require 'debug'

# Generic FileHandler
class FileHandler
  def initialize(file_path)
    @file_path = file_path
  end

  # Usage:
  # FileHandler.new('/path_to_file').read_lines do |line|
  #   # process line
  # end
  def read_lines
    File.foreach(@file_path, chomp: true).map do |line|
      yield(line)
    end
  end

  # Usage:
  # file_content = FileHandler.new('/path_to_file').read_file(
  def read_file
    File.read(@file_path)
  end
end

class PuzzleSolver
  def initialize(file_handler, debug: false)
    @handler = file_handler
    @debug = debug
  end

  def debug(message)
    puts message if @debug
  end

  def print_debug(message)
    print message if @debug
  end

  def solve
    raise NotImplementedError, 'Please implement this method in subclasses.'
  end
end

class HomeworkSolver < PuzzleSolver
  def calculate(operator, int_array)
    int_array.reduce(operator)
  end

  def solve
    lines = @handler.read_file.split("\n")
    operator_line = lines[-1].split(' ').map(&:to_sym)
    number_lines = lines[0...-1].map(&:chars)
    start_indices = lines[-1].chars.map.with_index {|x, i| x == ' ' ? nil : i }.reject {|x| x.nil?}

    solutions = start_indices.map.with_index do |index, i|
      start = index
      final = (i < start_indices.length - 1) ? start_indices[i + 1] - 2 : number_lines[0].length - 1
      operator = operator_line[i]
      numbers = number_lines.map {|x| x[start..final]}

      integers = []
      total_nums = numbers[0].length
      curr_index = total_nums - 1

      while curr_index >= 0
        integers << numbers.map {|digits| digits[curr_index]}.join.to_i
        curr_index -= 1
      end
      calculate(operator, integers)
    end

    solutions.sum
  end
end


if ARGV[0].nil? || ARGV[0].empty?
  puts "Usage: ruby #{__FILE__} <file_name> [debug]"
  exit 1
end
file_path = ARGV[0]
debug = (ARGV[1] == "debug")
file_handler = FileHandler.new(file_path)

## Puzzle-specific
cls = HomeworkSolver
##

puts "The answer is: #{cls.new(file_handler, debug:).solve}"