/*
* 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.beam.sdk.state;
import java.util.Map;
import org.apache.beam.sdk.annotations.Experimental;
import org.apache.beam.sdk.annotations.Experimental.Kind;
/**
* A {@link ReadableState} cell mapping keys to values.
*
* <p>Implementations of this form of state are expected to implement map operations efficiently
* as supported by some associated backing key-value store.
*
* @param <K> the type of keys maintained by this map
* @param <V> the type of mapped values
*/
@Experimental(Kind.STATE)
public interface MapState<K, V> extends State {
/** Associates the specified value with the specified key in this state. */
void put(K key, V value);
/**
* A deferred read-followed-by-write.
*
* <p>When {@code read()} is called on the result or state is committed, it forces a read of the
* map and reconciliation with any pending modifications.
*
* <p>If the specified key is not already associated with a value (or is mapped to {@code null})
* associates it with the given value and returns {@code null}, else returns the current value.
*/
ReadableState<V> putIfAbsent(K key, V value);
/** Remove the mapping for a key from this map if it is present. */
void remove(K key);
/**
* A deferred lookup.
*
* <p>A user is encouraged to call {@code get} for all relevant keys and call {@code readLater()}
* on the results.
*
* <p>When {@code read()} is called, a particular state implementation is encouraged to perform
* all pending reads in a single batch.
*/
ReadableState<V> get(K key);
/** Returns an {@link Iterable} over the keys contained in this map. */
ReadableState<Iterable<K>> keys();
/** Returns an {@link Iterable} over the values contained in this map. */
ReadableState<Iterable<V>> values();
/** Returns an {@link Iterable} over the key-value pairs contained in this map. */
ReadableState<Iterable<Map.Entry<K, V>>> entries();
}