CollectionItemByIndexAccessor.java

package fr.openwide.core.jpa.more.business.difference.access;

import java.util.Arrays;
import java.util.Collection;

import com.google.common.collect.Iterables;

import de.danielbechler.diff.access.Accessor;
import de.danielbechler.diff.selector.ElementSelector;
import fr.openwide.core.jpa.more.business.difference.selector.CollectionItemByIndexSelector;

public class CollectionItemByIndexAccessor<T> implements Accessor, IKeyAwareAccessor<Integer> {
	
	private final int index;

	public CollectionItemByIndexAccessor(int index) {
		this.index = index;
	}
	
	@Override
	public Integer getKey() {
		return index;
	}

	@SuppressWarnings("unchecked")
	private static <T> Collection<T> objectAsCollection(final Object object) {
		if (object == null) {
			return null; // NOSONAR
		} else if (object instanceof Collection) {
			return (Collection<T>) object;
		} else if (object instanceof Object[]) {
			return Arrays.asList((T[]) object);
		}
		throw new IllegalArgumentException(object.getClass().toString());
	}

	@Override
	public ElementSelector getElementSelector() {
		return new CollectionItemByIndexSelector(index);
	}

	@Override
	public void set(final Object target, final Object value) {
		throw new UnsupportedOperationException("Cannot set value on collection/array items.");
	}

	@Override
	public Object get(final Object target) {
		final Collection<T> targetCollection = objectAsCollection(target);
		if (targetCollection == null) {
			return null;
		}
		return Iterables.get(targetCollection, index, null);
	}

	@Override
	public void unset(final Object target) {
		throw new UnsupportedOperationException("Cannot unset value on collection/array items.");
	}

	@Override
	public String toString() {
		return "collection/array item " + getElementSelector();
	}
}