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Wicket Extensions is a rich component library for the Wicket framework.
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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.wicket.extensions.ajax;

import java.util.ArrayList;
import java.util.List;

import org.apache.commons.fileupload2.core.FileItem;
import org.apache.commons.fileupload2.core.FileUploadException;
import org.apache.wicket.Component;
import org.apache.wicket.WicketRuntimeException;
import org.apache.wicket.ajax.AjaxEventBehavior;
import org.apache.wicket.ajax.AjaxRequestTarget;
import org.apache.wicket.ajax.attributes.AjaxCallListener;
import org.apache.wicket.ajax.attributes.AjaxRequestAttributes;
import org.apache.wicket.ajax.attributes.AjaxRequestAttributes.Method;
import org.apache.wicket.core.util.string.CssUtils;
import org.apache.wicket.markup.head.IHeaderResponse;
import org.apache.wicket.markup.head.JavaScriptHeaderItem;
import org.apache.wicket.markup.html.form.upload.FileUpload;
import org.apache.wicket.protocol.http.servlet.MultipartServletWebRequest;
import org.apache.wicket.protocol.http.servlet.ServletWebRequest;
import org.apache.wicket.request.resource.PackageResourceReference;
import org.apache.wicket.request.resource.ResourceReference;
import org.apache.wicket.util.lang.Args;
import org.apache.wicket.util.lang.Bytes;

/**
 * Uploads files from a drop event.
 *
 * @author Andrew Kondratev
 * @author svenmeier
 */
public class AjaxFileDropBehavior extends AjaxEventBehavior
{

	public static final String DRAG_OVER_CLASS_KEY = CssUtils.key(AjaxFileDropBehavior.class, "dragover");

	private static final ResourceReference JS = new PackageResourceReference(
		AjaxFileDropBehavior.class, "wicket-ajaxupload.js");

	/**
	 * Maximum size of all uploaded files in bytes in a request.
	 */
	private Bytes maxSize;

	/**
	 * Maximum size of file of upload in bytes (if there are more than one) in a request.
	 */
	private Bytes fileMaxSize;

	/**
	 * Maximum amount of files in request.
	 * A value of -1 indicates no maximum.
	 */
	private long fileCountMax = -1L;

	private String parameterName = "f";

	/**
	 * Listen for 'dragover' and 'drop' events and prevent them, only 'drop' will initiate
	 * an Ajax request.
	 */
	public AjaxFileDropBehavior()
	{
		super("dragenter dragover dragleave drop");
	}

	@Override
	public void renderHead(Component component, IHeaderResponse response)
	{
		super.renderHead(component, response);

		response.render(JavaScriptHeaderItem.forReference(JS));
	}

	@Override
	protected void updateAjaxAttributes(AjaxRequestAttributes attributes)
	{
		super.updateAjaxAttributes(attributes);

		attributes.setMultipart(true);
		attributes.setMethod(Method.POST);
		// default must be prevented, otherwise browser will consume the dataTransfer
		attributes.setPreventDefault(true);

		attributes.getAjaxCallListeners().add(new AjaxCallListener() {
			@Override
			public CharSequence getPrecondition(Component component)
			{
				String css = getComponent().getString(DRAG_OVER_CLASS_KEY);

				return String.format("jQuery('#' + attrs.c).toggleClass('%s', attrs.event.type === 'dragover'); return (attrs.event.type === 'drop');", css);
			}
		});

		attributes.getDynamicExtraParameters()
			.add(String.format(
				"return Wicket.DataTransfer.getFilesAsParamArray(attrs.event.originalEvent, '%s');",
				parameterName));
	}

	@Override
	protected void onEvent(AjaxRequestTarget target)
	{
		try
		{
			ServletWebRequest request = (ServletWebRequest)getComponent().getRequest();
			final MultipartServletWebRequest multipartWebRequest = request
				.newMultipartWebRequest(getMaxSize(), getComponent().getPage().getId());
			multipartWebRequest.setFileMaxSize(getFileMaxSize());
			multipartWebRequest.setFileCountMax(getFileCountMax());
			multipartWebRequest.parseFileParts();

			// TODO: Can't this be detected from header?
			getComponent().getRequestCycle().setRequest(multipartWebRequest);

			ArrayList fileUploads = new ArrayList<>();

			// Get the item for the path
			final List fileItems = multipartWebRequest.getFile(parameterName);

			if (fileItems != null)
			{
				for (FileItem item : fileItems)
				{
					fileUploads.add(new FileUpload(item));
				}
			}

			onFileUpload(target, fileUploads);
		}
		catch (final FileUploadException fux)
		{
			onError(target, fux);
		}
	}

	public Bytes getMaxSize()
	{
		if (maxSize == null)
		{
			maxSize = getComponent().getApplication().getApplicationSettings()
				.getDefaultMaximumUploadSize();
		}
		return maxSize;
	}

	/**
	 * Set the maximum upload size.
	 *
	 * @param maxSize maximum size, must not be null
	 */
	public void setMaxSize(Bytes maxSize)
	{
		Args.notNull(maxSize, "maxSize");
		this.maxSize = maxSize;
	}

	public Bytes getFileMaxSize()
	{
		return fileMaxSize;
	}

	/**
	 * Set an optional maximum size per file.
	 *
	 * @param fileMaxSize maximum size for each uploaded file
	 */
	public void setFileMaxSize(Bytes fileMaxSize)
	{
		this.fileMaxSize = fileMaxSize;
	}

	/**
	 * Gets maximum count of files
	 *
	 * @return
	 */
	public long getFileCountMax()
	{
		return fileCountMax;
	}

	/**
	 * Sets maximum amount of files in upload request.
	 *
	 * @param fileCountMax
	 */
	public void setFileCountMax(long fileCountMax)
	{
		this.fileCountMax = fileCountMax;
	}

	/**
	 * Hook method called after a file was uploaded.
	 * 
	 * Note: {@link #onError(AjaxRequestTarget, FileUploadException)} is called instead when
	 * uploading failed
	 *
	 * @param target
	 *            the current request handler
	 * @param files
	 *            uploaded files
	 */
	protected void onFileUpload(AjaxRequestTarget target, List files)
	{
	}

	/**
	 * Hook method called to handle any error during uploading of the file.
	 * 
	 * Default implementation re-throws the exception.
	 *
	 * @param target
	 *            the current request handler
	 * @param fux
	 *            the error that occurred
	 */
	protected void onError(AjaxRequestTarget target, FileUploadException fux)
	{
		throw new WicketRuntimeException(fux);
	}
}