Use cache busting for css/js files

On app init, short hashes are generated from file checksums to use for
cache busting. These hashes are added into the full file name and used
to symlink to the actual file contents. These symlinks are loaded in the
jinja templates for each page, and can tell the browser to load a new
file if the hash changes.

This is only in place for css and js files, but can be extended in the
future for other file types if needed.

app/__init__.py

@@ -2,6 +2,7 @@ from app.filter import clean_query
 from app.request import send_tor_signal
 from app.utils.session import generate_user_key
 from app.utils.bangs import gen_bangs_json
+from app.utils.misc import gen_file_hash
 from flask import Flask
 from flask_session import Session
 import json
@@ -30,6 +31,9 @@ app.config['APP_ROOT'] = os.getenv(
 app.config['STATIC_FOLDER'] = os.getenv(
     'STATIC_FOLDER',
     os.path.join(app.config['APP_ROOT'], 'static'))
+app.config['BUILD_FOLDER'] = os.path.join(
+    app.config['STATIC_FOLDER'], 'build')
+app.config['CACHE_BUSTING_MAP'] = {}
 app.config['LANGUAGES'] = json.load(open(
     os.path.join(app.config['STATIC_FOLDER'], 'settings/languages.json')))
 app.config['COUNTRIES'] = json.load(open(
@@ -73,9 +77,6 @@ app.config['CSP'] = 'default-src \'none\';' \
                     'connect-src \'self\';' \
                     'form-action \'self\';'
 
-# Templating functions
-app.jinja_env.globals.update(clean_query=clean_query)
-
 if not os.path.exists(app.config['CONFIG_PATH']):
     os.makedirs(app.config['CONFIG_PATH'])
 
@@ -88,6 +89,31 @@ if not os.path.exists(app.config['BANG_PATH']):
 if not os.path.exists(app.config['BANG_FILE']):
     gen_bangs_json(app.config['BANG_FILE'])
 
+# Build new mapping of static files for cache busting
+if not os.path.exists(app.config['BUILD_FOLDER']):
+    os.makedirs(app.config['BUILD_FOLDER'])
+
+cache_busting_dirs = ['css', 'js']
+for cb_dir in cache_busting_dirs:
+    full_cb_dir = os.path.join(app.config['STATIC_FOLDER'], cb_dir)
+    for cb_file in os.listdir(full_cb_dir):
+        # Create hash from current file state
+        full_cb_path = os.path.join(full_cb_dir, cb_file)
+        cb_file_link = gen_file_hash(full_cb_dir, cb_file)
+        build_path = os.path.join(app.config['BUILD_FOLDER'], cb_file_link)
+        os.symlink(full_cb_path, build_path)
+
+        # Create mapping for relative path urls
+        map_path = build_path.replace(app.config['APP_ROOT'], '')
+        if map_path.startswith('/'):
+            map_path = map_path[1:]
+        app.config['CACHE_BUSTING_MAP'][cb_file] = map_path
+
+# Templating functions
+app.jinja_env.globals.update(clean_query=clean_query)
+app.jinja_env.globals.update(
+    cb_url=lambda f: app.config['CACHE_BUSTING_MAP'][f])
+
 Session(app)
 
 # Attempt to acquire tor identity, to determine if Tor config is available

app/static/css/system-theme.css

@@ -1,2 +0,0 @@
-@import "/static/css/light-theme.css" screen;
-@import "/static/css/dark-theme.css" screen and (prefers-color-scheme: dark);

app/templates/display.html

@@ -5,14 +5,21 @@
         <link rel="search" href="opensearch.xml" type="application/opensearchdescription+xml" title="Whoogle Search">
         <meta name="viewport" content="width=device-width, initial-scale=1.0">
         <meta name="referrer" content="no-referrer">
-        <link rel="stylesheet" href="static/css/input.css">
-        <link rel="stylesheet" href="static/css/search.css">
-        <link rel="stylesheet" href="static/css/variables.css">
-        <link rel="stylesheet" href="static/css/header.css">
-        {% if config.theme %}
-        <link rel="stylesheet" href="static/css/{{ config.theme }}-theme.css"/>
+        <link rel="stylesheet" href="{{ cb_url('input.css') }}">
+        <link rel="stylesheet" href="{{ cb_url('search.css') }}">
+        <link rel="stylesheet" href="{{ cb_url('variables.css') }}">
+        <link rel="stylesheet" href="{{ cb_url('header.css') }}">
+        {% if config.theme  %}
+            {% if config.theme == 'system' %}
+            <style>
+                @import "{{ cb_url('light-theme.css') }}" screen;
+                @import "{{ cb_url('dark-theme.css') }}" screen and (prefers-color-scheme: dark);
+            </style>
+            {% else %}
+            <link rel="stylesheet" href="{{ cb_url(config.theme + '-theme.css') }}"/>
+            {% endif %}
         {% else %}
-        <link rel="stylesheet" href="static/css/{{ 'dark' if config.dark else 'light' }}-theme.css"/>
+		<link rel="stylesheet" href="{{ cb_url(('dark' if config.dark else 'light') + '-theme.css') }}"/>
         {% endif %}
         <style>{{ config.style }}</style>
         <title>{{ clean_query(query) }} - Whoogle Search</title>
@@ -33,7 +40,7 @@
             <a id="gh-link" href="https://github.com/benbusby/whoogle-search">{{ translation['github-link'] }}</a>
         </p>
     </footer>
-	<script src="static/js/autocomplete.js"></script>
-	<script src="static/js/utils.js"></script>
-	<script src="static/js/keyboard.js"></script>
+    <script src="{{ cb_url('autocomplete.js') }}"></script>
+    <script src="{{ cb_url('utils.js') }}"></script>
+    <script src="{{ cb_url('keyboard.js') }}"></script>
 </html>

app/templates/header.html

@@ -62,4 +62,4 @@
     </header>
 {% endif %}
 
-<script type="text/javascript" src="static/js/header.js"></script>
+<script type="text/javascript" src="{{ cb_url('header.js') }}"></script>

app/templates/index.html

@@ -17,17 +17,24 @@
 		<meta name="referrer" content="no-referrer">
 		<meta name="msapplication-TileColor" content="#ffffff">
 		<meta name="msapplication-TileImage" content="static/img/favicon/ms-icon-144x144.png">
-		<script type="text/javascript" src="static/js/autocomplete.js"></script>
-		<script type="text/javascript" src="static/js/controller.js"></script>
+        <script type="text/javascript" src="{{ cb_url('autocomplete.js') }}"></script>
+        <script type="text/javascript" src="{{ cb_url('controller.js') }}"></script>
 		<link rel="search" href="opensearch.xml" type="application/opensearchdescription+xml" title="Whoogle Search">
 		<meta name="viewport" content="width=device-width, initial-scale=1.0">
-		<link rel="stylesheet" href="static/css/variables.css">
+        <link rel="stylesheet" href="{{ cb_url('variables.css') }}">
         {% if config.theme  %}
-		<link rel="stylesheet" href="static/css/{{ config.theme }}-theme.css"/>
+            {% if config.theme == 'system' %}
+            <style>
+                @import "{{ cb_url('light-theme.css') }}" screen;
+                @import "{{ cb_url('dark-theme.css') }}" screen and (prefers-color-scheme: dark);
+            </style>
+            {% else %}
+            <link rel="stylesheet" href="{{ cb_url(config.theme + '-theme.css') }}"/>
+            {% endif %}
         {% else %}
-		<link rel="stylesheet" href="static/css/{{ 'dark' if config.dark else 'light' }}-theme.css"/>
+		<link rel="stylesheet" href="{{ cb_url(('dark' if config.dark else 'light') + '-theme.css') }}"/>
         {% endif %}
-		<link rel="stylesheet" href="static/css/main.css">
+        <link rel="stylesheet" href="{{ cb_url('main.css') }}">
 		<noscript>
 			<style>
 				#main { display: inherit !important; }

app/templates/logo.html

@@ -1,4 +1,4 @@
-    <link rel="stylesheet" href="static/css/logo.css">
+    <link rel="stylesheet" href="{{ cb_url('logo.css') }}">
     <svg id="Layer_1" class="whoogle-svg" data-name="Layer 1" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 1028 254">
         <defs>
             <style>

app/utils/misc.py

@@ -0,0 +1,10 @@
+import hashlib
+import os
+
+
+def gen_file_hash(path: str, static_file: str) -> str:
+    file_contents = open(os.path.join(path, static_file), 'rb').read()
+    file_hash = hashlib.md5(file_contents).hexdigest()[:8]
+    filename_split = os.path.splitext(static_file)
+
+    return filename_split[0] + '.' + file_hash + filename_split[-1]

run

@@ -12,6 +12,8 @@ SUBDIR="${1:-app}"
 export APP_ROOT="$SCRIPT_DIR/$SUBDIR"
 export STATIC_FOLDER="$APP_ROOT/static"
 
+rm -rf $STATIC_FOLDER/build
+
 # Check for regular vs test run
 if [[ "$SUBDIR" == "test" ]]; then
     # Set up static files for testing