Merge pull request #60 from VianneyMI/57-expressions-and-operators-up…

…grades

57-expressions-and-operators-upgrades

changelog.md

@@ -1,5 +1,37 @@
 # Release Notes
 
+## 0.16.0
+
+
+### New Features
+
+* Created S object (represents $ sign since it is not a valid variable name in python) to store all MongoDB operators and to create references to fields
+* Created SS object (represents $$) to store aggregation variables and referenes to user variables
+* Interfaced a chunk of new operators(add, divide, multiply, pow, substract, cond, if_null, switch, millisecond, date_from_string, date_to_string, type_)
+* Integrated new operators in Expressions class
+
+
+### Refactoring
+
+* Redefined Expressions completely. Simplified and clarified how they can be used when using this package.
+* Removed index module that was at the root of the package (monggregate.index.py -> ø) 
+* Removed expressions subpackage (monggregate.expression -> ø)
+* Moved expressions fields module to the root of the package (monggregate.expressions.fields.py -> monggregate.fields.py)
+* Removed expressions aggregation_variables module (monggregate.expression.aggregation_variables.py -> ø)
+* Moved the enums that were defined in index to a more relevant place. Ex OperatorEnum is now in monggregate.operators.py
+
+### Breaking Changes
+
+* Operators now return python objects rather than expressions/statements. 
+  NOTE: The wording might change for clarification purposes.
+        statement might be renamed expression and resolve might renamed express
+        To do so, some arguments might need to be renamed in the operators
+* Expressions subpackage has been exploded and some parts have been deleted
+
+### Documentation
+
+* Updated readme to reflect changes in the packge. Readme now focuses on the recommended way to use the package and clarifies how to use MongoDB operators.
+
 ## 0.15.0
 
 ### Fixes

monggregate/__init__.py

@@ -1,7 +1,9 @@
 """App Package"""
 
+from monggregate.expressions import Expression
+from monggregate.dollar import S, SS
 from monggregate.pipeline import Pipeline
-from monggregate.expressions.expressions import Expression
+
 
 __version__ = "0.15.0"
 __author__ = "Vianney Mixtur"

monggregate/base.py

@@ -1,9 +1,13 @@
-"""Module defining the base class of the package"""
+"""
+Module defining the base classes of the package.
+
+All the classes of the package inherit from one of the classes defined in this module.
+"""
 
 # Standard Library imports
 #----------------------------
 from abc import ABC, abstractmethod
-from typing import Any
+from typing import Any, TypeGuard
 
 # 3rd Party imports
 # ---------------------------
@@ -15,7 +19,14 @@
 
 from humps.main import camelize
 
+class Singleton:
+    """Singleton metaclass"""
 
+    _instance = None
+    def __new__(cls, *args, **kwargs):
+        if not isinstance(cls._instance, cls):
+            cls._instance = object.__new__(cls, *args, **kwargs)
+        return cls._instance
 
 class BaseModel(pyd.BaseModel, ABC):
     """Mongreggate base class"""
@@ -45,10 +56,10 @@ class Config(pyd.BaseConfig):
         allow_population_by_field_name = True
         underscore_attrs_are_private = True
         smart_union = True
-        #alias_generator = camelize
+        alias_generator = camelize
 
 
-def isbasemodel(instance:Any)->bool:
+def isbasemodel(instance:Any)->TypeGuard[BaseModel]:
     """Returns true if instance is an instance of BaseModel"""
 
     return isinstance(instance, BaseModel)