huginn/app/models/scenario.rb

class Scenario < ActiveRecord::Base
  include HasGuid

  belongs_to :user, :counter_cache => :scenario_count, :inverse_of => :scenarios
  has_many :scenario_memberships, :dependent => :destroy, :inverse_of => :scenario
  has_many :agents, :through => :scenario_memberships, :inverse_of => :scenarios

  validates_presence_of :name, :user

  validates_format_of :tag_fg_color, :tag_bg_color,
    # Regex adapted from: http://stackoverflow.com/a/1636354/3130625
    :with => /\A#(?:[0-9a-fA-F]{3}){1,2}\z/, :allow_nil => true,
    :message => "must be a valid hex color."

  validate :agents_are_owned

  def destroy_with_mode(mode)
    case mode
    when 'all_agents'
      Agent.destroy(agents.pluck(:id))
    when 'unique_agents'
      Agent.destroy(unique_agent_ids)
    end

    destroy
  end

  def self.icons
    @icons ||= begin
      YAML.load_file(Rails.root.join('config/icons.yml'))
    end
  end

  private

  def unique_agent_ids
    agents.joins(:scenario_memberships)
          .group('scenario_memberships.agent_id')
          .having('count(scenario_memberships.agent_id) = 1')
          .pluck('scenario_memberships.agent_id')
  end

  def agents_are_owned
    unless agents.all? { |s| s.user == user }
      errors.add(:agents, 'must be owned by you')
    end
  end
end