adding wrapper class/design pattern to support plugins

transport/iowrapper.py

@@ -0,0 +1,47 @@
+"""
+This class is a wrapper around read/write classes of cloud,sql,nosql,other packages
+The wrapper allows for application of plugins as pre-post conditions
+"""    
+class IO:
+    """
+    Base wrapper class for read/write
+    """
+    def __init__(self,_agent,loader):
+        self._agent = _agent
+        self._loader = loader
+    def meta (self,**_args):
+        if hasattr(self._agent,'meta') :
+            return self._agent.meta(**_args)
+        return []
+
+    def close(self):
+        if hasattr(self._agent,'close') :
+            self._agent.close()
+    def apply(self):
+        """
+        applying pre/post conditions given a pipeline expression
+        """
+        for _pointer in self._loader :
+            _data = _pointer(_data)
+    def apply(self,_query):
+        if hasattr(self._agent,'apply') :
+            return self._agent.apply(_query)
+        return None
+class IReader(IO):
+    def __init__(self,_agent,pipeline=None):
+        super().__init__(_agent,pipeline)
+    def read(self,**_args):
+        _data = self._agent.read(**_args)
+        if self._loader and self._loader.ratio() > 0 :
+            _data = self._loader.apply(_data)
+        #
+        # output data 
+        return _data
+class IWriter(IO):
+    def __init__(self,_agent,pipeline=None):
+        super().__init__(_agent,pipeline)  
+    def write(self,_data,**_args):
+        if self._loader and self._loader.ratio() > 0 :
+            _data = self._loader.apply(_data)
+
+        self._agent.write(_data,**_args)