Silly redis implementation

Question

This is a silly Redis implementation that handles only three commands: INFO, ECHO, PING.

The implementation is based on streams:

var _ = require('lodash')
var expect = require('chai').expect;
var assert = require('chai').assert;
var redis = require('redis')
var split = require('split')
var net = require('net');
var util = require('util');
var Transform = require('stream').Transform;
function makeCommand(parts) {
 var parts = _.filter(parts, (_, i) => i % 2 === 1)
 return {
 command: _.first(parts),
 args: _.drop(parts)
 }
}
function CommandParser(options) {
 if (!(this instanceof CommandParser)) {
 return new CommandParser(options)
 }
 Transform.call(this, {readableObjectMode: true})
 this.__counter = 0
 this.__parts = []
}
util.inherits(CommandParser, Transform);
CommandParser.prototype._transform = function(chunk, encoding, done) {
 var str = chunk.toString('utf-8')
 if(this.__counter == 0) {
 assert(str[0] == '*')
 this.__counter = Number(_.drop(str)) * 2
 } else {
 console.log(this.__counter, str)
 this.__parts.push(str)
 this.__counter--
 }
 if(this.__counter === 0 && !_.isEmpty(this.__parts)) {
 console.log('here')
 var command = makeCommand(this.__parts)
 console.log(command)
 this.push(command)
 this.__parts = []
 }
 done()
};
function CommandProcessor(options) {
 if (!(this instanceof CommandProcessor)) {
 return new CommandProcessor(options)
 }
 Transform.call(this, {writableObjectMode: true})
}
util.inherits(CommandProcessor, Transform);
CommandProcessor.prototype._transform = function(command, encoding, done) {
 switch (command.command) {
 case 'ping':
 done(null, '+pong\r\n')
 break;
 case 'info':
 done(null, '9ドル\r\nsome info\r\n')
 break;
 case 'echo':
 done(null, `\$${command.args[0].length}\r\n${command.args[0]}\r\n`)
 break;
 default:
 console.log(command)
 assert.fail()
 }
};
var TEST_PORT = 6380
var server = net.createServer(function(socket) {
 var commandParser = new CommandParser()
 var commandProcessor = new CommandProcessor()
 socket
 .pipe(split())
 .pipe(commandParser)
 .pipe(commandProcessor)
 .pipe(socket)
});
server.listen(6380, '127.0.0.1')

You can use the standard redis client to work with it. I'm mostly interested in any advice about node streams, but any other ideas are welcome too.

Answer 1

var parts = _.filter(parts, (_, i) => i % 2 === 1) this looks like a habit from python. I do not recommend shadowing lodash in any part of the code, it is harder to read.

• kharandziuk: how do you recommend to rewrite the code?
• Jan Grz: anything that does not shadow _ the lodash variable, try:var parts = _.filter(parts, (e, i) => i % 2 === 1)

Answer 2

You can simplify the whole thing by using a library such as this.

Your stream, I believe, should be a duplex, one onto which you write command into redis, and read output from redis. For example, sockets are duplex (net.Socket).