## migrations
class CreateUsers < ActiveRecord::Migration
  def self.up
    create_table :users do |t|
      t.string :name
      t.timestamps
    end
  end

  def self.down
    drop_table :users
  end
end
##
class CreateKonnections < ActiveRecord::Migration
  def self.up
    create_table :konnections do |t|
      t.integer :first_user_id
      t.integer :second_user_id
      t.timestamps
    end

    # join table
    create_table :konnections_users, :id => false do |t|
      t.integer :konnection_id
      t.integer :user_id
    end

  end

  def self.down
    drop_table :konnections
    drop_table :konnections_users
  end
end


## User
class User < ActiveRecord::Base
  has_and_belongs_to_many :konnections, :join_table => :konnections_users

  def create_konnection(user_to_connect)
    transaction do
      konnection = Konnection.create(:first_user => self, :second_user => user_to_connect)
      self.konnections << konnection
      user_to_connect.konnections << konnection
    end
  end
end


## Konnection
class Konnection < ActiveRecord::Base
  belongs_to :first_user,  :class_name => 'User'
  belongs_to :second_user, :class_name => 'User'

  def user
    # self.user_id returns a string! we need to convert it to an id before we can compare id:s
    self.user_id.to_i == self.first_user_id ? self.second_user : self.first_user
  end
end

## console
# >> User.first.name
# => "Allan"
# >> User.last.name
# => "Lucy"
# >> User.first.create_konnection(User.last)
# => [#<Konnection id: 1, first_user_id: 1, second_user_id: 2, created_at: "2008-10-31 20:20:41", updated_at: "2008-10-31 20:20:41">]
# >> User.first.konnections.first.user.name
# => "Lucy"
# >> User.last.konnections.first.user.name
# => "Allan"
# >>