app/helpers/numbered_pagination_helper.rb

   1 module NumberedPaginationHelper
   2   def numbered_pagination(top_page, active_page: top_page + 1, window_half_size: 50, step_size: 50, &)
   3     lists = []
   4
   5     if top_page <= 5
   6       lists << tag.ul(:class => "pagination pagination-sm mt-1") do
   7         (1..top_page).each do |page|
   8           concat numbered_pagination_item(page, **yield(page), :active => page == active_page)
   9         end
  10       end
  11     else
  12       start_list_pages = 1..(active_page < 3 ? active_page + 1 : 1)
  13       end_list_pages = (active_page > top_page - 2 ? active_page - 1 : top_page)..top_page
  14
  15       middle_list_page_sentinels = [start_list_pages.last, end_list_pages.first]
  16       middle_list_page_steps = Range.new(*middle_list_page_sentinels).filter { |page| (page % step_size).zero? }
  17       middle_list_page_window = Range.new([active_page - window_half_size, start_list_pages.last].max,
  18                                           [active_page + window_half_size, end_list_pages.first].min).to_a
  19       middle_list_pages_with_sentinels = (middle_list_page_sentinels | middle_list_page_steps | middle_list_page_window).sort
  20       middle_list_pages_with_sentinels_and_gaps = [middle_list_pages_with_sentinels.first] +
  21                                                   middle_list_pages_with_sentinels.each_cons(2).flat_map do |previous_page, page|
  22                                                     page == previous_page + 1 ? [page] : [:gap, page]
  23                                                   end
  24       middle_list_pages_with_small_gaps_filled = middle_list_pages_with_sentinels_and_gaps.each_cons(3).map do |previous_page, page, next_page|
  25         if page == :gap && previous_page != :gap && next_page != :gap && next_page - previous_page == 2
  26           previous_page + 1
  27         else
  28           page
  29         end
  30       end
  31       middle_list_pages = middle_list_pages_with_small_gaps_filled
  32
  33       lists << tag.ul(:id => "versions-navigation-list-start",
  34                       :class => "pagination pagination-sm mt-1") do
  35         start_list_pages.each do |page|
  36           concat numbered_pagination_item(page, **yield(page), :active => page == active_page,
  37                                                                :edge => [false, page == start_list_pages.last],
  38                                                                :edge_border => true)
  39         end
  40       end
  41       lists << tag.ul(:id => "versions-navigation-list-middle",
  42                       :class => [
  43                         "pagination pagination-sm",
  44                         "overflow-x-auto pb-3", # horizontal scrollbar with reserved space below
  45                         "pt-1 px-1 mx-n1", # space reserved for focus outlines
  46                         "position-relative" # required for centering when clicking current page links ("Version #n" on pages showing element versions)
  47                       ]) do
  48         middle_list_pages.each_with_index do |page, i|
  49           edge = [i.zero?, i == middle_list_pages.length - 1]
  50           if page == :gap
  51             concat numbered_pagination_item("...", :edge => edge)
  52           else
  53             concat numbered_pagination_item(page, **yield(page), :active => page == active_page, :edge => edge)
  54           end
  55         end
  56       end
  57       lists << tag.ul(:id => "versions-navigation-list-end",
  58                       :class => "pagination pagination-sm mt-1") do
  59         end_list_pages.each do |page|
  60           concat numbered_pagination_item(page, **yield(page), :active => page == active_page,
  61                                                                :edge => [page == end_list_pages.first, false],
  62                                                                :edge_border => true)
  63         end
  64       end
  65     end
  66
  67     tag.div safe_join(lists), :class => "d-flex align-items-start"
  68   end
  69
  70   private
  71
  72   def numbered_pagination_item(body, href: nil, title: nil, active: false, edge: [false, false], edge_border: false)
  73     link_class = ["page-link", { "rounded-start-0" => edge.first,
  74                                  "border-start-0" => edge.first && !edge_border,
  75                                  "rounded-end-0" => edge.last,
  76                                  "border-end-0" => edge.last && !edge_border }]
  77     link = if href
  78              link_to body, href, :class => link_class, :title => title
  79            else
  80              tag.span body, :class => link_class
  81            end
  82     tag.li link, :id => ("versions-navigation-active-page-item" if active),
  83                  :class => ["page-item", { "disabled" => !href, "active" => active }]
  84   end
  85 end