/*
 * 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.cep;

import org.apache.flink.api.common.functions.Function;

import java.io.Serializable;
import java.util.List;
import java.util.Map;

/**
 * Base interface for a pattern timeout function. A pattern timeout function is called with a map
 * containing the timed out partial events which can be accessed by their names and the timestamp
 * when the timeout occurred. The names depend on the definition of the {@link
 * org.apache.flink.cep.pattern.Pattern}. The timeout method returns exactly one result. If you want
 * to return more than one result, then you have to implement a {@link PatternFlatTimeoutFunction}.
 *
 * <pre>{@code
 * PatternStream<IN> pattern = ...;
 *
 * DataStream<OUT> result = pattern.select(..., new MyPatternTimeoutFunction());
 * }</pre>
 *
 * @param <IN> Type of the input elements
 * @param <OUT> Type of the output element
 */
public interface PatternTimeoutFunction<IN, OUT> extends Function, Serializable {

    /**
     * Generates a timeout result from the given map of events and timeout timestamp. The partial
     * events are identified by their names. Only one resulting element can be generated.
     *
     * @param pattern Map containing the found partial pattern. Events are identified by their names
     * @param timeoutTimestamp Timestamp of the timeout
     * @return Resulting timeout element
     * @throws Exception This method may throw exceptions. Throwing an exception will cause the
     *     operation to fail and may trigger recovery.
     */
    OUT timeout(Map<String, List<IN>> pattern, long timeoutTimestamp) throws Exception;
}
