diff --git a/command.py b/command.py
index 85917da..2f14af5 100644
--- a/command.py
+++ b/command.py
@@ -227,7 +227,7 @@ def cmd_play_file(bot, user, text, command, parameter, do_not_refresh_cache=Fals
 
     # if parameter is {index}
     if parameter.isdigit():
-        music_wrappers = get_cached_wrappers_from_dicts(bot, var.music_db.query_music(Condition()
+        music_wrappers = get_cached_wrappers_from_dicts(var.music_db.query_music(Condition()
                                                                                       .and_equal('type', 'file')
                                                                                       .order_by('path')
                                                                                       .limit(1)
@@ -240,7 +240,7 @@ def cmd_play_file(bot, user, text, command, parameter, do_not_refresh_cache=Fals
             return
 
     # assume parameter is a path
-    music_wrappers = get_cached_wrappers_from_dicts(bot, var.music_db.query_music(Condition().and_equal('path', parameter)), user)
+    music_wrappers = get_cached_wrappers_from_dicts(var.music_db.query_music(Condition().and_equal('path', parameter)), user)
     if music_wrappers:
         var.playlist.append(music_wrappers[0])
         log.info("cmd: add to playlist: " + music_wrappers[0].format_debug_string())
@@ -248,7 +248,7 @@ def cmd_play_file(bot, user, text, command, parameter, do_not_refresh_cache=Fals
         return
 
     # assume parameter is a folder
-    music_wrappers = get_cached_wrappers_from_dicts(bot, var.music_db.query_music(Condition()
+    music_wrappers = get_cached_wrappers_from_dicts(var.music_db.query_music(Condition()
                                                          .and_equal('type', 'file')
                                                          .and_like('path', parameter + '%')), user)
     if music_wrappers:
@@ -268,7 +268,7 @@ def cmd_play_file(bot, user, text, command, parameter, do_not_refresh_cache=Fals
                                        .and_equal('type', 'file')
                                        .and_like('path', '%' + parameter + '%', case_sensitive=False))
     if len(matches) == 1:
-        music_wrapper = get_cached_wrapper_from_dict(bot, matches[0], user)
+        music_wrapper = get_cached_wrapper_from_dict(matches[0], user)
         var.playlist.append(music_wrapper)
         log.info("cmd: add to playlist: " + music_wrapper.format_debug_string())
         bot.send_msg(constants.strings('file_added', item=music_wrapper.format_song_string()), text)
@@ -286,7 +286,7 @@ def cmd_play_file(bot, user, text, command, parameter, do_not_refresh_cache=Fals
     if do_not_refresh_cache:
         bot.send_msg(constants.strings("no_file"), text)
     else:
-        var.cache.build_dir_cache(bot)
+        var.cache.build_dir_cache()
         cmd_play_file(bot, user, text, command, parameter, do_not_refresh_cache=True)
 
 
@@ -304,7 +304,7 @@ def cmd_play_file_match(bot, user, text, command, parameter, do_not_refresh_cach
                 match = re.search(parameter, file)
                 if match and match[0]:
                     count += 1
-                    music_wrapper = get_cached_wrapper(dict_to_item(bot, file_dict), user)
+                    music_wrapper = get_cached_wrapper(dict_to_item(file_dict), user)
                     music_wrappers.append(music_wrapper)
                     log.info("cmd: add to playlist: " + music_wrapper.format_debug_string())
                     msgs.append("<li><b>{}</b> ({})</li>".format(music_wrapper.item().title,
@@ -323,7 +323,7 @@ def cmd_play_file_match(bot, user, text, command, parameter, do_not_refresh_cach
                 if do_not_refresh_cache:
                     bot.send_msg(constants.strings("no_file"), text)
                 else:
-                    var.cache.build_dir_cache(bot)
+                    var.cache.build_dir_cache()
                     cmd_play_file_match(bot, user, text, command, parameter, do_not_refresh_cache=True)
 
         except re.error as e:
@@ -338,7 +338,7 @@ def cmd_play_url(bot, user, text, command, parameter):
 
     url = util.get_url_from_input(parameter)
     if url:
-        music_wrapper = get_cached_wrapper_from_scrap(bot, type='url', url=url, user=user)
+        music_wrapper = get_cached_wrapper_from_scrap(type='url', url=url, user=user)
         var.playlist.append(music_wrapper)
 
         log.info("cmd: add to playlist: " + music_wrapper.format_debug_string())
@@ -364,7 +364,7 @@ def cmd_play_playlist(bot, user, text, command, parameter):
     items = get_playlist_info(url=url, start_index=offset, user=user)
     if len(items) > 0:
         items = var.playlist.extend(list(map(
-            lambda item: get_cached_wrapper_from_scrap(bot, **item), items)))
+            lambda item: get_cached_wrapper_from_scrap(**item), items)))
         for music in items:
             log.info("cmd: add to playlist: " + music.format_debug_string())
     else:
@@ -389,7 +389,7 @@ def cmd_play_radio(bot, user, text, command, parameter):
             parameter = parameter.split()[0]
         url = util.get_url_from_input(parameter)
         if url:
-            music_wrapper = get_cached_wrapper_from_scrap(bot, type='radio', url=url, user=user)
+            music_wrapper = get_cached_wrapper_from_scrap(type='radio', url=url, user=user)
 
             var.playlist.append(music_wrapper)
             log.info("cmd: add to playlist: " + music_wrapper.format_debug_string())
@@ -489,7 +489,7 @@ def cmd_rb_play(bot, user, text, command, parameter):
         url = radiobrowser.geturl_byid(parameter)
         if url != "-1":
             log.info('cmd: Found url: ' + url)
-            music_wrapper = get_cached_wrapper_from_scrap(bot, type='radio', url=url, name=stationname, user=user)
+            music_wrapper = get_cached_wrapper_from_scrap(type='radio', url=url, name=stationname, user=user)
             var.playlist.append(music_wrapper)
             log.info("cmd: add to playlist: " + music_wrapper.format_debug_string())
             bot.async_download_next()
@@ -870,7 +870,7 @@ def cmd_play_tags(bot, user, text, command, parameter):
 
     tags = parameter.split(",")
     tags = list(map(lambda t: t.strip(), tags))
-    music_wrappers = get_cached_wrappers_by_tags(bot, tags, user)
+    music_wrappers = get_cached_wrappers_by_tags(tags, user)
     for music_wrapper in music_wrappers:
         count += 1
         log.info("cmd: add to playlist: " + music_wrapper.format_debug_string())
@@ -991,7 +991,7 @@ def cmd_find_tagged(bot, user, text, command, parameter):
     song_shortlist = music_dicts
 
     for i, music_dict in enumerate(music_dicts):
-        item = dict_to_item(bot, music_dict)
+        item = dict_to_item(music_dict)
         count += 1
         if count > ITEMS_PER_PAGE:
             break
@@ -1024,7 +1024,7 @@ def cmd_search_library(bot, user, text, command, parameter):
 
     music_dicts = var.music_db.query_music_by_keywords(keywords)
     if music_dicts:
-        items = dicts_to_items(bot, music_dicts)
+        items = dicts_to_items(music_dicts)
         song_shortlist = music_dicts
 
         if len(items) == 1:
@@ -1061,7 +1061,7 @@ def cmd_shortlist(bot, user, text, command, parameter):
         music_wrappers = []
         for kwargs in song_shortlist:
             kwargs['user'] = user
-            music_wrapper = get_cached_wrapper_from_scrap(bot, **kwargs)
+            music_wrapper = get_cached_wrapper_from_scrap(**kwargs)
             music_wrappers.append(music_wrapper)
             log.info("cmd: add to playlist: " + music_wrapper.format_debug_string())
             msgs.append("<li>[{}] <b>{}</b></li>".format(music_wrapper.item().type, music_wrapper.item().title))
@@ -1085,7 +1085,7 @@ def cmd_shortlist(bot, user, text, command, parameter):
             if 1 <= index <= len(song_shortlist):
                 kwargs = song_shortlist[index - 1]
                 kwargs['user'] = user
-                music_wrapper = get_cached_wrapper_from_scrap(bot, **kwargs)
+                music_wrapper = get_cached_wrapper_from_scrap(**kwargs)
                 music_wrappers.append(music_wrapper)
                 log.info("cmd: add to playlist: " + music_wrapper.format_debug_string())
                 msgs.append("<li>[{}] <b>{}</b></li>".format(music_wrapper.item().type, music_wrapper.item().title))
@@ -1104,7 +1104,7 @@ def cmd_shortlist(bot, user, text, command, parameter):
         if 1 <= index <= len(song_shortlist):
             kwargs = song_shortlist[index - 1]
             kwargs['user'] = user
-            music_wrapper = get_cached_wrapper_from_scrap(bot, **kwargs)
+            music_wrapper = get_cached_wrapper_from_scrap(**kwargs)
             var.playlist.append(music_wrapper)
             log.info("cmd: add to playlist: " + music_wrapper.format_debug_string())
             bot.send_channel_msg(constants.strings('file_added', item=music_wrapper.format_song_string()))
@@ -1128,7 +1128,7 @@ def cmd_delete_from_library(bot, user, text, command, parameter):
             if 1 <= index <= len(song_shortlist):
                 music_dict = song_shortlist[index - 1]
                 if 'id' in music_dict:
-                    music_wrapper = get_cached_wrapper_by_id(bot, music_dict['id'], user)
+                    music_wrapper = get_cached_wrapper_by_id(music_dict['id'], user)
                     log.info("cmd: remove from library: " + music_wrapper.format_debug_string())
                     msgs.append("<li>[{}] <b>{}</b></li>".format(music_wrapper.item().type, music_wrapper.item().title))
                     var.playlist.remove_by_id(music_dict['id'])
@@ -1150,7 +1150,7 @@ def cmd_delete_from_library(bot, user, text, command, parameter):
         if 1 <= index <= len(song_shortlist):
             music_dict = song_shortlist[index - 1]
             if 'id' in music_dict:
-                music_wrapper = get_cached_wrapper_by_id(bot, music_dict['id'], user)
+                music_wrapper = get_cached_wrapper_by_id(music_dict['id'], user)
                 bot.send_msg(constants.strings('file_deleted', item=music_wrapper.format_song_string()), text)
                 log.info("cmd: remove from library: " + music_wrapper.format_debug_string())
                 var.playlist.remove_by_id(music_dict['id'])
@@ -1177,7 +1177,7 @@ def cmd_drop_database(bot, user, text, command, parameter):
 def cmd_refresh_cache(bot, user, text, command, parameter):
     global log
     if bot.is_admin(user):
-        var.cache.build_dir_cache(bot)
+        var.cache.build_dir_cache()
         log.info("command: Local file cache refreshed.")
         bot.send_msg(constants.strings('cache_refreshed'), text)
     else:
diff --git a/configuration.default.ini b/configuration.default.ini
index 38bd2ca..fea11d1 100644
--- a/configuration.default.ini
+++ b/configuration.default.ini
@@ -204,8 +204,8 @@ page_instruction = Page {current}/{total}. Use <i>!{command} {{page}}</i> to nav
 records_omitted = ...
 bad_url = Bad URL requested.
 preconfigurated_radio = Preconfigurated Radio available:
-unable_download = Error while downloading music...
-unable_play = Unable to play {item}. Removed from the library.
+unable_download = Unable to download <b>{item}</b>. Removed from the library.
+unable_play = Unable to play <b>{item}</b>. Removed from the library.
 which_command = Do you mean <br /> {commands}
 multiple_matches = File not found! Possible candidates:
 queue_contents = Items on the playlist:
diff --git a/interface.py b/interface.py
index adc5cd0..fd8c794 100644
--- a/interface.py
+++ b/interface.py
@@ -253,7 +253,7 @@ def post():
             log.debug("web: Post request from %s: %s" % (request.remote_addr, str(request.form)))
 
         if 'add_item_at_once' in request.form:
-            music_wrapper = get_cached_wrapper_by_id(var.bot, request.form['add_item_at_once'], user)
+            music_wrapper = get_cached_wrapper_by_id(request.form['add_item_at_once'], user)
             if music_wrapper:
                 var.playlist.insert(var.playlist.current_index + 1, music_wrapper)
                 log.info('web: add to playlist(next): ' + music_wrapper.format_debug_string())
@@ -265,7 +265,7 @@ def post():
                 abort(404)
 
         if 'add_item_bottom' in request.form:
-            music_wrapper = get_cached_wrapper_by_id(var.bot, request.form['add_item_bottom'], user)
+            music_wrapper = get_cached_wrapper_by_id(request.form['add_item_bottom'], user)
 
             if music_wrapper:
                 var.playlist.append(music_wrapper)
@@ -274,7 +274,7 @@ def post():
                 abort(404)
 
         elif 'add_item_next' in request.form:
-            music_wrapper = get_cached_wrapper_by_id(var.bot, request.form['add_item_next'], user)
+            music_wrapper = get_cached_wrapper_by_id(request.form['add_item_next'], user)
             if music_wrapper:
                 var.playlist.insert(var.playlist.current_index + 1, music_wrapper)
                 log.info('web: add to playlist(next): ' + music_wrapper.format_debug_string())
@@ -282,7 +282,7 @@ def post():
                 abort(404)
 
         elif 'add_url' in request.form:
-            music_wrapper = get_cached_wrapper_from_scrap(var.bot, type='url', url=request.form['add_url'], user=user)
+            music_wrapper = get_cached_wrapper_from_scrap(type='url', url=request.form['add_url'], user=user)
             var.playlist.append(music_wrapper)
 
             log.info("web: add to playlist: " + music_wrapper.format_debug_string())
@@ -292,7 +292,7 @@ def post():
 
         elif 'add_radio' in request.form:
             url = request.form['add_radio']
-            music_wrapper = get_cached_wrapper_from_scrap(var.bot, type='radio', url=url, user=user)
+            music_wrapper = get_cached_wrapper_from_scrap(type='radio', url=url, user=user)
             var.playlist.append(music_wrapper)
 
             log.info("cmd: add to playlist: " + music_wrapper.format_debug_string())
@@ -335,7 +335,7 @@ def post():
         elif 'delete_item_from_library' in request.form:
             _id = request.form['delete_item_from_library']
             var.playlist.remove_by_id(_id)
-            item = var.cache.get_item_by_id(var.bot, _id)
+            item = var.cache.get_item_by_id(_id)
 
             if os.path.isfile(item.uri()):
                 log.info("web: delete file " + item.uri())
@@ -345,7 +345,7 @@ def post():
             time.sleep(0.1)
 
         elif 'add_tag' in request.form:
-            music_wrappers = get_cached_wrappers_by_tags(var.bot, [request.form['add_tag']], user)
+            music_wrappers = get_cached_wrappers_by_tags([request.form['add_tag']], user)
             for music_wrapper in music_wrappers:
                 log.info("cmd: add to playlist: " + music_wrapper.format_debug_string())
             var.playlist.extend(music_wrappers)
@@ -373,7 +373,7 @@ def post():
                 var.db.set('playlist', 'playback_mode', "autoplay")
                 log.info("web: playback mode changed to autoplay.")
             if action == "rescan":
-                var.cache.build_dir_cache(var.bot)
+                var.cache.build_dir_cache()
                 log.info("web: Local file cache refreshed.")
             elif action == "stop":
                 if var.config.getboolean("bot", "clear_when_stop_in_oneshot", fallback=False) \
@@ -462,7 +462,7 @@ def library():
                 return ('', 204)
 
             if request.form['action'] == 'add':
-                items = dicts_to_items(var.bot, var.music_db.query_music(condition))
+                items = dicts_to_items(var.music_db.query_music(condition))
                 music_wrappers = []
                 for item in items:
                     music_wrapper = get_cached_wrapper(item, user)
@@ -474,10 +474,10 @@ def library():
 
                 return redirect("./", code=302)
             elif request.form['action'] == 'delete':
-                items = dicts_to_items(var.bot, var.music_db.query_music(condition))
+                items = dicts_to_items(var.music_db.query_music(condition))
                 for item in items:
                     var.playlist.remove_by_id(item.id)
-                    item = var.cache.get_item_by_id(var.bot, item.id)
+                    item = var.cache.get_item_by_id(item.id)
 
                     if os.path.isfile(item.uri()):
                         log.info("web: delete file " + item.uri())
@@ -500,7 +500,7 @@ def library():
                     current_page = 1
 
                 condition.limit(ITEM_PER_PAGE)
-                items = dicts_to_items(var.bot, var.music_db.query_music(condition))
+                items = dicts_to_items(var.music_db.query_music(condition))
 
                 results = []
                 for item in items:
@@ -531,7 +531,7 @@ def library():
         elif request.form['action'] == 'edit_tags':
             tags = list(dict.fromkeys(request.form['tags'].split(","))) # remove duplicated items
             if request.form['id'] in var.cache:
-                music_wrapper = get_cached_wrapper_by_id(var.bot, request.form['id'], user)
+                music_wrapper = get_cached_wrapper_by_id(request.form['id'], user)
                 music_wrapper.clear_tags()
                 music_wrapper.add_tags(tags)
                 var.playlist.version += 1
@@ -591,7 +591,7 @@ def upload():
         else:
             continue
 
-    var.cache.build_dir_cache(var.bot)
+    var.cache.build_dir_cache()
     var.music_db.manage_special_tags()
     log.info("web: Local file cache refreshed.")
 
@@ -603,8 +603,7 @@ def download():
     global log
 
     if 'id' in request.args and request.args['id']:
-        item = dicts_to_items(var.bot,
-                               var.music_db.query_music(
+        item = dicts_to_items(var.music_db.query_music(
                                    Condition().and_equal('id', request.args['id'])))[0]
 
         requested_file = item.uri()
@@ -618,7 +617,7 @@ def download():
 
     else:
         condition = build_library_query_condition(request.args)
-        items = dicts_to_items(var.bot, var.music_db.query_music(condition))
+        items = dicts_to_items(var.music_db.query_music(condition))
 
         zipfile = util.zipdir([item.uri() for item in items])
 
diff --git a/media/cache.py b/media/cache.py
index 6834820..68551a5 100644
--- a/media/cache.py
+++ b/media/cache.py
@@ -21,12 +21,12 @@ class MusicCache(dict):
         self.log = logging.getLogger("bot")
         self.dir_lock = threading.Lock()
 
-    def get_item_by_id(self, bot, id):  # Why all these functions need a bot? Because it need the bot to send message!
+    def get_item_by_id(self, id):
         if id in self:
             return self[id]
 
         # if not cached, query the database
-        item = self.fetch(bot, id)
+        item = self.fetch(id)
         if item is not None:
             self[id] = item
             self.log.debug("library: music found in database: %s" % item.format_debug_string())
@@ -36,7 +36,7 @@ class MusicCache(dict):
             # print(id)
             # raise KeyError("Unable to fetch item from the database! Please try to refresh the cache by !recache.")
 
-    def get_item(self, bot, **kwargs):
+    def get_item(self, **kwargs):
         # kwargs should provide type and id, and parameters to build the item if not existed in the library.
         # if cached
         if 'id' in kwargs:
@@ -48,31 +48,31 @@ class MusicCache(dict):
             return self[id]
 
         # if not cached, query the database
-        item = self.fetch(bot, id)
+        item = self.fetch(id)
         if item is not None:
             self[id] = item
             self.log.debug("library: music found in database: %s" % item.format_debug_string())
             return item
 
         # if not in the database, build one
-        self[id] = item_builders[kwargs['type']](bot, **kwargs)  # newly built item will not be saved immediately
+        self[id] = item_builders[kwargs['type']](**kwargs)  # newly built item will not be saved immediately
         return self[id]
 
-    def get_items_by_tags(self, bot, tags):
+    def get_items_by_tags(self, tags):
         music_dicts = self.db.query_music_by_tags(tags)
         items = []
         if music_dicts:
             for music_dict in music_dicts:
                 id = music_dict['id']
-                self[id] = dict_to_item(bot, music_dict)
+                self[id] = dict_to_item(music_dict)
                 items.append(self[id])
 
         return items
 
-    def fetch(self, bot, id):
+    def fetch(self, id):
         music_dict = self.db.query_music_by_id(id)
         if music_dict:
-            self[id] = dict_to_item(bot, music_dict)
+            self[id] = dict_to_item(music_dict)
             return self[id]
         else:
             return None
@@ -83,7 +83,7 @@ class MusicCache(dict):
         self.db.manage_special_tags()
 
     def free_and_delete(self, id):
-        item = self.get_item_by_id(None, id)
+        item = self.get_item_by_id(id)
         if item:
             self.log.debug("library: DELETE item from the database: %s" % item.format_debug_string())
 
@@ -104,14 +104,14 @@ class MusicCache(dict):
         self.log.debug("library: all cache freed")
         self.clear()
 
-    def build_dir_cache(self, bot):
+    def build_dir_cache(self):
         self.dir_lock.acquire()
         self.log.info("library: rebuild directory cache")
         files = util.get_recursive_file_list_sorted(var.music_folder)
         for file in files:
             results = self.db.query_music(Condition().and_equal('path', file))
             if not results:
-                item = item_builders['file'](bot, path=file)
+                item = item_builders['file'](path=file)
                 self.log.debug("library: music save into database: %s" % item.format_debug_string())
                 self.db.insert_music(item.to_dict())
 
@@ -207,33 +207,33 @@ def get_cached_wrappers(items, user):
 
     return wrappers
 
-def get_cached_wrapper_from_scrap(bot, **kwargs):
-    item = var.cache.get_item(bot, **kwargs)
+def get_cached_wrapper_from_scrap(**kwargs):
+    item = var.cache.get_item(**kwargs)
     if 'user' not in kwargs:
         raise KeyError("Which user added this song?")
     return CachedItemWrapper(var.cache, item.id, kwargs['type'], kwargs['user'])
 
-def get_cached_wrapper_from_dict(bot, dict_from_db, user):
+def get_cached_wrapper_from_dict(dict_from_db, user):
     if dict_from_db:
-        item = dict_to_item(bot, dict_from_db)
+        item = dict_to_item(dict_from_db)
         return get_cached_wrapper(item, user)
     return None
 
-def get_cached_wrappers_from_dicts(bot, dicts_from_db, user):
+def get_cached_wrappers_from_dicts(dicts_from_db, user):
     items = []
     for dict_from_db in dicts_from_db:
         if dict_from_db:
-            items.append(get_cached_wrapper_from_dict(bot, dict_from_db, user))
+            items.append(get_cached_wrapper_from_dict(dict_from_db, user))
 
     return items
 
-def get_cached_wrapper_by_id(bot, id, user):
-    item = var.cache.get_item_by_id(bot, id)
+def get_cached_wrapper_by_id(id, user):
+    item = var.cache.get_item_by_id(id)
     if item:
         return CachedItemWrapper(var.cache, item.id, item.type, user)
 
-def get_cached_wrappers_by_tags(bot, tags, user):
-    items = var.cache.get_items_by_tags(bot, tags)
+def get_cached_wrappers_by_tags(tags, user):
+    items = var.cache.get_items_by_tags(tags)
     ret = []
     for item in items:
         ret.append(CachedItemWrapper(var.cache, item.id, item.type, user))
diff --git a/media/file.py b/media/file.py
index 91f52a3..a0bcd70 100644
--- a/media/file.py
+++ b/media/file.py
@@ -7,7 +7,7 @@ import mutagen
 from PIL import Image
 
 import variables as var
-from media.item import BaseItem, item_builders, item_loaders, item_id_generators
+from media.item import BaseItem, item_builders, item_loaders, item_id_generators, ValidationFailedError
 import constants
 
 '''
@@ -22,12 +22,12 @@ type : file
 '''
 
 
-def file_item_builder(bot, **kwargs):
-    return FileItem(bot, kwargs['path'])
+def file_item_builder(**kwargs):
+    return FileItem(kwargs['path'])
 
 
-def file_item_loader(bot, _dict):
-    return FileItem(bot, "", _dict)
+def file_item_loader(_dict):
+    return FileItem("", _dict)
 
 
 def file_item_id_generator(**kwargs):
@@ -40,9 +40,9 @@ item_id_generators['file'] = file_item_id_generator
 
 
 class FileItem(BaseItem):
-    def __init__(self, bot, path, from_dict=None):
+    def __init__(self, path, from_dict=None):
         if not from_dict:
-            super().__init__(bot)
+            super().__init__()
             self.path = path
             self.title = ""
             self.artist = ""
@@ -53,7 +53,7 @@ class FileItem(BaseItem):
                 self.ready = "yes"
             self.keywords = self.title + " " + self.artist
         else:
-            super().__init__(bot, from_dict)
+            super().__init__(from_dict)
             self.artist = from_dict['artist']
             self.thumbnail = from_dict['thumbnail']
             if not self.validate():
@@ -71,8 +71,7 @@ class FileItem(BaseItem):
         if not os.path.exists(self.uri()):
             self.log.info(
                 "file: music file missed for %s" % self.format_debug_string())
-            self.send_client_message(constants.strings('file_missed', file=self.path))
-            return False
+            raise ValidationFailedError(constants.strings('file_missed', file=self.path))
 
         if not self.keywords:
             self.keywords = self.title + " " + self.artist # migrate from previous version
diff --git a/media/item.py b/media/item.py
index 44d9477..6c1fe33 100644
--- a/media/item.py
+++ b/media/item.py
@@ -5,12 +5,12 @@ item_loaders = {}
 item_id_generators = {}
 
 
-def example_builder(bot, **kwargs):
-    return BaseItem(bot)
+def example_builder(**kwargs):
+    return BaseItem()
 
 
-def example_loader(bot, _dict):
-    return BaseItem(bot, from_dict=_dict)
+def example_loader(_dict):
+    return BaseItem(from_dict=_dict)
 
 
 def example_id_generator(**kwargs):
@@ -22,22 +22,28 @@ item_loaders['base'] = example_loader
 item_id_generators['base'] = example_id_generator
 
 
-def dicts_to_items(bot, music_dicts):
+def dicts_to_items(music_dicts):
     items = []
     for music_dict in music_dicts:
         type = music_dict['type']
-        items.append(item_loaders[type](bot, music_dict))
+        items.append(item_loaders[type](music_dict))
     return items
 
 
-def dict_to_item(bot, music_dict):
+def dict_to_item(music_dict):
     type = music_dict['type']
-    return item_loaders[type](bot, music_dict)
+    return item_loaders[type](music_dict)
 
+class ValidationFailedError(Exception):
+    def __init__(self, msg = None):
+        self.msg = msg
+
+class PreparationFailedError(Exception):
+    def __init__(self, msg = None):
+        self.msg = msg
 
 class BaseItem:
-    def __init__(self, bot, from_dict=None):
-        self.bot = bot
+    def __init__(self, from_dict=None):
         self.log = logging.getLogger("bot")
         self.type = "base"
         self.title = ""
@@ -64,7 +70,7 @@ class BaseItem:
         return True if self.ready == "failed" else False
 
     def validate(self):
-        return False
+        raise ValidationFailedError(None)
 
     def uri(self):
         raise
@@ -104,10 +110,6 @@ class BaseItem:
     def display_type(self):
         return ""
 
-    def send_client_message(self, msg):
-        if self.bot:
-            self.bot.send_channel_msg(msg) # TODO: this is way too ugly. It mixed up bot with items. Change it into exceptions in the future.
-
     def to_dict(self):
         return {"type": self.type,
                 "id": self.id,
diff --git a/media/playlist.py b/media/playlist.py
index b515703..4f11da1 100644
--- a/media/playlist.py
+++ b/media/playlist.py
@@ -7,6 +7,7 @@ import time
 import variables as var
 from media.cache import CachedItemWrapper, get_cached_wrapper_from_dict, get_cached_wrapper_by_id
 from database import Condition
+from media.item import ValidationFailedError, PreparationFailedError
 
 
 def get_playlist(mode, _list=None, index=None):
@@ -196,7 +197,7 @@ class BasePlaylist(list):
             items.sort(key=lambda v: int(v[0]))
             for item in items:
                 item = json.loads(item[1])
-                music_wrapper = get_cached_wrapper_by_id(var.bot, item['id'], item['user'])
+                music_wrapper = get_cached_wrapper_by_id(item['id'], item['user'])
                 if music_wrapper:
                     music_wrappers.append(music_wrapper)
             self.from_list(music_wrappers, current_index)
@@ -224,33 +225,23 @@ class BasePlaylist(list):
             item = self.pending_items.pop()
             self.log.debug("playlist: validating %s" % item.format_debug_string())
             ver = item.version
-            if not item.validate() or item.is_failed():
+
+            try:
+                item.validate()
+            except ValidationFailedError as e:
                 self.log.debug("playlist: validating failed.")
+                if var.bot:
+                    var.bot.send_channel_msg(e.msg)
                 var.cache.free_and_delete(item.id)
                 self.remove_by_id(item.id)
                 continue
+
             if item.version > ver:
                 self.version += 1
 
         self.log.debug("playlist: validating finished.")
         self.validating_thread_lock.release()
 
-    def async_prepare(self, index):
-        th = threading.Thread(
-            target=self._prepare, name="Prepare-" + self[index].id[:7], args=(index,))
-        self.log.info(
-            "%s: start preparing item in thread: " % self[index].item().type + self[index].format_debug_string())
-        th.daemon = True
-        th.start()
-        return th
-
-    def _prepare(self, index):
-        item = self[index]
-        ver = item.version
-        item.prepare()
-        if item.version > ver:
-            self.version += 1
-
 
 class OneshotPlaylist(BasePlaylist):
     def __init__(self):
@@ -363,7 +354,7 @@ class AutoPlaylist(OneshotPlaylist):
                                                     Condition().and_like('tags', "%don't autoplay,%")))
 
         if dicts:
-            _list = [get_cached_wrapper_from_dict(var.bot, _dict, "AutoPlay") for _dict in dicts]
+            _list = [get_cached_wrapper_from_dict(_dict, "AutoPlay") for _dict in dicts]
             self.from_list(_list, -1)
 
     # def from_list(self, _list, current_index):
diff --git a/media/radio.py b/media/radio.py
index f7e10e5..d56bdb9 100644
--- a/media/radio.py
+++ b/media/radio.py
@@ -86,15 +86,15 @@ def get_radio_title(url):
     return url
 
 
-def radio_item_builder(bot, **kwargs):
+def radio_item_builder(**kwargs):
     if 'name' in kwargs:
-        return RadioItem(bot, kwargs['url'], kwargs['name'])
+        return RadioItem(kwargs['url'], kwargs['name'])
     else:
-        return RadioItem(bot, kwargs['url'], '')
+        return RadioItem(kwargs['url'], '')
 
 
-def radio_item_loader(bot, _dict):
-    return RadioItem(bot, "", "", _dict)
+def radio_item_loader(_dict):
+    return RadioItem("", "", _dict)
 
 
 def radio_item_id_generator(**kwargs):
@@ -107,9 +107,9 @@ item_id_generators['radio'] = radio_item_id_generator
 
 
 class RadioItem(BaseItem):
-    def __init__(self, bot, url, name="", from_dict=None):
+    def __init__(self, url, name="", from_dict=None):
         if from_dict is None:
-            super().__init__(bot)
+            super().__init__()
             self.url = url
             if not name:
                 self.title = get_radio_server_description(self.url)  # The title of the radio station
@@ -117,7 +117,7 @@ class RadioItem(BaseItem):
                 self.title = name
             self.id = hashlib.md5(url.encode()).hexdigest()
         else:
-            super().__init__(bot, from_dict)
+            super().__init__(from_dict)
             self.url = from_dict['url']
             self.title = from_dict['title']
 
diff --git a/media/url.py b/media/url.py
index 2ae011f..07cc797 100644
--- a/media/url.py
+++ b/media/url.py
@@ -12,18 +12,19 @@ import base64
 import constants
 import media
 import variables as var
-from media.item import BaseItem, item_builders, item_loaders, item_id_generators
+from media.item import BaseItem, item_builders, item_loaders, item_id_generators, ValidationFailedError, \
+    PreparationFailedError
 import media.system
 
 log = logging.getLogger("bot")
 
 
-def url_item_builder(bot, **kwargs):
-    return URLItem(bot, kwargs['url'])
+def url_item_builder(**kwargs):
+    return URLItem(kwargs['url'])
 
 
-def url_item_loader(bot, _dict):
-    return URLItem(bot, "", _dict)
+def url_item_loader(_dict):
+    return URLItem("", _dict)
 
 
 def url_item_id_generator(**kwargs):
@@ -36,10 +37,10 @@ item_id_generators['url'] = url_item_id_generator
 
 
 class URLItem(BaseItem):
-    def __init__(self, bot, url, from_dict=None):
+    def __init__(self, url, from_dict=None):
         self.validating_lock = threading.Lock()
         if from_dict is None:
-            super().__init__(bot)
+            super().__init__()
             self.url = url if url[-1] != "/" else url[:-1]
             self.title = ''
             self.duration = 0
@@ -47,7 +48,7 @@ class URLItem(BaseItem):
             self.path = var.tmp_folder + self.id + ".mp3"
             self.thumbnail = ''
         else:
-            super().__init__(bot, from_dict)
+            super().__init__(from_dict)
             self.url = from_dict['url']
             self.duration = from_dict['duration']
             self.path = from_dict['path']
@@ -77,10 +78,10 @@ class URLItem(BaseItem):
             self.validating_lock.release()
             return True
 
-        if self.ready == 'failed':
-            self.validating_lock.release()
-            return False
-
+        # if self.ready == 'failed':
+        #     self.validating_lock.release()
+        #     return False
+        #
         if os.path.exists(self.path):
             self.validating_lock.release()
             self.ready = "yes"
@@ -97,8 +98,7 @@ class URLItem(BaseItem):
             # Check the length, useful in case of playlist, it wasn't checked before)
             log.info(
                 "url: " + self.url + " has a duration of " + str(self.duration) + " min -- too long")
-            self.send_client_message(constants.strings('too_long', song=self.title))
-            return False
+            raise ValidationFailedError(constants.strings('too_long', song=self.title))
         else:
             self.ready = "validated"
             self.version += 1  # notify wrapper to save me
@@ -136,8 +136,7 @@ class URLItem(BaseItem):
         if not succeed:
             self.ready = 'failed'
             self.log.error("url: error while fetching info from the URL")
-            self.send_client_message(constants.strings('unable_download'))
-            return False
+            raise ValidationFailedError(constants.strings('unable_download', item=self.format_title()))
 
     def _download(self):
         media.system.clear_tmp_folder(var.tmp_folder, var.config.getint('bot', 'tmp_folder_max_size'))
@@ -190,10 +189,9 @@ class URLItem(BaseItem):
             else:
                 for f in glob.glob(base_path + "*"):
                     os.remove(f)
-                self.send_client_message(constants.strings('unable_download'))
                 self.ready = "failed"
                 self.downloading = False
-                return False
+                raise PreparationFailedError(constants.strings('unable_download', item=self.format_title()))
 
     def _read_thumbnail_from_file(self, path_thumbnail):
         if os.path.isfile(path_thumbnail):
diff --git a/media/url_from_playlist.py b/media/url_from_playlist.py
index 99b6007..96af820 100644
--- a/media/url_from_playlist.py
+++ b/media/url_from_playlist.py
@@ -51,16 +51,15 @@ def get_playlist_info(url, start_index=0, user=""):
     return items
 
 
-def playlist_url_item_builder(bot, **kwargs):
-    return PlaylistURLItem(bot,
-                           kwargs['url'],
+def playlist_url_item_builder(**kwargs):
+    return PlaylistURLItem(kwargs['url'],
                            kwargs['title'],
                            kwargs['playlist_url'],
                            kwargs['playlist_title'])
 
 
-def playlist_url_item_loader(bot, _dict):
-    return PlaylistURLItem(bot, "", "", "", "", _dict)
+def playlist_url_item_loader(_dict):
+    return PlaylistURLItem("", "", "", "", _dict)
 
 
 item_builders['url_from_playlist'] = playlist_url_item_builder
@@ -69,14 +68,14 @@ item_id_generators['url_from_playlist'] = url_item_id_generator
 
 
 class PlaylistURLItem(URLItem):
-    def __init__(self, bot, url, title, playlist_url, playlist_title, from_dict=None):
+    def __init__(self, url, title, playlist_url, playlist_title, from_dict=None):
         if from_dict is None:
-            super().__init__(bot, url)
+            super().__init__(url)
             self.title = title
             self.playlist_url = playlist_url
             self.playlist_title = playlist_title
         else:
-            super().__init__(bot, "", from_dict)
+            super().__init__("", from_dict)
             self.playlist_title = from_dict['playlist_title']
             self.playlist_url = from_dict['playlist_url']
 
diff --git a/mumbleBot.py b/mumbleBot.py
index ac3ec83..b71d914 100644
--- a/mumbleBot.py
+++ b/mumbleBot.py
@@ -24,6 +24,7 @@ import command
 import constants
 from database import SettingsDatabase, MusicDatabase
 import media.system
+from media.item import ValidationFailedError, PreparationFailedError
 from media.playlist import BasePlaylist
 from media.cache import MusicCache
 
@@ -393,14 +394,36 @@ class MumbleBot:
             # however, for performance consideration, youtube playlist won't be validate when added.
             # the validation has to be done here.
             next = var.playlist.next_item()
-            if next.validate():
+            try:
+                next.validate()
                 if not next.is_ready():
-                    var.playlist.async_prepare(var.playlist.next_index())
+                    self.async_download(next)
+
                 break
-            else:
+            except ValidationFailedError as e:
+                self.send_channel_msg(e.msg)
                 var.playlist.remove_by_id(next.id)
                 var.cache.free_and_delete(next.id)
 
+    def async_download(self, item):
+        th = threading.Thread(
+            target=self._download, name="Prepare-" + item.id[:7], args=(item,))
+        self.log.info("bot: start preparing item in thread: %s" % item.format_debug_string())
+        th.daemon = True
+        th.start()
+        return th
+
+    def _download(self, item):
+        ver = item.version
+        try:
+            item.prepare()
+        except PreparationFailedError as e:
+            self.send_channel_msg(e.msg)
+            return False
+
+        if item.version > ver:
+            var.playlist.version += 1
+
     # =======================
     #          Loop
     # =======================
@@ -460,13 +483,17 @@ class MumbleBot:
                 if not self.wait_for_ready: # if wait_for_ready flag is not true, move to the next song.
                     if var.playlist.next():
                         current = var.playlist.current_item()
-                        if current.validate():
+                        try:
+                            current.validate()
                             if not current.is_ready():
                                 self.log.info("bot: current music isn't ready, start downloading.")
-                                var.playlist.async_prepare(var.playlist.current_index)
-                                self.send_channel_msg(constants.strings('download_in_progress', item=current.format_title()))
+                                self.async_download(current)
+                                self.send_channel_msg(
+                                    constants.strings('download_in_progress', item=current.format_title()))
                             self.wait_for_ready = True
-                        else:
+
+                        except ValidationFailedError as e:
+                            self.send_channel_msg(e.msg)
                             var.playlist.remove_by_id(current.id)
                             var.cache.free_and_delete(current.id)
                     else:
@@ -480,6 +507,7 @@ class MumbleBot:
                             self.async_download_next()
                         elif current.is_failed():
                             var.playlist.remove_by_id(current.id)
+                            self.wait_for_ready = False
                         else:
                             self._loop_status = 'Wait for the next item to be ready'
                     else:
@@ -709,7 +737,7 @@ if __name__ == '__main__':
     command.register_all_commands(var.bot)
 
     if var.config.get("bot", "refresh_cache_on_startup", fallback=True):
-        var.cache.build_dir_cache(var.bot)
+        var.cache.build_dir_cache()
 
     # load playlist
     if var.config.getboolean('bot', 'save_playlist', fallback=True):