common_followers

#!/usr/bin/ruby
# Trivial little twitter script
# Pass it a list of names as command line arguments
# and it will return a list of all people who follow everyone in the
# list.
# A person is implicitly assumed to follow themselves, so if foo follows
# bar and bar follows foo then common_followers foo bar would include
# both foo and bar in the output, but if bar did not follow foo it 
# would include neither.

require "rubygems"
require "httparty"

class Twitter
  include HTTParty
  base_uri "http://twitter.com"
  format :json
   
  def self.follower_ids(user)
    get "/followers/ids/#{user}.json"
  end

  def self.username_for_id(user)
    details(user)["screen_name"]
  end

  def self.id_for_username(user)
    details(user)["id"]
  end

  def self.details(user)
    (get "/users/show.json", :query => { :id => user })
  end
end

require "set"

intersection = nil;

if __FILE__ == $0
ARGV.each do |user|
  followers = Set[*Twitter.follower_ids(user)]  
  id = Twitter.id_for_username(user)
  followers.add id
  if !intersection
    intersection = followers
  else
    intersection &= followers 
  end
end

intersection.each do |user|
  puts Twitter.username_for_id(user)
end
end

gistfile2.txt