ConditionalOpNode.java
/*
* Copyright 2023 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;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
/** Dynamic data nodes which yield result based on the given condition. */
class ConditionalOpNode<T> implements DynamicDataNode<T> {
private final DynamicTypeValueReceiverWithPreUpdate<T> mTrueValueIncomingCallback;
private final DynamicTypeValueReceiverWithPreUpdate<T> mFalseValueIncomingCallback;
private final DynamicTypeValueReceiverWithPreUpdate<Boolean> mConditionIncomingCallback;
final DynamicTypeValueReceiverWithPreUpdate<T> mDownstream;
@Nullable Boolean mLastConditional;
@Nullable T mLastTrueValue;
@Nullable T mLastFalseValue;
// Counters to track how many "in-flight" updates are pending for each input. If any of these
// are >0, then we're still waiting for onData() to be called for one of the callbacks, so we
// shouldn't emit any values until they have all resolved.
int mPendingConditionalUpdates = 0;
int mPendingTrueValueUpdates = 0;
int mPendingFalseValueUpdates = 0;
ConditionalOpNode(DynamicTypeValueReceiverWithPreUpdate<T> downstream) {
mDownstream = downstream;
// These classes refer to this.handleUpdate, which is @UnderInitialization when these
// initializers run, and hence raise an error. It's invalid to annotate
// handle{Pre}StateUpdate as @UnderInitialization (since it refers to initialized fields),
// and moving this assignment into the constructor yields the same error (since one of the
// fields has to be assigned first, when the class is still under initialization).
//
// The only path to get these is via get*IncomingCallback, which can only be called when the
// class is initialized (and which also cannot be called from a sub-constructor, as that
// will again complain that it's calling something which is @UnderInitialization). Given
// that, suppressing the warning in onData should be safe.
mTrueValueIncomingCallback =
new DynamicTypeValueReceiverWithPreUpdate<T>() {
@Override
public void onPreUpdate() {
mPendingTrueValueUpdates++;
if (mPendingTrueValueUpdates == 1
&& mPendingFalseValueUpdates == 0
&& mPendingConditionalUpdates == 0) {
mDownstream.onPreUpdate();
}
}
@SuppressWarnings("method.invocation")
@Override
public void onData(@NonNull T newData) {
if (mPendingTrueValueUpdates > 0) {
mPendingTrueValueUpdates--;
}
mLastTrueValue = newData;
handleUpdate();
}
@SuppressWarnings("method.invocation")
@Override
public void onInvalidated() {
if (mPendingTrueValueUpdates > 0) {
mPendingTrueValueUpdates--;
}
mLastTrueValue = null;
handleUpdate();
}
};
mFalseValueIncomingCallback =
new DynamicTypeValueReceiverWithPreUpdate<T>() {
@Override
public void onPreUpdate() {
mPendingFalseValueUpdates++;
if (mPendingTrueValueUpdates == 0
&& mPendingFalseValueUpdates == 1
&& mPendingConditionalUpdates == 0) {
mDownstream.onPreUpdate();
}
}
@SuppressWarnings("method.invocation")
@Override
public void onData(@NonNull T newData) {
if (mPendingFalseValueUpdates > 0) {
mPendingFalseValueUpdates--;
}
mLastFalseValue = newData;
handleUpdate();
}
@SuppressWarnings("method.invocation")
@Override
public void onInvalidated() {
if (mPendingFalseValueUpdates > 0) {
mPendingFalseValueUpdates--;
}
mLastFalseValue = null;
handleUpdate();
}
};
mConditionIncomingCallback =
new DynamicTypeValueReceiverWithPreUpdate<Boolean>() {
@Override
public void onPreUpdate() {
mPendingConditionalUpdates++;
if (mPendingTrueValueUpdates == 0
&& mPendingFalseValueUpdates == 0
&& mPendingConditionalUpdates == 1) {
mDownstream.onPreUpdate();
}
}
@SuppressWarnings("method.invocation")
@Override
public void onData(@NonNull Boolean newData) {
if (mPendingConditionalUpdates > 0) {
mPendingConditionalUpdates--;
}
mLastConditional = newData;
handleUpdate();
}
@SuppressWarnings("method.invocation")
@Override
public void onInvalidated() {
if (mPendingConditionalUpdates > 0) {
mPendingConditionalUpdates--;
}
mLastConditional = null;
handleUpdate();
}
};
}
public DynamicTypeValueReceiverWithPreUpdate<T> getTrueValueIncomingCallback() {
return mTrueValueIncomingCallback;
}
public DynamicTypeValueReceiverWithPreUpdate<T> getFalseValueIncomingCallback() {
return mFalseValueIncomingCallback;
}
public DynamicTypeValueReceiverWithPreUpdate<Boolean> getConditionIncomingCallback() {
return mConditionIncomingCallback;
}
void handleUpdate() {
if (mPendingTrueValueUpdates > 0
|| mPendingFalseValueUpdates > 0
|| mPendingConditionalUpdates > 0) {
return;
}
if (mLastTrueValue == null || mLastFalseValue == null || mLastConditional == null) {
mDownstream.onInvalidated();
return;
}
if (mLastConditional) {
mDownstream.onData(mLastTrueValue);
} else {
mDownstream.onData(mLastFalseValue);
}
}
}