feat(messages): add link preview for URLs in messages

blueprints/messages/link_preview.py

@@ -0,0 +1,89 @@
+"""
+Link Preview — fetch Open Graph metadata for URLs in messages.
+"""
+
+import re
+import logging
+import requests
+from html.parser import HTMLParser
+from urllib.parse import urlparse
+
+logger = logging.getLogger(__name__)
+
+URL_REGEX = re.compile(r'https?://[^\s<>"\']+')
+INTERNAL_DOMAINS = ['nordabiznes.pl', 'staging.nordabiznes.pl', 'localhost']
+
+
+class OGParser(HTMLParser):
+    """Parse og: meta tags and title from HTML head."""
+    def __init__(self):
+        super().__init__()
+        self.og = {}
+        self.title = None
+        self._in_title = False
+        self._title_data = []
+
+    def handle_starttag(self, tag, attrs):
+        if tag == 'meta':
+            d = dict(attrs)
+            prop = d.get('property', '') or d.get('name', '')
+            content = d.get('content', '')
+            if prop in ('og:title', 'og:description', 'og:image'):
+                self.og[prop.replace('og:', '')] = content
+            elif prop == 'description' and 'description' not in self.og:
+                self.og['description'] = content
+        elif tag == 'title':
+            self._in_title = True
+
+    def handle_data(self, data):
+        if self._in_title:
+            self._title_data.append(data)
+
+    def handle_endtag(self, tag):
+        if tag == 'title':
+            self._in_title = False
+            self.title = ''.join(self._title_data).strip()
+
+
+def fetch_link_preview(text):
+    """Extract first URL from text and fetch OG metadata. Returns dict or None."""
+    # Strip HTML tags for URL detection
+    clean = re.sub(r'<[^>]+>', '', text or '')
+    urls = URL_REGEX.findall(clean)
+    if not urls:
+        return None
+
+    url = urls[0]
+
+    # Skip internal links
+    parsed = urlparse(url)
+    if parsed.hostname and any(parsed.hostname.endswith(d) for d in INTERNAL_DOMAINS):
+        return None
+
+    try:
+        resp = requests.get(url, timeout=3, headers={
+            'User-Agent': 'NordaBiznes/1.0 (Link Preview)'
+        }, allow_redirects=True)
+        resp.raise_for_status()
+
+        content_type = resp.headers.get('content-type', '')
+        if 'text/html' not in content_type:
+            return None
+
+        html = resp.text[:100_000]
+        parser = OGParser()
+        parser.feed(html)
+
+        title = parser.og.get('title') or parser.title
+        if not title:
+            return None
+
+        return {
+            'url': url,
+            'title': title[:200],
+            'description': (parser.og.get('description') or '')[:300],
+            'image': parser.og.get('image', ''),
+        }
+    except Exception as e:
+        logger.debug(f"Link preview failed for {url}: {e}")
+        return None