class UniversalOrbitMap
  attr_reader :orbits, :bodies
  def initialize(orbits)
    @orbits = orbits
    body_names = orbits.map(&:orbitee) | orbits.map(&:orbiter)
    @bodies = body_names.to_h { |name| [name, Body.new(name)] }
    orbits.each do |orbit|
      bodies[orbit.orbitee].orbiters << orbit.orbiter
      bodies[orbit.orbiter].orbiting = bodies[orbit.orbitee]
    end
  end
                 
  def self.for(input)
    new input.split("\n").map { |line| Orbit.for line }
  end

  def path_between(to, from)
    to_chain = bodies[to].orbit_chain.map(&:name)
    from_chain = bodies[from].orbit_chain.map(&:name)
    common_chain = to_chain & from_chain
    (from_chain - common_chain) + (to_chain - common_chain).reverse
  end

  class Body
    attr_reader :name, :orbiters
    attr_accessor :orbiting
    def initialize(name)
      @name = name
      @orbiting = nil
      @orbiters = []
    end

    def orbit_chain
      chain = [orbiting]
      while chain.last
        chain << chain.last.orbiting
      end
      chain[..-2]
    end
  end

  class Orbit
    attr_accessor :orbitee, :orbiter, :orbitee_name, :orbiter_name
    def initialize(orbitee, orbiter)
      @orbiter = orbiter
      @orbiter_name = orbiter
      @orbitee = orbitee
      @orbitee_name = orbitee
    end

    def self.for(line)
      new *line.split(")")
    end
  end
end