Check in a simple pure-python based Markdown previewer.

third_party/Python-Markdown/markdown/extensions/meta.py

+"""
+Meta Data Extension for Python-Markdown
+=======================================
+
+This extension adds Meta Data handling to markdown.
+
+See <https://pythonhosted.org/Markdown/extensions/meta_data.html>
+for documentation.
+
+Original code Copyright 2007-2008 [Waylan Limberg](http://achinghead.com).
+
+All changes Copyright 2008-2014 The Python Markdown Project
+
+License: [BSD](http://www.opensource.org/licenses/bsd-license.php)
+
+"""
+
+from __future__ import absolute_import
+from __future__ import unicode_literals
+from . import Extension
+from ..preprocessors import Preprocessor
+import re
+import logging
+
+log = logging.getLogger('MARKDOWN')
+
+# Global Vars
+META_RE = re.compile(r'^[ ]{0,3}(?P<key>[A-Za-z0-9_-]+):\s*(?P<value>.*)')
+META_MORE_RE = re.compile(r'^[ ]{4,}(?P<value>.*)')
+BEGIN_RE = re.compile(r'^-{3}(\s.*)?')
+END_RE = re.compile(r'^(-{3}|\.{3})(\s.*)?')
+
+
+class MetaExtension (Extension):
+    """ Meta-Data extension for Python-Markdown. """
+
+    def extendMarkdown(self, md, md_globals):
+        """ Add MetaPreprocessor to Markdown instance. """
+        md.preprocessors.add("meta",
+                             MetaPreprocessor(md),
+                             ">normalize_whitespace")
+
+
+class MetaPreprocessor(Preprocessor):
+    """ Get Meta-Data. """
+
+    def run(self, lines):
+        """ Parse Meta-Data and store in Markdown.Meta. """
+        meta = {}
+        key = None
+        if lines and BEGIN_RE.match(lines[0]):
+            lines.pop(0)
+        while lines:
+            line = lines.pop(0)
+            m1 = META_RE.match(line)
+            if line.strip() == '' or END_RE.match(line):
+                break  # blank line or end of YAML header - done
+            if m1:
+                key = m1.group('key').lower().strip()
+                value = m1.group('value').strip()
+                try:
+                    meta[key].append(value)
+                except KeyError:
+                    meta[key] = [value]
+            else:
+                m2 = META_MORE_RE.match(line)
+                if m2 and key:
+                    # Add another line to existing key
+                    meta[key].append(m2.group('value').strip())
+                else:
+                    lines.insert(0, line)
+                    break  # no meta data - done
+        self.markdown.Meta = meta
+        return lines
+
+
+def makeExtension(*args, **kwargs):
+    return MetaExtension(*args, **kwargs)