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This module bridges Table/SQL API and runtime. It contains all resources that are required during pre-flight and runtime phase. The content of this module is work-in-progress. It will replace flink-table-planner once it is stable. See FLINK-11439 and FLIP-32 for more details.
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/*
 * 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.flink.table.planner.functions.aggfunctions;

import org.apache.flink.table.api.DataTypes;
import org.apache.flink.table.api.TableException;
import org.apache.flink.table.expressions.Expression;
import org.apache.flink.table.expressions.UnresolvedReferenceExpression;
import org.apache.flink.table.types.DataType;
import org.apache.flink.table.types.logical.DecimalType;
import org.apache.flink.table.types.logical.utils.LogicalTypeMerging;

import static org.apache.flink.table.expressions.ApiExpressionUtils.unresolvedRef;
import static org.apache.flink.table.planner.expressions.ExpressionBuilder.ifThenElse;
import static org.apache.flink.table.planner.expressions.ExpressionBuilder.isNull;
import static org.apache.flink.table.planner.expressions.ExpressionBuilder.lessThan;
import static org.apache.flink.table.planner.expressions.ExpressionBuilder.literal;
import static org.apache.flink.table.planner.expressions.ExpressionBuilder.nullOf;
import static org.apache.flink.table.planner.expressions.ExpressionBuilder.or;
import static org.apache.flink.table.planner.expressions.ExpressionBuilder.plus;

/** built-in IncrSum aggregate function, negative number is discarded to ensure the monotonicity. */
public abstract class IncrSumAggFunction extends DeclarativeAggregateFunction {
    private UnresolvedReferenceExpression sum = unresolvedRef("sum");

    @Override
    public int operandCount() {
        return 1;
    }

    @Override
    public UnresolvedReferenceExpression[] aggBufferAttributes() {
        return new UnresolvedReferenceExpression[] {sum};
    }

    @Override
    public DataType[] getAggBufferTypes() {
        return new DataType[] {getResultType()};
    }

    @Override
    public Expression[] initialValuesExpressions() {
        return new Expression[] {/* sum = */ nullOf(getResultType())};
    }

    @Override
    public Expression[] accumulateExpressions() {
        return new Expression[] {
            /* sum = */ ifThenElse(
                    or(isNull(operand(0)), lessThan(operand(0), literal(0L))),
                    sum,
                    ifThenElse(isNull(sum), operand(0), plus(sum, operand(0))))
        };
    }

    @Override
    public Expression[] retractExpressions() {
        throw new TableException(
                "This function does not support retraction, Please choose SumWithRetractAggFunction.");
    }

    @Override
    public Expression[] mergeExpressions() {
        return new Expression[] {
            /* sum = */ ifThenElse(
                    isNull(mergeOperand(sum)),
                    sum,
                    ifThenElse(isNull(sum), mergeOperand(sum), plus(sum, mergeOperand(sum))))
        };
    }

    @Override
    public Expression getValueExpression() {
        return sum;
    }

    /** Built-in Int IncrSum aggregate function. */
    public static class IntIncrSumAggFunction extends IncrSumAggFunction {

        @Override
        public DataType getResultType() {
            return DataTypes.INT();
        }
    }

    /** Built-in Byte IncrSum aggregate function. */
    public static class ByteIncrSumAggFunction extends IncrSumAggFunction {
        @Override
        public DataType getResultType() {
            return DataTypes.TINYINT();
        }
    }

    /** Built-in Short IncrSum aggregate function. */
    public static class ShortIncrSumAggFunction extends IncrSumAggFunction {
        @Override
        public DataType getResultType() {
            return DataTypes.SMALLINT();
        }
    }

    /** Built-in Long IncrSum aggregate function. */
    public static class LongIncrSumAggFunction extends IncrSumAggFunction {
        @Override
        public DataType getResultType() {
            return DataTypes.BIGINT();
        }
    }

    /** Built-in Float IncrSum aggregate function. */
    public static class FloatIncrSumAggFunction extends IncrSumAggFunction {
        @Override
        public DataType getResultType() {
            return DataTypes.FLOAT();
        }
    }

    /** Built-in Double IncrSum aggregate function. */
    public static class DoubleIncrSumAggFunction extends IncrSumAggFunction {
        @Override
        public DataType getResultType() {
            return DataTypes.DOUBLE();
        }
    }

    /** Built-in Decimal IncrSum aggregate function. */
    public static class DecimalIncrSumAggFunction extends IncrSumAggFunction {
        private DecimalType decimalType;

        public DecimalIncrSumAggFunction(DecimalType decimalType) {
            this.decimalType = decimalType;
        }

        @Override
        public DataType getResultType() {
            DecimalType sumType = (DecimalType) LogicalTypeMerging.findSumAggType(decimalType);
            return DataTypes.DECIMAL(sumType.getPrecision(), sumType.getScale());
        }
    }
}