'use strict';

exports = module.exports = {
    start,
    stop
};

const LOG_FILENAME = 'app.log';

const assert = require('assert'),
    dgram = require('dgram'),
    fs = require('fs'),
    path = require('path'),
    parser = require('nsyslog-parser');

let server = null;

function start(options, callback) {
    assert.strictEqual(typeof options, 'object');
    assert.strictEqual(typeof options.port, 'number');
    assert.strictEqual(typeof options.logFolder, 'string');
    assert.strictEqual(typeof callback, 'function');

    server = dgram.createSocket('udp4');

    server.on('error', function (error) {
        callback(error);
    }).on('listening', function () {
        callback();
    }).on('message', function (msg /*, rinfo */) {
        const info = parser(msg.toString());

        if (!info || !info.appName) return console.log('Ignore unknown app log:', msg.toString());

        // remove line breaks to avoid holes in the log file
        // we do not ignore empty log lines, to allow gaps for potential ease of readability
        const message = info.message.replace(/\n/g, '');

        const filePath = path.join(options.logFolder, info.appName);
        const fileName = path.join(filePath, LOG_FILENAME);

        try {
            fs.mkdirSync(filePath, { recursive: true });
            fs.appendFileSync(fileName, info.ts.toISOString() + ' ' + message + '\n');
        } catch (error) {
            console.error(error);
        }
    }).bind(options.port);
}

function stop(callback) {
    assert.strictEqual(typeof callback, 'function');

    if (!server) return callback();

    server.close();

    server = null;

    callback();
}