aprs-parser/lib/Message/MessageParser.js

JavaScript library for parsing APRS packets

'use strict';
const AbstractParser = require('../AbstractParser.js');

const Callsign = require('../Callsign.js');
const Message = require('./../MessageModels/Message.js');

function MessageParser() {

}

const tryParseMsgId = function (messageBody) {
    const posId = messageBody.indexOf('{');

    if (posId < 0) {
        return {content: messageBody};
    } else {
        const idString = messageBody.substr(posId + 1);
        if (!idString.match('^[0-9]{1,5}')) {
            throw new Error('Wrong message id?');
        }
        else {
            return {content: messageBody.substr(0, posId), id: parseInt(idString)};
        }
    }
};

MessageParser.constructor = MessageParser;
MessageParser.prototype = Object.create(AbstractParser.prototype);

MessageParser.prototype.isMatching = function (bodyContent) {
    return bodyContent[0] == ':';
};

MessageParser.prototype.tryParse = function (bodyContent, aprsMessageHeader) {
    const addressee = new Callsign(bodyContent.substr(1, 9).trim());
    const message = new Message(addressee);

    if (bodyContent[10] != ':') {
        throw Error('Wrong message format');
    }

    //remove :9 characters:
    const messageBody = bodyContent.substr(11);

    if (messageBody.startsWith('ack') || messageBody.startsWith('rej')) {
        const ackRejIdString = messageBody.substr(3);
        if (!ackRejIdString.match('^[0-9]{1,5}')) {
            throw new Error('Wrong ACK/REJ id?');
        }

        message.setId(parseInt(ackRejIdString));

        if (messageBody.startsWith('ack'))
            message.setToAck();
        else
            message.setToRej();
    }
    else {
        const parsedMessage = tryParseMsgId(messageBody);
        message.setText(parsedMessage.content);

        if (parsedMessage.id)
            message.setId(parsedMessage.id);
    }

    return message;
};

MessageParser.prototype.getParserName = function () {
    return 'MessageParser';
};

module.exports = MessageParser;