/*
 * 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.util;

import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;
import com.google.common.io.CharStreams;
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 org.apache.commons.codec.DecoderException;
import org.apache.commons.codec.binary.Hex;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Parses PCEP messages from a text file. Messages need to follow this formatting:
 *
 * Received PCEP Open message. Length:28.
 *
 * 20 01 00 1c 01 10 00 18 20 1e 78 03 00 10 00 04 00 00 00 05 00 1a 00 04 00 00 00 b4
 */
public final class PCEPHexDumpParser {
    private static final int MINIMAL_LENGTH = 4;
    private static final Logger LOG = LoggerFactory.getLogger(PCEPHexDumpParser.class);
    private static final String LENGTH = "LENGTH:";

    private PCEPHexDumpParser() {

    }

    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();
        }
    }

    private static List<byte[]> parseMessages(final String c) {
        final String content = clearWhiteSpaceToUpper(c);

        final List<byte[]> messages = Lists.newLinkedList();
        int idx = content.indexOf(LENGTH, 0);
        while (idx > -1) {
            // next chars are final length, ending with '.'
            final int lengthIdx = idx + LENGTH.length();
            final int messageIdx = content.indexOf('.', lengthIdx);
            final int length = Integer.parseInt(content.substring(lengthIdx, messageIdx));
            // dot
            final int messageEndIdx = messageIdx + (length * 2) + 1;

            // Assert that message is longer than minimum 4(header.length == 4)
            // If length in PCEP 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);

            // dot
            final String hexMessage = content.substring(messageIdx + 1, messageEndIdx);
            byte[] message = null;
            try {
                message = Hex.decodeHex(hexMessage.toCharArray());
            } catch (final DecoderException e) {
                throw new IllegalArgumentException("Failed to decode message", e);
            }
            messages.add(message);
            idx = messageEndIdx;
            idx = content.indexOf(LENGTH, idx);
        }
        LOG.info("Succesfully extracted {} messages", messages.size());
        return messages;
    }

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