generate_categories.rb

# Jekyll category page generator.
# http://recursive-design.com/projects/jekyll-plugins/
#
# Version: 0.1.4 (201101061053)
#
# Copyright (c) 2010 Dave Perrett, http://recursive-design.com/
# Licensed under the MIT license (http://www.opensource.org/licenses/mit-license.php)
#
# A generator that creates category pages for jekyll sites. 
#
# To use it, simply drop this script into the _plugins directory of your Jekyll site. You should 
# also create a file called 'category_index.html' in the _layouts directory of your jekyll site 
# with the following contents (note: you should remove the leading '# ' characters):
#
# ================================== COPY BELOW THIS LINE ==================================
# ---
# layout: default
# ---
# 
# <h1 class="category">{{ page.title }}</h1>
# <ul class="posts">
# {% for post in site.categories[page.category] %}
#     <div>{{ post.date | date_to_html_string }}</div>
#     <h2><a href="{{ post.url }}">{{ post.title }}</a></h2>
#     <div class="categories">Filed under {{ post.categories | category_links }}</div>
# {% endfor %}
# </ul>
# ================================== COPY ABOVE THIS LINE ==================================
# 
# You can alter the _layout_ setting if you wish to use an alternate layout, and obviously you
# can change the HTML above as you see fit. 
#
# When you compile your jekyll site, this plugin will loop through the list of categories in your 
# site, and use the layout above to generate a page for each one with a list of links to the 
# individual posts.
#
# Included filters :
# - category_links:      Outputs the list of categories as comma-separated <a> links.
# - date_to_html_string: Outputs the post.date as formatted html, with hooks for CSS styling.
#
# Available _config.yml settings :
# - category_dir:          The subfolder to build category pages in (default is 'categories').
# - category_title_prefix: The string used before the category name in the page title (default is 
#                          'Category: ').
module Jekyll
  
  
  # The CategoryIndex class creates a single category page for the specified category.
  class CategoryIndex < Page
    
    # Initializes a new CategoryIndex.
    #
    #  +base+         is the String path to the <source>.
    #  +category_dir+ is the String path between <source> and the category folder.
    #  +category+     is the category currently being processed.
    def initialize(site, base, category_dir, category)
      @site = site
      @base = base
      @dir  = category_dir
      @name = 'index.html'
      self.process(@name)
      # Read the YAML data from the layout page.
      self.read_yaml(File.join(base, '_layouts'), 'category_index.html')
      self.data['category']    = category
      # Set the title for this page.
      title_prefix             = site.config['category_title_prefix'] || 'Category: '
      self.data['title']       = "#{title_prefix}#{site.tags.keys[site.categories.keys.index(category)]}"
      # Set the meta-description for this page.
      meta_description_prefix  = site.config['category_meta_description_prefix'] || 'Category: '
      self.data['description'] = "#{meta_description_prefix}#{category}"
    end
    
  end
  
  
  # The Site class is a built-in Jekyll class with access to global site config information.
  class Site
    
    # Creates an instance of CategoryIndex for each category page, renders it, and 
    # writes the output to a file.
    #
    #  +category_dir+ is the String path to the category folder.
    #  +category+     is the category currently being processed.
    def write_category_index(category_dir, category)
      index = CategoryIndex.new(self, self.source, category_dir, category)
      
      cat_posts = self.categories[category].reverse
      pages = Pager.calculate_pages(cat_posts, self.config['paginate'].to_i)
      (1..pages).each do |num_page|
        pager = Pager.new(self.config, num_page, cat_posts, pages)
        if num_page > 1
          newpage = CategoryIndex.new(self, self.source, category_dir, category)
          newpage.pager = pager
          newpage.dir = File.join(category_dir, "page/#{num_page}")
          self.pages << newpage
        else
          index.pager = pager
        end
      end
      
      index.render(self.layouts, site_payload)
      index.write(self.dest)
      # Record the fact that this page has been added, otherwise Site::cleanup will remove it.
      self.pages << index
      
    end
    
    # Loops through the list of category pages and processes each one.
    def write_category_indexes
      if self.layouts.key? 'category_index'
        dir = self.config['category_dir'] || 'categories'
        self.categories.keys.each do |category|
          self.write_category_index(File.join(dir, category), category)
        end
        
      # Throw an exception if the layout couldn't be found.
      else
        throw "No 'category_index' layout found."
      end
    end
    
  end
  
  
  # Jekyll hook - the generate method is called by jekyll, and generates all of the category pages.
  class GenerateCategories < Generator
    safe true
    priority :low

    def generate(site)
      site.write_category_indexes
    end

  end
  
  
  # Adds some extra filters used during the category creation process.
  module Filters
    
    # Outputs a list of categories as comma-separated <a> links. This is used
    # to output the category list for each post on a category page.
    #
    #  +categories+ is the list of categories to format.
    #
    # Returns string
    def category_links(categories)
      categories = categories.sort!.map do |item|
        '<a href="/blog/category/'+item+'/">'+item+'</a>'
      end
      
      connector = "and"
      case categories.length
      when 0
        ""
      when 1
        categories[0].to_s
      when 2
        "#{categories[0]} #{connector} #{categories[1]}"
      else
        "#{categories[0...-1].join(', ')}, #{connector} #{categories[-1]}"
      end
    end
    
    # Outputs the post.date as formatted html, with hooks for CSS styling.
    #
    #  +date+ is the date object to format as HTML.
    #
    # Returns string
    def date_to_html_string(date)
      result = '<span class="month">' + date.strftime('%b').upcase + '</span> '
      result += date.strftime('<span class="day">%d</span> ')
      result += date.strftime('<span class="year">%Y</span> ')
      result
    end
    
  end
  
end

pagination.rb

module Jekyll

  class Pagination < Generator
    safe true

    def generate(site)
      site.pages.dup.each do |page|
        paginate(site, page) if Pager.pagination_enabled?(site.config, page.name)
      end
    end

    # Paginates the blog's posts. Renders the index.html file into paginated
    # directories, ie: page2/index.html, page3/index.html, etc and adds more
    # site-wide data.
    #   +page+ is the index.html Page that requires pagination
    #
    # {"paginator" => { "page" => <Number>,
    #                   "per_page" => <Number>,
    #                   "posts" => [<Post>],
    #                   "total_posts" => <Number>,
    #                   "total_pages" => <Number>,
    #                   "previous_page" => <Number>,
    #                   "next_page" => <Number> }}
    def paginate(site, page)
      all_posts = site.site_payload['site']['posts']
      pages = Pager.calculate_pages(all_posts, site.config['paginate'].to_i)
      (1..pages).each do |num_page|
        pager = Pager.new(site.config, num_page, all_posts, pages)
        if num_page > 1
          newpage = Page.new(site, site.source, page.dir, page.name)
          newpage.pager = pager
          newpage.dir = File.join(page.dir, "page/#{num_page}")
          site.pages << newpage
        else
          page.pager = pager
        end
      end
    end

  end

  class Pager
    attr_reader :page, :per_page, :posts, :total_posts, :total_pages, :previous_page, :next_page

    def self.calculate_pages(all_posts, per_page)
      num_pages = all_posts.size / per_page.to_i
      num_pages = num_pages + 1 if all_posts.size % per_page.to_i != 0
      num_pages
    end

    def self.pagination_enabled?(config, file)
      file == 'index.html' && !config['paginate'].nil?
    end

    def initialize(config, page, all_posts, num_pages = nil)
      @page = page
      @per_page = config['paginate'].to_i
      @total_pages = num_pages || Pager.calculate_pages(all_posts, @per_page)

      if @page > @total_pages
        raise RuntimeError, "page number can't be greater than total pages: #{@page} > #{@total_pages}"
      end

      init = (@page - 1) * @per_page
      offset = (init + @per_page - 1) >= all_posts.size ? all_posts.size : (init + @per_page - 1)

      @total_posts = all_posts.size
      @posts = all_posts[init..offset]
      @previous_page = @page != 1 ? @page - 1 : nil
      @next_page = @page != @total_pages ? @page + 1 : nil
    end

    def to_liquid
      {
        'page' => page,
        'per_page' => per_page,
        'posts' => posts,
        'total_posts' => total_posts,
        'total_pages' => total_pages,
        'previous_page' => previous_page,
        'next_page' => next_page
      }
    end
  end

end