fix(Subtitle): Optionalise constructor args, add doc-string & checks

Some HLS playlists can have extremely limited information so to accommodate this we need to make the Subtitle track support having almost no information. This isn't ideal but it's really the only solution.

devine/core/tracks/subtitle.py

@@ -74,22 +74,22 @@ class Subtitle(Track):
                 return Subtitle.Codec.TimedTextMarkupLang
             raise ValueError(f"The Content Profile '{profile}' is not a supported Subtitle Codec")
 
-    def __init__(self, *args: Any, codec: Subtitle.Codec, cc: bool = False, sdh: bool = False, forced: bool = False,
+    def __init__(
-                 **kwargs: Any):
+        self,
+        *args: Any,
+        codec: Optional[Subtitle.Codec] = None,
+        cc: bool = False,
+        sdh: bool = False,
+        forced: bool = False,
+        **kwargs: Any
+    ):
         """
-        Information on Subtitle Types:
+        Create a new Subtitle track object.
-            https://bit.ly/2Oe4fLC (3PlayMedia Blog on SUB vs CC vs SDH).
-            However, I wouldn't pay much attention to the claims about SDH needing to
-            be in the original source language. It's logically not true.
-
-            CC == Closed Captions. Source: Basically every site.
-            SDH = Subtitles for the Deaf or Hard-of-Hearing. Source: Basically every site.
-            HOH = Exact same as SDH. Is a term used in the UK. Source: https://bit.ly/2PGJatz (ICO UK)
-
-            More in-depth information, examples, and stuff to look for can be found in the Parameter
-            explanation list below.
 
         Parameters:
+            codec: A Subtitle.Codec enum representing the subtitle format.
+                If not specified, MediaInfo will be used to retrieve the format
+                once the track has been downloaded.
             cc: Closed Caption.
                 - Intended as if you couldn't hear the audio at all.
                 - Can have Sound as well as Dialogue, but doesn't have to.
@@ -125,17 +125,46 @@ class Subtitle(Track):
                      no other way to reliably work with Forced subtitles where multiple
                      forced subtitles may be in the output file. Just know what to expect
                      with "forced" subtitles.
+
+        Note: If codec is not specified some checks may be skipped or assume a value.
+        Specifying as much information as possible is highly recommended.
+
+        Information on Subtitle Types:
+            https://bit.ly/2Oe4fLC (3PlayMedia Blog on SUB vs CC vs SDH).
+            However, I wouldn't pay much attention to the claims about SDH needing to
+            be in the original source language. It's logically not true.
+
+            CC == Closed Captions. Source: Basically every site.
+            SDH = Subtitles for the Deaf or Hard-of-Hearing. Source: Basically every site.
+            HOH = Exact same as SDH. Is a term used in the UK. Source: https://bit.ly/2PGJatz (ICO UK)
+
+            More in-depth information, examples, and stuff to look for can be found in the Parameter
+            explanation list above.
         """
         super().__init__(*args, **kwargs)
+
+        if not isinstance(codec, (Subtitle.Codec, type(None))):
+            raise TypeError(f"Expected codec to be a {Subtitle.Codec}, not {codec!r}")
+        if not isinstance(cc, (bool, int)) or (isinstance(cc, int) and cc not in (0, 1)):
+            raise TypeError(f"Expected cc to be a {bool} or bool-like {int}, not {cc!r}")
+        if not isinstance(sdh, (bool, int)) or (isinstance(sdh, int) and sdh not in (0, 1)):
+            raise TypeError(f"Expected sdh to be a {bool} or bool-like {int}, not {sdh!r}")
+        if not isinstance(forced, (bool, int)) or (isinstance(forced, int) and forced not in (0, 1)):
+            raise TypeError(f"Expected forced to be a {bool} or bool-like {int}, not {forced!r}")
+
         self.codec = codec
+
         self.cc = bool(cc)
         self.sdh = bool(sdh)
+        self.forced = bool(forced)
+
         if self.cc and self.sdh:
             raise ValueError("A text track cannot be both CC and SDH.")
-        self.forced = bool(forced)
+
-        if (self.cc or self.sdh) and self.forced:
+        if self.forced and (self.cc or self.sdh):
             raise ValueError("A text track cannot be CC/SDH as well as Forced.")
 
+        # TODO: Migrate to new event observer system
         # Called after Track has been converted to another format
         self.OnConverted: Optional[Callable[[Subtitle.Codec], None]] = None