Make it possible to extract video id from url

pytchat/util/extract_video_id.py

@@ -0,0 +1,25 @@
+import re
+from .. exceptions import InvalidVideoIdException
+
+
+PATTERN = re.compile(r"((?<=(v|V)/)|(?<=be/)|(?<=(\?|\&)v=)|(?<=embed/))([\w-]+)")
+YT_VIDEO_ID_LENGTH = 11
+
+
+def extract_video_id(url_or_id: str) -> str:
+    ret = ''
+    if type(url_or_id) != str:
+        raise TypeError(f"{url_or_id}: URL or VideoID must be str, but {type(url_or_id)} is passed.")
+    if len(url_or_id) == YT_VIDEO_ID_LENGTH:
+        return url_or_id
+    match = re.search(PATTERN, url_or_id)
+    if match is None:
+        raise InvalidVideoIdException(url_or_id)
+    try:
+        ret = match.group(4)
+    except IndexError:
+        raise InvalidVideoIdException(url_or_id)
+
+    if ret is None or len(ret) != YT_VIDEO_ID_LENGTH:
+        raise InvalidVideoIdException(url_or_id)
+    return ret