/*
 * Copyright (C) 2002-2022 Sebastiano Vigna
 *
 * 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 PACKAGE;

import java.util.Spliterator;
#if KEYS_PRIMITIVE
import java.util.function.Consumer;
#endif

/** A type-specific {@link Spliterator}; provides an additional methods to avoid (un)boxing, and
 * the possibility to skip elements.
 *
 * @author C. Sean Young &lt;csyoung@google.com&gt;
 * @see Spliterator
 * @since 8.5.0
 */

#if KEYS_INT_LONG_DOUBLE
public interface KEY_SPLITERATOR KEY_GENERIC extends JDK_PRIMITIVE_SPLITERATOR {
#elif KEYS_PRIMITIVE
public interface KEY_SPLITERATOR KEY_GENERIC extends Spliterator.OfPrimitive<KEY_GENERIC_CLASS, KEY_CONSUMER, KEY_SPLITERATOR KEY_GENERIC> {
#else
public interface KEY_SPLITERATOR KEY_GENERIC extends Spliterator<KEY_GENERIC_CLASS> {
#endif

#if KEYS_PRIMITIVE

	// tryAdvance(KEY_CONSUMER action) declaration inherited from super interface.

	/** {@inheritDoc}
	 * @deprecated Please use the corresponding type-specific method instead. */
	@Deprecated
	@Override
	default boolean tryAdvance(final Consumer<? super KEY_GENERIC_CLASS> action) {
		// The instanceof and cast is required for performance. Without it, calls routed through this
		// overload using a primitive consumer would go through the slow lambda.
		return tryAdvance(action instanceof METHOD_ARG_KEY_CONSUMER ? (METHOD_ARG_KEY_CONSUMER)action : (METHOD_ARG_KEY_CONSUMER) action::accept);
	}

#if KEYS_INT_LONG_DOUBLE
	// Because our primitive Consumer interface extends both the JDK's primitive
	// and object Consumer interfaces, calling this method with it would be ambiguous.
	// This overload exists to pass it to the proper primitive overload.
	/**
	 * Attempts to perform the action on the next element, or do nothing
	 * but return {@code false} if there are no remaining elements.
	 *
	 * <p><b>WARNING</b>: Overriding this method is almost always a mistake, as this
	 * overload only exists to disambiguate. Instead, override the {@code tryAdvance()} overload
	 * that uses the JDK's primitive consumer type (e.g., {@link java.util.function.IntConsumer}).
	 *
	 * <br>If Java supported final default methods, this would be one, but sadly it does not.
	 *
	 * <p>If you checked and are overriding the version with {@code java.util.function.XConsumer}, and
	 * still see this warning, then your IDE is incorrectly conflating this method with the proper
	 * method to override, and you can safely ignore this message.
	 *
	 * @param action the action to be performed on the next element.
	 * @return whether there was a next element the action was performed on
	 * @see java.util.Spliterator#tryAdvance(java.util.function.Consumer)
	 */
	default boolean tryAdvance(final KEY_CONSUMER action) {
		return tryAdvance((JDK_PRIMITIVE_KEY_CONSUMER) action);
	}
#endif

	// forEachRemaining(KEY_CONSUMER action) default impl inherited from super interface.

	/** {@inheritDoc}
	 * @deprecated Please use the corresponding type-specific method instead. */
	@Deprecated
	@Override
	default void forEachRemaining(final Consumer<? super KEY_GENERIC_CLASS> action) {
		// The instanceof and cast is required for performance. Without it, calls routed through this
		// overload using a primitive consumer would go through the slow lambda.
		// This is not just theoretical; Oracle's Stream implementation (Pipeline) routes primitive
		// consumer calls through this overload, and the difference in performance is an order
		// of magnitude.
		forEachRemaining(action instanceof METHOD_ARG_KEY_CONSUMER ? (METHOD_ARG_KEY_CONSUMER)action : (METHOD_ARG_KEY_CONSUMER) action::accept);
	}

#endif

#if KEYS_INT_LONG_DOUBLE
	// Because our primitive Consumer interface extends both the JDK's primitive
	// and object Consumer interfaces, calling this method with it would be ambiguous.
	// This overload exists to pass it to the proper primitive overload.
	/**
	 * Performs the given action for each remaining element until all elements
	 * have been processed or the action throws an exception.
	 *
	 * <p><b>WARNING</b>: Overriding this method is almost always a mistake, as this
	 * overload only exists to disambiguate. Instead, override the {@code forEachRemaining()} overload
	 * that uses the JDK's primitive consumer type (e.g. {@link java.util.function.IntConsumer}).
	 *
	 * <p>If Java supported final default methods, this would be one, but sadly it does not.
	 *
	 * <p>If you checked and are overriding the version with {@code java.util.function.XConsumer}, and
	 * still see this warning, then your IDE is incorrectly conflating this method with the proper
	 * method to override, and you can safely ignore this message.
	 *
	 * @param action the action to be performed for each element.
	 * @see java.util.Spliterator#forEachRemaining(java.util.function.Consumer)
	 */
	default void forEachRemaining(final KEY_CONSUMER action) {
		forEachRemaining((JDK_PRIMITIVE_KEY_CONSUMER) action);
	}
#endif

	/** Skips the given number of elements.
	 *
	 * <p>The effect of this call is exactly the same as that of calling {@link #tryAdvance} for
	 * {@code n} times (possibly stopping if {@link #tryAdvance} returns false).
	 * The action called will do nothing; elements will be discarded.
	 *
	 * @implSpec This default implementation is linear in n. It is expected concrete implementations
	 * that are capable of it will override it to run lower time, but be prepared for linear time.
	 *
	 * @param n the number of elements to skip.
	 * @return the number of elements actually skipped.
	 * @see Spliterator#tryAdvance
	 */
	default long skip(final long n) {
		if (n < 0) throw new IllegalArgumentException("Argument must be nonnegative: " + n);
		long i = n;
		while(i-- != 0 && tryAdvance((KEY_GENERIC_TYPE unused) -> {})) {}  // No loop body; logic all happens in conditional
		return n - i - 1;
	}

	/**
	  * {@inheritDoc}
	  *
	  * @apiNote Note that this specification strengthens the one given in {@link Spliterator#trySplit()}.
	  */
	@Override
	KEY_SPLITERATOR KEY_GENERIC trySplit();

#if KEYS_PRIMITIVE
	/**
	  * {@inheritDoc}
	  *
	  * @apiNote Note that this specification strengthens the one given in {@link Spliterator#getComparator()}.
	  */
	@Override
	default KEY_COMPARATOR KEY_SUPER_GENERIC getComparator() {
		throw new IllegalStateException();
	}
#endif
}
