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 * Copyright (c) 2012, 2016, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */
package java.util.stream;

import java.util.Optional;
import java.util.OptionalDouble;
import java.util.OptionalInt;
import java.util.OptionalLong;
import java.util.Spliterator;
import java.util.concurrent.CountedCompleter;
import java.util.function.Predicate;
import java.util.function.Supplier;

/**
 * Factory for instances of a short-circuiting {@code TerminalOp} that searches
 * for an element in a stream pipeline, and terminates when it finds one.
 * Supported variants include find-first (find the first element in the
 * encounter order) and find-any (find any element, may not be the first in
 * encounter order.)
 *
 * @since 1.8
 */
final class FindOps {

 private FindOps() { }

 /**
 * Constructs a {@code TerminalOp} for streams of objects.
 *
 * @param <T> the type of elements of the stream
 * @param mustFindFirst whether the {@code TerminalOp} must produce the
 * first element in the encounter order
 * @return a {@code TerminalOp} implementing the find operation
 */
 @SuppressWarnings("unchecked")
 public static <T> TerminalOp<T, Optional<T>> makeRef(boolean mustFindFirst) {
 return (TerminalOp<T, Optional<T>>)
 (mustFindFirst ? FindSink.OfRef.OP_FIND_FIRST : FindSink.OfRef.OP_FIND_ANY);
 }

 /**
 * Constructs a {@code TerminalOp} for streams of ints.
 *
 * @param mustFindFirst whether the {@code TerminalOp} must produce the
 * first element in the encounter order
 * @return a {@code TerminalOp} implementing the find operation
 */
 public static TerminalOp<Integer, OptionalInt> makeInt(boolean mustFindFirst) {
 return mustFindFirst ? FindSink.OfInt.OP_FIND_FIRST : FindSink.OfInt.OP_FIND_ANY;
 }

 /**
 * Constructs a {@code TerminalOp} for streams of longs.
 *
 * @param mustFindFirst whether the {@code TerminalOp} must produce the
 * first element in the encounter order
 * @return a {@code TerminalOp} implementing the find operation
 */
 public static TerminalOp<Long, OptionalLong> makeLong(boolean mustFindFirst) {
 return mustFindFirst ? FindSink.OfLong.OP_FIND_FIRST : FindSink.OfLong.OP_FIND_ANY;
 }

 /**
 * Constructs a {@code FindOp} for streams of doubles.
 *
 * @param mustFindFirst whether the {@code TerminalOp} must produce the
 * first element in the encounter order
 * @return a {@code TerminalOp} implementing the find operation
 */
 public static TerminalOp<Double, OptionalDouble> makeDouble(boolean mustFindFirst) {
 return mustFindFirst ? FindSink.OfDouble.OP_FIND_FIRST : FindSink.OfDouble.OP_FIND_ANY;
 }

 /**
 * A short-circuiting {@code TerminalOp} that searches for an element in a
 * stream pipeline, and terminates when it finds one. Implements both
 * find-first (find the first element in the encounter order) and find-any
 * (find any element, may not be the first in encounter order.)
 *
 * @param <T> the output type of the stream pipeline
 * @param <O> the result type of the find operation, typically an optional
 * type
 */
 private static final class FindOp<T, O> implements TerminalOp<T, O> {
 private final StreamShape shape;
 final int opFlags;
 final O emptyValue;
 final Predicate<O> presentPredicate;
 final Supplier<TerminalSink<T, O>> sinkSupplier;

 /**
 * Constructs a {@code FindOp}.
 *
 * @param mustFindFirst if true, must find the first element in
 * encounter order, otherwise can find any element
 * @param shape stream shape of elements to search
 * @param emptyValue result value corresponding to "found nothing"
 * @param presentPredicate {@code Predicate} on result value
 * corresponding to "found something"
 * @param sinkSupplier supplier for a {@code TerminalSink} implementing
 * the matching functionality
 */
 FindOp(boolean mustFindFirst,
 StreamShape shape,
 O emptyValue,
 Predicate<O> presentPredicate,
 Supplier<TerminalSink<T, O>> sinkSupplier) {
 this.opFlags = StreamOpFlag.IS_SHORT_CIRCUIT | (mustFindFirst ? 0 : StreamOpFlag.NOT_ORDERED);
 this.shape = shape;
 this.emptyValue = emptyValue;
 this.presentPredicate = presentPredicate;
 this.sinkSupplier = sinkSupplier;
 }

 @Override
 public int getOpFlags() {
 return opFlags;
 }

 @Override
 public StreamShape inputShape() {
 return shape;
 }

 @Override
 public <S> O evaluateSequential(PipelineHelper<T> helper,
 Spliterator<S> spliterator) {
 O result = helper.wrapAndCopyInto(sinkSupplier.get(), spliterator).get();
 return result != null ? result : emptyValue;
 }

 @Override
 public <P_IN> O evaluateParallel(PipelineHelper<T> helper,
 Spliterator<P_IN> spliterator) {
 // This takes into account the upstream ops flags and the terminal
 // op flags and therefore takes into account findFirst or findAny
 boolean mustFindFirst = StreamOpFlag.ORDERED.isKnown(helper.getStreamAndOpFlags());
 return new FindTask<>(this, mustFindFirst, helper, spliterator).invoke();
 }
 }

 /**
 * Implementation of @{code TerminalSink} that implements the find
 * functionality, requesting cancellation when something has been found
 *
 * @param <T> The type of input element
 * @param <O> The result type, typically an optional type
 */
 private abstract static class FindSink<T, O> implements TerminalSink<T, O> {
 boolean hasValue;
 T value;

 FindSink() {} // Avoid creation of special accessor

 @Override
 public void accept(T value) {
 if (!hasValue) {
 hasValue = true;
 this.value = value;
 }
 }

 @Override
 public boolean cancellationRequested() {
 return hasValue;
 }

 /** Specialization of {@code FindSink} for reference streams */
 static final class OfRef<T> extends FindSink<T, Optional<T>> {
 @Override
 public Optional<T> get() {
 return hasValue ? Optional.of(value) : null;
 }

 static final TerminalOp<?, ?> OP_FIND_FIRST = new FindOp<>(true,
 StreamShape.REFERENCE, Optional.empty(),
 Optional::isPresent, FindSink.OfRef::new);

 static final TerminalOp<?, ?> OP_FIND_ANY = new FindOp<>(false,
 StreamShape.REFERENCE, Optional.empty(),
 Optional::isPresent, FindSink.OfRef::new);
 }

 /** Specialization of {@code FindSink} for int streams */
 static final class OfInt extends FindSink<Integer, OptionalInt>
 implements Sink.OfInt {
 @Override
 public void accept(int value) {
 // Boxing is OK here, since few values will actually flow into the sink
 accept((Integer) value);
 }

 @Override
 public OptionalInt get() {
 return hasValue ? OptionalInt.of(value) : null;
 }

 static final TerminalOp<Integer, OptionalInt> OP_FIND_FIRST = new FindOp<>(true,
 StreamShape.INT_VALUE, OptionalInt.empty(),
 OptionalInt::isPresent, FindSink.OfInt::new);
 static final TerminalOp<Integer, OptionalInt> OP_FIND_ANY = new FindOp<>(false,
 StreamShape.INT_VALUE, OptionalInt.empty(),
 OptionalInt::isPresent, FindSink.OfInt::new);
 }

 /** Specialization of {@code FindSink} for long streams */
 static final class OfLong extends FindSink<Long, OptionalLong>
 implements Sink.OfLong {
 @Override
 public void accept(long value) {
 // Boxing is OK here, since few values will actually flow into the sink
 accept((Long) value);
 }

 @Override
 public OptionalLong get() {
 return hasValue ? OptionalLong.of(value) : null;
 }

 static final TerminalOp<Long, OptionalLong> OP_FIND_FIRST = new FindOp<>(true,
 StreamShape.LONG_VALUE, OptionalLong.empty(),
 OptionalLong::isPresent, FindSink.OfLong::new);
 static final TerminalOp<Long, OptionalLong> OP_FIND_ANY = new FindOp<>(false,
 StreamShape.LONG_VALUE, OptionalLong.empty(),
 OptionalLong::isPresent, FindSink.OfLong::new);
 }

 /** Specialization of {@code FindSink} for double streams */
 static final class OfDouble extends FindSink<Double, OptionalDouble>
 implements Sink.OfDouble {
 @Override
 public void accept(double value) {
 // Boxing is OK here, since few values will actually flow into the sink
 accept((Double) value);
 }

 @Override
 public OptionalDouble get() {
 return hasValue ? OptionalDouble.of(value) : null;
 }

 static final TerminalOp<Double, OptionalDouble> OP_FIND_FIRST = new FindOp<>(true,
 StreamShape.DOUBLE_VALUE, OptionalDouble.empty(),
 OptionalDouble::isPresent, FindSink.OfDouble::new);
 static final TerminalOp<Double, OptionalDouble> OP_FIND_ANY = new FindOp<>(false,
 StreamShape.DOUBLE_VALUE, OptionalDouble.empty(),
 OptionalDouble::isPresent, FindSink.OfDouble::new);
 }
 }

 /**
 * {@code ForkJoinTask} implementing parallel short-circuiting search
 * @param <P_IN> Input element type to the stream pipeline
 * @param <P_OUT> Output element type from the stream pipeline
 * @param <O> Result type from the find operation
 */
 @SuppressWarnings("serial")
 private static final class FindTask<P_IN, P_OUT, O>
 extends AbstractShortCircuitTask<P_IN, P_OUT, O, FindTask<P_IN, P_OUT, O>> {
 private final FindOp<P_OUT, O> op;
 private final boolean mustFindFirst;

 FindTask(FindOp<P_OUT, O> op,
 boolean mustFindFirst,
 PipelineHelper<P_OUT> helper,
 Spliterator<P_IN> spliterator) {
 super(helper, spliterator);
 this.mustFindFirst = mustFindFirst;
 this.op = op;
 }

 FindTask(FindTask<P_IN, P_OUT, O> parent, Spliterator<P_IN> spliterator) {
 super(parent, spliterator);
 this.mustFindFirst = parent.mustFindFirst;
 this.op = parent.op;
 }

 @Override
 protected FindTask<P_IN, P_OUT, O> makeChild(Spliterator<P_IN> spliterator) {
 return new FindTask<>(this, spliterator);
 }

 @Override
 protected O getEmptyResult() {
 return op.emptyValue;
 }

 private void foundResult(O answer) {
 if (isLeftmostNode())
 shortCircuit(answer);
 else
 cancelLaterNodes();
 }

 @Override
 protected O doLeaf() {
 O result = helper.wrapAndCopyInto(op.sinkSupplier.get(), spliterator).get();
 if (!mustFindFirst) {
 if (result != null)
 shortCircuit(result);
 return null;
 }
 else {
 if (result != null) {
 foundResult(result);
 return result;
 }
 else
 return null;
 }
 }

 @Override
 public void onCompletion(CountedCompleter<?> caller) {
 if (mustFindFirst) {
 for (FindTask<P_IN, P_OUT, O> child = leftChild, p = null; child != p;
 p = child, child = rightChild) {
 O result = child.getLocalResult();
 if (result != null && op.presentPredicate.test(result)) {
 setLocalResult(result);
 foundResult(result);
 break;
 }
 }
 }
 super.onCompletion(caller);
 }
 }
}