package org.warp.commonutils.type;

import it.unimi.dsi.fastutil.objects.ObjectLinkedOpenHashSet;
import java.util.LinkedHashSet;
import java.util.NoSuchElementException;

/**
 * A stack but with the behavior of a Linked HashSet
 *
 * <p>A stack must provide the classical {@link #push(Object)} and
 * {@link #pop()} operations, but may be also <em>peekable</em>
 * to some extent: it may provide just the {@link #top()} function,
 * or even a more powerful {@link #peek(int)} method that provides
 * access to all elements on the stack (indexed from the top, which
 * has index 0).
 */

public interface StackSet<K> {


	/** Pushes the given object on the stack.
	 *
	 * @param o the object that will become the new top of the stack.
	 * @return true if added, false if already present
	 */

	boolean push(K o);

	/** Pops the top off the stack.
	 *
	 * @return the top of the stack.
	 * @throws NoSuchElementException if the stack is empty.
	 */

	K pop();

	/** Checks whether the stack is empty.
	 *
	 * @return true if the stack is empty.
	 */

	boolean isEmpty();

	/** Peeks at the top of the stack (optional operation).
	 *
	 * <p>This default implementation returns {@link #peek(int) peek(0)}.
	 *
	 * @return the top of the stack.
	 * @throws NoSuchElementException if the stack is empty.
	 */

	default K top()  {
		return peek(0);
	}

	/** Peeks at an element on the stack (optional operation).
	 *
	 * <p>This default implementation just throws an {@link UnsupportedOperationException}.
	 *
	 * @param i an index from the stop of the stack (0 represents the top).
	 * @return the {@code i}-th element on the stack.
	 * @throws IndexOutOfBoundsException if the designated element does not exist..
	 */

	default K peek(int i) {
		throw new UnsupportedOperationException();
	}

	static <T> StackSet<T> create() {
		return new HashStackSet<>();
	}

	static <T> StackSet<T> wrap(LinkedHashSet<T> linkedHashSet) {
		return new JavaStackSetWrapper<>(linkedHashSet);
	}

	static <T> StackSet<T> wrap(ObjectLinkedOpenHashSet<T> linkedHashSet) {
		return new FastUtilStackSetWrapper<>(linkedHashSet);
	}

	static <T> StackSet<T> wrap(ObjectLinkedOpenHashSet<T> linkedHashSet, AddStrategy addStrategy) {
		return new FastUtilStackSetWrapper<>(linkedHashSet, addStrategy);
	}

}