flash_star.rb

require 'pry'

class FlashStar
  RELATION = {# {{{
    A: [
      %i(B),
      %i(E),
      %i(J I C),
      %i(F G D),
    ],
    B: [
      %i(A),
      %i(J F E),
      %i(I H D),
      %i(C)
    ],
    C: [
      %i(B),
      %i(I J A),
      %i(H G E),
      %i(D)
    ],
    D: [
      %i(H I B),
      %i(G F A),
      %i(E)
    ],
    E: [
      %i(A),
      %i(F J B),
      %i(G H C),
      %i(D)
    ],
    F: [
      %i(E),
      %i(A),
      %i(J B),
      %i(G D)
    ],
    G: [
      %i(F A),
      %i(E),
      %i(D),
      %i(H C)
    ],
    H: [
      %i(G E),
      %i(D),
      %i(C),
      %i(I B)
    ],
    I: [
      %i(J A),
      %i(H D),
      %i(C),
      %i(B)
    ],
    J: [
      %i(A),
      %i(F E),
      %i(I C),
      %i(B)
    ]
  }.freeze# }}}

  def emit(label)
    to_h[label] = !to_h[label]
    propagation_changed(label)
  end

  def to_h
    @to_a ||= {
      A: false,
      B: false,
      C: false,
      D: false,
      E: false,
      F: true,
      G: true,
      H: true,
      I: true,
      J: true
    }
  end

  def to_s
    to_h.values.map { |bool| bool ? 'R' : 'W' }.join
  end

  private

  def propagation_changed(label)
    relations = RELATION[label]
    current = to_h[label]

    relations.each do |related_labels|
      check_related_labels(label, related_labels, current)
    end

    inspect
  end

  def check_related_labels(label, related_labels, current)
    related_labels.each_with_index do |related_label, index|
      next if index.zero?

      if to_h[related_label] == current
        related_labels[0...index].each do |_label|
          to_h[_label] = current
        end

        return
      end
    end
  end
end

expected_result = [
  ['A', 'RWWWWRRRRR'],
  ['F', 'WWWWWWWRRW'],
  ['J', 'WWWWWWRRWW'],
  ['AA', 'WWWWWWWRWW'],
  ['IC', 'WWRWWRRRWW'],
  ['FC', 'WWRWWWWRRW'],
  ['AE', 'RWWWRRRRRR'],
  ['GJ', 'WWWWWWWWWW'],
  ['CCB', 'WRWWWRWWWR'],
  ['BEF', 'WRWWRWWRRR'],
  ['JGD', 'WWWRWWWWWW'],
  ['IHCC', 'WWWWWRWWWW'],
  ['AIDD', 'RWWWWRRWWR'],
  ['IJFA', 'RWWWWWWWWW'],
  ['ABCDE', 'RRRRRRRRRR'],
  ['ICEBA', 'RRRWRRRRRR'],
  ['DAHHD', 'RWWWWRWWWR'],
  ['GJIJC', 'WWRWWWWWRR'],
  ['FGHIJ', 'WWWWWWWWRR'],
  ['HJICGA', 'RWRWWRRRRR'],
  ['IBCIGC', 'WRWWWWWWWW'],
  ['BIJJJB', 'WWWWWWRWWW'],
  ['DCBCHGD', 'WRWWWWWRRW'],
  ['JEABDHD', 'RRWWRRRWRR'],
  ['JHFADHE', 'RWWRRRRRWW'],
  ['HDGGDBIB', 'WWWWWWWWWW'],
  ['IIDIHCCG', 'WWWRWRRWWW'],
  # ['BBFBICIE', 'WRRWRRRWWW'],
  ['HJHCFBJGG', 'WRRWWWWRRW'],
  ['AJJIEAAII', 'RWWWRWWWWR'],
  ['AIDHJFGAE', 'WWWRRWWWWW'],
  ['FGBGHCBHJJ', 'WWRWWWWRRW'],
  ['EFIGIGGHHJ', 'WWWWRRRWWR'],
  ['HGAFDIFFFF', 'RWWRWRRRRW'],
  ['AABBCCDDEE', 'WWWWWWWWWW'],
  ['ABCDEFGHIJ', 'RRRRRWWWWW'],
  ['FGHIJABCDE', 'RRRRRRRRRR'],
]

expected_result.each do |input, output|
  flash_star = FlashStar.new

  input.split('').each do |label|
    flash_star.emit(label.to_sym)
  end

  puts flash_star.to_s == output
end