Nanoc pagination

pagination_helper.rb

module PaginationHelper
  
  # The main pagination method, you should only need to call this
  # Returns full HTML markup for pagination links
  def pagination(page, pages, uri)
    html, ul = [], []
    html << pagination_position(page, pages)
    if pages > 1
      ul << pagination_previous_link(page, uri)
      ul << pagination_page_links(page, pages, uri)
      ul << pagination_next_link(page, pages, uri)
      html << content_tag(:ul, ul.join)
    end
    content_tag :nav, html.join, :id => "pagination"
  end
  
  # Returns paragraph with pagination position
  def pagination_position(page, pages)
    content_tag :p, "Page #{page} of #{pages}"
  end
  
  # Returns the "previous" pagination link
  def pagination_previous_link(page, uri)
    text = "&laquo; Prev"
    content_tag :li, (page > 1 ? link_to(text, "#{uri}page/#{page-1}") : content_tag(:span, text)), :class => "prev"
  end
  
  # Returns the "next" pagination link
  def pagination_next_link(page, pages, uri)
    text = "Next &raquo;"
    content_tag :li, (page < pages ? link_to(text, "#{uri}page/#{page+1}") : content_tag(:span, text)), :class => "prev"
  end
  
  # Returns all the page number pagination links
  def pagination_page_links(page, pages, uri)
    visible_page_numbers(page, pages).collect do |pg|
      content_tag(:li, link_to(pg, "#{uri}page/#{pg}"), :class => ("current" if pg == page))
    end.join
  end
  
  # Returns an array of visible page numbers
  # Borrowed from will_paginate implementation
  # https://github.com/mislav/will_paginate/blob/master/lib/will_paginate/view_helpers.rb
  def visible_page_numbers(current_page, total_pages)
    inner_window, outer_window = 4, 4
    window_from = current_page - inner_window
    window_to = current_page + inner_window

    # adjust lower or upper limit if other is out of bounds
    if window_to > total_pages
      window_from -= window_to - total_pages
      window_to = total_pages
    end
    if window_from < 1
      window_to += 1 - window_from
      window_from = 1
      window_to = total_pages if window_to > total_pages
    end

    visible   = (1..total_pages).to_a
    left_gap  = (2 + outer_window)...window_from
    right_gap = (window_to + 1)...(total_pages - outer_window)
    visible  -= left_gap.to_a  if left_gap.last - left_gap.first > 1
    visible  -= right_gap.to_a if right_gap.last - right_gap.first > 1

    visible
  end
    
end