From b46481557785b15d405d10bbe905f26fa548c01c Mon Sep 17 00:00:00 2001
From: Yorick Peterse <yorickpeterse@gmail.com>
Date: Sat, 15 Nov 2014 18:27:15 +0100
Subject: [PATCH] Fixed AST generation for nth-(first|last)-of-type.

---
 lib/oga/css/parser.y                          |  48 +------
 .../pseudo_classes/nth_last_of_type_spec.rb   | 120 ++++++++----------
 .../parser/pseudo_classes/nth_of_type_spec.rb | 119 ++++++++---------
 3 files changed, 108 insertions(+), 179 deletions(-)

diff --git a/lib/oga/css/parser.y b/lib/oga/css/parser.y
index 2d270e2..e8d5675 100644
--- a/lib/oga/css/parser.y
+++ b/lib/oga/css/parser.y
@@ -424,10 +424,11 @@ end
   ##
   # @param [String] count_axis
   # @param [AST::Node] arg
+  # @param [AST::Node] count_test
   # @return [AST::Node]
   #
-  def generate_nth_child(count_axis, arg)
-    count_call = s(:call, 'count', s(:axis, count_axis, s(:test, nil, '*')))
+  def generate_nth_child(count_axis, arg, count_test = s(:test, nil, '*'))
+    count_call = s(:call, 'count', s(:axis, count_axis, count_test))
 
    # literal 2, 4, etc
     if int_node?(arg)
@@ -462,9 +463,7 @@ end
   # @return [AST::Node]
   #
   def on_pseudo_class_nth_of_type(arg)
-    position_node = s(:call, 'position')
-
-    return generate_nth_of_type(arg, position_node)
+    return generate_nth_child('preceding-sibling', arg, current_element)
   end
 
   ##
@@ -474,44 +473,7 @@ end
   # @return [AST::Node]
   #
   def on_pseudo_class_nth_last_of_type(arg)
-    position_node = s(
-      :add,
-      s(:sub, s(:call, 'last'), s(:call, 'position')),
-      s(:int, 1)
-    )
-
-    return generate_nth_of_type(arg, position_node)
-  end
-
-  ##
-  # @param [AST::Node] arg
-  # @param [AST::Node] position_node
-  # @return [AST::Node]
-  #
-  def generate_nth_of_type(arg, position_node)
-    # literal 2, 4, etc
-    if int_node?(arg)
-      node = s(:eq, position_node, arg)
-    else
-      step, offset = *arg
-      compare      = step_comparison(step)
-
-      # 2n+2, 2n-4, etc
-      if offset
-        mod_val = step_modulo_value(step)
-        node    = s(
-          :and,
-          s(compare, position_node, offset),
-          s(:eq, s(:mod, s(:sub, position_node, offset), mod_val), s(:int, 0))
-        )
-
-      # 2n, n, -2n
-      else
-        node = s(:eq, s(:mod, position_node, step), s(:int, 0))
-      end
-    end
-
-    return node
+    return generate_nth_child('following-sibling', arg, current_element)
   end
 
   ##
diff --git a/spec/oga/css/parser/pseudo_classes/nth_last_of_type_spec.rb b/spec/oga/css/parser/pseudo_classes/nth_last_of_type_spec.rb
index 15d3d28..f2024dd 100644
--- a/spec/oga/css/parser/pseudo_classes/nth_last_of_type_spec.rb
+++ b/spec/oga/css/parser/pseudo_classes/nth_last_of_type_spec.rb
@@ -2,109 +2,93 @@ require 'spec_helper'
 
 describe Oga::CSS::Parser do
   context ':nth-last-of-type pseudo class' do
+    example 'parse the x:nth-last-of-type(1) pseudo class' do
+      parse_css('x:nth-last-of-type(1)').should == parse_xpath(
+        'descendant::x[count(following-sibling::x) = 0]'
+      )
+    end
+
     example 'parse the :nth-last-of-type(1) pseudo class' do
       parse_css(':nth-last-of-type(1)').should == parse_xpath(
-        'descendant::*[(last() - position() + 1) = 1]'
+        'descendant::*[count(following-sibling::*) = 0]'
       )
     end
 
-    example 'parse the :nth-last-of-type(2n) pseudo class' do
-      parse_css(':nth-last-of-type(2n)').should == parse_xpath(
-        'descendant::*[((last() - position() + 1) mod 2) = 0]'
+    example 'parse the :nth-last-of-type(2) pseudo class' do
+      parse_css(':nth-last-of-type(2)').should == parse_xpath(
+        'descendant::*[count(following-sibling::*) = 1]'
       )
     end
 
-    example 'parse the :nth-last-of-type(3n) pseudo class' do
-      parse_css(':nth-last-of-type(3n)').should == parse_xpath(
-        'descendant::*[((last() - position() + 1) mod 3) = 0]'
+    example 'parse the x:nth-last-of-type(even) pseudo class' do
+      parse_css('x:nth-last-of-type(even)').should == parse_xpath(
+        'descendant::x[((count(following-sibling::x) + 1) mod 2) = 0]'
       )
     end
 
-    example 'parse the :nth-last-of-type(2n+5) pseudo class' do
-      parse_css(':nth-last-of-type(2n+5)').should == parse_xpath(
-        'descendant::*[((last() - position() + 1) >= 5) ' \
-          'and ((((last() - position() + 1) - 5) mod 2) = 0)]'
+    example 'parse the x:nth-last-of-type(odd) pseudo class' do
+      parse_css('x:nth-last-of-type(odd)').should == parse_xpath(
+        'descendant::x[(count(following-sibling::x) + 1) >= 1 ' \
+          'and (((count(following-sibling::x) + 1) - 1) mod 2) = 0]'
       )
     end
 
-    example 'parse the :nth-last-of-type(3n+5) pseudo class' do
-      parse_css(':nth-last-of-type(3n+5)').should == parse_xpath(
-        'descendant::*[((last() - position() + 1) >= 5) ' \
-          'and ((((last() - position() + 1) - 5) mod 3) = 0)]'
+    example 'parse the x:nth-last-of-type(n) pseudo class' do
+      parse_css('x:nth-last-of-type(n)').should == parse_xpath(
+        'descendant::x[((count(following-sibling::x) + 1) mod 1) = 0]'
       )
     end
 
-    example 'parse the :nth-last-of-type(2n-5) pseudo class' do
-      parse_css(':nth-last-of-type(2n-5)').should == parse_xpath(
-        'descendant::*[((last() - position() + 1) >= 1) ' \
-          'and ((((last() - position() + 1) - 1) mod 2) = 0)]'
+    example 'parse the x:nth-last-of-type(-n) pseudo class' do
+      parse_css('x:nth-last-of-type(-n)').should == parse_xpath(
+        'descendant::x[((count(following-sibling::x) + 1) mod 1) = 0]'
       )
     end
 
-    example 'parse the :nth-last-of-type(2n-6) pseudo class' do
-      parse_css(':nth-last-of-type(2n-6)').should == parse_xpath(
-        'descendant::*[((last() - position() + 1) >= 2) ' \
-          'and ((((last() - position() + 1) - 2) mod 2) = 0)]'
+    example 'parse the x:nth-last-of-type(-n+6) pseudo class' do
+      parse_css('x:nth-last-of-type(-n+6)').should == parse_xpath(
+        'descendant::x[((count(following-sibling::x) + 1) <= 6) ' \
+          'and (((count(following-sibling::x) + 1) - 6) mod 1) = 0]'
       )
     end
 
-    example 'parse the :nth-last-of-type(-2n+5) pseudo class' do
-      parse_css(':nth-last-of-type(-2n+5)').should == parse_xpath(
-        'descendant::*[((last() - position() + 1) <= 5) ' \
-          'and (((last() - position() + 1) - 5) mod 2) = 0]'
+    example 'parse the x:nth-last-of-type(n+5) pseudo class' do
+      parse_css('x:nth-last-of-type(n+5)').should == parse_xpath(
+        'descendant::x[(count(following-sibling::x) + 1) >= 5 ' \
+          'and (((count(following-sibling::x) + 1) - 5) mod 1) = 0]'
       )
     end
 
-    example 'parse the :nth-last-of-type(-2n-5) pseudo class' do
-      parse_css(':nth-last-of-type(-2n-5)').should == parse_xpath(
-        'descendant::*[((last() - position() + 1) <= -1) ' \
-          'and (((last() - position() + 1) - -1) mod 2) = 0]'
+    example 'parse the x:nth-last-of-type(2n) pseudo class' do
+      parse_css('x:nth-last-of-type(2n)')
+        .should == parse_css('x:nth-last-of-type(even)')
+    end
+
+    example 'parse the x:nth-last-of-type(2n+1) pseudo class' do
+      parse_css('x:nth-last-of-type(2n+1)').should == parse_xpath(
+        'descendant::x[(count(following-sibling::x) + 1) >= 1 ' \
+          'and (((count(following-sibling::x) + 1) - 1) mod 2) = 0]'
       )
     end
 
-    example 'parse the :nth-last-of-type(-2n-6) pseudo class' do
-      parse_css(':nth-last-of-type(-2n-6)').should == parse_xpath(
-        'descendant::*[((last() - position() + 1) <= -2) ' \
-          'and (((last() - position() + 1) - -2) mod 2) = 0]'
+    example 'parse the x:nth-last-of-type(3n+1) pseudo class' do
+      parse_css('x:nth-last-of-type(3n+1)').should == parse_xpath(
+        'descendant::x[(count(following-sibling::x) + 1) >= 1 ' \
+          'and (((count(following-sibling::x) + 1) - 1) mod 3) = 0]'
       )
     end
 
-    example 'parse the :nth-last-of-type(even) pseudo class' do
-      parse_css(':nth-last-of-type(even)').should == parse_xpath(
-        'descendant::*[((last() - position() + 1) mod 2) = 0]'
+    example 'parse the x:nth-last-of-type(2n-6) pseudo class' do
+      parse_css('x:nth-last-of-type(2n-6)').should == parse_xpath(
+        'descendant::x[(count(following-sibling::x) + 1) >= 2 ' \
+          'and (((count(following-sibling::x) + 1) - 2) mod 2) = 0]'
       )
     end
 
-    example 'parse the :nth-last-of-type(odd) pseudo class' do
-      parse_css(':nth-last-of-type(odd)').should == parse_xpath(
-        'descendant::*[((last() - position() + 1) >= 1) ' \
-          'and ((((last() - position() + 1) - 1) mod 2) = 0)]'
-      )
-    end
-
-    example 'parse the :nth-last-of-type(n) pseudo class' do
-      parse_css(':nth-last-of-type(n)').should == parse_xpath(
-        'descendant::*[((last() - position() + 1) mod 1) = 0]'
-      )
-    end
-
-    example 'parse the :nth-last-of-type(n+5) pseudo class' do
-      parse_css(':nth-last-of-type(n+5)').should == parse_xpath(
-        'descendant::*[(last() - position() + 1) >= 5 ' \
-          'and (((last() - position() + 1) - 5) mod 1) = 0]'
-      )
-    end
-
-    example 'parse the :nth-last-of-type(-n) pseudo class' do
-      parse_css(':nth-last-of-type(-n)').should == parse_xpath(
-        'descendant::*[((last() - position() + 1) mod 1) = 0]'
-      )
-    end
-
-    example 'parse the :nth-last-of-type(-n+5) pseudo class' do
-      parse_css(':nth-last-of-type(-n+5)').should == parse_xpath(
-        'descendant::*[((last() - position() + 1) <= 5) ' \
-          'and (((last() - position() + 1) - 5) mod 1) = 0]'
+    example 'parse the x:nth-last-of-type(-2n+6) pseudo class' do
+      parse_css('x:nth-last-of-type(-2n+6)').should == parse_xpath(
+        'descendant::x[((count(following-sibling::x) + 1) <= 6) ' \
+          'and (((count(following-sibling::x) + 1) - 6) mod 2) = 0]'
       )
     end
   end
diff --git a/spec/oga/css/parser/pseudo_classes/nth_of_type_spec.rb b/spec/oga/css/parser/pseudo_classes/nth_of_type_spec.rb
index f6238af..d816c80 100644
--- a/spec/oga/css/parser/pseudo_classes/nth_of_type_spec.rb
+++ b/spec/oga/css/parser/pseudo_classes/nth_of_type_spec.rb
@@ -2,109 +2,92 @@ require 'spec_helper'
 
 describe Oga::CSS::Parser do
   context ':nth-of-type pseudo class' do
+    example 'parse the x:nth-of-type(1) pseudo class' do
+      parse_css('x:nth-of-type(1)').should == parse_xpath(
+        'descendant::x[count(preceding-sibling::x) = 0]'
+      )
+    end
+
     example 'parse the :nth-of-type(1) pseudo class' do
       parse_css(':nth-of-type(1)').should == parse_xpath(
-        'descendant::*[position() = 1]'
+        'descendant::*[count(preceding-sibling::*) = 0]'
       )
     end
 
-    example 'parse the :nth-of-type(2n) pseudo class' do
-      parse_css(':nth-of-type(2n)').should == parse_xpath(
-        'descendant::*[(position() mod 2) = 0]'
+    example 'parse the :nth-of-type(2) pseudo class' do
+      parse_css(':nth-of-type(2)').should == parse_xpath(
+        'descendant::*[count(preceding-sibling::*) = 1]'
       )
     end
 
-    example 'parse the :nth-of-type(3n) pseudo class' do
-      parse_css(':nth-of-type(3n)').should == parse_xpath(
-        'descendant::*[(position() mod 3) = 0]'
+    example 'parse the x:nth-of-type(even) pseudo class' do
+      parse_css('x:nth-of-type(even)').should == parse_xpath(
+        'descendant::x[((count(preceding-sibling::x) + 1) mod 2) = 0]'
       )
     end
 
-    example 'parse the :nth-of-type(2n+5) pseudo class' do
-      parse_css(':nth-of-type(2n+5)').should == parse_xpath(
-        'descendant::*[(position() >= 5) ' \
-          'and (((position() - 5) mod 2) = 0)]'
+    example 'parse the x:nth-of-type(odd) pseudo class' do
+      parse_css('x:nth-of-type(odd)').should == parse_xpath(
+        'descendant::x[(count(preceding-sibling::x) + 1) >= 1 ' \
+          'and (((count(preceding-sibling::x) + 1) - 1) mod 2) = 0]'
       )
     end
 
-    example 'parse the :nth-of-type(3n+5) pseudo class' do
-      parse_css(':nth-of-type(3n+5)').should == parse_xpath(
-        'descendant::*[(position() >= 5) ' \
-          'and (((position() - 5) mod 3) = 0)]'
+    example 'parse the x:nth-of-type(n) pseudo class' do
+      parse_css('x:nth-of-type(n)').should == parse_xpath(
+        'descendant::x[((count(preceding-sibling::x) + 1) mod 1) = 0]'
       )
     end
 
-    example 'parse the :nth-of-type(2n-5) pseudo class' do
-      parse_css(':nth-of-type(2n-5)').should == parse_xpath(
-        'descendant::*[(position() >= 1) ' \
-          'and (((position() - 1) mod 2) = 0)]'
+    example 'parse the x:nth-of-type(-n) pseudo class' do
+      parse_css('x:nth-of-type(-n)').should == parse_xpath(
+        'descendant::x[((count(preceding-sibling::x) + 1) mod 1) = 0]'
       )
     end
 
-    example 'parse the :nth-of-type(2n-6) pseudo class' do
-      parse_css(':nth-of-type(2n-6)').should == parse_xpath(
-        'descendant::*[(position() >= 2) ' \
-          'and (((position() - 2) mod 2) = 0)]'
+    example 'parse the x:nth-of-type(-n+6) pseudo class' do
+      parse_css('x:nth-of-type(-n+6)').should == parse_xpath(
+        'descendant::x[((count(preceding-sibling::x) + 1) <= 6) ' \
+          'and (((count(preceding-sibling::x) + 1) - 6) mod 1) = 0]'
       )
     end
 
-    example 'parse the :nth-of-type(-2n+5) pseudo class' do
-      parse_css(':nth-of-type(-2n+5)').should == parse_xpath(
-        'descendant::*[(position() <= 5) ' \
-          'and ((position() - 5) mod 2) = 0]'
+    example 'parse the x:nth-of-type(n+5) pseudo class' do
+      parse_css('x:nth-of-type(n+5)').should == parse_xpath(
+        'descendant::x[(count(preceding-sibling::x) + 1) >= 5 ' \
+          'and (((count(preceding-sibling::x) + 1) - 5) mod 1) = 0]'
       )
     end
 
-    example 'parse the :nth-of-type(-2n-5) pseudo class' do
-      parse_css(':nth-of-type(-2n-5)').should == parse_xpath(
-        'descendant::*[(position() <= -1) ' \
-          'and ((position() - -1) mod 2) = 0]'
+    example 'parse the x:nth-of-type(2n) pseudo class' do
+      parse_css('x:nth-of-type(2n)').should == parse_css('x:nth-of-type(even)')
+    end
+
+    example 'parse the x:nth-of-type(2n+1) pseudo class' do
+      parse_css('x:nth-of-type(2n+1)').should == parse_xpath(
+        'descendant::x[(count(preceding-sibling::x) + 1) >= 1 ' \
+          'and (((count(preceding-sibling::x) + 1) - 1) mod 2) = 0]'
       )
     end
 
-    example 'parse the :nth-of-type(-2n-6) pseudo class' do
-      parse_css(':nth-of-type(-2n-6)').should == parse_xpath(
-        'descendant::*[(position() <= -2) ' \
-          'and ((position() - -2) mod 2) = 0]'
+    example 'parse the x:nth-of-type(3n+1) pseudo class' do
+      parse_css('x:nth-of-type(3n+1)').should == parse_xpath(
+        'descendant::x[(count(preceding-sibling::x) + 1) >= 1 ' \
+          'and (((count(preceding-sibling::x) + 1) - 1) mod 3) = 0]'
       )
     end
 
-    example 'parse the :nth-of-type(even) pseudo class' do
-      parse_css(':nth-of-type(even)').should == parse_xpath(
-        'descendant::*[(position() mod 2) = 0]'
+    example 'parse the x:nth-of-type(2n-6) pseudo class' do
+      parse_css('x:nth-of-type(2n-6)').should == parse_xpath(
+        'descendant::x[(count(preceding-sibling::x) + 1) >= 2 ' \
+          'and (((count(preceding-sibling::x) + 1) - 2) mod 2) = 0]'
       )
     end
 
-    example 'parse the :nth-of-type(odd) pseudo class' do
-      parse_css(':nth-of-type(odd)').should == parse_xpath(
-        'descendant::*[(position() >= 1) ' \
-          'and (((position() - 1) mod 2) = 0)]'
-      )
-    end
-
-    example 'parse the :nth-of-type(n) pseudo class' do
-      parse_css(':nth-of-type(n)').should == parse_xpath(
-        'descendant::*[(position() mod 1) =0]'
-      )
-    end
-
-    example 'parse the :nth-of-type(n+5) pseudo class' do
-      parse_css(':nth-of-type(n+5)').should == parse_xpath(
-        'descendant::*[position() >= 5 ' \
-          'and ((position() - 5) mod 1) = 0]'
-      )
-    end
-
-    example 'parse the :nth-of-type(-n) pseudo class' do
-      parse_css(':nth-of-type(-n)').should == parse_xpath(
-        'descendant::*[(position() mod 1) = 0]'
-      )
-    end
-
-    example 'parse the :nth-of-type(-n+5) pseudo class' do
-      parse_css(':nth-of-type(-n+5)').should == parse_xpath(
-        'descendant::*[(position() <= 5) ' \
-          'and ((position() - 5) mod 1) = 0]'
+    example 'parse the x:nth-of-type(-2n+6) pseudo class' do
+      parse_css('x:nth-of-type(-2n+6)').should == parse_xpath(
+        'descendant::x[((count(preceding-sibling::x) + 1) <= 6) ' \
+          'and (((count(preceding-sibling::x) + 1) - 6) mod 2) = 0]'
       )
     end
   end