also refactored core.meow into seperate files in hope that it'll help solve circular imports

core/base_rule.py

@@ -0,0 +1,81 @@
+
+"""
+This file contains the base MEOW rule defintion. This should be inherited from 
+for all rule instances.
+
+Author(s): David Marchant
+"""
+
+from typing import Any
+
+from core.base_pattern import BasePattern
+from core.base_recipe import BaseRecipe
+from core.correctness.vars import get_drt_imp_msg, VALID_RULE_NAME_CHARS
+from core.correctness.validation import valid_string, check_type, \
+    check_implementation
+
+
+class BaseRule:
+    # A unique identifier for the rule
+    name:str
+    # A pattern to be used in rule triggering
+    pattern:BasePattern
+    # A recipe to be used in rule execution
+    recipe:BaseRecipe
+    # The string name of the pattern class that can be used to create this rule
+    pattern_type:str=""
+    # The string name of the recipe class that can be used to create this rule
+    recipe_type:str=""
+    def __init__(self, name:str, pattern:BasePattern, recipe:BaseRecipe):
+        """BaseRule Constructor. This will check that any class inheriting 
+        from it implements its validation functions. It will then call these on
+        the input parameters."""
+        check_implementation(type(self)._is_valid_pattern, BaseRule)
+        check_implementation(type(self)._is_valid_recipe, BaseRule)
+        self.__check_types_set()
+        self._is_valid_name(name)
+        self.name = name
+        self._is_valid_pattern(pattern)
+        self.pattern = pattern
+        self._is_valid_recipe(recipe)
+        self.recipe = recipe
+        check_type(pattern, BasePattern, hint="BaseRule.pattern")
+        check_type(recipe, BaseRecipe, hint="BaseRule.recipe")
+        if pattern.recipe != recipe.name:
+            raise ValueError(f"Cannot create Rule {name}. Pattern "
+                f"{pattern.name} does not identify Recipe {recipe.name}. It "
+                f"uses {pattern.recipe}")
+
+    def __new__(cls, *args, **kwargs):
+        """A check that this base class is not instantiated itself, only 
+        inherited from"""
+        if cls is BaseRule:
+            msg = get_drt_imp_msg(BaseRule)
+            raise TypeError(msg)
+        return object.__new__(cls)
+
+    def _is_valid_name(self, name:str)->None:
+        """Validation check for 'name' variable from main constructor. Is 
+        automatically called during initialisation. This does not need to be 
+        overridden by child classes."""
+        valid_string(name, VALID_RULE_NAME_CHARS)
+
+    def _is_valid_pattern(self, pattern:Any)->None:
+        """Validation check for 'pattern' variable from main constructor. Must 
+        be implemented by any child class."""
+        pass
+
+    def _is_valid_recipe(self, recipe:Any)->None:
+        """Validation check for 'recipe' variable from main constructor. Must 
+        be implemented by any child class."""
+        pass
+
+    def __check_types_set(self)->None:
+        """Validation check that the self.pattern_type and self.recipe_type 
+        attributes have been set in a child class."""
+        if self.pattern_type == "":
+            raise AttributeError(f"Rule Class '{self.__class__.__name__}' "
+                "does not set a pattern_type.")
+        if self.recipe_type == "":
+            raise AttributeError(f"Rule Class '{self.__class__.__name__}' "
+                "does not set a recipe_type.")