config.ru

require 'rubygems'                                                                                                                                                        
require 'sinatra'                                                                                                                                                         
require 'service'                                                                                                                                                         
                                                                                                                                                                          
root_dir = ::File.dirname(__FILE__)                                                                                                                                       
                                                                                                                                                                          
set :environment, ENV['RACK_ENV'].to_sym                                                                                                                                  
set :app_file,    ::File.join(root_dir, 'service.rb')                                                                                                                     
set :root,        root_dir                                                                                                                                                
                                                                                                                                                                          
disable :run                                                                                                                                                              
                                                                                                                                                                          
run Sinatra::Application

service.rb

#!/usr/bin/env ruby
# encoding: utf-8

require 'json'
require 'sinatra'
require 'open-uri'
require 'datamapper'

Reddit = 'http://www.reddit.com'
Database = "/var/www/applications/reverse_reddit/reddit.db"

Thread.abort_on_exception = true
DataMapper.setup :default, "sqlite3://#{Database}"

class Submission
  include DataMapper::Resource

  property :id,        Serial
  property :url,       Text
  property :name,      Text
  property :nsfw,      Boolean
  property :subreddit, String
  property :permalink, Text

  def self.create_from_json json
    new.tap do |this|
      this.url       = json['url']
      this.name      = json['title']
      this.nsfw      = json['over_18']
      this.subreddit = json['subreddit']
      this.permalink = json['permalink']
    end.save
  end

  def to_json
    {
      url: url,
      nsfw: nsfw,
      title: name,
      status: 200,
      subreddit: subreddit,
      permalink: permalink
    }.to_json
  end
end

# 1. a person who has the charge or care of something, esp a building, or someone
class Warden
  def self.work
    Warden.new do |warden|
      loop do
        warden.patrol and sleep 30 # bacon
      end
    end
  end

  def initialize
    yield self if block_given?
  end

  def patrol
    open "#{Reddit}/r/all/new.json?sort=new" do |response|
      json = JSON.parse response.read
      json['data']['children'].each do |submission|
        data = submission['data']

        if not Submission.first permalink: data['permalink']
          if Submission.create_from_json data
            puts "==> new submission: #{data['title'].inspect} ..."
          end
        end
      end
    end
  end
end

# Preload the database
DataMapper.auto_upgrade!

# Let the Warden work in the background
Thread.new &Warden.method(:work)

# /reverse?url=<url>
get '/reverse' do
  if not params[:url]
    { status: 400, error: "missing url" }.to_json
  else
    if submission = Submission.first(url: params[:url])
      submission.to_json
    else
      { status: 404, error: "no reddit submission found" }.to_json
    end
  end
end

get '/all' do
  [?[, Submission.all.map(&:to_json), ?]].join
end

error do
  { status: 500, error: "internal server error" }.to_json
end

not_found do
  { status: 404, error: "unknown method" }.to_json
end