Add admonition styles for notes, tips, warnings, etc.

There are currently 4 styles: INFO, TIP, CAUTION, DANGER

In a doc they are used like:

NOTE: This is a note

1 files changed, 42 insertions, 0 deletions

diff --git a/lib/filters/admonition.rb b/lib/filters/admonition.rb
new file mode 100644
index 00000000..4bf5a080
--- /dev/null
+++ b/lib/filters/admonition.rb
@@ -0,0 +1,42 @@
+# encoding: utf-8
+
+# Adapted from the admonition code on http://nanoc.ws/
+class AdmonitionFilter < Nanoc::Filter
+
+  identifier :admonition
+
+  BOOTSTRAP_MAPPING = {
+    'tip'     => 'success',
+    'note'    => 'info',
+    'caution' => 'warning',
+    'danger'  => 'danger',
+  }
+
+  FONT_AWESOME_MAPPING = {
+    'note'    =>  'pencil',
+    'tip'     =>  'info-circle',
+    'warning' =>  'exclamation-triangle',
+    'danger'  =>  'bolt',
+  }
+
+  def run(content, params = {})
+    # `#dup` is necessary because `.fragment` modifies the incoming string. Ew!
+    # See https://github.com/sparklemotion/nokogiri/issues/1077
+    doc = Nokogiri::HTML.fragment(content.dup)
+    doc.css('p').each do |para|
+      content = para.inner_html
+      next if content !~ /\A(TIP|NOTE|CAUTION|DANGER): (.*)\Z/m
+      new_content = generate($1.downcase, $2)
+      para.replace(new_content)
+    end
+    doc.to_s
+  end
+
+  def generate(kind, content)
+    %[<div class="admonition-wrapper #{kind}">] +
+    %[<div class="admonition alert alert-#{BOOTSTRAP_MAPPING[kind]}">] +
+    content +
+    %[</div></div>]
+  end
+
+end