Merge pull request #86 from iiegn/feature-offset_filter

Add --offset filter option to accompany --max

features/filter.feature

@@ -106,6 +106,40 @@ Feature: BibTeX
     And I should not see "Programming Ruby" in "_site/scholar.html"
     And I should see "The Ruby Programming Language" in "_site/scholar.html"
 
+  @tags @offset
+  Scenario: Start listing entries with an offset
+    Given I have a scholar configuration with:
+      | key    | value             |
+      | source | ./_bibliography   |
+    And I have a "_bibliography" directory
+    And I have a file "_bibliography/references.bib":
+      """
+      @book{ruby,
+        title     = {The Ruby Programming Language},
+        author    = {Flanagan, David and Matsumoto, Yukihiro},
+        year      = {2008},
+        publisher = {O'Reilly Media}
+      }
+      @book{pickaxe,
+        title     = {Programming Ruby 1.9: The Pragmatic Programmer's Guide},
+        author    = {Thomas, Dave and Fowler, Chad and Hunt, Andy},
+        year      = {2009},
+        edition   = 3,
+        publisher = {Pragmatic Bookshelf}
+      }
+      """
+    And I have a page "scholar.html":
+      """
+      ---
+      ---
+      {% bibliography --offset 1 %}
+      """
+    When I run jekyll
+    Then the _site directory should exist
+    And the "_site/scholar.html" file should exist
+    And I should see "Programming Ruby" in "_site/scholar.html"
+    And I should not see "The Ruby Programming Language" in "_site/scholar.html"
+
   @tags @urls
   Scenario: URLs as text
     Given I have a scholar configuration with:

lib/jekyll/scholar/tags/bibliography.rb

@@ -42,7 +42,7 @@ module Jekyll
           cited_keys.clear
         end
 
-        items = items.take(max.to_i) if limit_entries?
+        items = items[offset..max] if limit_entries?
 
         bibliography = items.each_with_index.map { |entry, index|
           reference = bibliography_tag(entry, index + 1)

lib/jekyll/scholar/utilities.rb

@@ -14,7 +14,7 @@ module Jekyll
     # #site readers
     module Utilities
 
-      attr_reader :config, :site, :context, :prefix, :text, :max
+      attr_reader :config, :site, :context, :prefix, :text, :offset, :max
 
       def split_arguments(arguments)
 
@@ -63,8 +63,12 @@ module Jekyll
             locators << locator
           end
 
+          opts.on('-o', '--offset OFFSET') do |offset|
+            @offset = offset.to_i
+          end
+
           opts.on('-m', '--max MAX') do |max|
-            @max = max
+            @max = max.to_i
           end
 
           opts.on('-s', '--style STYLE') do |style|
@@ -76,7 +80,7 @@ module Jekyll
           end
         end
 
-        argv = arguments.split(/(\B-[cCfqptTslmA]|\B--(?:cited(_in_order)?|file|query|prefix|text|style|template|locator|max|suppress_author|))/)
+        argv = arguments.split(/(\B-[cCfqptTslomA]|\B--(?:cited(_in_order)?|file|query|prefix|text|style|template|locator|offset|max|suppress_author|))/)
 
         parser.parse argv.map(&:strip).reject(&:empty?)
       end
@@ -135,8 +139,16 @@ module Jekyll
         sort bibliography[query || config['query']]
       end
 
+      def offset
+        @offset ||= 0
+      end
+
+      def max
+        @max.nil? ? -1 : @max + offset - 1
+      end
+
       def limit_entries?
-        !max.nil?
+        !offset.nil? || !max.nil?
       end
 
       def sort(unsorted)