Standardisation 4

copienator/filesystem.py

@@ -41,3 +41,43 @@ def staged_directory(destination: str | Path):
             _remove_path(staging)
         if not committed and backup.exists() and not target.exists():
             backup.replace(target)
+
+
+@contextmanager
+def staged_files(destination: str | Path):
+    """Stage a set of files and merge them into a directory with rollback."""
+    target = Path(destination)
+    target.parent.mkdir(parents=True, exist_ok=True)
+    token = uuid.uuid4().hex
+    staging = target.parent / f".{target.name}.{token}.files.tmp"
+    backup = target.parent / f".{target.name}.{token}.files.backup"
+    staging.mkdir()
+    committed: list[Path] = []
+    try:
+        yield staging
+        staged = sorted(path for path in staging.iterdir() if path.is_file())
+        target.mkdir(parents=True, exist_ok=True)
+        backup.mkdir()
+        try:
+            for source in staged:
+                destination_path = target / source.name
+                if destination_path.exists() or destination_path.is_symlink():
+                    destination_path.replace(backup / source.name)
+                source.replace(destination_path)
+                committed.append(destination_path)
+        except Exception:
+            for destination_path in reversed(committed):
+                _remove_path(destination_path)
+            for saved in backup.iterdir():
+                saved.replace(target / saved.name)
+            raise
+        _remove_path(backup)
+    finally:
+        if staging.exists():
+            _remove_path(staging)
+        if backup.exists():
+            for saved in backup.iterdir():
+                destination_path = target / saved.name
+                if not destination_path.exists():
+                    saved.replace(destination_path)
+            _remove_path(backup)