#!/usr/bin/env ruby

require_relative '../common'

class Day02 < Day
  def part1
    input.each_with_object(Position.new) { |cmd, position| position.process cmd }.result
  end

  def part2
    input.each_with_object(Position.new(use_aim: true)) { |cmd, position| position.process cmd }.result
  end

  class Position
    def initialize(use_aim: false)
      @use_aim = use_aim

      @horizontal_position = 0
      @depth = 0
      @aim = 0
    end

    def process command
      direction, value = command.match(/\A(forward|down|up) ([0-9]+)\z/).captures
      send direction, value.to_i
    end

    def result
      @horizontal_position * @depth
    end

    private

    def forward value
      @horizontal_position += value
      @depth += @aim * value if @use_aim
    end

    def down value
      if @use_aim
        @aim += value
      else
        @depth += value
      end
    end

    def up value
      if @use_aim
        @aim -= value
      else
        @depth -= value
      end
    end
  end
end

Day02.run