/*
 * Copyright 2000-2016 Vaadin Ltd.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package com.vaadin.event.dd.acceptcriteria;

import com.vaadin.event.Transferable;
import com.vaadin.event.dd.DragAndDropEvent;
import com.vaadin.server.PaintException;
import com.vaadin.server.PaintTarget;

/**
 * A Criterion that checks whether {@link Transferable} contains given data
 * flavor. The developer might for example accept the incoming data only if it
 * contains "Url" or "Text".
 *
 * @since 6.3
 */
public class ContainsDataFlavor extends ClientSideCriterion {

    private final String dataFlavorId;

    /**
     * Constructs a new instance of {@link ContainsDataFlavor}.
     *
     * @param dataFlawor
     *            the type of data that will be checked from
     *            {@link Transferable}
     */
    public ContainsDataFlavor(String dataFlawor) {
        dataFlavorId = dataFlawor;
    }

    @Override
    public void paintContent(PaintTarget target) throws PaintException {
        super.paintContent(target);
        target.addAttribute("p", dataFlavorId);
    }

    @Override
    public boolean accept(DragAndDropEvent dragEvent) {
        return dragEvent.getTransferable().getDataFlavors()
                .contains(dataFlavorId);
    }

    @Override
    protected String getIdentifier() {
        // extending classes use client side implementation from this class
        return ContainsDataFlavor.class.getCanonicalName();
    }
}