Markdowner: use Nokogiri for html rewriting

brute forcing changes by regexps gets things wrong sometimes, so use
nokogiri to parse the html output of rdiscount and do changes on
individual nodes, then turn back into a string

we lose the ability to move punctuation inside of auto-generated
links, but i don't see any easy/definitive way to do this properly.

closes #242
closes #209

extras/markdowner.rb

@@ -13,35 +13,38 @@ class Markdowner
       args.push :no_image
     end
 
-    html = RDiscount.new(text.to_s, *args).to_html
+    ng = Nokogiri::HTML(RDiscount.new(text.to_s, *args).to_html)
 
-    # change <h1> headings to just emphasis tags
-    html.gsub!(/<(\/)?h(\d)>/) {|_| "<#{$1}strong>" }
-
-    # fix links that got the trailing punctuation appended to move it outside
-    # the link
-    html.gsub!(/<a ([^>]+)([\.\!\,])">([^>]+)([\.\!\,])<\/a>/) {|_|
-      if $2.to_s == $4.to_s
-        "<a #{$1}\">#{$3}</a>#{$2}"
-      else
-        _
-      end
-    }
+    # change <h1>, <h2>, etc. headings to just bold tags
+    ng.css("h1, h2, h3, h4, h5, h6").each do |h|
+      h.name = "strong"
+    end
 
     # make links have rel=nofollow
-    html.gsub!(/<a href/, "<a rel=\"nofollow\" href")
+    ng.css("a").each do |h|
+      h[:rel] = "nofollow"
+    end
 
-    if !opts[:disable_profile_links]
+    unless opts[:disable_profile_links]
       # make @username link to that user's profile
-      html.gsub!(/\B\@([\w\-]+)/) do |u|
-        if User.exists?(:username => u[1 .. -1])
-          "<a href=\"/u/#{u[1 .. -1]}\">#{u}</a>"
-        else
-          u
+      ng.search("//text()").each do |t|
+        if t.parent && t.parent.name.downcase == "a"
+          # don't replace inside <a>s
+          next
         end
+
+        tx = t.text.gsub(/\B\@([\w\-]+)/) do |u|
+          if User.exists?(:username => u[1 .. -1])
+            "<a href=\"/u/#{u[1 .. -1]}\">#{u}</a>"
+          else
+            u
+          end
+        end
+
+        t.replace(tx)
       end
     end
 
-    html
+    ng.at_css("body").inner_html
   end
 end

spec/models/markdowner_spec.rb

@@ -3,30 +3,24 @@ require "spec_helper"
 describe Markdowner do
   it "parses simple markdown" do
     Markdowner.to_html("hello there *italics* and **bold**!").should ==
-      "<p>hello there <em>italics</em> and <strong>bold</strong>!</p>\n"
+      "<p>hello there <em>italics</em> and <strong>bold</strong>!</p>"
   end
 
   it "turns @username into a link if @username exists" do
     User.make!(:username => "blahblah")
 
     Markdowner.to_html("hi @blahblah test").should ==
-      "<p>hi <a href=\"/u/blahblah\">@blahblah</a> test</p>\n"
+      "<p>hi <a href=\"/u/blahblah\">@blahblah</a> test</p>"
 
     Markdowner.to_html("hi @flimflam test").should ==
-      "<p>hi @flimflam test</p>\n"
-  end
-
-  it "moves punctuation outside of auto-generated links" do
-    Markdowner.to_html("hi http://example.com/a! test").should ==
-      "<p>hi <a rel=\"nofollow\" " <<
-        "href=\"http://example.com/a\">http://example.com/a</a>! test</p>\n"
+      "<p>hi @flimflam test</p>"
   end
 
   # bug#209
   it "keeps punctuation inside of auto-generated links when using brackets" do
     Markdowner.to_html("hi <http://example.com/a.> test").should ==
-      "<p>hi <a rel=\"nofollow\" " <<
-        "href=\"http://example.com/a.\">http://example.com/a.</a> test</p>\n"
+      "<p>hi <a href=\"http://example.com/a.\" rel=\"nofollow\">" <<
+        "http://example.com/a.</a> test</p>"
   end
 
   # bug#242
@@ -34,11 +28,11 @@ describe Markdowner do
     User.make!(:username => "blahblah")
 
     Markdowner.to_html("hi http://example.com/@blahblah/ test").should ==
-      "<p>hi <a rel=\"nofollow\" " <<
-        "href=\"http://example.com/@blahblah/\">http://example.com/@blahblah</a></p>\n"
+      "<p>hi <a href=\"http://example.com/@blahblah/\" rel=\"nofollow\">" <<
+        "http://example.com/@blahblah/</a> test</p>"
 
     Markdowner.to_html("hi [test](http://example.com/@blahblah/)").should ==
-      "<p>hi <a rel=\"nofollow\" " <<
-        "href=\"http://example.com/@blahblah/\">test</a></p>\n"
+      "<p>hi <a href=\"http://example.com/@blahblah/\" rel=\"nofollow\">" <<
+        "test</a></p>"
   end
 end