/*
 * 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.tika.server.writer;

import javax.ws.rs.Produces;
import javax.ws.rs.WebApplicationException;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.MultivaluedMap;
import javax.ws.rs.ext.MessageBodyWriter;
import javax.ws.rs.ext.Provider;

import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.lang.annotation.Annotation;
import java.lang.reflect.Type;

import org.apache.tika.metadata.Metadata;

import static java.nio.charset.StandardCharsets.UTF_8;

/**
 * Returns simple text string for a particular metadata value.
 * This assumes that the metadata object only has one key;
 * if there is more than one key or no keys, this will throw a webapp exception.
 * <p/>
 * This will choose the first value returned for the one key.
 */
@Provider
@Produces(MediaType.TEXT_PLAIN)
public class TextMessageBodyWriter implements MessageBodyWriter<Metadata> {

    public boolean isWriteable(Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType) {
        return mediaType.equals(MediaType.TEXT_PLAIN_TYPE) && Metadata.class.isAssignableFrom(type);
    }

    public long getSize(Metadata data, Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType) {
        return -1;
    }

    @Override
    @SuppressWarnings("resource")
    public void writeTo(Metadata metadata, Class<?> type, Type genericType, Annotation[] annotations,
                        MediaType mediaType, MultivaluedMap<String, Object> httpHeaders, OutputStream entityStream) throws IOException,
            WebApplicationException {

        if (metadata.names().length != 1) {
            throw new WebApplicationException("Metadata object must only have one entry!");
        }
        Writer writer = new OutputStreamWriter(entityStream, UTF_8);

        for (String name : metadata.names()) {
            writer.write(metadata.get(name));
        }

        // Don't close, just flush the stream
        writer.flush();
    }
}