🎨 Improved logging

- One unlimited log file per session
- Up to 3 session logs kept at any time
- Log compressed via lzma

src/logging/session_file_handler.py

@@ -0,0 +1,70 @@
+import lzma
+from io import StringIO
+from logging import StreamHandler
+from lzma import FORMAT_XZ, PRESET_DEFAULT
+from os import PathLike
+from pathlib import Path
+
+
+class SessionFileHandler(StreamHandler):
+    """
+    A logging handler that writes to a new file on every app restart.
+    The files are compressed and older sessions logs are kept up to a small limit.
+    """
+
+    backup_count: int
+    filename: Path
+    log_file: StringIO = None
+
+    def create_dir(self) -> None:
+        """Create the log dir if needed"""
+        self.filename.parent.mkdir(exist_ok=True)
+
+    def rotate_file(self, file: Path):
+        """Rotate a file's number suffix and remove it if it's too old"""
+
+        # Skip non interesting dir entries
+        if not (file.is_file() and file.name.startswith(self.filename.name)):
+            return
+
+        # Compute the new number suffix
+        suffixes = file.suffixes
+        has_number = len(suffixes) != len(self.filename.suffixes)
+        current_number = 0 if not has_number else int(suffixes[-1][1:])
+        new_number = current_number + 1
+
+        # Rename with new number suffix
+        if has_number:
+            suffixes.pop()
+        suffixes.append(f".{new_number}")
+        stem = file.name.split(".", maxsplit=1)[0]
+        new_name = stem + "".join(suffixes)
+        print(f"Log file renamed: {file.name} -> {new_name}")
+        file = file.rename(file.with_name(new_name))
+
+        # Remove older files
+        if new_number > self.backup_count:
+            print(f"Log file deleted: {file.name}")
+            file.unlink()
+            return
+
+    def rotate(self) -> None:
+        """Rotate the numbered suffix on the log files and remove old ones"""
+        files = list(self.filename.parent.iterdir())
+        files.sort(key=lambda file: file.name, reverse=True)
+        for file in files:
+            self.rotate_file(file)
+
+    def __init__(self, filename: PathLike, backup_count: int = 2) -> None:
+        self.filename = Path(filename)
+        self.backup_count = backup_count
+        self.create_dir()
+        self.rotate()
+        self.log_file = lzma.open(
+            self.filename, "at", format=FORMAT_XZ, preset=PRESET_DEFAULT
+        )
+        super().__init__(self.log_file)
+
+    def close(self) -> None:
+        self.log_file.close()
+        super().close()