Remove classic pagination

app/controllers/changesets_controller.rb

@@ -79,28 +79,33 @@ def show
     @changeset = Changeset.find(params[:id])
     case turbo_frame_request_id
     when "changeset_nodes"
-      @node_pages, @nodes = paginate(:old_nodes, :conditions => { :changeset_id => @changeset.id }, :per_page => 20, :parameter => "node_page")
-      render :partial => "elements", :locals => { :type => "node", :elements => @nodes, :pages => @node_pages }
+      load_nodes
+
+      render :partial => "elements", :locals => { :type => "node", :paginator => @nodes_paginator }
     when "changeset_ways"
-      @way_pages, @ways = paginate(:old_ways, :conditions => { :changeset_id => @changeset.id }, :per_page => 20, :parameter => "way_page")
-      render :partial => "elements", :locals => { :type => "way", :elements => @ways, :pages => @way_pages }
+      load_ways
+
+      render :partial => "elements", :locals => { :type => "way", :paginator => @ways_paginator }
     when "changeset_relations"
-      @relation_pages, @relations = paginate(:old_relations, :conditions => { :changeset_id => @changeset.id }, :per_page => 20, :parameter => "relation_page")
-      render :partial => "elements", :locals => { :type => "relation", :elements => @relations, :pages => @relation_pages }
+      load_relations
+
+      render :partial => "elements", :locals => { :type => "relation", :paginator => @relations_paginator }
     else
       @comments = if current_user&.moderator?
                     @changeset.comments.unscope(:where => :visible).includes(:author)
                   else
                     @changeset.comments.includes(:author)
                   end
-      @node_pages, @nodes = paginate(:old_nodes, :conditions => { :changeset_id => @changeset.id }, :per_page => 20, :parameter => "node_page")
-      @way_pages, @ways = paginate(:old_ways, :conditions => { :changeset_id => @changeset.id }, :per_page => 20, :parameter => "way_page")
-      @relation_pages, @relations = paginate(:old_relations, :conditions => { :changeset_id => @changeset.id }, :per_page => 20, :parameter => "relation_page")
+      load_nodes
+      load_ways
+      load_relations
+
       if @changeset.user.active? && @changeset.user.data_public?
         changesets = conditions_nonempty(@changeset.user.changesets)
         @next_by_user = changesets.where("id > ?", @changeset.id).reorder(:id => :asc).first
         @prev_by_user = changesets.where(:id => ...@changeset.id).reorder(:id => :desc).first
       end
+
       render :layout => map_layout
     end
   rescue ActiveRecord::RecordNotFound
@@ -163,4 +168,50 @@ def conditions_bbox(changesets, bbox)
   def conditions_nonempty(changesets)
     changesets.where("num_changes > 0")
   end
+
+  def load_nodes
+    nodes = OldNode.where(:changeset => @changeset)
+    @nodes_paginator = ElementsPaginator.new(nodes, 20, params[:node_page])
+  end
+
+  def load_ways
+    ways = OldWay.where(:changeset => @changeset)
+    @ways_paginator = ElementsPaginator.new(ways, 20, params[:way_page])
+  end
+
+  def load_relations
+    relations = OldRelation.where(:changeset => @changeset)
+    @relations_paginator = ElementsPaginator.new(relations, 20, params[:relation_page])
+  end
+
+  class ElementsPaginator
+    attr_reader :elements_count, :elements_per_page, :current_page, :current_page_elements
+
+    def initialize(elements, elements_per_page, current_page = 1)
+      @elements_count = elements.count
+      @elements_per_page = elements_per_page.to_i
+      @current_page = current_page.to_i.clamp(1, pages_count)
+      @current_page_elements = elements.offset(@elements_per_page * (@current_page - 1)).limit(@elements_per_page)
+    end
+
+    def pages_count
+      [1, 1 + ((elements_count - 1) / elements_per_page)].max
+    end
+
+    def pages
+      1..pages_count
+    end
+
+    def pages_window(window_size, page = current_page)
+      [page - window_size, pages.first].max..[page + window_size, pages.last].min
+    end
+
+    def lower_element_number(page = current_page)
+      (elements_per_page * (page - 1)) + 1
+    end
+
+    def upper_element_number(page = current_page)
+      [elements_per_page * page, elements_count].min
+    end
+  end
 end

app/helpers/browse_helper.rb

@@ -70,33 +70,56 @@ def link_follow(object)
     "nofollow" if object.tags.empty?
   end
 
-  def type_and_paginated_count(type, pages, selected_page = pages.current_page)
-    if pages.page_count == 1
+  def type_and_paginated_count(type, paginator, page = paginator.current_page)
+    if paginator.pages_count <= 1
       t ".#{type.pluralize}",
-        :count => pages.item_count
+        :count => paginator.elements_count
     else
       t ".#{type.pluralize}_paginated",
-        :x => selected_page.first_item,
-        :y => selected_page.last_item,
-        :count => pages.item_count
+        :x => paginator.lower_element_number(page),
+        :y => paginator.upper_element_number(page),
+        :count => paginator.elements_count
     end
   end
 
-  def sidebar_classic_pagination(pages, page_param)
+  def sidebar_classic_pagination(paginator, page_param)
+    window_size = 2
     max_width_for_default_padding = 35
 
+    pages = paginator.pages
+    window = paginator.pages_window(window_size)
+    page_items = []
+
+    if window.first != pages.first
+      page_items.push [pages.first.to_s, pages.first]
+      page_items.push ["...", "disabled"] if window.first - pages.first > 1
+    end
+
+    window.each do |page|
+      if paginator.current_page == page
+        page_items.push [page.to_s, "active"]
+      else
+        page_items.push [page.to_s, page]
+      end
+    end
+
+    if window.last != pages.last
+      page_items.push ["...", "disabled"] if pages.last - window.last > 1
+      page_items.push [pages.last.to_s, pages.last]
+    end
+
     width = 0
-    pagination_items(pages, {}).each do |body|
+    page_items.each do |body|
       width += 2 # padding width
       width += body.length
     end
     link_classes = ["page-link", { "px-1" => width > max_width_for_default_padding }]
 
     tag.ul :class => "pagination pagination-sm mb-1 ms-auto" do
-      pagination_items(pages, {}).each do |body, page_or_class|
+      page_items.each do |body, page_or_class|
         linked = !(page_or_class.is_a? String)
         link = if linked
-                 link_to body, url_for(page_param => page_or_class.number), :class => link_classes, **yield(page_or_class)
+                 link_to body, url_for(page_param => page_or_class), :class => link_classes, **yield(page_or_class)
                else
                  tag.span body, :class => link_classes
                end

app/views/changesets/_elements.html.erb

@@ -1,7 +1,7 @@
 <%= turbo_frame_tag "changeset_#{type.pluralize}" do %>
-  <%= render :partial => "paging_nav", :locals => { :type => type, :pages => pages } %>
+  <%= render :partial => "paging_nav", :locals => { :type => type, :paginator => paginator } %>
   <ul class="list-unstyled" data-turbo="false">
-    <% elements.each do |element| %>
+    <% paginator.current_page_elements.each do |element| %>
       <%= element_list_item type, element do
             t "printable_name.current_and_old_links_html",
               :current_link => link_to(printable_element_name(element), :controller => type.pluralize, :action => :show, :id => element.id[0]),

app/views/changesets/_paging_nav.html.erb

@@ -1,9 +1,9 @@
 <div class="d-flex flex-wrap gap-2">
-  <h4 class="fs-5 mb-0"><%= type_and_paginated_count(type, pages) %></h4>
-  <% if pages.page_count > 1 %>
-    <%= sidebar_classic_pagination(pages, "#{type}_page") do |page|
+  <h4 class="fs-5 mb-0"><%= type_and_paginated_count(type, paginator) %></h4>
+  <% if paginator.pages_count > 1 %>
+    <%= sidebar_classic_pagination(paginator, "#{type}_page") do |page|
           {
-            :title => type_and_paginated_count(type, pages, page),
+            :title => type_and_paginated_count(type, paginator, page),
             :data => { :turbo => "true" }
           }
         end %>

app/views/changesets/show.html.erb

@@ -89,16 +89,16 @@
     <% end %>
   <% end %>
 
-  <% unless @ways.empty? %>
-    <%= render :partial => "elements", :locals => { :type => "way", :elements => @ways, :pages => @way_pages } %>
+  <% unless @ways_paginator.current_page_elements.empty? %>
+    <%= render :partial => "elements", :locals => { :type => "way", :paginator => @ways_paginator } %>
   <% end %>
 
-  <% unless @relations.empty? %>
-    <%= render :partial => "elements", :locals => { :type => "relation", :elements => @relations, :pages => @relation_pages } %>
+  <% unless @relations_paginator.current_page_elements.empty? %>
+    <%= render :partial => "elements", :locals => { :type => "relation", :paginator => @relations_paginator } %>
   <% end %>
 
-  <% unless @nodes.empty? %>
-    <%= render :partial => "elements", :locals => { :type => "node", :elements => @nodes, :pages => @node_pages } %>
+  <% unless @nodes_paginator.current_page_elements.empty? %>
+    <%= render :partial => "elements", :locals => { :type => "node", :paginator => @nodes_paginator } %>
   <% end %>
 </div>