core/src/main/java/org/apache/any23/extractor/ExampleInputOutput.java

/*
 * 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.any23.extractor;

import org.apache.any23.source.MemCopyFactory;
import org.apache.any23.source.StringDocumentSource;
import org.apache.any23.writer.TripleHandler;
import org.apache.any23.writer.TripleHandlerException;
import org.apache.any23.writer.TurtleWriter;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;

/**
 * A reporter for example input and output of an extractor. Example input is part of every extractor's metadata; example
 * output is obtained by running the extractor on its own example input. This is useful as a documentation device.
 *
 * @author Richard Cyganiak (richard@cyganiak.de)
 */
public class ExampleInputOutput {

    private final ExtractorFactory<?> factory;

    public ExampleInputOutput(String extractorName) {
        this(ExtractorRegistryImpl.getInstance().getFactory(extractorName));
    }

    public ExampleInputOutput(ExtractorFactory<?> factory) {
        this.factory = factory;
    }

    public String getExampleInput() throws IOException {
        if (factory.getExampleInput() == null) {
            return null;
        }
        if (isBlindExtractor()) {
            return null;
        }
        InputStream in = factory.createExtractor().getClass().getResourceAsStream(factory.getExampleInput());
        if (in == null) {
            throw new IllegalArgumentException("Example input resource not found for extractor "
                    + factory.getExtractorName() + ": " + factory.getExampleInput());
        }
        return new String(MemCopyFactory.toByteArray(in), "utf-8");
    }

    public String getExampleIRI() {
        if (factory.getExampleInput() == null) {
            return null;
        }
        if (isBlindExtractor()) {
            return factory.getExampleInput(); // Should be a IRI.
        }
        return "http://example.com/";
    }

    public String getExampleOutput() throws IOException, ExtractionException {
        if (factory.getExampleInput() == null) {
            return null;
        }
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        TripleHandler writer = new TurtleWriter(out);
        new SingleDocumentExtraction(new StringDocumentSource(getExampleInput(), getExampleIRI()), factory, writer)
                .run();
        try {
            writer.close();
        } catch (TripleHandlerException e) {
            throw new ExtractionException("Error while closing the triple handler", e);
        }
        return out.toString("utf-8");
    }

    private boolean isBlindExtractor() {
        return factory.createExtractor() instanceof Extractor.BlindExtractor;
    }

}