Untitled

#!/usr/bin/env ruby -w

class Paginate
  WRAP = 4
  TAGS = %w[ div p a ].map { |s| ["<#{s}>", "</#{s}>"] }.to_h
  TAGS.merge! TAGS.invert

  def process input
    line   = []
    result = [line]
    stack  = []
    count  = 0

    input.each do |word|
      case word
      when /^<\// then               # close tag
        if TAGS[word] then

          stack.pop

          if count % WRAP == 0 && line.last == TAGS[word] then
            line.pop
          else
            line.push word
          end
        end
      when /^</ then                 # open tag
        if TAGS[word] then
          stack.push word
          line.push word
        end
      else                           # word
        line.push word

        count += 1

        if count % WRAP == 0 then
          line.concat stack.reverse.map { |s| TAGS[s] }

          line = stack.dup
          result.push line
        end
      end
    end

    result.map { |words| words.join " " }
  end
end

require "minitest/autorun"

class TestPaginate < Minitest::Test
  def assert_process exp, input
    assert_equal exp, Paginate.new.process(input)
  end

  def test_strip_unsupported_tags
    assert_process [""], %w[<html>]
  end

  def test_keep_supported_tags
    assert_process ["<div>"], %w[<div>]
  end

  def test_enumerate_non_tags
    assert_process ["two words"], %w[two words]
  end

  def test_wrap_at_length
    assert_process ["one two three four", "five"], %w[one two three four five]
  end

  def test_wrap_at_length_with_tags
    expected = [
            "<div> <p> here's a short <a> sentence </a> </p> </div>",
            "<div> <p> <a> that should </a>",
           ]

    input = [
          "<div>", "<p>", "here's", "a", "short", "<a>",
          "sentence", "that", "should", "</a>"
         ]
    assert_process expected, input
  end

  def test_final_goal
    expected = [
            "<div> <p> here's a short <a> sentence </a> </p> </div>",
            "<div> <p> <a> that should </a> be paginated </p> </div>",
            "<div> according to the rules </div>",
            "<div> above. </div>",
           ]

    input = [
          "<html>", "<div>", "<p>", "here's", "a", "short", "<a>",
          "sentence", "that", "should", "</a>", "be", "paginated", "</p>",
          "<i>", "according", "</i>", "to", "the", "rules", "above.", "</div>",
          "</html>"
         ]
    assert_process expected, input
  end
end