"use strict";
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const Sender = require('./sender').Sender;
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const SQL_SERVER_BROWSER_PORT = 1434;
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const TIMEOUT = 2 * 1000;
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const RETRIES = 3; // There are three bytes at the start of the response, whose purpose is unknown.
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const MYSTERY_HEADER_LENGTH = 3; // Most of the functionality has been determined from from jTDS's MSSqlServerInfo class.
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class InstanceLookup {
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constructor() {} // Wrapper allows for stubbing Sender when unit testing instance-lookup.
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createSender(host, port, request) {
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return new Sender(host, port, request);
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}
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instanceLookup(options, callback) {
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const server = options.server;
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if (typeof server !== 'string') {
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throw new TypeError('Invalid arguments: "server" must be a string');
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}
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const instanceName = options.instanceName;
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if (typeof instanceName !== 'string') {
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throw new TypeError('Invalid arguments: "instanceName" must be a string');
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}
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const timeout = options.timeout === undefined ? TIMEOUT : options.timeout;
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if (typeof timeout !== 'number') {
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throw new TypeError('Invalid arguments: "timeout" must be a number');
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}
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const retries = options.retries === undefined ? RETRIES : options.retries;
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if (typeof retries !== 'number') {
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throw new TypeError('Invalid arguments: "retries" must be a number');
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}
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if (typeof callback !== 'function') {
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throw new TypeError('Invalid arguments: "callback" must be a function');
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}
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let sender,
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timer,
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retriesLeft = retries;
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const onTimeout = () => {
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sender.cancel();
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makeAttempt();
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};
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const makeAttempt = () => {
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if (retriesLeft > 0) {
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retriesLeft--;
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const request = Buffer.from([0x02]);
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sender = this.createSender(options.server, SQL_SERVER_BROWSER_PORT, request);
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sender.execute((err, message) => {
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clearTimeout(timer);
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if (err) {
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callback('Failed to lookup instance on ' + server + ' - ' + err.message);
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return;
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} else {
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message = message.toString('ascii', MYSTERY_HEADER_LENGTH);
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const port = this.parseBrowserResponse(message, instanceName);
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if (port) {
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callback(undefined, port);
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} else {
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callback('Port for ' + instanceName + ' not found in ' + options.server);
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}
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}
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});
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timer = setTimeout(onTimeout, timeout);
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} else {
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callback('Failed to get response from SQL Server Browser on ' + server);
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}
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};
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makeAttempt();
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}
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parseBrowserResponse(response, instanceName) {
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let getPort;
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const instances = response.split(';;');
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for (let i = 0, len = instances.length; i < len; i++) {
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const instance = instances[i];
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const parts = instance.split(';');
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for (let p = 0, partsLen = parts.length; p < partsLen; p += 2) {
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const name = parts[p];
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const value = parts[p + 1];
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if (name === 'tcp' && getPort) {
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const port = parseInt(value, 10);
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return port;
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}
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if (name === 'InstanceName') {
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if (value.toUpperCase() === instanceName.toUpperCase()) {
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getPort = true;
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} else {
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getPort = false;
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}
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}
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}
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}
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}
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}
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module.exports.InstanceLookup = InstanceLookup;
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