posts' pagination

lib/jekyll/pager.rb

@@ -0,0 +1,45 @@
+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