From 4a519d4dad5ffcd10bd9d46256cf1c57e585b87d Mon Sep 17 00:00:00 2001
From: Simon Sawert <simon@sawert.se>
Date: Sat, 26 Sep 2026 11:12:19 +0200
Subject: [PATCH] fix: add stub for CircuitPython `storage` module

- Add `storage` stub with `getmount`, `remount` and USB drive toggles
- Report the root mount as writable, `remount` updates the flag
- Add tests for the stub
---
 matrixbox_simulator/device/cpstubs/storage.py | 36 +++++++++++++++++++
 tests/test_storage_stub.py                    | 13 +++++++
 2 files changed, 49 insertions(+)
 create mode 100644 matrixbox_simulator/device/cpstubs/storage.py
 create mode 100644 tests/test_storage_stub.py

diff --git a/matrixbox_simulator/device/cpstubs/storage.py b/matrixbox_simulator/device/cpstubs/storage.py
new file mode 100644
index 0000000..28aedcd
--- /dev/null
+++ b/matrixbox_simulator/device/cpstubs/storage.py
@@ -0,0 +1,36 @@
+"""Stand-in for CircuitPython's `storage`. The simulated filesystem has no
+USB host competing for it, so it starts writable from code's point of view
+and USB drive toggling is a no-op.
+
+https://docs.circuitpython.org/en/latest/shared-bindings/storage/
+"""
+
+
+class VfsFat:
+    def __init__(self, readonly: bool = False) -> None:
+        self.readonly = readonly
+        self.label = "CIRCUITPY"
+
+
+_root_mount = VfsFat()
+
+
+def getmount(mount_path: str) -> VfsFat:
+    return _root_mount
+
+
+def remount(
+    mount_path: str,
+    readonly: bool = False,
+    *,
+    disable_concurrent_write_protection: bool = False,
+) -> None:
+    getmount(mount_path).readonly = readonly
+
+
+def disable_usb_drive() -> None:
+    pass
+
+
+def enable_usb_drive() -> None:
+    pass
diff --git a/tests/test_storage_stub.py b/tests/test_storage_stub.py
new file mode 100644
index 0000000..eba0f6f
--- /dev/null
+++ b/tests/test_storage_stub.py
@@ -0,0 +1,13 @@
+from matrixbox_simulator.device.cpstubs import storage
+
+
+def test_root_mount_starts_writable() -> None:
+    assert storage.getmount("/").readonly is False
+
+
+def test_remount_updates_readonly_flag() -> None:
+    storage.remount("/", True)
+    assert storage.getmount("/").readonly is True
+
+    storage.remount("/", False)
+    assert storage.getmount("/").readonly is False