Add abstract Tagger, IPTCTagger implementation

phototag/tags.py

@@ -0,0 +1,102 @@
+from abc import ABC
+from pathlib import Path
+from typing import List, Set
+
+import iptcinfo3
+
+
+class Tagger(ABC):
+    """
+    A base class for all Taggers
+    """
+
+    def __init__(self, path: Path) -> None:
+        self.path = path
+        self.__saved = True
+        self.__current_tags = set(self.__load())
+
+    @property
+    def current_tags(self) -> Set[str]:
+        """The current tags in the tagger instance"""
+        return self.__current_tags
+
+    @property
+    def saved(self) -> bool:
+        """Whether the current tags have been saved to the filesystem"""
+        return self.__saved
+
+    def reload(self) -> None:
+        """
+        Reloads the tags from the filesystem. Discards any unsaved changes.
+        """
+        self.__current_tags = set(self.__load())
+        self.__saved = True
+
+    def save(self) -> None:
+        """
+        Saves the current tags to the filesystem.
+        """
+        self.save()
+        self.__saved = True
+
+    def add(self, tag: str) -> None:
+        """
+        Adds a tag to the tagger
+        :param tag: The tag to add
+        """
+        self.__current_tags.add(tag)
+
+    def remove(self, tag: str) -> None:
+        """
+        Removes a tag from the tagger
+        :param tag: The tag to remove
+        """
+        self.__current_tags.remove(tag)
+
+    def clear(self) -> None:
+        """
+        Clears all current tags
+        """
+        self.__current_tags.clear()
+
+    def extend(self, tags: List[str]) -> None:
+        """
+        Extends the current tags with a list of tags
+        :param tags: The tags to add
+        """
+        self.__current_tags.update(tags)
+
+    def __load(self) -> List[str]:
+        """
+        Filesystem loading implementation.
+        """
+        raise NotImplementedError()
+
+    def __save(self) -> None:
+        """
+        Filesystem saving implementation
+        """
+        raise NotImplementedError()
+
+
+class IPTCTagger(Tagger):
+    def __init__(self, path: Path) -> None:
+        super().__init__(path)
+
+        self.iptc = iptcinfo3.IPTCInfo(str(path))
+
+    def __load(self) -> List[str]:
+        """
+        Loads the tags from the filesystem
+        :return: The tags
+        """
+        return self.iptc['keywords']
+
+    def __save(self) -> None:
+        """
+        Saves the tags to the filesystem
+        """
+        self.iptc['keywords'] = list(self.__current_tags)
+        self.iptc.save()
+
+# TODO: XMPTagger implementation