/********************************************************************************
 * Copyright (c) 2015-2019 Contributors to the Eclipse Foundation
 *
 * See the NOTICE file(s) distributed with this work for additional
 * information regarding copyright ownership.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 ********************************************************************************/

package org.eclipse.mdm.businessobjects.utils;

import static org.eclipse.mdm.businessobjects.boundary.ResourceConstants.MEDIATYPE_APPLICATION_PROTOBUF;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.annotation.Annotation;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Type;

import javax.ws.rs.Consumes;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.MultivaluedMap;
import javax.ws.rs.ext.MessageBodyReader;
import javax.ws.rs.ext.MessageBodyWriter;
import javax.ws.rs.ext.Provider;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.io.ByteStreams;
import com.google.protobuf.AbstractMessage;
import com.google.protobuf.CodedInputStream;
import com.google.protobuf.InvalidProtocolBufferException;
import com.google.protobuf.Message;

/**
 * MessageBodyProvider for handling protobuf payloads.
 * 
 */
@Provider
@Consumes({ MEDIATYPE_APPLICATION_PROTOBUF })
@Produces({ MEDIATYPE_APPLICATION_PROTOBUF })
public class ProtobufMessageBodyProvider implements MessageBodyReader<Message>, MessageBodyWriter<Message> {
	private static final Logger LOG = LoggerFactory.getLogger(ProtobufMessageBodyProvider.class);

	private static final int DEFAULT_SIZE_LIMIT = 64 << 20; // 64MB
	private static final int MAX_SIZE = DEFAULT_SIZE_LIMIT;

	/*
	 * (non-Javadoc)
	 * 
	 * @see javax.ws.rs.ext.MessageBodyReader#isReadable(java.lang.Class,
	 * java.lang.reflect.Type, java.lang.annotation.Annotation[],
	 * javax.ws.rs.core.MediaType)
	 */
	@Override
	public boolean isReadable(final Class<?> type, final Type genericType, final Annotation[] annotations,
			final MediaType mediaType) {
		return Message.class.isAssignableFrom(type);
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see javax.ws.rs.ext.MessageBodyReader#readFrom(java.lang.Class,
	 * java.lang.reflect.Type, java.lang.annotation.Annotation[],
	 * javax.ws.rs.core.MediaType, javax.ws.rs.core.MultivaluedMap,
	 * java.io.InputStream)
	 */
	@Override
	public Message readFrom(final Class<Message> type, final Type genericType, final Annotation[] annotations,
			final MediaType mediaType, final MultivaluedMap<String, String> httpHeaders, final InputStream entityStream)
			throws IOException {
		try {
			final Method newBuilder = type.getMethod("newBuilder");
			final AbstractMessage.Builder<?> builder = (AbstractMessage.Builder<?>) newBuilder.invoke(type);

			CodedInputStream in = CodedInputStream.newInstance(entityStream);
			in.setSizeLimit(MAX_SIZE);

			byte[] b = ByteStreams.toByteArray(entityStream);
			LOG.debug("Reading type {} with size {}.", genericType, b.length);
			return builder.mergeFrom(b).build();
		} catch (InvalidProtocolBufferException e) {
			throw new IOException("Could not read Protobuf entity!", e);
		} catch (NoSuchMethodException | InvocationTargetException | IllegalAccessException e) {
			throw new IOException("Could not retrive builder for type " + genericType, e);
		}
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see javax.ws.rs.ext.MessageBodyWriter#getSize(java.lang.Object,
	 * java.lang.Class, java.lang.reflect.Type, java.lang.annotation.Annotation[],
	 * javax.ws.rs.core.MediaType)
	 */
	@Override
	public long getSize(final Message m, final Class<?> type, final Type genericType, final Annotation[] annotations,
			final MediaType mediaType) {
		return -1; // as method is not actually used by JAX-RS
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see javax.ws.rs.ext.MessageBodyWriter#isWriteable(java.lang.Class,
	 * java.lang.reflect.Type, java.lang.annotation.Annotation[],
	 * javax.ws.rs.core.MediaType)
	 */
	@Override
	public boolean isWriteable(final Class<?> type, final Type genericType, final Annotation[] annotations,
			final MediaType mediaType) {
		return Message.class.isAssignableFrom(type);
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see javax.ws.rs.ext.MessageBodyWriter#writeTo(java.lang.Object,
	 * java.lang.Class, java.lang.reflect.Type, java.lang.annotation.Annotation[],
	 * javax.ws.rs.core.MediaType, javax.ws.rs.core.MultivaluedMap,
	 * java.io.OutputStream)
	 */
	@Override
	public void writeTo(final Message m, final Class<?> type, final Type genericType, final Annotation[] annotations,
			final MediaType mediaType, final MultivaluedMap<String, Object> httpHeaders,
			final OutputStream entityStream) throws IOException {

		if (LOG.isDebugEnabled()) {
			LOG.debug("Writing type {} with size {}.", genericType, m.getSerializedSize());
		}
		m.writeTo(entityStream);
	}

}