require "./common.cr"

LINE_COUNT = 637061
recipes = Deque(Int32).new
recipes << 3
recipes << 7
elves = [0, 1]

def add_recipes(recipes, elves)
  new_num = elves.map { |it| recipes[it] }.sum
  new_num.to_s.chars.map(&.to_i32).each do |n|
    recipes << n
  end

  elves.each_with_index do |elf, index|
    elves[index] = (elf + recipes[elf] + 1) % recipes.size
  end
end

def index?(recipes, sequence, start_at = 0)
  return nil if recipes.size < sequence.size
  (recipes.size-sequence.size+1-start_at).times do |offset|
    correct = true
    sequence.each_with_index do |s, i|
      correct &= (recipes[start_at + offset + i] == s)
      break unless correct
    end
    return start_at + offset if correct
  end
  return nil
end

# Part 1
while recipes.size < LINE_COUNT + 10
  add_recipes(recipes, elves)
end

puts recipes.to_a[-10..-1].map(&.to_s).join

# Part 2
digits = LINE_COUNT.to_s.chars.map(&.to_i32)
index = nil
old_size = 0
until (index = index?(recipes, digits, Math.max(old_size - 10, 0)))
  old_size = recipes.size
  add_recipes(recipes, elves)
end
puts index