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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.bridging;

import org.apache.flink.annotation.Internal;
import org.apache.flink.table.catalog.DataTypeFactory;
import org.apache.flink.table.functions.FunctionDefinition;
import org.apache.flink.table.functions.FunctionIdentifier;
import org.apache.flink.table.functions.FunctionKind;
import org.apache.flink.table.functions.FunctionRequirement;
import org.apache.flink.table.planner.calcite.FlinkTypeFactory;
import org.apache.flink.table.types.DataType;
import org.apache.flink.table.types.inference.TypeInference;

import org.apache.calcite.rel.type.RelDataType;
import org.apache.calcite.sql.SqlAggFunction;
import org.apache.calcite.sql.SqlKind;
import org.apache.calcite.util.Optionality;

import javax.annotation.Nullable;

import java.util.List;
import java.util.Optional;

import static org.apache.flink.table.planner.functions.bridging.BridgingUtils.createName;
import static org.apache.flink.table.planner.functions.bridging.BridgingUtils.createParamTypes;
import static org.apache.flink.table.planner.functions.bridging.BridgingUtils.createSqlFunctionCategory;
import static org.apache.flink.table.planner.functions.bridging.BridgingUtils.createSqlIdentifier;
import static org.apache.flink.table.planner.functions.bridging.BridgingUtils.createSqlOperandTypeChecker;
import static org.apache.flink.table.planner.functions.bridging.BridgingUtils.createSqlOperandTypeInference;
import static org.apache.flink.table.planner.functions.bridging.BridgingUtils.createSqlReturnTypeInference;
import static org.apache.flink.util.Preconditions.checkState;

/**
 * Bridges {@link FunctionDefinition} to Calcite's representation of an aggregating function
 * (either a system or user-defined function).
 */
@Internal
public final class BridgingSqlAggFunction extends SqlAggFunction {

	private final DataTypeFactory dataTypeFactory;

	private final FlinkTypeFactory typeFactory;

	private final @Nullable FunctionIdentifier identifier;

	private final FunctionDefinition definition;

	private final TypeInference typeInference;

	private final List paramTypes;

	private BridgingSqlAggFunction(
			DataTypeFactory dataTypeFactory,
			FlinkTypeFactory typeFactory,
			SqlKind kind,
			@Nullable FunctionIdentifier identifier,
			FunctionDefinition definition,
			TypeInference typeInference) {
		super(
			createName(identifier, definition),
			createSqlIdentifier(identifier),
			kind,
			createSqlReturnTypeInference(dataTypeFactory, definition, typeInference),
			createSqlOperandTypeInference(dataTypeFactory, definition, typeInference),
			createSqlOperandTypeChecker(dataTypeFactory, definition, typeInference),
			createSqlFunctionCategory(identifier),
			createOrderRequirement(),
			createOverWindowRequirement(definition),
			createGroupOrderRequirement());

		this.dataTypeFactory = dataTypeFactory;
		this.typeFactory = typeFactory;
		this.identifier = identifier;
		this.definition = definition;
		this.typeInference = typeInference;
		this.paramTypes = createParamTypes(typeFactory, typeInference);
	}

	/**
	 * Creates an instance of a aggregating function (either a system or user-defined function).
	 *
	 * @param dataTypeFactory used for creating {@link DataType}
	 * @param typeFactory used for bridging to {@link RelDataType}
	 * @param kind commonly used SQL standard function; use {@link SqlKind#OTHER_FUNCTION} if this function
	 *             cannot be mapped to a common function kind.
	 * @param identifier catalog identifier
	 * @param definition system or user-defined {@link FunctionDefinition}
	 * @param typeInference type inference logic
	 */
	public static BridgingSqlAggFunction of(
			DataTypeFactory dataTypeFactory,
			FlinkTypeFactory typeFactory,
			SqlKind kind,
			FunctionIdentifier identifier,
			FunctionDefinition definition,
			TypeInference typeInference) {

		checkState(
			definition.getKind() == FunctionKind.AGGREGATE || definition.getKind() == FunctionKind.TABLE_AGGREGATE,
			"Aggregating function kind expected.");

		return new BridgingSqlAggFunction(
			dataTypeFactory,
			typeFactory,
			kind,
			identifier,
			definition,
			typeInference);
	}

	public DataTypeFactory getDataTypeFactory() {
		return dataTypeFactory;
	}

	public FlinkTypeFactory getTypeFactory() {
		return typeFactory;
	}

	public Optional getIdentifier() {
		return Optional.ofNullable(identifier);
	}

	public FunctionDefinition getDefinition() {
		return definition;
	}

	public TypeInference getTypeInference() {
		return typeInference;
	}

	@Override
	public List getParamTypes() {
		return paramTypes;
	}

	@Override
	public List getParamNames() {
		if (typeInference.getNamedArguments().isPresent()) {
			return typeInference.getNamedArguments().get();
		}
		return super.getParamNames();
	}

	@Override
	public boolean isDeterministic() {
		return definition.isDeterministic();
	}

	// --------------------------------------------------------------------------------------------

	private static boolean createOrderRequirement() {
		return false;
	}

	private static boolean createOverWindowRequirement(FunctionDefinition definition) {
		return definition.getRequirements().contains(FunctionRequirement.OVER_WINDOW_ONLY);
	}

	private static Optionality createGroupOrderRequirement() {
		return Optionality.FORBIDDEN;
	}
}