Again fixed caching, also documentation

plugin-server.py

@@ -68,14 +68,22 @@ def plugin_file(plugin, path):
         return "File not found", 404
 
     mt, _encoding = mimetypes.guess_type(path)
+
+    # if in cache, load etag and content, set status code to 304
     if check_cache(full_path):
         result = redis.get(full_path + ":content")
+        etag = str(redis.get(full_path + ":etag"))
         status_code = 304
+
+    # else, make search-and-replace and save to redis (+etag)
     else:
         replace_with = "{}/{}".format(URL, plugin)
         status_code = 200
+        etag = generate_etag()
+
         with open(full_path, 'rb') as fp:
             content_bytes = fp.read()
+
         try:
             content = content_bytes.decode('UTF-8')
             result = content.replace(REPLACE_STRING, replace_with)
@@ -84,15 +92,21 @@ def plugin_file(plugin, path):
             result = content_bytes
 
         redis.set(full_path + ":content", result)
+        redis.set(full_path + ":etag", etag)
 
     resp = Response(result, mimetype=mt)
     resp.headers.add('Access-Control-Allow-Origin', '*')
-    resp.headers.add('ETag', generate_etag())
-    resp.status_code = status_code
+    resp.headers.add('ETag', etag)
 
-    # return everything if cached response is not allowed
+    # if browser does not have a cached etag -> 200
     if 'If-None-Match' not in request.headers:
         resp.status_code = 200
+    # then check if it is the latest etag, else -> 200
+    elif request.headers['If-None-Match'] != etag:
+        resp.status_code = 200
+    # else just set whatever was predetermined
+    else:
+        resp.status_code = status_code
 
     return resp