Friendship queries

friendship.rb

class Friendship < ActiveRecord::Base
  belongs_to :requester, class_name: 'User'
  belongs_to :accepter,  class_name: 'User'

  scope :pending_and_confirmed, -> { unscope(where: :accepted_at) }
  scope :confirmed, -> { unscope(where: :accepted_at).where.not(accepted_at: nil) }
  scope :pending,   -> { unscope(where: :accepted_at).where(accepted_at: nil) }

  scope :by_user, ->(user) { where('requester_id = :user_id OR accepter_id = :user_id', user_id: user) }

  default_scope { confirmed }
end

user.rb

class User < ActiveRecord::Base

  module FriendshipScopes
    def pending
      merge Friendship.pending
    end

    def confirmed
      merge Friendship.confirmed
    end

    def pending_and_confirmed
      merge Friendship.pending_and_confirmed
    end
  end

  has_many :requested_friendships, ->{ extending FriendshipScopes }, class_name: 'Friendship', foreign_key: 'requester_id'
  has_many :accepted_friendships,  ->{ extending FriendshipScopes }, class_name: 'Friendship', foreign_key: 'accepter_id'

  has_many :requested_friends, ->{ extending FriendshipScopes }, through: :requested_friendships, source: :accepter
  has_many :accepted_friends,  ->{ extending FriendshipScopes }, through: :accepted_friendships,  source: :requester

  def friendships
    Friendship.by_user self
  end

  def friends(scope = nil)
    unless scope
      requested_friends + accepted_friends
    else
      requested_friends.send(scope) + accepted_friends.send(scope)
    end
  end
end