Refactor embedding metadata to media

spotdl/metadata/embedder_base.py

@@ -0,0 +1,88 @@
+import os
+
+from abc import ABC
+from abc import abstractmethod
+
+class EmbedderBase(ABC):
+    """
+    The class must define the supported media file encoding
+    formats here using a static variable - such as:
+
+    >>> supported_formats = ("mp3", "opus", "flac")
+    """
+    supported_formats = ()
+
+    @abstractmethod
+    def __init__(self):
+        """
+        For every supported format, there must be a corresponding
+        method that applies metadata on this format.
+
+        Such as if mp3 is supported, there must exist a method named
+        `as_mp3` on this class that applies metadata on mp3 files.
+        """
+        # self.targets = { fmt: eval(str("self.as_" + fmt))
+        #                  for fmt in self.supported_formats }
+        #
+        # TODO: The above code seems to fail for some reason
+        #       I do not know.
+        self.targets = {}
+        for fmt in self.supported_formats:
+            # FIXME: Calling `eval` is dangerous here!
+            self.targets[fmt] = eval("self.as_" + fmt)
+
+    def get_encoding(self, path):
+        """
+        This method must determine the encoding for a local
+        audio file. Such as "mp3", "wav", "m4a", etc.
+        """
+        _, extension = os.path.splitext(path)
+        # Ignore the initial dot from file extension
+        return extension[1:]
+
+    def apply_metadata(self, path, metadata, encoding=None):
+        """
+        This method must automatically detect the media encoding
+        format from file path and embed the corresponding metadata
+        on the given file by calling an appropriate submethod.
+        """
+        if encoding is None:
+            encoding = self.get_encoding(path)
+        if encoding not in self.supported_formats:
+            raise TypeError(
+                'The input format ("{}") is not supported.'.format(
+                encoding,
+            ))
+        embed_on_given_format = self.targets[encoding]
+        embed_on_given_format(path, metadata)
+
+    def as_mp3(self, path, metadata):
+        """
+        Method for mp3 support. This method might be defined in
+        a subclass.
+
+        Other methods for additional supported formats must also
+        be declared here.
+        """
+        raise NotImplementedError
+
+    def as_opus(self, path, metadata):
+        """
+        Method for opus support. This method might be defined in
+        a subclass.
+
+        Other methods for additional supported formats must also
+        be declared here.
+        """
+        raise NotImplementedError
+
+    def as_flac(self, path, metadata):
+        """
+        Method for flac support. This method might be defined in
+        a subclass.
+
+        Other methods for additional supported formats must also
+        be declared here.
+        """
+        raise NotImplementedError
+