require 'debug'

class ValidIdFilter
  def initialize(file_path)
    @file_path = file_path
  end

  def sum_invalid_ids(debug: false)
    ranges = parse_input(File.read(@file_path))
    invalid_ids = ranges.flat_map {|range| get_invalid_ids_from_range(range)}
    invalid_ids.sum
  end

  private

  # @param [Range] e.g., 11-22
  # @return [<Integer>] array of invalid ids in range
  def get_invalid_ids_from_range(range)
    range.select {|element| invalid_id?(element)}
  end

  def invalid_id?(integer)
    # ID is invalid if it is made only of some sequence of digits repeated twice
    string = integer.to_s
    num_digits = string.length

    # some sequence repeated twice => number of digits must be even
    return false if num_digits % 2 != 0

    half_length = num_digits / 2

    string[0...half_length] == string[half_length..-1]
  end

  # @param [String] full input e.g., "11-22,33-604,..."
  # @return [<Range>] e.g., [11..22, 33..604, ...]
  def parse_input(input)
    input.split(',').map {|range| to_range(range)}
  end

  # @param [String] e.g., "11-22"
  # @return [Range] e.g., 11..22 (inclusive)
  def to_range(string)
    boundaries = string.split('-').map(&:to_i)
    raise "Invalid boundaries for #{string}, got #{boundaries.inspect}" if boundaries.length != 2
    Range.new(boundaries[0], boundaries[1])
  end
end

if ARGV[0].nil? || ARGV[0].empty?
  puts "Usage: ruby part1.rb <file_name> [debug]"
  exit 1
end

debug = (ARGV[1] == "debug")
filter = ValidIdFilter.new(ARGV[0])
puts "The answer is: #{filter.sum_invalid_ids(debug:)}"