/******************************************************************************
 * Copyright (c) 2016 TypeFox and others.
 * 
 * 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,
 * or the Eclipse Distribution License v. 1.0 which is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 * 
 * SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
 ******************************************************************************/
package org.eclipse.lsp4j.jsonrpc.json;

import java.io.IOException;
import java.io.OutputStream;
import java.nio.charset.StandardCharsets;

import org.eclipse.lsp4j.jsonrpc.JsonRpcException;
import org.eclipse.lsp4j.jsonrpc.MessageConsumer;
import org.eclipse.lsp4j.jsonrpc.messages.Message;

/**
 * A message consumer that serializes messages to JSON and sends them to an output stream.
 */
public class StreamMessageConsumer implements MessageConsumer, MessageConstants {

	private final String encoding;
	private final MessageJsonHandler jsonHandler;

	private final Object outputLock = new Object();

	private OutputStream output;

	public StreamMessageConsumer(MessageJsonHandler jsonHandler) {
		this(null, StandardCharsets.UTF_8.name(), jsonHandler);
	}

	public StreamMessageConsumer(OutputStream output, MessageJsonHandler jsonHandler) {
		this(output, StandardCharsets.UTF_8.name(), jsonHandler);
	}

	public StreamMessageConsumer(OutputStream output, String encoding, MessageJsonHandler jsonHandler) {
		this.output = output;
		this.encoding = encoding;
		this.jsonHandler = jsonHandler;
	}

	public OutputStream getOutput() {
		return output;
	}

	public void setOutput(OutputStream output) {
		this.output = output;
	}

	@Override
	public void consume(Message message) {
		try {
			String content = jsonHandler.serialize(message);
			byte[] contentBytes = content.getBytes(encoding);
			int contentLength = contentBytes.length;

			String header = getHeader(contentLength);
			byte[] headerBytes = header.getBytes(StandardCharsets.US_ASCII);

			synchronized (outputLock) {
				output.write(headerBytes);
				output.write(contentBytes);
				output.flush();
			}
		} catch (IOException exception) {
			throw new JsonRpcException(exception);
		}
	}

	/**
	 * Construct a header to be prepended to the actual content. This implementation writes
	 * {@code Content-Length} and {@code Content-Type} attributes according to the LSP specification.
	 */
	protected String getHeader(int contentLength) {
		StringBuilder headerBuilder = new StringBuilder();
		appendHeader(headerBuilder, CONTENT_LENGTH_HEADER, contentLength).append(CRLF);
		if (!StandardCharsets.UTF_8.name().equals(encoding)) {
			appendHeader(headerBuilder, CONTENT_TYPE_HEADER, JSON_MIME_TYPE);
			headerBuilder.append("; charset=").append(encoding).append(CRLF);
		}
		headerBuilder.append(CRLF);
		return headerBuilder.toString();
	}

	/**
	 * Append a header attribute to the given builder.
	 */
	protected StringBuilder appendHeader(StringBuilder builder, String name, Object value) {
		return builder.append(name).append(": ").append(value);
	}

}