class Laboratories
  attr_reader :layers
  def initialize(layers)
    @layers = layers
  end

  def self.for(input)
    new input.split("\n").map(&Layer.method(:new))
  end

  def split_count
    layers.reduce([layers.first.blank_beams, 0]) do |acc, layer|
      out = layer.split_beams acc[0]
      [out[0], out[1] + acc[1]]
    end[1]
  end

  def count_tachyon_lifetimes
    @memo = {}
    count_lifetimes layers.first.line.index("S"), 0
  end

  def count_lifetimes(position, layer)
    return @memo["#{position}/#{layer}"] if @memo.key? "#{position}/#{layer}"

    lt = if layer >= layers.count
      1
    else
      if layers[layer].line[position] == "^"
        count_lifetimes(position - 1, layer + 1) + count_lifetimes(position + 1, layer + 1)
      else
        count_lifetimes position, layer + 1
      end
    end
    @memo["#{position}/#{layer}"] = lt
    lt
  end

  class Tachyon
    attr_reader :lab, :position, :layer
    def initialize(lab, position, layer=0)
      @lab = lab
      @position = position
      @layer = layer
    end

    def count_lifetimes
      if layer >= lab.layers.count
        1
      else
        if at_splitter?
          self.class.new(lab, position - 1, layer + 1).count_lifetimes + 
            self.class.new(lab, position + 1, layer + 1).count_lifetimes
        else
          self.class.new(lab, position, layer + 1).count_lifetimes
        end
      end
    end

    def at_splitter?
      lab.layers[layer].line[position] == "^"
    end
  end

  class Layer
    attr_reader :line
    def initialize(line)
      @line = line
    end

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

    def blank_beams
      Array.new(line.length, false)
    end

    def split_beams(input_beams)
      split_count = 0
      output = 0.upto(line.length - 1).map do |i|
        if line[i] == "^"
          split_count += 1 if input_beams[i]
          false
        elsif i > 0 && line[i - 1] == "^" && input_beams[i - 1]
          true
        elsif i < (line.length - 1) && line[i + 1] == "^" && input_beams[i + 1]
          true
        elsif line[i] == "S"
          true
        else
          input_beams[i]
        end
      end
      [output, split_count]
    end
  end
end