Bold search query in results (#487)

This modifies the search result page by bold-ing all appearances
of any word in the original query. If portions of the query are in
quotes (i.e. "ice cream"), only exact matches of the sequence of
words will be made bold.

Co-authored-by: Ben Busby <noreply+git@benbusby.com>

app/utils/results.py

@@ -2,6 +2,8 @@ from bs4 import BeautifulSoup
 import os
 import urllib.parse as urlparse
 from urllib.parse import parse_qs
+import re
+from bs4 import NavigableString
 
 
 SKIP_ARGS = ['ref_src', 'utm']
@@ -34,6 +36,45 @@ SITE_ALTS = {
 }
 
 
+def bold_search_terms(response: str, query: str) -> BeautifulSoup:
+    """Wraps all search terms in bold tags (<b>). If any terms are wrapped
+    in quotes, only that exact phrase will be made bold.
+
+    Args:
+        response: The initial response body for the query
+        query: The original search query
+
+    Returns:
+        BeautifulSoup: modified soup object with bold items
+    """
+    response = BeautifulSoup(response, 'html.parser')
+
+    def replace_any_case(element: NavigableString, target_word: str) -> None:
+        # Replace all instances of the word, but maintaining the same case in
+        # the replacement
+        element.replace_with(
+            element.replace(
+                target_word.lower(), f'<b>{target_word.lower()}</b>'
+            ).replace(
+                target_word.capitalize(), f'<b>{target_word.capitalize()}</b>'
+            ).replace(
+                target_word.title(), f'<b>{target_word.title()}</b>'
+            ).replace(
+                target_word.upper(), f'<b>{target_word.upper()}</b>'
+            )
+        )
+
+    # Split all words out of query, grouping the ones wrapped in quotes
+    for word in re.split(r'\s+(?=[^"]*(?:"[^"]*"[^"]*)*$)', query):
+        word = re.sub(r'[^A-Za-z0-9 ]+', '', word)
+        target = response.find_all(
+            text=re.compile(r'' + re.escape(word), re.I))
+        for nav_str in target:
+            replace_any_case(nav_str, word)
+
+    return response
+
+
 def has_ad_content(element: str) -> bool:
     """Inspects an HTML element for ad related content