no change, just more pep8-friendly, and use dict comprehension

[plcapi.git] / PLC / Accessor.py

diff --git a/PLC/Accessor.py b/PLC/Accessor.py
index 39e7872..e32add4 100644 (file)
--- a/PLC/Accessor.py
+++ b/PLC/Accessor.py
@@ -9,59 +9,109 @@
 # by the Factory, you need to restart your python instance / web server
 # as the cached information then becomes wrong
 
+from PLC.Logger import logger
+
 from PLC.TagTypes import TagTypes, TagType
 from PLC.Roles import Roles, Role
 
 # implementation
-class Accessor (object) :
-    """This is placeholder for storing accessor-related tag checkers.
-Methods in this class are defined by the accessors factory
+class Accessor(object):
+    """
+    This is a placeholder for storing accessor-related tag checkers.
+    Methods in this class are defined by the accessors factory
 
-This is implemented as a singleton, so we can cache results over time"""
+    Class is implemented as a singleton, so we can cache results over time
+    """
 
     _instance = None
 
-    def __init__ (self, api):
-        self.api=api
+    tag_locators = {}
+
+    def __init__(self, api):
+        self.api = api
         # 'tagname'=>'tag_id'
-        self.cache={}
+        self.cache = {}
+        self.hash_name_to_role = {role['name']: role for role in Roles(api)}
+
+    def has_cache(self, tagname):
+        return self.cache.has_key(tagname)
 
-    def has_cache (self,tagname): return self.cache.has_key(tagname)
-    def get_cache (self,tagname): return self.cache[tagname]
-    def set_cache (self,tagname,tag_id): self.cache[tagname]=tag_id
+    def get_cache(self, tagname):
+        return self.cache[tagname]
 
-    def locate_or_create_tag (self, tagname, category, description, roles):
+    def set_cache(self, tagname, tag_type):
+        self.cache[tagname] = tag_type
+
+    def locate_or_create_tag(self, tagname, category,
+                             description, roles, enforce=False):
         "search tag type from tagname & create if needed"
 
         # cached ?
-        if self.has_cache (tagname):
+        if self.has_cache(tagname):
             return self.get_cache(tagname)
         # search
-        tag_types = TagTypes (self.api, {'tagname':tagname})
+        tag_types = TagTypes(self.api, {'tagname': tagname})
         if tag_types:
             tag_type = tag_types[0]
+            # enforce should only be set by
+            # 'service plc start accessors' sequence
+            if enforce:
+                try:
+                    tag_type.update({'category': category,
+                                     'description': description})
+                    tag_type.sync()
+                    roles_to_add = set(roles).difference(set(tag_type['roles']))
+                    for rolename in roles_to_add:
+                        tag_type.add_role(self.hash_name_to_role[rolename])
+                    roles_to_delete = set(tag_type['roles']). difference(set(roles))
+                    for rolename in roles_to_delete:
+                        tag_type.remove_role(self.hash_name_to_role[rolename])
+                except:
+                    logger.exception(
+                        "WARNING, Could not enforce tag type, tagname={}\n"
+                        .format(tagname))
+
+
         else:
             # not found: create it
-            tag_type_fields = {'tagname':tagname,
-                               'category' :  category,
-                               'description' : description}
-            tag_type = TagType (self.api, tag_type_fields)
+            tag_type_fields = {'tagname': tagname,
+                               'category':  category,
+                               'description': description}
+            tag_type = TagType(self.api, tag_type_fields)
             tag_type.sync()
             for role in roles:
-                try: 
-                    role_obj=Roles (self.api, role)[0]
+                try:
+                    role_obj = Roles(self.api, role)[0]
                     tag_type.add_role(role_obj)
                 except:
                     # xxx todo find a more appropriate way of notifying this
-                    print "Accessor.locate_or_create_tag: Could not add role %r to tag_type %s"%(role,tagname)
-        tag_type_id = tag_type['tag_type_id']
-        self.set_cache(tagname,tag_type_id)
-        return tag_type_id
+                    logger.exception("Accessor.locate_or_create_tag: "
+                                     "Could not add role {} to tag_type {}"
+                                     .format(role,tagname))
+        self.set_cache(tagname, tag_type)
+        return tag_type
+
+    # a locator is a function that retrieves - or creates - a tag_type instance
+    @staticmethod
+    def register_tag_locator(name, tag_locator):
+        Accessor.tag_locators[name] = tag_locator
+
+    @staticmethod
+    def retrieve_tag_locator(name):
+        return Accessor.tag_locators[name]
 
+    # this is designed to be part of the 'service plc start' sequence
+    # it ensures the creation of all the tagtypes defined
+    # in the various accessors, and enforces consistency to the DB
+    # it's not easy to have define_accessors do this because at
+    # load-time as we do not have an instance of API yet
+    def run_all_tag_locators(self):
+        for (name, tag_locator) in Accessor.tag_locators.items():
+            tag_locator(self, enforce=True)
 
 ####################
 # make it a singleton so we can cache stuff in there over time
-def AccessorSingleton (api):
+def AccessorSingleton(api):
     if not Accessor._instance:
         Accessor._instance = Accessor(api)
     return Accessor._instance