Doorkeeper + Guestlist

disco.gemspec

Gem::Specification.new do |s|
  s.name        = 'disco'
  s.version     = '0.0.1'
  s.platform    = Gem::Platform::RUBY
  s.author      = 'Kevin Melchert'
  s.email       = '[email protected]'
  s.summary     = 'MongoDB + Omniauth = Guestlist + Doorkeeper.'
  s.description = 'MongoDB + Omniauth = Guestlist + Doorkeeper.'
 
  s.files         = ['disco.rb']
  s.require_path  = '.'
end

disco.rb

# 1. A user has never used your site before. They have no User model and no Identities either.
# 2. A user is logged out but they have logged into your site with a provider previously. 
#    They are now signing in with the same one again.
# 3. Just as above but they are now signing in with a different provider.
# 4. A user is logged in with a provider but they try to login with the same provider again.
# 5. A user is logged in but they try to login with a different provider.

module Disco
  class Doorkeeper
    def initialize(guestlist, omniauth, known_id=nil)
      @guestlist = guestlist
      @omniauth  = omniauth
      @known_id  = known_id
    end
  
    def grant_access?
      !!user
    end
  
    def user
      @user ||= @guestlist.register(@known_id, token, info)
    end
  
    def token
      { p: @omniauth["provider"], u: @omniauth["uid"] }
    end
    
    def info
      @omniauth["info"]
    end
  end
  
  class Guestlist
    def initialize(collection, field: 'auth')
      @list, @field = collection, field
      @list.ensure_index(@field => 1)
    end
  
    def find(user_id)
      @list.find_one(_id: user_id) if user_id
    end
    
    # returns a user record
    def register(*args)
      @list.find_and_modify(Query.build(@field, *args).to_mongo)
    end
  end
  
  class Query
    def self.build(field, user_id, token, info={})
      (user_id ? KnownUserQuery : UnknownUserQuery).new(field, user_id, token, info)
    end
    
    def initialize(field, user_id, token, info={})
      @field, @token, @user_id, @info = field, token, user_id, info
    end
    
    def to_mongo
      { query: selector, update: params, new: true }
    end
  end

  # on create it will set tokens array with the supplied token
  # on update it will set the last login timestamp
  class UnknownUserQuery < Query
    def selector
      { @field => @token }
    end
    
    def params
      {
        "$setOnInsert" => { @field => [@token] }.merge(@info),
        "$set" => { last_login: Time.now.utc }
      }
    end
    
    def to_mongo
      super.merge(upsert: true)
    end
  end
  
  # just adds the token to an existing record of a logged in user
  class KnownUserQuery < Query
    def selector
      { _id: @user_id }
    end
    
    def params
      { "$addToSet" => { @field => @token } }
    end
  end
end

usage.rb

#user_collection = Mongo::Collection...
guestlist  = Guestlist.new(user_collection)

doorkeeper = Doorkeeper.new(guestlist, request.params["omniauth.auth"], session[:user_id])

if doorkeeper.grant_access?
  session[:user_id] = doorkeeper.user["_id"]
  redirect_to "/"
else
  redirect_to "/login"
end


def current_user
  guestlist.find(session[:user_id])
end