radiorabe / raar / 11900633159

module NonOverlappable

  extend ActiveSupport::Concern

  included do

    validate :assert_not_overlapping

  end

  private

  def assert_not_overlapping

    scope = self.class.within(started_at, finished_at)

    scope = scope.where.not(id: id) if persisted?

    if scope.exists?

      errors.add(:started_at, :must_not_overlap)

      throw :abort

    end

  end

  module ClassMethods

    def within(start, finish)

      where("#{table_name}.finished_at > ? AND #{table_name}.started_at < ?", start, finish)

    end

  end

end