posts' pagination

features/pagination.feature

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+Feature: Site pagination
+  In order to paginate my blog
+  As a blog's user
+  I want divide the posts in several pages
+  
+  Scenario: Create pages
+    Given I have a configuration file with "paginate" set to "1"
+    And I have a _layouts directory
+    And I have an "index.html" file that contains "Basic Site"
+    And I have a _posts directory
+    And I have the following post:
+      | title    | date      | layout  | content                               |
+      | Wargames | 3/27/2009 | default | The only winning move is not to play. |
+      | Wargames2 | 4/27/2009 | default | The only winning move is not to play2. |
+    When I run jekyll
+    Then the _site/page2 directory should exist
+    And the _site/page2/index.html file should exist
+  
+  
+  
+
+  

lib/jekyll/pager.rb

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+module Jekyll
+  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.abs + 1 if all_posts.size % per_page.to_i != 0
+      num_pages
+    end
+    
+    def self.pagination_enabled?(config, file)
+      File.basename(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 grater 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_hash
+      {
+        '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

test/test_pager.rb

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+require File.dirname(__FILE__) + '/helper'
+
+class TestPager < Test::Unit::TestCase
+  
+  def setup
+    stub(Jekyll).configuration do
+      Jekyll::DEFAULTS.merge({'source' => source_dir, 'destination' => dest_dir,
+        'paginate' => 2})
+    end
+
+    @config = Jekyll.configuration
+    @site = Site.new(@config)
+    @posts = @site.read_posts('')
+  end
+  
+  def teardown
+    @config = Jekyll.configuration('paginate' => nil)
+  end
+  
+  def test_calculate_pages
+    assert_equal(2, Pager.calculate_pages(@posts, @config['paginate']))
+  end
+
+  def test_create_first_pager
+    pager = Pager.new(@config, 1, @posts)
+    assert_equal(@config['paginate'].to_i, pager.posts.size)
+    assert_equal(2, pager.total_pages)
+    assert_nil(pager.previous_page)
+    assert_equal(2, pager.next_page)
+  end
+  
+  def test_create_second_pager
+    pager = Pager.new(@config, 2, @posts)
+    assert_equal(@posts.size - @config['paginate'].to_i, pager.posts.size)
+    assert_equal(2, pager.total_pages)
+    assert_equal(1, pager.previous_page)
+    assert_nil(pager.next_page)
+  end
+  
+  def test_create_third_pager
+    assert_raise(RuntimeError) { Pager.new(@config, 3, @posts) }
+  end
+  
+  def test_pagination_enabled_with_command_option
+    assert_equal(true, Pager.pagination_enabled?(@config, 'index.html'))
+  end
+end