TemporaryChartImageWriter.java

/*
 * See the NOTICE file distributed with this work for additional
 * information regarding copyright ownership.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
package org.xwiki.rendering.internal.macro.chart;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.net.URLEncoder;

import javax.inject.Inject;
import javax.inject.Named;
import javax.inject.Singleton;

import org.apache.commons.io.IOUtils;
import org.xwiki.bridge.DocumentAccessBridge;
import org.xwiki.component.annotation.Component;
import org.xwiki.environment.Environment;
import org.xwiki.model.EntityType;
import org.xwiki.model.ModelContext;
import org.xwiki.model.reference.DocumentReference;
import org.xwiki.model.reference.EntityReference;
import org.xwiki.rendering.macro.MacroExecutionException;

/**
 * Save generated Chart images to a temporary storage location.
 *
 * @version $Id: 4ff842aa7e6df69dcc5224ed9f5963bf94c32949 $
 * @since 4.2M3
 */
@Component
@Named("tmp")
@Singleton
public class TemporaryChartImageWriter implements ChartImageWriter
{
    /**
     * Default encoding used for encoding wiki, space, page and image file names when generating the Image in the
     * temporary folder.
     */
    private static final String DEFAULT_ENCODING = "UTF-8";

    /**
     * The module name used when creating temporary files. This is the module used by the temporary resource action to
     * retrieve the temporary image file.
     */
    private static final String MODULE_NAME = "chart";

    /**
     * Space part of the temporary location where generated chart image are stored.
     */
    private static final String SPACE = "space";

    /**
     * Page part of the temporary location where generated chart image are stored.
     */
    private static final String PAGE = "page";

    /**
     * Used to get the temporary directory.
     */
    @Inject
    private Environment environment;

    /**
     * Used to get the current wiki.
     */
    @Inject
    private ModelContext modelContext;

    /**
     * Used to compute the URL to the temporary stored image generated by the chart.
     */
    @Inject
    private DocumentAccessBridge documentAccessBridge;

    @Override
    public void writeImage(ImageId imageId, byte[] imageData) throws MacroExecutionException
    {
        File imageFile = getStorageLocation(imageId);

        FileOutputStream fos = null;
        try {
            fos = new FileOutputStream(imageFile);
            fos.write(imageData);
            fos.close();
        } catch (IOException e) {
            throw new MacroExecutionException("Failed to write the generated chart image", e);
        } finally {
            IOUtils.closeQuietly(fos);
        }
    }

    /**
     * Compute the location where to store the generated chart image.
     *
     * @param imageId the image id that we use to generate a unique storage location
     * @return the location where to store the generated chart image
     * @throws MacroExecutionException if an error happened when computing the location
     */
    protected File getStorageLocation(ImageId imageId) throws MacroExecutionException
    {
        File directory;
        try {
            String currentWiki = URLEncoder.encode(getCurrentWiki(), DEFAULT_ENCODING);
            // TODO: We need to decide if it's ok to use the the hardcoded "space/page" or if we want to use the
            // current document in which case we need to extract it from the XDOM. The reason I haven't done it
            // by default is because it takes more time and the image id seems unique enough to not cause collisions.
            directory = new File(this.environment.getTemporaryDirectory(),
                String.format("temp/%s/%s/%s/%s", MODULE_NAME, currentWiki, SPACE, PAGE));
            directory.mkdirs();
        } catch (Exception e) {
            // Should not happen since UTF8 encoding should always be present
            throw new MacroExecutionException("Failed to compute chart image location", e);
        }
        File locationFile = new File(directory, String.format("%s.png", imageId.getId()));
        return locationFile;
    }

    /**
     * @return the current wiki
     * @throws MacroExecutionException if the current wiki couldn't be found
     */
    private String getCurrentWiki() throws MacroExecutionException
    {
        EntityReference reference = this.modelContext.getCurrentEntityReference();
        if (reference == null) {
            // This shouldn't happen since there's always supposed to be a current wiki
            throw new MacroExecutionException("The current wiki couldn't be computed");
        }
        return reference.extractReference(EntityType.WIKI).getName();
    }

    @Override
    public String getURL(ImageId imageId) throws MacroExecutionException
    {
        DocumentReference reference = new DocumentReference(getCurrentWiki(), SPACE, PAGE);
        String prefix = this.documentAccessBridge.getDocumentURL(reference, "temp", null, null);
        return String.format("%s/%s/%s.png", prefix, MODULE_NAME, imageId.getId());
    }
}