From 562aae86f3e290c319ae9c792e9fecd821666f33 Mon Sep 17 00:00:00 2001
From: Thomas Sileo <t@a4.io>
Date: Sun, 25 Aug 2019 00:16:39 +0200
Subject: [PATCH] Code highlighting

---
 app.py                    |  2 ++
 requirements.txt          |  1 +
 templates/layout.html     |  1 +
 templates/utils.html      |  4 ++--
 utils/highlight.py        | 30 ++++++++++++++++++++++++++++++
 utils/template_filters.py |  6 ++++++
 6 files changed, 42 insertions(+), 2 deletions(-)
 create mode 100644 utils/highlight.py

diff --git a/app.py b/app.py
index bc16091..bf2f838 100644
--- a/app.py
+++ b/app.py
@@ -72,6 +72,7 @@ from core.shared import noindex
 from core.shared import paginated_query
 from utils.blacklist import is_blacklisted
 from utils.emojis import EMOJIS
+from utils.highlight import HIGHLIGHT_CSS
 from utils.key import get_secret_key
 from utils.template_filters import filters
 
@@ -153,6 +154,7 @@ def inject_config():
         else 0,
         me=ME,
         base_url=config.BASE_URL,
+        highlight_css=HIGHLIGHT_CSS,
     )
 
 
diff --git a/requirements.txt b/requirements.txt
index 3e81189..5c0a865 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -24,3 +24,4 @@ pyyaml
 pillow
 emoji-unicode
 html5lib
+Pygments
diff --git a/templates/layout.html b/templates/layout.html
index a71eab7..be29498 100644
--- a/templates/layout.html
+++ b/templates/layout.html
@@ -21,6 +21,7 @@
     width: 25px;
     height: 25px;
 }
+{{ highlight_css }}
 </style>
 {% block headers %}{% endblock %}
 </head>
diff --git a/templates/utils.html b/templates/utils.html
index caeace5..10a2303 100644
--- a/templates/utils.html
+++ b/templates/utils.html
@@ -77,7 +77,7 @@
     {% if obj | has_type(['Article', 'Page']) %}
         {{ obj.name }} <a href="{{ obj | url_or_id | get_url }}">{{ obj | url_or_id | get_url }}</a>
     {% elif obj | has_type('Question') %}
-        {{ obj.content | clean | replace_custom_emojis(obj) | safe }}
+        {{ obj.content | clean | replace_custom_emojis(obj) | code_highlight | safe }}
 
         
         <ul style="list-style:none;padding:0;">
@@ -146,7 +146,7 @@
 
 
     {% else %}
-	{{ obj.content | clean | replace_custom_emojis(obj) | safe }}
+	{{ obj.content | clean | replace_custom_emojis(obj) | code_highlight | safe }}
     {% endif %}
 	</div>
 
diff --git a/utils/highlight.py b/utils/highlight.py
new file mode 100644
index 0000000..74fa16f
--- /dev/null
+++ b/utils/highlight.py
@@ -0,0 +1,30 @@
+from functools import lru_cache
+
+from bs4 import BeautifulSoup
+from pygments import highlight as phighlight
+from pygments.formatters import HtmlFormatter
+from pygments.lexers import guess_lexer
+
+from config import THEME_STYLE
+from config import ThemeStyle
+
+_FORMATTER = HtmlFormatter(
+    style="default" if THEME_STYLE == ThemeStyle.LIGHT else "vim"
+)
+
+HIGHLIGHT_CSS = _FORMATTER.get_style_defs()
+
+
+@lru_cache(512)
+def highlight(html: str) -> str:
+    soup = BeautifulSoup(html, "html5lib")
+    for code in soup.find_all("code"):
+        if not code.parent.name == "pre":
+            continue
+        lexer = guess_lexer(code.text)
+        tag = BeautifulSoup(phighlight(code.text, lexer, _FORMATTER)).body.next
+        pre = code.parent
+        pre.replaceWith(tag)
+    out = soup.body
+    out.name = "div"
+    return str(out)
diff --git a/utils/template_filters.py b/utils/template_filters.py
index 11987d1..0e42231 100644
--- a/utils/template_filters.py
+++ b/utils/template_filters.py
@@ -21,6 +21,7 @@ from config import ID
 from config import MEDIA_CACHE
 from core.activitypub import _answer_key
 from utils import parse_datetime
+from utils.highlight import highlight
 from utils.media import Kind
 from utils.media import _is_img
 
@@ -47,6 +48,11 @@ def visibility_is_public(v: str) -> bool:
     return v in [ap.Visibility.PUBLIC.name, ap.Visibility.UNLISTED.name]
 
 
+@filters.app_template_filter()
+def code_highlight(content):
+    return highlight(content)
+
+
 @filters.app_template_filter()
 def emojify(text):
     return emoji_unicode.replace(