A simple TextAid server written in Ruby using Sinatra.

config.ru

require './textaid-server'
run TextAid::Server

Gemfile

source 'https://rubygems.org'

gem 'rake'
gem 'sinatra'

Gemfile.lock

GEM
  remote: https://rubygems.org/
  specs:
    rack (1.5.2)
    rack-protection (1.5.0)
      rack
    rake (10.1.0)
    sinatra (1.4.3)
      rack (~> 1.4)
      rack-protection (~> 1.4)
      tilt (~> 1.3, >= 1.3.4)
    tilt (1.4.1)

PLATFORMS
  ruby

DEPENDENCIES
  rake
  sinatra

textaid-server.rb

require 'sinatra'
require 'tempfile'

module TextAid
  class Server < Sinatra::Base
    post '/' do
      text = request.env['rack.input'].read
      editor = ENV['EDITOR']
      file = Tempfile.new([params[:id], '.txt'])

      begin
        file.write(text)
        file.close

        command = "#{editor} #{file.path}"
        pid = spawn(command, in: STDIN, out: STDOUT, err: STDERR)
        Process.waitpid(pid)

        text = IO.read(file.path).strip
      ensure
        file.unlink
      end

      text
    end
  end
end