Ruby universal orbit map

ruby/2019/6/bin/problem

@@ -0,0 +1,9 @@
+#!/usr/bin/env ruby
+
+require "universal_orbit_map"
+
+map = UniversalOrbitMap.for STDIN.read.chomp
+
+puts "Part 1: #{map.bodies.values.map(&:orbit_chain).map(&:length).sum}"
+
+puts "Part 2: #{map.path_between("YOU", "SAN").length}"

ruby/2019/6/lib/universal_orbit_map.rb

@@ -0,0 +1,55 @@
+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