From d9f09b0d866f97a859c9b437474928e7a9e8c1b6 Mon Sep 17 00:00:00 2001
From: wakonig_k <klaus.wakonig@psi.ch>
Date: Fri, 8 Mar 2024 13:39:34 +0100
Subject: [PATCH] feat: added computed signal

---
 ophyd_devices/__init__.py             |   5 +-
 ophyd_devices/utils/dynamic_pseudo.py | 122 ++++++++++++++++++++++++++
 2 files changed, 125 insertions(+), 2 deletions(-)
 create mode 100644 ophyd_devices/utils/dynamic_pseudo.py

diff --git a/ophyd_devices/__init__.py b/ophyd_devices/__init__.py
index 8205c20..4fc1976 100644
--- a/ophyd_devices/__init__.py
+++ b/ophyd_devices/__init__.py
@@ -7,18 +7,19 @@ from .galil.sgalil_ophyd import SGalilMotor
 from .npoint.npoint import NPointAxis
 from .rt_lamni import RtFlomniMotor, RtLamniMotor
 from .sim.sim import SimCamera
-from .sim.sim import SimMonitor
 from .sim.sim import SimFlyer
 from .sim.sim import SimFlyer as SynFlyer
+from .sim.sim import SimMonitor
 from .sim.sim import SimMonitor as SynAxisMonitor
 from .sim.sim import SimMonitor as SynGaussBEC
 from .sim.sim import SimPositioner
 from .sim.sim import SimPositioner as SynAxisOPAAS
 from .sim.sim import SynDeviceOPAAS
+from .sim.sim_frameworks import DeviceProxy, H5ImageReplayProxy, SlitProxy
 from .sim.sim_signals import ReadOnlySignal
-from .sim.sim_frameworks import DeviceProxy, SlitProxy, H5ImageReplayProxy
 from .sim.sim_signals import ReadOnlySignal as SynSignalRO
 from .sls_devices.sls_devices import SLSInfo, SLSOperatorMessages
 from .smaract.smaract_ophyd import SmaractMotor
 from .utils.bec_device_base import BECDeviceBase
+from .utils.dynamic_pseudo import ComputedSignal
 from .utils.static_device_test import launch
diff --git a/ophyd_devices/utils/dynamic_pseudo.py b/ophyd_devices/utils/dynamic_pseudo.py
new file mode 100644
index 0000000..097ce74
--- /dev/null
+++ b/ophyd_devices/utils/dynamic_pseudo.py
@@ -0,0 +1,122 @@
+"""
+This module provides a class for creating a pseudo signal that is computed from other signals.
+"""
+
+from functools import reduce
+
+from ophyd import SignalRO
+from ophyd.ophydobj import Kind
+
+
+def rgetattr(obj, attr, *args):
+    """See https://stackoverflow.com/questions/31174295/getattr-and-setattr-on-nested-objects"""
+
+    def _getattr(obj, attr):
+        return getattr(obj, attr, *args)
+
+    return reduce(_getattr, [obj] + attr.split("."))
+
+
+class ComputedSignal(SignalRO):
+    """
+    A read-only signal that is computed from other signals. The compute method should be a string
+    representation of a function that takes the input signals as arguments and returns the computed
+    value. The input signals should be provided as a list of strings that represent the path to the
+    signal in the device manager.
+    """
+
+    def __init__(
+        self,
+        *,
+        name,
+        value=0,
+        timestamp=None,
+        device_manager=None,
+        parent=None,
+        labels=None,
+        kind=Kind.hinted,
+        tolerance=None,
+        rtolerance=None,
+        metadata=None,
+        cl=None,
+        attr_name=""
+    ):
+        super().__init__(
+            name=name,
+            value=value,
+            timestamp=timestamp,
+            parent=parent,
+            labels=labels,
+            kind=kind,
+            tolerance=tolerance,
+            rtolerance=rtolerance,
+            metadata=metadata,
+            cl=cl,
+            attr_name=attr_name,
+        )
+        self._device_manager = device_manager
+        self._input_signals = []
+        self._signal_subs = []
+        self._compute_method = None
+
+    def _signal_callback(self, *args, **kwargs):
+        self._run_subs(sub_type=self.SUB_VALUE, old_value=None, value=self.get())
+
+    @property
+    def compute_method(self):
+        """
+        Set the compute method for the pseudo signal
+
+        Args:
+            compute_method (str): The compute method to be used. This should be a string
+                representation of a function that takes the input signals as arguments
+                and returns the computed value.
+
+        """
+        return self._compute_method
+
+    @compute_method.setter
+    def compute_method(self, method: str):
+        if not method.startswith("def"):
+            raise ValueError("The compute method should be a string representation of a function")
+
+        # get the function name
+        function_name = method.split("(")[0].split(" ")[1]
+        # pylint: disable=exec-used
+        exec(method)
+        self._compute_method = locals()[function_name]
+
+    @property
+    def input_signals(self):
+        """
+        Set the input signals for the pseudo signal
+
+        Args:
+            *input_vars: The input signals to be used for the computation
+
+        """
+        return self._input_signals
+
+    @input_signals.setter
+    def input_signals(self, input_vars):
+        if self._signal_subs:
+            for signal, sub_id in self._signal_subs:
+                signal.unsubscribe(sub_id)
+        signals = []
+        for signal in input_vars:
+            if isinstance(signal, str):
+                target = signal.replace("_", ".")
+                parts = target.split(".")
+                target = ".".join([parts[0], "obj"] + parts[1:])
+                obj = rgetattr(self._device_manager.devices, target)
+                sub_id = obj.subscribe(self._signal_callback)
+                self._signal_subs.append((obj, sub_id))
+                signals.append(obj)
+            else:
+                signals.append(signal)
+        self._input_signals = signals
+
+    def get(self):
+        if self._compute_method:
+            return self._compute_method(*self._input_signals)
+        return None