#!/usr/bin/env ruby

result = File.readlines("2.input").map(&:split).map { _1.map(&:to_i) }
  .select do |v|
    (v == v.sort || v == v.sort.reverse) &&
      v.each_cons(2).map { _1.sort.inject(:-).abs }.all? { 1 <= _1 && _1 <= 3 }
  end.size
puts result

require "rspec/autorun"
class Report < Array
  def self.from_line(line)
    new(line.split.map(&:to_i))
  end

  def safe?
    (increasing? || decreasing?) && within_limit?
  end

  def safe_with_dampener?
    dampened.any?(&:safe?)
  end

  private

  def dampened
    size.times.map { Report.new(except(_1)) }
  end

  def except(v)
    reject.with_index { |_, i| i == v }
  end

  def increasing?
    self == sort
  end

  def decreasing?
    self == sort.reverse
  end

  def within_limit?
    each_cons(2)
      .map { _1.sort.inject(:-).abs }
      .all? { 1 <= _1 && _1 <= 3 }
  end
end

input = File.readlines("2.input")

puts "2-1"
puts input
  .map { Report.from_line(_1) }
  .select(&:safe?)
  .size
puts "2-2"
puts input
  .map { Report.from_line(_1) }
  .select(&:safe_with_dampener?)
  .size

describe Report do
  [
    "48 51 52 53 52",
    "86 87 88 91 91",
    "22 25 28 31 32 36",
    "65 66 68 69 71 72 75 82"
  ].each do |line|
    it "returns safe? as false for #{line}" do
      expect(Report.from_line(line).safe?).to eq(false)
    end
  end

  [
    "1 2 3 4 5 6 7",
    "1 3 5 7 9",
    "9 8 7",
    "1 4 5 8"
  ].each do |line|
    it "returns safe? as true for #{line}" do
      expect(Report.from_line(line).safe?).to eq(true)
    end
  end
end