NodeJS proxy

#!/usr/bin/env node
'use strict';
var net = require('net'), tls = require('tls');
var HTTPParser = process.binding('http_parser').HTTPParser;

function main() {
    //convert `-key value` to cfg[key]=value
    var cfg = process.argv.slice(2/*skip ["node", "xxx.js"]*/).reduce(function (cfg, arg, i, argv) {
        return (i % 2 === 0 && (arg.slice(0, 1) === '-' && (cfg[arg.slice(1)] = argv[i + 1])), cfg);
    }, {local_host: '', local_port: 0, remote_host: '', remote_port: 0, usr: '', pwd: ''});
    cfg.local_host = cfg.local_host || 'localhost';
    cfg.local_port = (cfg.local_port & 0xffff) || 8080;
    cfg.remote_port = (cfg.remote_port & 0xffff) || 8080;
    cfg.is_remote_https = cfg.is_remote_https === 'true';
    cfg.ignore_https_cert = cfg.ignore_https_cert === 'true';

    if (!cfg.local_host || !cfg.local_port || !cfg.remote_host || !cfg.remote_port || !cfg.usr || !cfg.pwd)
        return console.error('Usage of parameters:\n'
            + '-local_host host\t' + 'Listening address. Default: localhost. (* means all interfaces)\n'
            + '-local_port port\t' + 'Listening port. Default: 8080\n'
            + '-remote_host host\t' + 'Real proxy/PAC server address\n'
            + '-remote_port port\t' + 'Real proxy/PAC server port. Default: 8080\n'
            + '-usr user\t\t' + 'Real proxy/PAC server user id\n'
            + '-pwd password\t\t' + 'Real proxy/PAC user password\n'
            + '\n'
            + '-is_remote_https true/false\t' + 'Talk to real proxy/PAC server with HTTPS. Default: false\n'
            + '-ignore_https_cert true/false\t' + 'ignore error when verify certificate of real proxy/PAC server. Default: false\n'
        );
    console.log('Using parameters: ' + JSON.stringify(cfg, null, '  '));
    cfg.buf_proxy_basic_auth = new Buffer('Proxy-Authorization: Basic ' + new Buffer(cfg.usr + ':' + cfg.pwd).toString('base64'));

    createPortForwarder(cfg.local_host, cfg.local_port, cfg.remote_host, cfg.remote_port, cfg.buf_proxy_basic_auth, cfg.is_remote_https, cfg.ignore_https_cert);
}

var CR = 0xd, LF = 0xa, BUF_CR = new Buffer([0xd]), BUF_CR_LF_CR_LF = new Buffer([0xd, 0xa, 0xd, 0xa]),
    BUF_LF_LF = new Buffer([0xa, 0xa]), BUF_PROXY_CONNECTION_CLOSE = new Buffer('Proxy-Connection: close');
var STATE_NONE = 0, STATE_FOUND_LF = 1, STATE_FOUND_LF_CR = 2;

function createPortForwarder(local_host, local_port, remote_host, remote_port, buf_proxy_basic_auth, is_remote_https, ignore_https_cert) {
    net.createServer({allowHalfOpen: true}, function (socket) {
        var realCon = (is_remote_https ? tls : net).connect({
            port: remote_port, host: remote_host, allowHalfOpen: true,
            rejectUnauthorized: !ignore_https_cert /*not used when is_remote_https false*/
        });
        realCon.on('data', function (buf) {
            //console.log('<<<<' + (Date.t=new Date()) + '.' + Date.t.getMilliseconds() + '\n' + buf.toString('ascii'));
            socket.write(buf);
            realCon.__haveGotData = true;
        }).on('end', function () {
            socket.end();
            if (!realCon.__haveGotData && !realCon.__haveShownError) {
                console.error('[LocalProxy(:' + local_port + ')][Connection to ' + remote_host + ':' + remote_port + '] Error: ended by remote peer');
                realCon.__haveShownError = true;
            }
        }).on('close', function () {
            socket.end();
            if (!realCon.__haveGotData && !realCon.__haveShownError) {
                console.error('[LocalProxy(:' + local_port + ')][Connection to ' + remote_host + ':' + remote_port + '] Error: reset by remote peer');
                realCon.__haveShownError = true;
            }
        }).on('error', function (err) {
            console.error('[LocalProxy(:' + local_port + ')][Connection to ' + remote_host + ':' + remote_port + '] ' + err);
            realCon.__haveShownError = true;
        });

        var parser = new HTTPParser(HTTPParser.REQUEST);
        parser[HTTPParser.kOnHeadersComplete] = function (versionMajor, versionMinor, headers, method,
                                                          url, statusCode, statusMessage, upgrade,
                                                          shouldKeepAlive) {
            parser.__is_headers_complete = true;
            parser.__upgrade = upgrade;
            parser.__method = method;
        };

        var state = STATE_NONE;

        socket.on('data', function (buf) {
            if (!parser) {
                realCon.write(buf);
                return
            }

            var buf_ary = [], unsavedStart = 0, buf_len = buf.length;

            for (var i = 0; i < buf_len; i++) {
                //find first LF
                if (state === STATE_NONE) {
                    if (buf[i] === LF) {
                        state = STATE_FOUND_LF;
                    }
                    continue;
                }

                //find second CR LF or LF
                if (buf[i] === LF) {
                    parser.__is_headers_complete = false;
                    parser.execute(buf.slice(unsavedStart, i + 1));

                    if (parser.__is_headers_complete) {
                        buf_ary.push(buf.slice(unsavedStart, buf[i - 1] === CR ? i - 1 : i));
                        //console.log('insert auth header');
                        buf_ary.push(buf_proxy_basic_auth);
                        buf_ary.push(state === STATE_FOUND_LF_CR ? BUF_CR_LF_CR_LF : BUF_LF_LF);

                        // stop intercepting packets if encountered TLS and WebSocket handshake
                        if (parser.__method === 5 /*CONNECT*/ || parser.__upgrade) {
                            parser.close();
                            parser = null;

                            buf_ary.push(buf.slice(i + 1));
                            realCon.write(Buffer.concat(buf_ary));

                            state = STATE_NONE;
                            return;
                        }

                        unsavedStart = i + 1;
                        state = STATE_NONE;
                    } else {
                        state = STATE_FOUND_LF;
                    }
                } else if (buf[i] === CR && state === STATE_FOUND_LF) {
                    state = STATE_FOUND_LF_CR;
                } else {
                    state = STATE_NONE;
                }
            }

            if (unsavedStart < buf_len) {
                buf = buf.slice(unsavedStart, buf_len);
                parser.execute(buf);
                buf_ary.push(buf);
            }

            realCon.write(Buffer.concat(buf_ary));

        }).on('end', cleanup).on('close', cleanup).on('error', function (err) {
            if (!socket.__cleanup) {
                console.error('[LocalProxy(:' + local_port + ')][Incoming connection] ' + err);
            }
        });

        function cleanup() {
            socket.__cleanup = true;
            if (parser) {
                parser.close();
                parser = null;
            }
            realCon.end();
        }
    }).on('error', function (err) {
        console.error('[LocalProxy(:' + local_port + ')] ' + err);
        process.exit(1);
    }).listen(local_port, local_host === '*' ? undefined : local_host, function () {
        console.log('[LocalProxy(:' + local_port + ')] OK: forward http://' + local_host + ':' + local_port + ' to ' + ' to http' + (is_remote_https ? 's' : '') + '://' + remote_host + ':' + remote_port);
    });
}

main();