/*******************************************************************************
 *
 * Copyright (c) 2004-2011 Oracle Corporation.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 * 
 *    Kohsuke Kawaguchi, Nikita Levyankov
 *
 *
 *******************************************************************************/ 

package hudson.util;

import com.thoughtworks.xstream.converters.Converter;
import com.thoughtworks.xstream.converters.MarshallingContext;
import com.thoughtworks.xstream.converters.UnmarshallingContext;
import com.thoughtworks.xstream.converters.collections.AbstractCollectionConverter;
import com.thoughtworks.xstream.io.HierarchicalStreamReader;
import com.thoughtworks.xstream.io.HierarchicalStreamWriter;
import com.thoughtworks.xstream.mapper.CannotResolveClassException;
import com.thoughtworks.xstream.mapper.Mapper;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import static java.util.logging.Level.FINE;

import java.util.logging.Logger;
import org.apache.commons.collections.CollectionUtils;

/**
 * {@link List}-like implementation that has copy-on-write semantics.
 *
 * <p> This class is suitable where highly concurrent access is needed, yet the
 * write operation is relatively uncommon.
 *
 * @author Kohsuke Kawaguchi
 */
public class CopyOnWriteList<E> implements Iterable<E> {

    private volatile List<? extends E> core;

    public CopyOnWriteList(List<E> core) {
        this(core, false);
    }

    private CopyOnWriteList(List<E> core, boolean noCopy) {
        this.core = noCopy ? core : new ArrayList<E>(core);
    }

    public CopyOnWriteList() {
        this.core = Collections.emptyList();
    }

    public synchronized void add(E e) {
        List<E> n = new ArrayList<E>(core);
        n.add(e);
        core = n;
    }

    public synchronized void addAll(Collection<? extends E> items) {
        List<E> n = new ArrayList<E>(core);
        n.addAll(items);
        core = n;
    }

    /**
     * Removes an item from the list.
     *
     * @return true if the list contained the item. False if it didn't, in which
     * case there's no change.
     */
    public synchronized boolean remove(E e) {
        List<E> n = new ArrayList<E>(core);
        boolean r = n.remove(e);
        core = n;
        return r;
    }

    /**
     * Returns an iterator.
     */
    public Iterator<E> iterator() {
        final Iterator<? extends E> itr = core.iterator();
        return new Iterator<E>() {
            private E last;

            public boolean hasNext() {
                return itr.hasNext();
            }

            public E next() {
                return last = itr.next();
            }

            public void remove() {
                CopyOnWriteList.this.remove(last);
            }
        };
    }

    /**
     * Completely replaces this list by the contents of the given list.
     */
    public void replaceBy(CopyOnWriteList<? extends E> that) {
        this.core = that.core;
    }

    /**
     * Completely replaces this list by the contents of the given list.
     */
    public void replaceBy(Collection<? extends E> that) {
        this.core = new ArrayList<E>(that);
    }

    /**
     * Completely replaces this list by the contents of the given list.
     */
    public void replaceBy(E... that) {
        replaceBy(Arrays.asList(that));
    }

    public void clear() {
        this.core = new ArrayList<E>();
    }

    public E[] toArray(E[] array) {
        return core.toArray(array);
    }

    public List<E> getView() {
        return Collections.unmodifiableList(core);
    }

    public void addAllTo(Collection<? super E> dst) {
        dst.addAll(core);
    }

    public E get(int index) {
        return core.get(index);
    }

    public boolean isEmpty() {
        return core.isEmpty();
    }

    public int size() {
        return core.size();
    }

    /**
     * {@link Converter} implementation for XStream.
     */
    public static final class ConverterImpl extends AbstractCollectionConverter {

        public ConverterImpl(Mapper mapper) {
            super(mapper);
        }

        public boolean canConvert(Class type) {
            return type == CopyOnWriteList.class;
        }

        public void marshal(Object source, HierarchicalStreamWriter writer, MarshallingContext context) {
            for (Object o : (CopyOnWriteList) source) {
                writeItem(o, context, writer);
            }
        }

        @SuppressWarnings("unchecked")
        public CopyOnWriteList unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) {
            // read the items from xml into a list
            List items = new ArrayList();
            while (reader.hasMoreChildren()) {
                reader.moveDown();
                try {
                    Object item = readItem(reader, context, items);
                    items.add(item);
                } catch (CannotResolveClassException e) {
                    LOGGER.log(FINE, "Failed to resolve class", e);
                    RobustReflectionConverter.addErrorInContext(context, e);
                } catch (LinkageError e) {
                    LOGGER.log(FINE, "Failed to resolve class", e);
                    RobustReflectionConverter.addErrorInContext(context, e);
                }
                reader.moveUp();
            }

            return new CopyOnWriteList(items, true);
        }
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }

        CopyOnWriteList that = (CopyOnWriteList) o;
        return CollectionUtils.isEqualCollection(this.core, that.core);
    }

    @Override
    public int hashCode() {
        return core != null ? core.hashCode() : 0;
    }
    private static final Logger LOGGER = Logger.getLogger(CopyOnWriteList.class.getName());
}