Improve header id generation

1 files changed, 8 insertions, 1 deletions

diff --git a/panfry/page.py b/panfry/page.py
index 01d9fcb..42eda1e 100755
--- a/panfry/page.py
+++ b/panfry/page.py
@@ -35,7 +35,14 @@ class TOCItem:
 
     @property
     def header_id(self):
-        remove = re.compile('[+~!@#$%^&*\(\){}\[\];:"\',.<>?/\`]')
+        # - Remove all formatting, links, etc.
+        # - Remove all punctuation, except underscores, hyphens, and periods.
+        # - Replace all spaces and newlines with hyphens.
+        # - Convert all alphabetic characters to lowercase.
+        # - Remove everything up to the first letter (identifiers may not begin
+        #   with a number or punctuation mark).
+
+        remove = re.compile('^[^a-zA-Z]|[+~!@#$%^&*\(\){}\[\];:"\',<>?/\`]')
         header_id = self.heading.lower().replace('\n', ' ').replace(' ', '-')
         return remove.sub('', header_id)