libmidi_io: backends: Add backend utils

Change-Id: I87dc9953c00fc087863312d626d2e78f5c3f0f6e

Author: SebaUbuntu

Diff for: libmidi_io/backends/__init__.py

@@ -4,3 +4,38 @@
 # SPDX-License-Identifier: LGPL-3.0-or-later
 #
 """MIDI I/O backends."""
+
+from importlib import import_module
+from pathlib import Path
+from pkgutil import iter_modules
+from typing import Dict
+
+from libmidi_io.types.backend import BackendModule
+
+backends_path = Path(__file__).parent
+
+def get_available_backends() -> Dict[str, BackendModule]:
+	"""Return a list of available MIDI I/O backends."""
+	backends = {}
+
+	for _, name, _ in iter_modules([str(backends_path)]):
+		try:
+			module = import_module(f'{__name__}.{name}')
+		except Exception:
+			continue
+
+		if not hasattr(module, 'get_devices') or not hasattr(module, 'Port'):
+			continue
+
+		backends[name] = module
+
+	return backends
+
+def get_backend(name: str) -> BackendModule:
+	"""Return a backend module by name."""
+	backends = get_available_backends()
+
+	if name not in backends:
+		raise ValueError(f"Unknown backend {name!r}")
+
+	return backends[name]