Rinaldi Fonseca rinaldifonseca

GenStage Tutorial

Introduction

So what is GenStage? From the official documentation, it is a "specification and computational flow for Elixir", but what does that mean to us?
There is a lot to something that can be described as that vague, and here we'll take a dive in and build something on top of it to understand its goals. We could go into the technical and theoretical implications of this, but instead lets try a pragmatic approach to really just get it to work.

First, Let's imagine we have a server that constantly emits numbers. It starts at the state of the number we give it, then counts up in one from there onward. This is what we would call our producer.

Not all random values are created equal - for security-related code, you need a specific kind of random value.

A summary of this article, if you don't want to read the entire thing:

Don't use Math.random(). There are extremely few cases where Math.random() is the right answer. Don't use it, unless you've read this entire article, and determined that it's necessary for your case.
Don't use crypto.getRandomBytes directly. While it's a CSPRNG, it's easy to bias the result when 'transforming' it, such that the output becomes more predictable.
If you want to generate random tokens or API keys: Use uuid, specifically the uuid.v4() method. Avoid node-uuid - it's not the same package, and doesn't produce reliably secure random values.
If you want to generate random numbers in a range: Use random-number-csprng.

You should seriously consider reading the entire article, though - it's

JWT Auth + Refresh Tokens in Rails

This is just some code I recently used in my development application in order to add token-based authentication for my api-only rails app. The api-client was to be consumed by a mobile application, so I needed an authentication solution that would keep the user logged in indefinetly and the only way to do this was either using refresh tokens or sliding sessions.

I also needed a way to both blacklist and whitelist tokens based on a unique identifier (jti)

Before trying it out DIY, I considered using:

Integrate Gem/Engine and main Rails app

Overview

Paths
Routes
Add functionality to controller
Improving (Extending or overriding) Engine functionality
Helpers
Assets

rails plugin new <project_name> -T -d postgresql --dummy-path=spec/dummy --skip-turbolinks --skip-spring --mountable

-T skips the creation of the test directory and the use of Test::Unit
--dummy-path=spec/dummy sets up your dummy app in a spec directory
--skip-turbolinks & --skip-spring creates a project that does not use turbolinks or spring
--mountable creates a "mountable" and namespace-isolated engine.

In Gemfile:

gem 'rspec-rails' - user rspec in place of minitest (docs)
gem 'capybara' - act as a user navigating your site in tests (docs)
gem 'factory_girl_rails' - easily generate database objects without repetitive code in tests (docs)
gem 'database_cleaner' - clean your database between tests (docs)

	iex(2)> pid = spawn Traps, :init, []
	waiting to die...
	#PID<0.92.0>
	Nobody tried to kill me! ^_^
	waiting to die...
	Nobody tried to kill me! ^_^
	waiting to die...
	iex(3)> Process.exit pid, :normal
	true
	(⊙＿⊙') somebody tried to kill me! {:EXIT, #PID<0.88.0>, :normal}

	defmodule Box do
	defmacro __using__(_env) do
	quote do
	import Box
	end
	end

	@doc """
	Define module with struct and typespec, in single line

	<!DOCTYPE html>
	<html>
	<head>
	<link href='https://fonts.googleapis.com/css?family=Roboto:300,400,500,700\|Material+Icons' rel="stylesheet">
	<link href="https://unpkg.com/vuetify/dist/vuetify.min.css" rel="stylesheet">
	<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no, minimal-ui">
	</head>
	<body>
	<div id="app">
	<v-app id="inspire">

	require 'logger'
	require 'byebug'

	require 'dry/monads'
	require 'dry/monads/do'
	require 'dry/matcher/result_matcher'

	module Dry
	module Transaction
	module Steps

	## PayRoll gem

	# lib/pay_roll.rb
	module PayRoll
	class << self
	attr_accessor :employee_directory
	def config
	yield self
	end
	end