Support for context variables and constants

platypush/config/__init__.py

@@ -1,7 +1,9 @@
+import datetime
 import errno
 import logging
 import os
 import socket
+import time
 import yaml
 
 """ Config singleton instance """
@@ -31,6 +33,11 @@ class Config(object):
         os.path.join(os.sep, 'etc', 'platypush', 'config.yaml'),
     ]
 
+    _default_constants = {
+        'today': datetime.date.today().isoformat,
+        'now': datetime.datetime.now().isoformat,
+    }
+
     _workdir_location = os.path.join(os.environ['HOME'], '.local', 'share', 'platypush')
 
     def __init__(self, cfgfile=None):
@@ -68,6 +75,9 @@ class Config(object):
         self.plugins = {}
         self.event_hooks = {}
         self.procedures = {}
+        self.constants = {}
+
+        self._init_constants()
         self._init_components()
 
 
@@ -115,6 +125,14 @@ class Config(object):
             else:
                 self.plugins[key] = self._config[key]
 
+    def _init_constants(self):
+        if 'constants' in self._config:
+            self.constants = self._config['constants']
+
+        for (key,value) in self._default_constants.items():
+            self.constants[key] = value
+
+
     @staticmethod
     def get_backends():
         global _default_config_instance
@@ -139,6 +157,25 @@ class Config(object):
         if _default_config_instance is None: _default_config_instance = Config()
         return _default_config_instance.procedures
 
+    @staticmethod
+    def get_constants():
+        global _default_config_instance
+        if _default_config_instance is None: _default_config_instance = Config()
+        constants = {}
+
+        for name in _default_config_instance.constants.keys():
+            constants[name] = Config.get_constant(name)
+        return constants
+
+    @staticmethod
+    def get_constant(name):
+        global _default_config_instance
+        if _default_config_instance is None: _default_config_instance = Config()
+
+        if name not in _default_config_instance.constants: return None
+        value = _default_config_instance.constants[name]
+        return value() if callable(value) else value
+
     @staticmethod
     def get_default_pusher_backend():
         """

platypush/message/request/__init__.py

@@ -69,8 +69,15 @@ class Request(Message):
 
 
     def _expand_context(self, event_args=None, **context):
+        from platypush.config import Config
+
         if event_args is None: event_args = copy.deepcopy(self.args)
 
+        constants = Config.get_constants()
+        context['constants'] = {}
+        for (name,value) in constants.items():
+            context['constants'][name] = value
+
         keys = []
         if isinstance(event_args, dict):
             keys = event_args.keys()