require 'debug'

module FileHandler
  def self.read_lines(file_path)
    File.readlines(file_path, chomp: true).map do |line|
      yield(line)
    end
  end

  def self.read_file(file_path)
    File.read(file_path)
  end
end

class JoltageCalculator
  def initialize(file_path, debug: false)
    @file_path = file_path
    @debug = debug
  end

  def calculate_total_joltage
    total = 0
    FileHandler.read_lines(@file_path) do |line|
      int_array = line.split('').map(&:to_i)
      total += calculate_joltage(int_array)
    end
    total
  end

  # @param [<integer>] bank
  def _calculate_joltage(bank)
    joltage = ''

    first_digit, first_pos = max_and_index_from_slice(bank, 1)

    joltage += first_digit.to_s


    sub_bank = bank.slice(first_pos + 1, bank.length)
    second_digit, _ = max_and_index_from_slice(sub_bank, 0)

    joltage += second_digit.to_s

    joltage.to_i
  end

  # @param [<integer>] bank
  def calculate_joltage(bank, total_digits: 12)
    joltage = ''

    current_offset = total_digits - 1

    while current_offset >= 0
      maximum, i = max_and_index_from_slice(bank, current_offset)

      joltage += maximum.to_s

      bank = bank.slice(i + 1, bank.length)
      current_offset -= 1
    end

    joltage.to_i
  end

  private

  # Get max and index from the first part of the array. Ignore the last `offset`
  # number of digits.
  # @param [<integer>] array
  # @param [integer] offset
  def max_and_index_from_slice(array, offset)
    maximum = array.slice(0, array.length - offset).max
    index = array.find_index(maximum)
    [maximum, index]
  end
end

if ARGV[0].nil? || ARGV[0].empty?
  puts "Usage: ruby part2.rb <file_name> [debug]"
  exit 1
end

debug = (ARGV[1] == "debug")
calculator = JoltageCalculator.new(ARGV[0], debug:)
puts "The answer is: #{calculator.calculate_total_joltage}"

# The answer is: 169077317650774

# real	0m0,260s
# user	0m0,222s
# sys	0m0,038s