Class: Praxis::Extensions::Pagination::HeaderGenerator

Inherits:
Object
  • Object
show all
Defined in:
lib/praxis/extensions/pagination/header_generator.rb

Class Method Summary collapse

Class Method Details

.build_cursor_headers(paginator:, last_value:, total_count: nil) ⇒ Object 



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# File 'lib/praxis/extensions/pagination/header_generator.rb', line 7

def self.build_cursor_headers(paginator:, last_value:, total_count: nil)
  %i[next prev first last].each_with_object({}) do |rel_name, info|
    case rel_name
    when :next
      # If we don't know the total, we'll try to go to the next page
      # but assume we're done if there isn't a last value...
      if last_value
        info[:next] = { by: paginator.by, from: last_value, items: paginator.items }
        info[:next][:total_count] = true if total_count.present?
      end
    when :prev
    # Not possible to go back
    when :first
      info[:first] = { by: paginator.by, items: paginator.items }
      info[:first][:total_count] = true if total_count.present?
    when :last
      # Not possible to scroll to last
    end
  end
end

.build_paging_headers(paginator:, total_count: nil) ⇒ Object

This is only for plain paging



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# File 'lib/praxis/extensions/pagination/header_generator.rb', line 29

def self.build_paging_headers(paginator:, total_count: nil)
  last_page = total_count.nil? ? nil : (total_count / (paginator.items * 1.0)).ceil
  %i[next prev first last].each_with_object({}) do |rel_name, info|
    num = case rel_name
          when :first
            1
          when :prev
            next if paginator.page < 2

            paginator.page - 1
          when :next
            # don't include this link if we know the total and we see there are no more pages
            next if last_page.present? && (paginator.page >= last_page)

            # if we don't know the total, we'll specify to the next page even if it ends up being blank
            paginator.page + 1
          when :last
            next if last_page.blank?

            last_page
          end
    info[rel_name] = {
      page: num,
      items: paginator.items,
      total_count: total_count.present?
    }
  end
end

.generate_headers(links:, current_url:, current_query_params:, total_count:) ⇒ Object 



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# File 'lib/praxis/extensions/pagination/header_generator.rb', line 58

def self.generate_headers(links:, current_url:, current_query_params:, total_count:)
  mapped = links.map do |(rel, info)|
    # Make sure to encode it our way (with comma-separated args, as it is our own syntax, and not a query string one)
    pagination_param = info.map { |(k, v)| "#{k}=#{v}" }.join(',')
    new_url = "#{current_url}?#{current_query_params.dup.merge(pagination: pagination_param).to_query}"

    LinkHeader::Link.new(new_url, [['rel', rel.to_s]])
  end
  link_header = LinkHeader.new(mapped)

  headers = { 'Link' => link_header.to_s }
  headers['Total-Count'] = total_count if total_count
  headers
end