Ruby script for generating Shopify app install link from local ENV, .env or a heroku deploy

create_link.rb

require 'base64'
require 'openssl'

HOST = 'https://www.example.com'

if ARGV.length != 1
  STDERR.puts "Pass in <shop> as param"
  exit
end

shop = ARGV[0]
@host = 'http://localhost:3000'

def fetch_dot_env_secret
  return nil unless File.exists? '.env'
  File.open('.env').readlines.each do |line|
    if line =~ /^SHOPIFY_APP_CLIENT_SECRET=(.*)$/
      return Regexp.last_match(1)
    end
  end
  nil
end

client_secrets = {}

if (env_secret = ENV['SHOPIFY_APP_CLIENT_SECRET'])
  client_secrets['From ENV SHOPIFY_APP_CLIENT_SECRET'] = -> { env_secret }
end

if (dot_env_secret = fetch_dot_env_secret)
  client_secrets['From .env'] = -> { dot_env_secret }
end

if (heroku_secret = `heroku config:get SHOPIFY_APP_CLIENT_SECRET -a my-heroku-app`.chomp)
  client_secrets['From heroku'] = -> { @host = HOST; heroku_secret }
end

puts "Select secret to use:"
client_secrets.keys.each_with_index do |key, i|
  puts "#{i}] #{key}"
end

index = STDIN.gets
key = client_secrets.keys[index.to_i]

client_secret = (client_secrets[key]).call

data = "shop=#{shop}.myshopify.com&timestamp=#{Time.now.to_i}"
hmac = OpenSSL::HMAC.hexdigest(OpenSSL::Digest::SHA256.new(), client_secret, data)

puts '-------'
puts key
puts "#{@host}/my-shopify-app?#{data}&hmac=#{hmac}"