AuthenticatorsRegistry.java

package org.carlspring.strongbox.authentication.registry;

import org.carlspring.strongbox.authentication.api.Authenticator;
import org.carlspring.strongbox.authentication.registry.support.xml.AuthenticatorsAdapter;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.NoSuchElementException;

/**
 * @author Przemyslaw Fusik
 */
@XmlRootElement
@XmlAccessorType(XmlAccessType.NONE)
public class AuthenticatorsRegistry
        implements Iterable<Authenticator>
{

    @XmlElement(name = "authenticators")
    @XmlJavaTypeAdapter(AuthenticatorsAdapter.class)
    private volatile Authenticator[] array;

    /**
     * Creates an empty registry.
     */
    public AuthenticatorsRegistry()
    {
        setArray(new Authenticator[0]);
    }

    /**
     * Creates a registry containing the elements of the specified
     * collection, in the order they are returned by the collection's
     * iterator.
     */
    public AuthenticatorsRegistry(Collection<? extends Authenticator> c)
    {
        reloadInternally(c);
    }

    private Authenticator[] getArray()
    {
        return array;
    }

    private void setArray(Authenticator[] elements)
    {
        array = Arrays.copyOf(elements, elements.length);
    }

    /**
     * Reloads the registry by replacing all authenticators using
     * given collection.
     *
     * @param c new collection of authenticators
     */
    public synchronized void reload(Collection<? extends Authenticator> c)
    {
        reloadInternally(c);
    }

    /**
     * Reorders elements in the registry.
     */
    public synchronized void reorder(int first,
                                     int second)
    {
        Authenticator[] elements = getArray();
        elements = Arrays.copyOf(elements, elements.length);
        final Authenticator firstA = elements[first];
        final Authenticator secondA = elements[second];
        elements[first] = secondA;
        elements[second] = firstA;
        setArray(elements);
    }

    public int size()
    {
        return getArray().length;
    }

    public boolean isEmpty()
    {
        return size() == 0;
    }

    private void reloadInternally(Collection<? extends Authenticator> c)
    {
        final Authenticator[] elements = c.toArray(new Authenticator[0]);
        setArray(elements);
    }

    @Override
    public String toString()
    {
        final StringBuilder builder = new StringBuilder();
        final Authenticator[] view = getArray();
        for (int index = 0; index < view.length; index++)
        {
            final Authenticator authenticator = view[index];
            builder.append(Arrays.toString(new Object[]{ index,
                                                         authenticator.getName() }));
        }
        return builder.toString();
    }

    @Override
    public Iterator<Authenticator> iterator()
    {
        return new COWIterator(getArray(), 0);
    }

    static final class COWIterator
            implements Iterator<Authenticator>
    {

        private final Authenticator[] snapshot;

        private int cursor;

        private COWIterator(Authenticator[] elements,
                            int initialCursor)
        {
            cursor = initialCursor;
            snapshot = Arrays.copyOf(elements, elements.length);
        }

        @Override
        public boolean hasNext()
        {
            return cursor < snapshot.length;
        }

        @Override
        public Authenticator next()
        {
            if (!hasNext())
            {
                throw new NoSuchElementException();
            }
            return snapshot[cursor++];
        }
    }
}