/*
 * Copyright Red Hat, Inc. and/or its affiliates
 * and other contributors as indicated by the @author tags and
 * the COPYRIGHT.txt file distributed with this work.
 *
 * 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.teiid.query.function.aggregate;

import java.util.List;

import org.teiid.api.exception.query.ExpressionEvaluationException;
import org.teiid.api.exception.query.FunctionExecutionException;
import org.teiid.core.TeiidComponentException;
import org.teiid.query.QueryPlugin;
import org.teiid.query.sql.symbol.AggregateSymbol.Type;
import org.teiid.query.util.CommandContext;

/**
 * computes rank/dense_rank
 */
public class RankingFunction extends AggregateFunction {
	
	private int count = 0;
	private int lastCount = 0;
	private Type type;
	
	public RankingFunction(Type function) {
		this.type = function;
	}

	@Override
	public void reset() {
		count = 0;
		lastCount = 0;
	}
	
	@Override
	public void addInputDirect(List<?> tuple, CommandContext commandContext)
			throws FunctionExecutionException, ExpressionEvaluationException,
			TeiidComponentException {
		if (type == Type.RANK) {
			if (count == Integer.MAX_VALUE) {
				throw new ExpressionEvaluationException(QueryPlugin.Event.TEIID31174, QueryPlugin.Util.gs(QueryPlugin.Event.TEIID31174));
			}
			count++;
		}
	}
	
	@Override
	public Object getResult(CommandContext commandContext) throws FunctionExecutionException,
			ExpressionEvaluationException, TeiidComponentException {
		if (type == Type.DENSE_RANK) {
			if (count == Integer.MAX_VALUE) {
				throw new ExpressionEvaluationException(QueryPlugin.Event.TEIID31174, QueryPlugin.Util.gs(QueryPlugin.Event.TEIID31174));
			}
			count++;
			return count;
		}
		int result = ++lastCount;
		lastCount = count;
		return result;
	}

}
