DynamicDataNode.java
/*
* Copyright 2022 The Android Open Source Project
*
* 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 androidx.wear.protolayout.expression.pipeline;
/**
* Node within a dynamic data pipeline.
*
* <p>Each node should either be a {@link DynamicDataSourceNode}, in which case it pushes data into
* the pipeline, or it should expose one or more callbacks (generally instances of {@link
* DynamicTypeValueReceiver}), which can be used by an upstream node to "push" data through the
* pipeline. A node would typically look like the following:
*
* <pre>{@code
* class IntToStringNode implements DynamicDataNode<String> {
* // The consumer on the downstream node to push data to.
* private final DynamicTypeValueReceiver<String> downstreamNode;
*
* private final DynamicTypeValueReceiver<Integer> myNode =
* new DynamicTypeValueReceiver<Integer>() {
* @Override
* public void onPreStateUpdate() {
* // Don't need to do anything here; just relay.
* downstreamNode.onPreStateUpdate();
* }
*
* @Override
* public void onStateUpdate(Integer newData) {
* downstreamNode.onStateUpdate(newData.toString());
* }
* };
*
* public DynamicTypeValueReceiver<Integer> getConsumer() { return myNode; }
* }
* }</pre>
*
* An upstream node (i.e. one which yields an Integer) would then push data in to this node, via the
* consumer returned from {@code IntToStringNode#getConsumer}.
*
* <p>Generally, node implementations will not use this interface directly; {@link
* DynamicDataTransformNode} and {@link DynamicDataBiTransformNode} provide canonical
* implementations for transforming data pushed from one or two source nodes, to a downstream node.
*
* @param <O> The data type that this node yields.
*/
interface DynamicDataNode<O> {}