Day 01 Part 02

.rb

class Calibration

  def self.calibration_of_instruction(instruction)
    sanitized_instruction = self.sanitize(instruction)
    "#{self.first_digit_of(sanitized_instruction).to_i}#{self.last_digit_of(sanitized_instruction)}".to_i
  end

  def self.first_digit_of(instruction)
    self.get_match_from_regex_or_empty(instruction, /^\D*(\d)/)
  end

  def self.last_digit_of(instruction)
    self.get_match_from_regex_or_empty(instruction, /(\d)\D*\Z/)
  end

  private

  def self.sanitize(instruction)
    sanitized_string = instruction
    {
      "one" => "o1e",
      "two" => "t2o",
      "three" => "t3e",
      "four" => "f4r",
      "five" => "f5e",
      "six" => "s6x",
      "seven" => "s7n",
      "eight" => "e8t",
      "nine" => "n9e",
    }.each{|k,v|
      sanitized_string.gsub!( k, v)
    }
    sanitized_string
  end

  def self.get_match_from_regex_or_empty(string, regexp)
    match = string.match(regexp)

    match.nil? ? '' : match[1]
  end

end

RSpec.describe "Calibration" do

  it 'return first digit of calibration value' do
    expect(Calibration.first_digit_of('')).to eq('')
    expect(Calibration.first_digit_of('1abc2')).to eq('1')
    expect(Calibration.first_digit_of('pqr3stu8vwx')).to eq('3')
    expect(Calibration.first_digit_of('ei47vrvjlpgcqthree87q')).to eq('4')

  end

  it 'return last digit of calibration value' do
    expect(Calibration.last_digit_of('')).to eq('')
    expect(Calibration.last_digit_of('treb7uchet')).to eq('7')
    expect(Calibration.last_digit_of('1abc2')).to eq('2')
    expect(Calibration.last_digit_of('ei47vrvjlpgcqthree39q')).to eq('9')
  end

  it 'returns calibration of single instruction' do
    expect(Calibration.calibration_of_instruction('1abc2')).to eq(12)
  end

  it 'solves provided sample' do
    sample_result = %w(1abc2 pqr3stu8vwx a1b2c3d4e5f treb7uchet).sum(0){|i| Calibration.calibration_of_instruction(i)}
    expect(sample_result).to eq(142)
  end

  it 'handles instruction containing numbers as string' do
    expect(Calibration.calibration_of_instruction('two1nine')).to eq(29)
    expect(Calibration.calibration_of_instruction('eightwothree')).to eq(83)
    expect(Calibration.calibration_of_instruction('abcone2threexyz')).to eq(13)
    expect(Calibration.calibration_of_instruction('4nineeightseven2')).to eq(42)
    expect(Calibration.calibration_of_instruction('zoneight234')).to eq(14)
    expect(Calibration.calibration_of_instruction('7pqrstsixteen')).to eq(76)
  end

  it 'solves my own input data' do
    result = File.readlines('Day01/Spec/day_01_input.txt', chomp:true).sum(0){|i| Calibration.calibration_of_instruction(i)}
    expect(result).to eq(53921)
  end

end