product.rb

  SIZES = %w(XXS XS S M L XL 2XL XXL 3XL) + ((20..49).step(0.3333333333333).map { |n| n.round(1) } + (35..49).map { |n| n + 0.5 }).sort
  SIZES_STR = SIZES.map { |s| s.to_s.gsub(/\.|0/, '') }

  def self.sort_sizes(a, b)
    # convert e.g. 433 to "43.3"
    a = a.scan(/\d{2}|.+/).join('.') if a.is_a?(String) and a.length == 3
    b = b.scan(/\d{2}|.+/).join('.') if b.is_a?(String) and b.length == 3

    # convert e.g. "43.3" to 43.4
    a = a.to_f unless a.match /[A-Z]+/
    b = b.to_f unless b.match /[A-Z]+/

    return 0 unless SIZES.include?(b)
    return 1 unless SIZES.include?(a)

    SIZES.index(a) <=> SIZES.index(b)
  end

  def self.pretify_size(size)
    size = size.sub ',', ''
    match = size.match(/^[0-9]{2}(\d)$/)
    return size unless match
    fraction = match[1]
    dict = {
        '3': '<span><sup>1</sup>&frasl;<sub>3</sub></span>',
        '5': '<span><sup>1</sup>&frasl;<sub>2</sub></span>',
        '7': '<span><sup>2</sup>&frasl;<sub>3</sub></span>'
    }

    size[0...-1] + dict[fraction.to_sym]
  end