shortener.rb

#!/usr/bin/env ruby

require 'sinatra'
require 'pp'

# env.oy/<random_str>

$data = {}

def generate_random_string(length = 5)
  chars = ('a'..'z').to_a + ('0'..'9').to_a
  (0...length).to_a.map{ chars[rand(chars.size)] }.join
end

def save(url)

  if existing_short_string = $data.key(url)
    return existing_short_string
  end

  random_string = ''
  loop do
    random_string = generate_random_string
    break unless $data[random_string]
  end
  $data[random_string] = url
  random_string
end

post '/' do
  url = params[:url]
  random_string = save(url)
  pp $data
  "your short url is available at /#{random_string}\n"
end

get '/:short_string' do
  redirect $data[params[:short_string]]
end