Implemented a first and basic version of a Rete rule engine

src/sheerkarete/alpha.py

@@ -0,0 +1,39 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:  # pragma: no cover
+    from typing import List
+    from sheerkarete.join_node import JoinNode
+    from sheerkarete.common import WME
+
+
+class AlphaMemory:
+
+    def __init__(self, key, condition, items=None, successors=None):
+        """
+        Stores a set of WMEs (items). If activating an activated wme does not
+        exist, then it addes it. It also right activates all of its successors,
+        which correspond to beta nodes.
+        :param items: set of WMEs that match this memory
+        :param successors: list of JoinNode
+        """
+        self.key = key
+        self.condition = condition
+        self.items: List[WME] = items if items else []
+        self.successors: List[JoinNode] = successors if successors else []
+        self.reference_count = 0
+
+    def activation(self, wme: WME) -> None:
+        """
+        Adds the WME to the alpha memory and then right activates the children
+        in the beta network. Note, these are activated in reversed order to
+        prevent duplicate matches.
+        """
+        if not self.condition.test(wme):
+            return
+
+        self.items.append(wme)
+        wme.amems.append(self)
+        for child in reversed(self.successors):
+            child.right_activation(wme)