EDIT

/**

* Copyright (C) 2018 EDIT

* European Distributed Institute of Taxonomy

* http://www.e-taxonomy.eu

*

* The contents of this file are subject to the Mozilla Public License Version 1.1

* See LICENSE.TXT at the top of this package for the full license terms.

*/

package eu.etaxonomy.cdm.vaadin.event.error;

import java.util.HashSet;

import java.util.Set;

import org.apache.log4j.Logger;

import com.vaadin.server.ErrorEvent;

import com.vaadin.server.ErrorHandler;

import com.vaadin.ui.Notification;

/**

 * Vaadin allows setting an com.vaadin.server.ErrorHandler for UIs and components.

 * The caveat with this built in approach is that there is only one {@link com.vaadin.server.ErrorHandler}

 * for any type of errors. This <code>DelegatingErrorHandler</code> allows registering handlers for specific types of errors.

 *

 * see https://dev.e-taxonomy.eu/redmine/issues/7241

 *

 * @author freimeier

 *

 */

public class DelegatingErrorHandler implements ErrorHandler{

    private static final long serialVersionUID = 3378605204517477112L;

    Set<ErrorTypeHandler<? extends Throwable>> handlers = new HashSet<>();

    public <E extends Throwable> void  registerHandler(ErrorTypeHandler<E> handler) {

        assert findHandler(handler.supports()) == null;

        handlers.add(handler);

    }

    @SuppressWarnings("unchecked")

    public <E extends Throwable> ErrorTypeHandler<E> findHandler(Class<E> errorClass){

        for(ErrorTypeHandler<?> h : handlers){

            if(h.supports().equals(errorClass)){

                return (ErrorTypeHandler<E>) h;

            }

        }

        return null;

    }

    /* (non-Javadoc)

     * @see com.vaadin.server.ErrorHandler#error(com.vaadin.server.ErrorEvent)

     */

    @Override

    public void error(ErrorEvent event) {

        boolean handlerFound = true;

        Throwable throwable = event.getThrowable();

        while(throwable != null){

            if(delegate(event, throwable)){

                break;

            }

            throwable = throwable.getCause();

        }

        if(!handlerFound){

            Notification.show(event.getThrowable().getMessage());

          }

    }

    private <E extends Throwable> boolean delegate(ErrorEvent event, E throwable){

        Class<E> errorClass = (Class<E>) throwable.getClass();

        Logger.getLogger(this.getClass()).debug(errorClass);

        ErrorTypeHandler<E> handler = findHandler(errorClass);

        if(handler != null){

            handler.handleError(event, throwable);

            return true;

        }

        return false;

    }

}