/*
 * Copyright (c) 1997, 2023, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 * questions.
 */
package Torello.Java.ReadOnly;

import Torello.Java.Additional.RemoveUnsupportedIterator;

import java.util.Spliterator;
import java.util.Spliterators;
import java.util.Collection;
import java.util.Set; // return Set.of(...)

/**
 * Immutable variant of Java Collections Framework interface
 * <CODE>java&#46;util&#46;Set&lt;E&gt;</CODE>.
 * 
 * <EMBED CLASS='external-html' DATA-JDK=ReadOnlySet DATA-FILE-ID=INTERFACES>
 * 
 * @param <E> the type of elements maintained by this set
 */
@Torello.JavaDoc.JDHeaderBackgroundImg(EmbedTagFileID="JDHBI_INTERFACE")
public interface ReadOnlySet<E> extends ReadOnlyCollection<E>
{
    // ********************************************************************************************
    // ********************************************************************************************
    // Query Operations
    // ********************************************************************************************
    // ********************************************************************************************


    /**
     * Returns the number of elements in this set (its cardinality).  If this set contains more
     * than {@code Integer.MAX_VALUE} elements, returns {@code Integer.MAX_VALUE}.
     *
     * @return the number of elements in this set (its cardinality)
     */
    int size();

    /**
     * Returns {@code TRUE} if this set contains no elements.
     * @return {@code TRUE} if this set contains no elements
     */
    boolean isEmpty();

    /**
     * Returns {@code TRUE} if this set contains the specified element.  More formally, returns
     * {@code TRUE} if and only if this set contains an element {@code e} such that
     * {@code Objects.equals(o, e)}.
     *
     * @param o element whose presence in this set is to be tested
     * @return {@code TRUE} if this set contains the specified element
     * 
     * @throws ClassCastException if the type of the specified element is incompatible with this
     * set (<a href="Collection.html#optional-restrictions">optional</a>)
     * 
     * @throws NullPointerException if the specified element is null and this set does not permit
     * null elements (<a href="Collection.html#optional-restrictions">optional</a>)
     */
    boolean contains(Object o);

    /**
     * Returns an iterator over the elements in this set.  The elements are returned in no
     * particular order (unless this set is an instance of some class that provides a guarantee).
     *
     * @return an iterator over the elements in this set
     */
    RemoveUnsupportedIterator<E> iterator();

    /**
     * Returns an array containing all of the elements in this set.  If this set makes any
     * guarantees as to what order its elements are returned by its iterator, this method must
     * return the elements in the same order.
     *
     * <BR /><BR />The returned array will be "safe" in that no references to it are maintained by this set.
     * (In other words, this method must allocate a new array even if this set is backed by an
     * array).  The caller is thus free to modify the returned array.
     *
     * <BR /><BR />This method acts as bridge between array-based and collection-based APIs.
     *
     * @return an array containing all the elements in this set
     */
    Object[] toArray();

    /**
     * Returns an array containing all of the elements in this set; the runtime type of the
     * returned array is that of the specified array.  If the set fits in the specified array, it
     * is returned therein.  Otherwise, a new array is allocated with the runtime type of the
     * specified array and the size of this set.
     *
     * <BR /><BR />If this set fits in the specified array with room to spare (i.e., the array has more
     * elements than this set), the element in the array immediately following the end of the set
     * is set to {@code null}.  (This is useful in determining the length of this set <i>only</i>
     * if the caller knows that this set does not contain any null elements.)
     *
     * <BR /><BR />If this set makes any guarantees as to what order its elements are returned by its
     * iterator, this method must return the elements in the same order.
     *
     * <BR /><BR />Like the {@link #toArray()} method, this method acts as bridge between array-based and
     * collection-based APIs.  Further, this method allows precise control over the runtime type of
     * the output array, and may, under certain circumstances, be used to save allocation costs.
     *
     * <BR /><BR />Suppose {@code x} is a set known to contain only strings.  The following code can be used
     * to dump the set into a newly allocated array of {@code String}:
     *
     * <pre>
     *     String[] y = x.toArray(new String[0]);</pre>
     *
     * Note that {@code toArray(new Object[0])} is identical in function to
     * {@code toArray()}.
     *
     * @param a the array into which the elements of this set are to be stored, if it is big
     * enough; otherwise, a new array of the same runtime type is allocated for this purpose.
     * 
     * @return an array containing all the elements in this set
     * 
     * @throws ArrayStoreException if the runtime type of the specified array is not a supertype of
     * the runtime type of every element in this set
     * 
     * @throws NullPointerException if the specified array is null
     */
    <T> T[] toArray(T[] a);


    // ********************************************************************************************
    // ********************************************************************************************
    // Bulk Operations
    // ********************************************************************************************
    // ********************************************************************************************


    /**
     * Returns {@code TRUE} if this set contains all of the elements of the specified collection.
     * If the specified collection is also a set, this method returns {@code TRUE} if it is a
     * <i>subset</i> of this set.
     *
     * @param  c collection to be checked for containment in this set
     * @return {@code TRUE} if this set contains all of the elements of the specified collection
     * 
     * @throws ClassCastException if the types of one or more elements in the specified collection
     * are incompatible with this set
     * (<a href="Collection.html#optional-restrictions">optional</a>)
     * 
     * @throws NullPointerException if the specified collection contains one or more null elements
     * and this set does not permit null elements
     * (<a href="Collection.html#optional-restrictions">optional</a>), or if the specified
     * collection is null
     * 
     * @see #contains(Object)
     */
    boolean containsAll(Collection<?> c);


    // ********************************************************************************************
    // ********************************************************************************************
    // Comparison and hashing
    // ********************************************************************************************
    // ********************************************************************************************


    /**
     * Compares the specified object with this set for equality.  Returns {@code TRUE} if the
     * specified object is also a set, the two sets have the same size, and every member of the
     * specified set is contained in this set (or equivalently, every member of this set is
     * contained in the specified set).  This definition ensures that the equals method works
     * properly across different implementations of the set interface.
     *
     * @param o object to be compared for equality with this set
     * @return {@code TRUE} if the specified object is equal to this set
     */
    boolean equals(Object o);

    /**
     * Returns the hash code value for this set.  The hash code of a set is defined to be the sum
     * of the hash codes of the elements in the set, where the hash code of a {@code null} element
     * is defined to be zero.  This ensures that {@code s1.equals(s2)} implies that
     * {@code s1.hashCode()==s2.hashCode()} for any two sets {@code s1} and
     * {@code s2}, as required by the general contract of {@code Object.hashCode}.
     *
     * @return the hash code value for this set
     * @see Object#equals(Object)
     * @see Set#equals(Object)
     */
    int hashCode();

    /**
     * Creates a {@code Spliterator} over the elements in this set.
     *
     * <BR /><BR />The {@code Spliterator} reports {@code Spliterator.DISTINCT}.  Implementations should
     * document the reporting of additional characteristic values.
     *
     * @implSpec
     * The default implementation creates a
     * <em><a href="Spliterator.html#binding">late-binding</a></em> spliterator from the set's
     * {@code Iterator}.
     * 
     * <BR /><BR />The created {@code Spliterator} additionally reports {@code Spliterator.SIZED}.
     *
     * @implNote
     * The created {@code Spliterator} additionally reports {@code Spliterator.SUBSIZED}.
     *
     * @return a {@code Spliterator} over the elements in this set
     */
    @Override
    default Spliterator<E> spliterator()
    { return Spliterators.spliterator(this.iterator(), this.size(), Spliterator.DISTINCT); }

    /**
     * Returns an unmodifiable set containing zero elements.
     * See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
     *
     * @param <E> the {@code Set}'s element type
     * @return an empty {@code Set}
     */
    @SuppressWarnings("unchecked")
    static <E> ReadOnlySet<E> of()
    { return InterfaceBuilder.toReadOnlySet(Set.of()); }

    /**
     * Returns an unmodifiable set containing one element.
     * See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
     *
     * @param <E> the {@code Set}'s element type
     * @param e1 the single element
     * 
     * @return a {@code Set} containing the specified element
     * @throws NullPointerException if the element is {@code null}
     */
    static <E> ReadOnlySet<E> of(E e1)
    { return InterfaceBuilder.toReadOnlySet(Set.of(e1)); }

    /**
     * Returns an unmodifiable set containing two elements.
     * See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
     *
     * @param <E> the {@code Set}'s element type
     * @param e1 the first element
     * @param e2 the second element
     * 
     * @return a {@code Set} containing the specified elements
     * @throws IllegalArgumentException if the elements are duplicates
     * @throws NullPointerException if an element is {@code null}
     */
    static <E> ReadOnlySet<E> of(E e1, E e2)
    { return InterfaceBuilder.toReadOnlySet(Set.of(e1, e2)); }

    /**
     * Returns an unmodifiable set containing three elements.
     * See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
     *
     * @param <E> the {@code Set}'s element type
     * @param e1 the first element
     * @param e2 the second element
     * @param e3 the third element
     * 
     * @return a {@code Set} containing the specified elements
     * @throws IllegalArgumentException if there are any duplicate elements
     * @throws NullPointerException if an element is {@code null}
     */
    static <E> ReadOnlySet<E> of(E e1, E e2, E e3)
    { return InterfaceBuilder.toReadOnlySet(Set.of(e1, e2, e3)); }

    /**
     * Returns an unmodifiable set containing four elements.
     * See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
     *
     * @param <E> the {@code Set}'s element type
     * @param e1 the first element
     * @param e2 the second element
     * @param e3 the third element
     * @param e4 the fourth element
     * 
     * @return a {@code Set} containing the specified elements
     * @throws IllegalArgumentException if there are any duplicate elements
     * @throws NullPointerException if an element is {@code null}
     */
    static <E> ReadOnlySet<E> of(E e1, E e2, E e3, E e4)
    { return InterfaceBuilder.toReadOnlySet(Set.of(e1, e2, e3, e4)); }

    /**
     * Returns an unmodifiable set containing five elements.
     * See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
     *
     * @param <E> the {@code Set}'s element type
     * @param e1 the first element
     * @param e2 the second element
     * @param e3 the third element
     * @param e4 the fourth element
     * @param e5 the fifth element
     * 
     * @return a {@code Set} containing the specified elements
     * @throws IllegalArgumentException if there are any duplicate elements
     * @throws NullPointerException if an element is {@code null}
     */
    static <E> ReadOnlySet<E> of(E e1, E e2, E e3, E e4, E e5)
    { return InterfaceBuilder.toReadOnlySet(Set.of(e1, e2, e3, e4, e5)); }

    /**
     * Returns an unmodifiable set containing six elements.
     * See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
     *
     * @param <E> the {@code Set}'s element type
     * @param e1 the first element
     * @param e2 the second element
     * @param e3 the third element
     * @param e4 the fourth element
     * @param e5 the fifth element
     * @param e6 the sixth element
     * 
     * @return a {@code Set} containing the specified elements
     * @throws IllegalArgumentException if there are any duplicate elements
     * @throws NullPointerException if an element is {@code null}
     */
    static <E> ReadOnlySet<E> of(E e1, E e2, E e3, E e4, E e5, E e6)
    { return InterfaceBuilder.toReadOnlySet(Set.of(e1, e2, e3, e4, e5, e6)); }

    /**
     * Returns an unmodifiable set containing seven elements.
     * See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
     *
     * @param <E> the {@code Set}'s element type
     * @param e1 the first element
     * @param e2 the second element
     * @param e3 the third element
     * @param e4 the fourth element
     * @param e5 the fifth element
     * @param e6 the sixth element
     * @param e7 the seventh element
     * 
     * @return a {@code Set} containing the specified elements
     * @throws IllegalArgumentException if there are any duplicate elements
     * @throws NullPointerException if an element is {@code null}
     */
    static <E> ReadOnlySet<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7)
    { return InterfaceBuilder.toReadOnlySet(Set.of(e1, e2, e3, e4, e5, e6, e7)); }

    /**
     * Returns an unmodifiable set containing eight elements.
     * See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
     *
     * @param <E> the {@code Set}'s element type
     * @param e1 the first element
     * @param e2 the second element
     * @param e3 the third element
     * @param e4 the fourth element
     * @param e5 the fifth element
     * @param e6 the sixth element
     * @param e7 the seventh element
     * @param e8 the eighth element
     * 
     * @return a {@code Set} containing the specified elements
     * @throws IllegalArgumentException if there are any duplicate elements
     * @throws NullPointerException if an element is {@code null}
     */
    static <E> ReadOnlySet<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8)
    { return InterfaceBuilder.toReadOnlySet(Set.of(e1, e2, e3, e4, e5, e6, e7, e8)); }

    /**
     * Returns an unmodifiable set containing nine elements.
     * See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
     *
     * @param <E> the {@code Set}'s element type
     * @param e1 the first element
     * @param e2 the second element
     * @param e3 the third element
     * @param e4 the fourth element
     * @param e5 the fifth element
     * @param e6 the sixth element
     * @param e7 the seventh element
     * @param e8 the eighth element
     * @param e9 the ninth element
     * 
     * @return a {@code Set} containing the specified elements
     * @throws IllegalArgumentException if there are any duplicate elements
     * @throws NullPointerException if an element is {@code null}
     */
    static <E> ReadOnlySet<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9)
    { return InterfaceBuilder.toReadOnlySet(Set.of(e1, e2, e3, e4, e5, e6, e7, e8, e9)); }

    /**
     * Returns an unmodifiable set containing ten elements.
     * See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
     *
     * @param <E> the {@code Set}'s element type
     * @param e1 the first element
     * @param e2 the second element
     * @param e3 the third element
     * @param e4 the fourth element
     * @param e5 the fifth element
     * @param e6 the sixth element
     * @param e7 the seventh element
     * @param e8 the eighth element
     * @param e9 the ninth element
     * @param e10 the tenth element
     * 
     * @return a {@code Set} containing the specified elements
     * @throws IllegalArgumentException if there are any duplicate elements
     * @throws NullPointerException if an element is {@code null}
     */
    static <E> ReadOnlySet<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10)
    { return InterfaceBuilder.toReadOnlySet(Set.of(e1, e2, e3, e4, e5, e6, e7, e8, e9, e10)); }

    /**
     * Returns an unmodifiable set containing an arbitrary number of elements.
     * See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
     *
     * @apiNote
     * This method also accepts a single array as an argument. The element type of
     * the resulting set will be the component type of the array, and the size of
     * the set will be equal to the length of the array. To create a set with
     * a single element that is an array, do the following:
     *
     * <pre>{@code
     *     String[] array = ... ;
     *     Set<String[]> list = Set.<String[]>of(array);
     * }</pre>
     *
     * This will cause the {@link ReadOnlySet#of(Object) ReadOnlySet.of(E)} method
     * to be invoked instead.
     *
     * @param <E> the {@code Set}'s element type
     * @param elements the elements to be contained in the set
     * @return a {@code Set} containing the specified elements
     * @throws IllegalArgumentException if there are any duplicate elements
     * @throws NullPointerException if an element is {@code null} or if the array is {@code null}
     */
    @SafeVarargs
    @SuppressWarnings("varargs")
    static <E> ReadOnlySet<E> of(E... elements)
    { return InterfaceBuilder.toReadOnlySet(Set.of(elements)); }

    /**
     * Returns an <a href="#unmodifiable">unmodifiable Set</a> containing the elements
     * of the given Collection. The given Collection must not be null, and it must not
     * contain any null elements. If the given Collection contains duplicate elements,
     * an arbitrary element of the duplicates is preserved. If the given Collection is
     * subsequently modified, the returned Set will not reflect such modifications.
     *
     * @implNote
     * If the given Collection is an <a href="#unmodifiable">unmodifiable Set</a>,
     * calling copyOf will generally not create a copy.
     *
     * @param <E> the {@code Set}'s element type
     * @param coll a {@code Collection} from which elements are drawn, must be non-null
     * @return a {@code Set} containing the elements of the given {@code Collection}
     * @throws NullPointerException if coll is null, or if it contains any nulls
     */
    @SuppressWarnings("unchecked")
    static <E> ReadOnlySet<E> copyOf(Collection<? extends E> coll)
    { return InterfaceBuilder.toReadOnlySet(Set.copyOf(coll)); }
}