class Ariadne::PaginationCalculator

def page_series
  return [] if pages <= 1
  return (1..pages).to_a if pages <= 5
  links = []
  links << 1
  if page <= 3
    # Near the beginning: 1 2 3 4 5 6 7 8 ... 20
    (2..8).each { |n| links << n if n <= pages }
    links << nil if pages > 8
    links << pages if pages > 8
  elsif page >= pages - 2
    # Near the end: 1 ... 13 14 15 16 17 18 19 20
    links << nil
    ((pages - 7)..pages).each { |n| links << n if n > 1 }
  else
    # Middle range: 1 ... 9 10 11 12 13 14 ... 20
    links << nil
    ((page - 2)..(page + 2)).each { |n| links << n }
    links << nil
    links << pages
  end
  links
end