From 64a8cc035fd56c98593be6ed0e1bb3a8ca6c033f Mon Sep 17 00:00:00 2001
From: hitz_s <stephan.hitz@psi.ch>
Date: Thu, 24 Sep 2026 08:08:21 +0200
Subject: [PATCH] Add curent_foil to reference foil changer

---
 debye_bec/devices/reffoilchanger.py           | 69 ++++++++++++++++++-
 .../file_writer/debye_nexus_structure.py      | 12 +++-
 2 files changed, 78 insertions(+), 3 deletions(-)

diff --git a/debye_bec/devices/reffoilchanger.py b/debye_bec/devices/reffoilchanger.py
index 9bd5a9c..d3daee9 100644
--- a/debye_bec/devices/reffoilchanger.py
+++ b/debye_bec/devices/reffoilchanger.py
@@ -5,8 +5,9 @@ from __future__ import annotations
 import enum
 from typing import TYPE_CHECKING
 
+from bec_lib.logger import bec_logger
 from ophyd import Component as Cpt
-from ophyd import EpicsSignal, EpicsSignalRO, EpicsSignalWithRBV
+from ophyd import EpicsSignal, EpicsSignalRO, EpicsSignalWithRBV, Signal
 from ophyd.status import DeviceStatus
 from ophyd_devices.interfaces.base_classes.psi_device_base import PSIDeviceBase
 from ophyd_devices.utils.errors import DeviceStopError
@@ -14,6 +15,8 @@ from ophyd_devices.utils.errors import DeviceStopError
 if TYPE_CHECKING:
     from bec_lib.devicemanager import ScanInfo
 
+logger = bec_logger.logger
+
 
 class Status(int, enum.Enum):
     """Enum class for the status field"""
@@ -34,6 +37,63 @@ class OpMode(int, enum.Enum):
     ERRORMODE = 3
 
 
+N_FOILS = 38
+
+
+class CurrentFoilSignal(Signal):
+    """
+    Soft signal reflecting the description of the foil currently
+    inserted. Recomputed whenever 'ref_rb', 'status' or any of the
+    `foilNN` signals on the parent device change.
+    """
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self._subscribed = False
+
+    def _foil_signal(self):
+        if self.parent.status.get() != Status.INSERTED:
+            return None
+        idx = self.parent.ref_rb.get()
+        try:
+            idx = int(round(idx)) + 1
+        except (TypeError, ValueError):
+            return None
+        return getattr(self.parent, f"foil{idx:02d}", None)
+
+    def _compute(self):
+        sig = self._foil_signal()
+        if sig is None:
+            return ""
+        try:
+            return sig.get()
+        except Exception:
+            logger.exception("current_foil: failed to read %s", sig.name)
+            return ""
+
+    def get(self, **kwargs):
+        self._readback = self._compute()
+        return self._readback
+
+    def _on_upstream_change(self, value=None, timestamp=None, **kwargs):
+        old_value = self._readback
+        new_value = self._compute()
+        self._readback = new_value
+        self._run_subs(
+            sub_type=self.SUB_VALUE, old_value=old_value, value=new_value, timestamp=timestamp
+        )
+
+    def subscribe_to_parent_signals(self):
+        if self._subscribed:
+            return
+        self.parent.ref_rb.subscribe(self._on_upstream_change, run=False)
+        self.parent.status.subscribe(self._on_upstream_change, run=False)
+        for i in range(1, N_FOILS + 1):
+            getattr(self.parent, f"foil{i:02d}").subscribe(self._on_upstream_change, run=False)
+        self._subscribed = True
+        self._readback = self._compute()
+
+
 class Reffoilchanger(PSIDeviceBase):
     """Class for the ES2 Reference Foil Changer"""
 
@@ -71,8 +131,12 @@ class Reffoilchanger(PSIDeviceBase):
     )
     ref_set = Cpt(EpicsSignal, suffix="ES2-REF:SELN-SET", kind="config", doc="Requested reference")
     ref_rb = Cpt(
-        EpicsSignalRO, suffix="ES2-REF:SELN-RB", kind="config", doc="Currently set reference"
+        EpicsSignalRO,
+        suffix="ES2-REF:SELN-RB",
+        kind="config",
+        doc="Currently set reference (angle)",
     )
+    current_foil = Cpt(CurrentFoilSignal, value="", kind="normal", doc="Inserted reference")
 
     foil01 = Cpt(EpicsSignalRO, suffix="ES-REFFOIL:FOIL01.DESC", kind="config", doc="Foil 01")
     foil02 = Cpt(EpicsSignalRO, suffix="ES-REFFOIL:FOIL02.DESC", kind="config", doc="Foil 02")
@@ -115,6 +179,7 @@ class Reffoilchanger(PSIDeviceBase):
 
     def __init__(self, *, name: str, prefix: str = "", scan_info: ScanInfo | None = None, **kwargs):
         super().__init__(name=name, prefix=prefix, scan_info=scan_info, **kwargs)
+        self.current_foil.subscribe_to_parent_signals()
 
         self.foils = [
             self.foil01,
diff --git a/debye_bec/file_writer/debye_nexus_structure.py b/debye_bec/file_writer/debye_nexus_structure.py
index 79f1044..f647b29 100644
--- a/debye_bec/file_writer/debye_nexus_structure.py
+++ b/debye_bec/file_writer/debye_nexus_structure.py
@@ -236,7 +236,9 @@ class DebyeNexusStructure(DefaultFormat):
                 self.configuration.get("nidaq", {}).get("nidaq_add_chans", {}).get("value")
             )
 
-            rle = self.configuration.get("nidaq", {}).get("nidaq_enable_compression", {}).get("value")
+            rle = (
+                self.configuration.get("nidaq", {}).get("nidaq_enable_compression", {}).get("value")
+            )
 
             measurement_mode = entry.create_group(name="mode")
             measurement_mode.attrs["NX_class"] = "NX_CHAR"
@@ -288,6 +290,14 @@ class DebyeNexusStructure(DefaultFormat):
                     )
                     ref_trans.attrs["NX_class"] = "NX_CHAR"
 
+                    foil = (
+                        self.device_manager.devices.reffoilchanger.read(cached=True)
+                        .get("current_foil")
+                        .get("value")
+                    )
+                    ref_foil = ai2ai4_active.create_dataset(name="Reference", data=foil)
+                    ref_foil.attrs["NX_class"] = "NX_CHAR"
+
             main_data = entry.create_group(name="data")
             main_data.attrs["NX_class"] = "NXdata"