Gadgetbridge/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/devices/withingssteelhr/communication/message/MessageBuilder.java

/*  Copyright (C) 2021 Frank Ertl

    This file is part of Gadgetbridge.

    Gadgetbridge is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as published
    by the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    Gadgetbridge is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>. */
package nodomain.freeyourgadget.gadgetbridge.service.devices.withingssteelhr.communication.message;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.Arrays;

import nodomain.freeyourgadget.gadgetbridge.service.btle.BLETypeConversions;
import nodomain.freeyourgadget.gadgetbridge.service.devices.withingssteelhr.WithingsSteelHRDeviceSupport;
import nodomain.freeyourgadget.gadgetbridge.util.StringUtils;

public class MessageBuilder {

    private static final Logger logger = LoggerFactory.getLogger(MessageBuilder.class);
    private WithingsSteelHRDeviceSupport support;
    private MessageFactory messageFactory;
    private ByteArrayOutputStream pendingMessage;
    private Message message;

    public MessageBuilder(WithingsSteelHRDeviceSupport support, MessageFactory messageFactory) {
        this.support = support;
        this.messageFactory = messageFactory;
    }

    public synchronized boolean buildMessage(byte[] rawData) {
        if (pendingMessage == null && rawData[0] == 0x01) {
            pendingMessage = new ByteArrayOutputStream();
        } else if (pendingMessage == null) {
            return false;
        }

        try {
            pendingMessage.write(rawData);
        } catch(IOException e) {
            logger.error("Could not write data to stream: " + StringUtils.bytesToHex(rawData));
            return false;
        }

        if (!isMessageComplete(pendingMessage.toByteArray())) {
            return false;
        } else {
            Message message = messageFactory.createMessageFromRawData(pendingMessage.toByteArray());
            pendingMessage = null;
            if (message == null) {
                logger.info("Cannot handle null message");
                return false;
            }

            this.message = message;
            return true;
        }
    }

    public Message getMessage() {
        return message;
    }

    private boolean isMessageComplete(byte[] messageData) {
        if (messageData.length < 5) {
            return false;
        }

        short totalDataLength = (short) BLETypeConversions.toInt16(messageData[4], messageData[3]);
        byte[] rawStructureData = Arrays.copyOfRange(messageData, 5, messageData.length);
        if (rawStructureData.length == totalDataLength) {
            return true;
        }

        return false;
    }
}