adapter.rb

class IdentityProviderAdapter
  def self.find(identity_provider_name, access_token, refresh_token)
    self.const_get(identity_provider_name.capitalize.constantize).new(access_token, refresh_token)
  end
end

class IdentityProviderAdapter::Facebook
  def initialize(access_token, refresh_token)
    @access_token = access_token
    @refresh_token = refresh_token
  end
  
  def email
    @email ||= client.get_object('me', fields: 'email')['email']
  end
  
  def email_verified
    @email_verified ||= #whatever
  end
  
  private
  
  def client
    @client ||= Koala::Facebook::API.new(@access_token)
  end
end

class IdentityProviderAdapter::Google
  # etc
end

class IdentityProviderAdapter::Office365
  # etc
end

class FetchEmailFromProviderIdentityWorker
  include Sidekiq::Worker

  def perform(id)
    identity Identity.find(id)

    adapter = IdentityProviderAdapter.find(identity.identity_provider, identity.access_token, identity.refresh_token)

    unless Identity.where(email: adapter.email).exist?
      identity.user.identities.create!({
        type: Identity::Email.name,
        email: adapter.email,
        verified: adapter.email_verified
      })
    end    
  end
end