/*
 * 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.Collection;
import java.util.Objects;
import java.util.function.Consumer;

#if KEYS_BYTE_CHAR_SHORT_FLOAT
import WIDENED_PACKAGE.KEY_WIDENED_ITERATOR;
import WIDENED_PACKAGE.WIDENED_ITERATORS;
import WIDENED_PACKAGE.KEY_WIDENED_SPLITERATOR;
import WIDENED_PACKAGE.WIDENED_SPLITERATORS;
#elif ! KEY_CLASS_Boolean
import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.IntFunction;
import java.util.function.Supplier;
#endif

#if ! KEYS_REFERENCE
import it.unimi.dsi.fastutil.objects.ObjectArrays;
#else
import java.util.function.Predicate;
#endif

/** A class providing static methods and objects that do useful things with type-specific collections.
 *
 * @see java.util.Collections
 */

public final class COLLECTIONS {

	private COLLECTIONS() {}

#if KEYS_PRIMITIVE && !KEY_TYPE_Boolean
	/* Only in the EmptyCollection class, where performance is critical, do we override the
	 * deprecated, Object based functional methods. For the rest, we just override the
	 * non-deprecated type-specific method, and let the default method from the interface
	 * filter into that. This is an extra method call and lambda creation, but it isn't worth
	 * complexifying the code generation for a case that is already marked as being inefficient.
	 */
#endif

	/** An immutable class representing an empty type-specific collection.
	 *
	 * <p>This class may be useful to implement your own in case you subclass
	 * a type-specific collection.
	 */

	public abstract static class EmptyCollection KEY_GENERIC extends ABSTRACT_COLLECTION KEY_GENERIC {
		protected EmptyCollection() {}

		@Override
		public boolean contains(KEY_TYPE k) { return false; }

		@Override
		public Object[] toArray() { return ObjectArrays.EMPTY_ARRAY; }

		@Override
		public <T> T[] toArray(T[] array) {
			if (array.length > 0) array[0] = null;
			return array;
		}

		@Override
		SUPPRESS_WARNINGS_KEY_UNCHECKED
		public KEY_BIDI_ITERATOR KEY_GENERIC iterator() { return ITERATORS.EMPTY_ITERATOR; }

		@Override
		SUPPRESS_WARNINGS_KEY_UNCHECKED
		public KEY_SPLITERATOR KEY_GENERIC spliterator() { return SPLITERATORS.EMPTY_SPLITERATOR; }

		@Override
		public int size() { return 0; }

		@Override
		public void clear() {}

		@Override
		public int hashCode() { return 0; }

		@Override
		public boolean equals(Object o) {
			if (o == this) return true;
			if (! (o instanceof Collection)) return false;
			return ((Collection<?>)o).isEmpty();
		}

		DEPRECATED_IF_KEYS_PRIMITIVE
		@Override
		public void forEach(final Consumer<? super KEY_GENERIC_CLASS> action) { }

		@Override
		public boolean containsAll(final Collection<?> c) { return c.isEmpty(); }

		@Override
		public boolean addAll(final Collection<? extends KEY_GENERIC_CLASS> c) { throw new UnsupportedOperationException(); }

		@Override
		public boolean removeAll(final Collection<?> c) { throw new UnsupportedOperationException(); }

		@Override
		public boolean retainAll(final Collection<?> c) { throw new UnsupportedOperationException(); }

#if KEYS_PRIMITIVE
		@Deprecated
#endif
		@Override
		public boolean removeIf(final java.util.function.Predicate<? super KEY_GENERIC_CLASS> filter) {
			Objects.requireNonNull(filter);
			return false;
		}
#if KEYS_PRIMITIVE

		@Override
		public KEY_TYPE[] TO_KEY_ARRAY() { return ARRAYS.EMPTY_ARRAY; }

		/* {@inheritDoc}
		 * @deprecated Please use {@code toArray()} instead&mdash;this method is redundant and will be removed in the future.
		 */
		@Deprecated
		@Override
		public KEY_TYPE[] TO_KEY_ARRAY(KEY_TYPE[] a) { return a; }

		@Override
		public void forEach(final METHOD_ARG_KEY_CONSUMER action) { }

		@Override
		public boolean containsAll(final COLLECTION c) { return c.isEmpty(); }

		@Override
		public boolean addAll(final COLLECTION c) { throw new UnsupportedOperationException(); }

		@Override
		public boolean removeAll(final COLLECTION c) { throw new UnsupportedOperationException(); }

		@Override
		public boolean retainAll(final COLLECTION c) { throw new UnsupportedOperationException(); }

		@Override
		public boolean removeIf(final METHOD_ARG_PREDICATE filter) {
			Objects.requireNonNull(filter);
			return false;
		}

#if KEYS_BYTE_CHAR_SHORT_FLOAT
		@Override
		public KEY_WIDENED_ITERATOR KEY_WIDENED_ITERATOR_METHOD() { return WIDENED_ITERATORS.EMPTY_ITERATOR; }

		@Override
		public KEY_WIDENED_SPLITERATOR KEY_WIDENED_SPLITERATOR_METHOD() { return WIDENED_SPLITERATORS.EMPTY_SPLITERATOR; }
#endif

#endif

	}


	/** A synchronized wrapper class for collections. */

	static class SynchronizedCollection KEY_GENERIC implements COLLECTION KEY_GENERIC, java.io.Serializable {

		private static final long serialVersionUID = -7046029254386353129L;

		protected final COLLECTION KEY_GENERIC collection;
		protected final Object sync;

		protected SynchronizedCollection(final COLLECTION KEY_GENERIC c, final Object sync) {
			this.collection = Objects.requireNonNull(c);
			this.sync = sync;
		}

		protected SynchronizedCollection(final COLLECTION KEY_GENERIC c) {
			this.collection = Objects.requireNonNull(c);
			this.sync = this;
		}

		@Override
		public boolean add(final KEY_GENERIC_TYPE k) { synchronized(sync) { return collection.add(k); } }

		@Override
		public boolean contains(final KEY_TYPE k) { synchronized(sync) { return collection.contains(k); } }

		@Override
		public boolean REMOVE(final KEY_TYPE k) { synchronized(sync) { return collection.REMOVE(k); } }

		@Override
		public int size() { synchronized(sync) { return collection.size(); } }

		@Override
		public boolean isEmpty() { synchronized(sync) { return collection.isEmpty(); } }

		@Override
		public KEY_TYPE[] TO_KEY_ARRAY() { synchronized(sync) { return collection.TO_KEY_ARRAY(); } }

#if KEYS_PRIMITIVE
		@Override
		public Object[] toArray() { synchronized(sync) { return collection.toArray(); } }

		/* {@inheritDoc}
		 * @deprecated Please use {@code toArray()} instead&mdash;this method is redundant and will be removed in the future.
		 */
		@Deprecated
		@Override
		public KEY_TYPE[] TO_KEY_ARRAY(final KEY_TYPE[] a) { return toArray(a); }

		@Override
		public KEY_TYPE[] toArray(final KEY_TYPE[] a) { synchronized(sync) { return collection.toArray(a); } }

		@Override
		public boolean addAll(final COLLECTION c) { synchronized(sync) { return collection.addAll(c); } }

		@Override
		public boolean containsAll(final COLLECTION c) { synchronized(sync) { return collection.containsAll(c); } }

		@Override
		public boolean removeAll(final COLLECTION c) { synchronized(sync) { return collection.removeAll(c); } }

		@Override
		public boolean retainAll(final COLLECTION c) { synchronized(sync) { return collection.retainAll(c); } }

		@Override
		@Deprecated
		public boolean add(final KEY_GENERIC_CLASS k) { synchronized(sync) { return collection.add(k); } }

		@Override
		@Deprecated
		public boolean contains(final Object k) { synchronized(sync) { return collection.contains(k); } }

		@Override
		@Deprecated
		public boolean remove(final Object k) { synchronized(sync) { return collection.remove(k); } }

#if defined JDK_PRIMITIVE_ITERATOR
		@Override
		public KEY_WIDENED_ITERATOR KEY_WIDENED_ITERATOR_METHOD() { return collection.KEY_WIDENED_ITERATOR_METHOD(); }

		@Override
		public KEY_WIDENED_SPLITERATOR KEY_WIDENED_SPLITERATOR_METHOD() { return collection.KEY_WIDENED_SPLITERATOR_METHOD(); }
#endif

#if defined JDK_PRIMITIVE_STREAM
		@Override
		public JDK_PRIMITIVE_STREAM KEY_WIDENED_STREAM_METHOD() { return collection.KEY_WIDENED_STREAM_METHOD(); }

		@Override
		public JDK_PRIMITIVE_STREAM KEY_WIDENED_PARALLEL_STREAM_METHOD() { return collection.KEY_WIDENED_PARALLEL_STREAM_METHOD(); }
#endif
#endif

		@Override
		public <T> T[] toArray(final T[] a) { synchronized(sync) { return collection.toArray(a); } }

		@Override
		public KEY_ITERATOR KEY_GENERIC iterator() { return collection.iterator(); }

		@Override
		public KEY_SPLITERATOR KEY_GENERIC spliterator() { return collection.spliterator(); }

#if defined JDK_PRIMITIVE_STREAM
		@Deprecated
#endif
		@Override
		public java.util.stream.Stream <KEY_GENERIC_CLASS> stream() { return collection.stream(); }

#if defined JDK_PRIMITIVE_STREAM
		@Deprecated
#endif
		@Override
		public java.util.stream.Stream <KEY_GENERIC_CLASS> parallelStream() { return collection.parallelStream(); }

		@Override
		public void forEach(final METHOD_ARG_KEY_CONSUMER action) { synchronized(sync) { collection.forEach(action); } }

		@Override
		public boolean addAll(final Collection<? extends KEY_GENERIC_CLASS> c) { synchronized(sync) { return collection.addAll(c); } }

		@Override
		public boolean containsAll(final Collection<?> c) { synchronized(sync) { return collection.containsAll(c); } }

		@Override
		public boolean removeAll(final Collection<?> c) { synchronized(sync) { return collection.removeAll(c); } }

		@Override
		public boolean retainAll(final Collection<?> c) { synchronized(sync) { return collection.retainAll(c); } }

		@Override
		public boolean removeIf(final METHOD_ARG_PREDICATE filter) { synchronized(sync) { return collection.removeIf(filter); } }

		@Override
		public void clear() { synchronized(sync) { collection.clear(); } }

		@Override
		public String toString() { synchronized(sync) { return collection.toString(); } }

		@Override
		public int hashCode() { synchronized(sync) { return collection.hashCode(); } }

		@Override
		public boolean equals(final Object o) { if (o == this) return true; synchronized(sync) { return collection.equals(o); } }

		private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
			synchronized(sync) { s.defaultWriteObject(); }
		}
	}


	/** Returns a synchronized collection backed by the specified collection.
	 *
	 * @param c the collection to be wrapped in a synchronized collection.
	 * @return a synchronized view of the specified collection.
	 * @see java.util.Collections#synchronizedCollection(Collection)
	 */
	public static KEY_GENERIC COLLECTION KEY_GENERIC synchronize(final COLLECTION KEY_GENERIC c) { return new SynchronizedCollection KEY_GENERIC_DIAMOND(c); }

	/** Returns a synchronized collection backed by the specified collection, using an assigned object to synchronize.
	 *
	 * @param c the collection to be wrapped in a synchronized collection.
	 * @param sync an object that will be used to synchronize the list access.
	 * @return a synchronized view of the specified collection.
	 * @see java.util.Collections#synchronizedCollection(Collection)
	 */

	public static KEY_GENERIC COLLECTION KEY_GENERIC synchronize(final COLLECTION KEY_GENERIC c, final Object sync) { return new SynchronizedCollection KEY_GENERIC_DIAMOND(c, sync); }


	/** An unmodifiable wrapper class for collections. */

	static class UnmodifiableCollection KEY_GENERIC implements COLLECTION KEY_GENERIC, java.io.Serializable {

		private static final long serialVersionUID = -7046029254386353129L;

		protected final COLLECTION KEY_EXTENDS_GENERIC collection;

		protected UnmodifiableCollection(final COLLECTION KEY_EXTENDS_GENERIC c) {
			this.collection = Objects.requireNonNull(c);
		}

		@Override
		public boolean add(final KEY_GENERIC_TYPE k) { throw new UnsupportedOperationException(); }

		@Override
		public boolean REMOVE(final KEY_TYPE k) { throw new UnsupportedOperationException(); }

		@Override
		public int size() { return collection.size(); }

		@Override
		public boolean isEmpty() { return collection.isEmpty(); }

		@Override
		public boolean contains(final KEY_TYPE o) { return collection.contains(o); }

		@Override
		public KEY_ITERATOR KEY_GENERIC iterator() { return ITERATORS.unmodifiable(collection.iterator()); }

		@Override
#if KEYS_PRIMITIVE
		public KEY_SPLITERATOR KEY_GENERIC spliterator() { return collection.spliterator(); }
#else
		@SuppressWarnings("unchecked")
		public KEY_SPLITERATOR KEY_GENERIC spliterator() { return (KEY_SPLITERATOR KEY_GENERIC)collection.spliterator(); }
#endif

#if defined JDK_PRIMITIVE_STREAM
		@Deprecated
#endif
		@Override
#if KEYS_PRIMITIVE
		public java.util.stream.Stream <KEY_GENERIC_CLASS> stream() { return collection.stream(); }
#else
		@SuppressWarnings("unchecked")
		public java.util.stream.Stream <KEY_GENERIC_CLASS> stream() { return (java.util.stream.Stream <KEY_GENERIC_CLASS>)collection.stream(); }
#endif

#if defined JDK_PRIMITIVE_STREAM
		@Deprecated
#endif
		@Override
#if KEYS_PRIMITIVE
		public java.util.stream.Stream <KEY_GENERIC_CLASS> parallelStream() { return collection.parallelStream(); }
#else
		@SuppressWarnings("unchecked")
		public java.util.stream.Stream <KEY_GENERIC_CLASS> parallelStream() { return (java.util.stream.Stream <KEY_GENERIC_CLASS>)collection.parallelStream(); }
#endif

		@Override
		public void clear() { throw new UnsupportedOperationException(); }

		@Override
		public <T> T[] toArray(final T[] a) { return collection.toArray(a); }

		@Override
		public Object[] toArray() { return collection.toArray(); }

		@Override
		public void forEach(final METHOD_ARG_KEY_CONSUMER action) { collection.forEach(action); }

		@Override
		public boolean containsAll(Collection<?> c) { return collection.containsAll(c); }

		@Override
		public boolean addAll(Collection<? extends KEY_GENERIC_CLASS> c) { throw new UnsupportedOperationException(); }

		@Override
		public boolean removeAll(Collection<?> c) { throw new UnsupportedOperationException(); }

		@Override
		public boolean retainAll(Collection<?> c) { throw new UnsupportedOperationException(); }

		@Override
		public boolean removeIf(final METHOD_ARG_PREDICATE filter) { throw new UnsupportedOperationException(); }

#if KEYS_PRIMITIVE
		@Override
		@Deprecated
		public boolean add(final KEY_GENERIC_CLASS k) { throw new UnsupportedOperationException(); }

		@Override
		@Deprecated
		public boolean contains(final Object k) { return collection.contains(k); }

		@Override
		@Deprecated
		public boolean remove(final Object k) { throw new UnsupportedOperationException(); }

		@Override
		public KEY_TYPE[] TO_KEY_ARRAY() { return collection.TO_KEY_ARRAY(); }

		/* {@inheritDoc}
		 * @deprecated Please use {@code toArray()} instead&mdash;this method is redundant.
		 */
		@Deprecated
		@Override
		public KEY_TYPE[] TO_KEY_ARRAY(final KEY_TYPE[] a) { return toArray(a); }

		@Override
		public KEY_TYPE[] toArray(final KEY_TYPE[] a) { return collection.toArray(a); }

		@Override
		public boolean containsAll(COLLECTION c) { return collection.containsAll(c); }

		@Override
		public boolean addAll(COLLECTION c) { throw new UnsupportedOperationException(); }

		@Override
		public boolean removeAll(COLLECTION c) { throw new UnsupportedOperationException(); }

		@Override
		public boolean retainAll(COLLECTION c) { throw new UnsupportedOperationException(); }

#if defined JDK_PRIMITIVE_ITERATOR
		@Override
		public KEY_WIDENED_ITERATOR KEY_WIDENED_ITERATOR_METHOD() { return collection.KEY_WIDENED_ITERATOR_METHOD(); }

		@Override
		public KEY_WIDENED_SPLITERATOR KEY_WIDENED_SPLITERATOR_METHOD() { return collection.KEY_WIDENED_SPLITERATOR_METHOD(); }
#endif

#if defined JDK_PRIMITIVE_STREAM
		@Override
		public JDK_PRIMITIVE_STREAM KEY_WIDENED_STREAM_METHOD() { return collection.KEY_WIDENED_STREAM_METHOD(); }

		@Override
		public JDK_PRIMITIVE_STREAM KEY_WIDENED_PARALLEL_STREAM_METHOD() { return collection.KEY_WIDENED_PARALLEL_STREAM_METHOD(); }
#endif
#endif

		@Override
		public String toString() { return collection.toString(); }

		@Override
		public int hashCode() { return collection.hashCode(); }

		@Override
		public boolean equals(final Object o) { if (o == this) return true; return collection.equals(o); }
	}


	/** Returns an unmodifiable collection backed by the specified collection.
	 *
	 * @param c the collection to be wrapped in an unmodifiable collection.
	 * @return an unmodifiable view of the specified collection.
	 * @see java.util.Collections#unmodifiableCollection(Collection)
	 */
	public static KEY_GENERIC COLLECTION KEY_GENERIC unmodifiable(final COLLECTION KEY_EXTENDS_GENERIC c) { return new UnmodifiableCollection KEY_GENERIC_DIAMOND(c); }

	/** A collection wrapper class for iterables. */

	public static class IterableCollection KEY_GENERIC extends ABSTRACT_COLLECTION KEY_GENERIC implements java.io.Serializable {

		private static final long serialVersionUID = -7046029254386353129L;

		protected final KEY_ITERABLE KEY_GENERIC iterable;

		protected IterableCollection(final KEY_ITERABLE KEY_GENERIC iterable) {
			this.iterable = Objects.requireNonNull(iterable);
		}

		@Override
		public int size() {
			long size = iterable.spliterator().getExactSizeIfKnown();
			if (size >= 0) return (int)Math.min(Integer.MAX_VALUE, size);
			int c = 0;
			final KEY_ITERATOR KEY_GENERIC iterator = iterator();
			while(iterator.hasNext()) {
				iterator.NEXT_KEY();
				c++;
			}

			return c;
		}

		@Override
		public boolean isEmpty() { return ! iterable.iterator().hasNext(); }

		@Override
		public KEY_ITERATOR KEY_GENERIC iterator() { return iterable.iterator(); }

		@Override
		public KEY_SPLITERATOR KEY_GENERIC spliterator() { return iterable.spliterator(); }

#if defined JDK_PRIMITIVE_ITERATOR && KEYS_PRIMITIVE
		@Override
		public KEY_WIDENED_ITERATOR KEY_WIDENED_ITERATOR_METHOD() { return iterable.KEY_WIDENED_ITERATOR_METHOD() ; }

		@Override
		public KEY_WIDENED_SPLITERATOR KEY_WIDENED_SPLITERATOR_METHOD() { return iterable.KEY_WIDENED_SPLITERATOR_METHOD() ; }
#endif
	}


	/** Returns an unmodifiable collection backed by the specified iterable.
	 *
	 * @param iterable the iterable object to be wrapped in an unmodifiable collection.
	 * @return an unmodifiable collection view of the specified iterable.
	 */
	public static KEY_GENERIC COLLECTION KEY_GENERIC asCollection(final KEY_ITERABLE KEY_GENERIC iterable) {
		if (iterable instanceof COLLECTION) return (COLLECTION KEY_GENERIC)iterable;
		// TODO test for Collection but not our collection, and make a wrapper for it.
		return new IterableCollection KEY_GENERIC_DIAMOND(iterable);
	}

#if KEYS_INT_LONG_DOUBLE || KEYS_REFERENCE  // Currently used for the collector methods, which only exist for the "first-class" primitives and object types.
	/** Helper class for size decreasing size estimation.
	 *
	 * <p>Used to implement {@code toXWithExpectedSize} to prevent allocating a data structure big enough for the full stream in every thread, when only one thread
	 * (typically the first one) is going to need to "see" all of it at some point.
	 *
	 * <p>Currently set to always assume a roughly split-by-two strategy from the {@link java.util.Spliterator} backing the
	 * {@link java.util.stream.Stream} (or primitive equivalent). This may perform worse for {@code Spliterator}s that don't
	 * (for example the ones that wrap an {@link java.util.Iterator} as a {@code Spliterator}). This is quite rare in practice however.
	 * But note that even in such cases, this would <em>still</em> perform no worse (modulo some trivial amount) then the default
	 * "flat size for every list" method of combining.
	 * A way to detect such cases and use a different size estimation strategy may come in the future.
	 *
	 * <p>See the {@linkplain #SizeDecreasingSupplier constructor} for requirements of the {@link #builder} functor.
	 */
	static class SizeDecreasingSupplier<
#if KEYS_REFERENCE
			K,
#endif
			C extends COLLECTION KEY_GENERIC> implements Supplier<C> {
		static final int RECOMMENDED_MIN_SIZE = 8;

		final AtomicInteger suppliedCount = new AtomicInteger(0);
		final int expectedFinalSize;
		final IntFunction<C> builder;

		/**
		 * Construct this {@link SizeDecreasingSupplier}.
		 *
		 * @param expectedFinalSize The expected size of the entire remaining contents of the {@code Stream}
		 *   and thus what size the Collection holding the final results should try to be preallocated to.
		 * @param builder the builder function.
		 *   <p>The input integer will be the size of the collection to preallocate.
		 *   <p>It is recommended that you allocate a minimum size if the given {@code size} is small.
		 *     {@link #RECOMMENDED_MIN_SIZE} gives a good enough ballpark for most cases.
		 *   <p>The subclass is free to use the default constructor for the Collection construction
		 *     instead of the {@code size} given
		 *     if {@code size} falls below the default size used for the default initial capacity for
		 *     that Collection implementation. Often such default constructors contain additional
		 *     optimizations that giving an explicit initial capacity would not do (even if given
		 *     the default capacity as the initial capacity explicitly).
		 *   <p>{@link Supplier#get() get()} of the {@link IntFunction} must return non-{@code null}.
		 */
		SizeDecreasingSupplier(int expectedFinalSize, IntFunction<C> builder) {
			this.expectedFinalSize = expectedFinalSize;
			this.builder = builder;
		}

		// This method may be worth pulling into a shared superclass.
		@Override
		public C get() {
			// The "correct" splitting (assuming split by two) would be
			// expectedFinalSize / floor(ln_2(++suppliedCount)). But that seems too much trouble to be worth it.
			// Instead we will take a simple harmonically decreasing ratio (1, 1/2, 1/3, 1/4)
			//
			// Round up int math (to round up, not down) adapted from https://stackoverflow.com/a/503201.
			int expectedNeededNextSize = 1 + ((expectedFinalSize - 1) / suppliedCount.incrementAndGet());
			if (expectedNeededNextSize < 0) {
				// Overflow (and weird below zero results) failsafe
				expectedNeededNextSize = RECOMMENDED_MIN_SIZE;
			}
			return builder.apply(expectedNeededNextSize);
		}
	}
#endif  // KEYS_INT_LONG_DOUBLE || KEYS_REFERENCE
}
