/*
 * Copyright (c) 2013 Cisco Systems, Inc. and others.  All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
 * and is available at http://www.eclipse.org/legal/epl-v10.html
 */
package org.opendaylight.protocol.bgp.util;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.List;

import javax.annotation.concurrent.Immutable;

import org.apache.commons.codec.DecoderException;
import org.apache.commons.codec.binary.Hex;
import org.opendaylight.protocol.util.ByteArray;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Preconditions;
import com.google.common.base.Strings;
import com.google.common.collect.Lists;
import com.google.common.io.CharStreams;

/**
 * Read text file, parse BGP messages. File can contain comments or other data. BGP messages are detected using 16 ff
 * marker. New lines and spaces are ignored. Use {@link ByteArray#bytesToHexString(byte[])} for serializing bytes to
 * this format.
 */
@Immutable
public final class HexDumpBGPFileParser {
	private static final int MINIMAL_LENGTH = 19;
	private static final Logger logger = LoggerFactory.getLogger(HexDumpBGPFileParser.class);
	private static final String FF_16 = Strings.repeat("FF", 16);

	private HexDumpBGPFileParser() {

	}

	public static List<byte[]> parseMessages(final File file) throws IOException {
		Preconditions.checkArgument(file != null, "Filename cannot be null");
		return parseMessages(new FileInputStream(file));
	}

	public static List<byte[]> parseMessages(final InputStream is) throws IOException {
		Preconditions.checkNotNull(is);
		try (InputStreamReader isr = new InputStreamReader(is)) {
			return parseMessages(CharStreams.toString(isr));
		} finally {
			is.close();
		}
	}

	public static List<byte[]> parseMessages(final String c) {
		final String content = clearWhiteSpaceToUpper(c);
		// search for 16 FFs

		final List<byte[]> messages = Lists.newLinkedList();
		int idx = 0;
		while ((idx = content.indexOf(FF_16, idx)) > -1) {
			// next 2 bytes are length
			final int lengthIdx = idx + 16 * 2;
			final int messageIdx = lengthIdx + 4;
			final String hexLength = content.substring(lengthIdx, messageIdx);
			byte[] byteLength = null;
			try {
				byteLength = Hex.decodeHex(hexLength.toCharArray());
			} catch (final DecoderException e) {
				throw new RuntimeException(e);
			}
			final int length = ByteArray.bytesToInt(byteLength);
			final int messageEndIdx = idx + length * 2;

			// Assert that message is longer than minimum 19(header.length == 19)
			// If length in BGP message would be 0, loop would never end
			Preconditions.checkArgument(length >= MINIMAL_LENGTH, "Invalid message at index " + idx + ", length atribute is lower than "
					+ MINIMAL_LENGTH);

			final String hexMessage = content.substring(idx, messageEndIdx);
			byte[] message = null;
			try {
				message = Hex.decodeHex(hexMessage.toCharArray());
			} catch (final DecoderException e) {
				new RuntimeException(e);
			}
			messages.add(message);
			idx = messageEndIdx;
		}
		logger.info("Succesfully extracted {} messages", messages.size());
		return messages;
	}

	@VisibleForTesting
	static String clearWhiteSpaceToUpper(final String line) {
		return line.replaceAll("\\s", "").toUpperCase();
	}

}