Parse @username links in markdown

KerbalStuff/kerbdown.py

@@ -2,10 +2,14 @@
 from urllib.parse import parse_qs, urlparse
 from typing import Dict, Any, Match, Tuple, Optional
 
+from flask import url_for
 from markdown import Markdown
 from markdown.extensions import Extension
 from markdown.inlinepatterns import InlineProcessor
 from xml.etree import ElementTree
+from markdown.util import AtomicString
+
+from .objects import User
 
 
 class EmbedInlineProcessor(InlineProcessor):
@@ -63,6 +67,45 @@ def _embed_youtube(self, vid_id: str) -> ElementTree.Element:
         return el
 
 
+class AtUsernameProcessor(InlineProcessor):
+    # Don't worry about re.compiling this, markdown.inlinepatterns.Pattern.__init__ does that for us
+    # Same as blueprints.accounts._username_re
+    USER_RE = r'@(?P<username>[A-Za-z0-9_]+)'
+
+    def __init__(self, md: Markdown, configs: Dict[str, Any]) -> None:
+        super().__init__(self.USER_RE, md)
+        self.configs = configs
+
+    def handleMatch(self, match: Match[str], data: str) -> Tuple[Optional[ElementTree.Element], Optional[int], Optional[int]]:  # type: ignore[override]
+        username = match.groupdict().get('username')
+        # Case insensitive lookup
+        user = User.query.filter(User.username.ilike(username)).first()
+        return ((self._profileLink(user), match.start(0), match.end(0))
+                # Keep original text if user not found
+                if user and user.public else (None, None, None))
+
+    @classmethod
+    def _profileLink(cls, user: User) -> ElementTree.Element:
+        # Make a link to the user's profile
+        elt = ElementTree.Element('a', href=url_for('profile.view_profile',
+                                                    username=user.username),
+                                       # Summarize user's profile in tooltip
+                                       title='\n'.join((f'{user.username}\'s profile',
+                                                        f'{cls._profileModCount(user)} mods',
+                                                        f'Joined {user.created.strftime("%Y-%m-%d")}')))
+        # Make it bold
+        strong = ElementTree.SubElement(elt, 'strong')
+        # AtomicString prevents Markdown from entering an infinite loop by processing the subelement's text again
+        strong.text = AtomicString(f'@{user.username}')
+        return elt
+
+    @staticmethod
+    def _profileModCount(user: User) -> int:
+        return len([m for m in user.mods + [sa.mod for sa in user.shared_authors
+                                            if sa.accepted]
+                    if m.published])
+
+
 class KerbDown(Extension):
     def __init__(self, **kwargs: str) -> None:
         super().__init__(**kwargs) # type: ignore[arg-type]
@@ -72,4 +115,5 @@ def __init__(self, **kwargs: str) -> None:
     def extendMarkdown(self, md: Markdown) -> None:
         # BUG: the base method signature is INVALID, it's a bug in flask-markdown
         md.inlinePatterns.register(EmbedInlineProcessor(md, self.config), 'embed', 200)
+        md.inlinePatterns.register(AtUsernameProcessor(md, self.config), 'atuser', 200)
         md.registerExtension(self)

templates/markdown.html

@@ -52,6 +52,9 @@ <h2>My super cool mod</h2>
     </blockquote>
     <p>You can use Markdown on your mod descriptions, profile page, and changelogs. The nice thing about using it in
     your changelogs is that it looks nice in plaintext, which is how it shows up in your user's email inboxes.</p>
+    <h2>User profile links</h2>
+    <p>You can create a link to a user's profile like this:</p>
+    <pre>@username</pre>
     <h2>Embedding videos and images</h2>
     <p>You can easily embed a single image like so (this came from the Markdown spec):</p>
     <pre>![](http://example.com/image.png)</pre>