From 18586a3f090263d3e8b320a3008b209ef56f2ab1 Mon Sep 17 00:00:00 2001
From: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
Date: Wed, 27 Mar 2019 14:32:40 +0100
Subject: [PATCH] params: move unit into datatypes, support for constant
 property

Change-Id: Ida7c8b5fd7d508d41d3b44ea98600f27f7f57dbd
Reviewed-on: https://forge.frm2.tum.de/review/20243
Tested-by: JenkinsCodeReview <bjoern_pedersen@frm2.tum.de>
Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
---
 secop/modules.py             |  2 +-
 secop/params.py              | 33 +++++++++++++++++++++++++++++----
 secop/protocol/dispatcher.py |  4 ++++
 test/test_params.py          |  2 +-
 4 files changed, 35 insertions(+), 6 deletions(-)

diff --git a/secop/modules.py b/secop/modules.py
index 85b388f..1ab5b71 100644
--- a/secop/modules.py
+++ b/secop/modules.py
@@ -204,7 +204,7 @@ class Module(object):
                 setattr(self, k, v)
             cfgdict.pop(k)
 
-        # Adopt units AFTER applying the cfgdict
+        # Modify units AFTER applying the cfgdict
         for k, v in self.accessibles.items():
             if not isinstance(v, Parameter):
                 continue
diff --git a/secop/params.py b/secop/params.py
index bc5e0a6..e3e8ddd 100644
--- a/secop/params.py
+++ b/secop/params.py
@@ -94,17 +94,18 @@ class Parameter(Accessible):
 
     # unit and datatype are not listed (handled separately)
     valid_properties = dict()
-    for prop in ('description', 'readonly', 'group', 'visibility', 'fmtstr', 'precision'):
+    for prop in ('description', 'readonly', 'group', 'visibility', 'constant'):
         valid_properties[prop] = prop
 
     def __init__(self,
                  description,
                  datatype=None,
                  default=unset_value,
-                 unit='',
                  readonly=True,
                  export=True,
                  poll=False,
+                 unit=u'',
+                 constant=None,
                  value=None, # swallow
                  timestamp=None, # swallow
                  optional=False,
@@ -121,10 +122,10 @@ class Parameter(Accessible):
         self.description = description
         self.datatype = datatype
         self.default = default
-        self.unit = unit
-        self.readonly = readonly
+        self.readonly = readonly if constant is None else True
         self.export = export
         self.optional = optional
+        self.constant = constant
 
         # note: auto-converts True/False to 1/0 which yield the expected
         # behaviour...
@@ -132,6 +133,14 @@ class Parameter(Accessible):
         for key in kwds:
             if key not in self.valid_properties:
                 raise ProgrammingError('%s is not a valid parameter property' % key)
+        if constant is not None:
+            # The value of the `constant` property should be the
+            # serialised version of the constant, or unset
+            constant = self.datatype.validate(constant)
+            self.constant = self.datatype.export_value(constant)
+        # helper. unit should be set on the datatype, not on the parameter!
+        if unit:
+            self.datatype.unit = unit
         self.__dict__.update(kwds)
         # internal caching: value and timestamp of last change...
         self.value = default
@@ -149,6 +158,16 @@ class Parameter(Accessible):
     def export_value(self):
         return self.datatype.export_value(self.value)
 
+    def _get_unit_(self):
+        return self.datatype.unit
+
+    def _set_unit_(self, unit):
+        self.datatype.unit = unit
+
+    unit = property(_get_unit_, _set_unit_)
+    del _get_unit_
+    del _set_unit_
+
 
 class Override(CountedObj):
     """Stores the overrides to be applied to a Parameter
@@ -177,7 +196,13 @@ class Override(CountedObj):
                 if key not in props and key not in type(obj).valid_properties:
                     raise ProgrammingError( "%s is not a valid %s property" %
                                            (key, type(obj).__name__))
+            if isinstance(obj, Parameter):
+                if u'constant' in self.kwds:
+                    constant = obj.datatype.validate(self.kwds.pop(u'constant'))
+                    self.kwds[u'constant'] = obj.datatype.export_value(constant)
+                    self.kwds[u'readonly'] = True
             props.update(self.kwds)
+
             if self.reorder:
                 props['ctr'] = self.ctr
             return type(obj)(**props)
diff --git a/secop/protocol/dispatcher.py b/secop/protocol/dispatcher.py
index e9cdd83..964133e 100644
--- a/secop/protocol/dispatcher.py
+++ b/secop/protocol/dispatcher.py
@@ -222,6 +222,8 @@ class Dispatcher(object):
         pobj = moduleobj.accessibles.get(pname, None)
         if pobj is None or not isinstance(pobj, Parameter):
             raise NoSuchParameterError('Module has no such parameter on this SEC-Node!')
+        if pobj.constant is not None:
+            raise ReadOnlyError('This parameter is constant and can not be accessed remotely.')
         if pobj.readonly:
             raise ReadOnlyError('This parameter can not be changed remotely.')
 
@@ -244,6 +246,8 @@ class Dispatcher(object):
         pobj = moduleobj.accessibles.get(pname, None)
         if pobj is None or not isinstance(pobj, Parameter):
             raise NoSuchParameterError('Module has no such parameter on this SEC-Node!')
+        if pobj.constant is not None:
+            raise ReadOnlyError('This parameter is constant and can not be accessed remotely.')
 
         readfunc = getattr(moduleobj, u'read_%s' % pname, None)
         if readfunc:
diff --git a/test/test_params.py b/test/test_params.py
index aa17499..3501582 100644
--- a/test/test_params.py
+++ b/test/test_params.py
@@ -41,7 +41,7 @@ def test_Command():
 
 def test_Parameter():
     p1 = Parameter('description1', datatype=BoolType, default=False)
-    p2 = Parameter('description2', datatype=BoolType, default=True)
+    p2 = Parameter('description2', datatype=BoolType, constant=True)
     assert p1 != p2
     assert p1.ctr != p2.ctr
     with pytest.raises(ValueError):