add rules evaluation engine

Signed-off-by: tdruez <tdruez@aboutcode.org>

Author: tdruez

policy/engine.py

@@ -0,0 +1,91 @@
+#
+# Copyright (c) nexB Inc. and others. All rights reserved.
+# DejaCode is a trademark of nexB Inc.
+# SPDX-License-Identifier: AGPL-3.0-only
+# See https://github.com/aboutcode-org/dejacode for support or download.
+# See https://aboutcode.org for more information about AboutCode FOSS projects.
+#
+
+from django.utils import timezone
+
+from notification.models import fire_webhooks
+from policy.models import PolicyRule
+from policy.rules import RULE_REGISTRY
+from product_portfolio.models import ProductPolicyViolation
+
+
+def evaluate_rule(policy_rule, product):
+    """
+    Evaluate a single PolicyRule against a product, create or update the
+    ProductPolicyViolation record, and fire the notification event on new violations
+    or resolutions.
+    Returns the ProductPolicyViolation instance, or None if no violation exists.
+    """
+    rule_handler = RULE_REGISTRY.get(policy_rule.rule_type)
+    if not rule_handler:
+        return None
+
+    violation_count = rule_handler.count_violations(policy_rule, product)
+
+    lookup = {"policy_rule": policy_rule, "product": product, "resolved": False}
+
+    if violation_count > 0:
+        violation, created = ProductPolicyViolation.objects.get_or_create(
+            **lookup,
+            defaults={"dataspace": policy_rule.dataspace, "violation_count": violation_count},
+        )
+        if not created:
+            violation.violation_count = violation_count
+            violation.save()
+        if created and policy_rule.event_name:
+            fire_violation_event(policy_rule, product, violation_count)
+        return violation
+    else:
+        resolved_count = ProductPolicyViolation.objects.filter(**lookup).update(
+            resolved=True,
+            resolved_date=timezone.now(),
+        )
+        if resolved_count and policy_rule.event_name:
+            fire_resolution_event(policy_rule, product)
+        return None
+
+
+def evaluate_rules(dataspace, product):
+    """
+    Evaluate all active PolicyRules for the given product.
+    Returns the list of active ProductPolicyViolation instances.
+    """
+    violations = []
+    for policy_rule in PolicyRule.objects.scope(dataspace).active():
+        violation = evaluate_rule(policy_rule, product)
+        if violation:
+            violations.append(violation)
+
+    return violations
+
+
+def fire_violation_event(policy_rule, product, violation_count):
+    fire_webhooks(
+        policy_rule.event_name,
+        instance=None,
+        dataspace=policy_rule.dataspace,
+        payload_override={
+            "rule": policy_rule.name,
+            "rule_type": policy_rule.rule_type,
+            "violation_count": violation_count,
+            "product": str(product),
+        },
+    )
+
+
+def fire_resolution_event(policy_rule, product):
+    fire_webhooks(
+        policy_rule.event_name,
+        instance=None,
+        dataspace=policy_rule.dataspace,
+        payload_override={
+            "rule": policy_rule.name,
+            "status": "resolved",
+            "product": str(product),
+        },
+    )