 * having been explicitly selected by the user. Since * is not expanded
	 * until after the ORDER BY columns have been pulled up, we may add a
	 * column, then later decide it is a duplicate of an explicitly selected
	 * column. In that case, this method is called, and it does the following:
	 * - resets addedColumnOffset to -1 to indicate this is not an added col
	 * - calls back to the OrderByList to adjust any other added cols
	 */
	void clearAddedColumnOffset()
	{
		list.closeGap(addedColumnOffset);
		addedColumnOffset = -1;
	}
	/**
	 * Adjust addedColumnOffset to reflect that a column has been removed
	 *
	 * This routine is called when a previously-added result column has been
	 * removed due to being detected as a duplicate. If that added column had
	 * a lower offset than our column, we decrement our offset to reflect that
	 * we have just been moved down one slot in the result column list.
	 *
	 * @param gap   offset of the column which has just been removed from list
	 */
	void collapseAddedColumnGap(int gap)
	{
		if (addedColumnOffset > gap)
			addedColumnOffset--;
	}


	/**
	 * Accept the visitor for all visitable children of this node.
	 *
	 * @param v the visitor
	 *
	 * @exception StandardException on error
	 */
    @Override
	void acceptChildren(Visitor v)
		throws StandardException
	{
		super.acceptChildren(v);

		if (expression != null)
		{
			expression = (ValueNode)expression.accept(v);
		}
	}

    ValueNode getExpression() {
        return expression;
    }
}
