feat(rules): add preemptive warning when creating conflicting rules

src/obligations.sql

@@ -51,8 +51,8 @@ BEGIN
           FROM morbac.rules p
           WHERE p.org_id = p_org_id
             AND p.modality = 'prohibition'
-            AND p.activity IN (SELECT activity FROM morbac.get_effective_activities(r.activity))
-            AND p.view IN (SELECT view FROM morbac.get_effective_views(r.view))
+            AND p.activity IN (SELECT ea.activity FROM morbac.get_effective_activities(r.activity) ea)
+            AND p.view IN (SELECT ev.view FROM morbac.get_effective_views(r.view) ev)
             AND p.role_id IN (
                 SELECT role_id FROM morbac.get_comprehensive_roles(p_user_id, p_org_id)
             )
@@ -108,8 +108,8 @@ BEGIN
           FROM morbac.rules p
           WHERE p.org_id = p_org_id
             AND p.modality IN ('prohibition', 'obligation')
-            AND p.activity IN (SELECT activity FROM morbac.get_effective_activities(r.activity))
-            AND p.view IN (SELECT view FROM morbac.get_effective_views(r.view))
+            AND p.activity IN (SELECT ea.activity FROM morbac.get_effective_activities(r.activity) ea)
+            AND p.view IN (SELECT ev.view FROM morbac.get_effective_views(r.view) ev)
             AND p.role_id IN (
                 SELECT role_id FROM morbac.get_comprehensive_roles(p_user_id, p_org_id)
             )

src/validation.sql

@@ -1,6 +1,16 @@
 -- =============================================================================
 -- VALIDATION FUNCTIONS
 -- =============================================================================
+--
+-- Rule conflict detection (from Multi-OrBAC paper):
+-- Conflicts exist when two rules share the same (org, role, activity, view, context)
+-- but their modalities create a situation where one permanently overrides the other:
+--   - prohibition + permission    -> permission is dead (always overridden)
+--   - prohibition + obligation    -> obligation is always voided
+--   - prohibition + recommendation -> recommendation is always voided
+--   - obligation  + recommendation -> recommendation is always voided
+--
+-- Note: hierarchy-based overlaps are intentional design, not flagged here.
 
 -- Check if role assignment would violate Separation of Duty
 CREATE OR REPLACE FUNCTION morbac.check_sod_violation(
@@ -80,3 +90,85 @@ $$;
 
 COMMENT ON FUNCTION morbac.check_cardinality_violation(UUID, BOOLEAN) IS
 'Returns error message if cardinality constraint would be violated, NULL otherwise';
+
+-- Detect direct modality conflicts for a candidate rule
+CREATE OR REPLACE FUNCTION morbac.detect_rule_conflicts(
+    p_org_id     UUID,
+    p_role_id    UUID,
+    p_activity   TEXT,
+    p_view       TEXT,
+    p_context_id UUID,
+    p_modality   morbac.modality,
+    p_exclude_id UUID DEFAULT NULL  -- exclude self on UPDATE
+)
+RETURNS TABLE(
+    conflicting_rule_id  UUID,
+    conflicting_modality morbac.modality,
+    description          TEXT
+)
+LANGUAGE plpgsql
+STABLE
+AS $$
+BEGIN
+    RETURN QUERY
+    SELECT
+        r.id,
+        r.modality,
+        CASE
+            WHEN p_modality = 'prohibition'
+                THEN 'prohibition voids existing ' || r.modality::text
+            WHEN r.modality = 'prohibition'
+                THEN p_modality::text || ' will always be overridden by existing prohibition'
+            WHEN p_modality = 'obligation' AND r.modality = 'recommendation'
+                THEN 'obligation voids existing recommendation'
+            ELSE
+                'recommendation will always be overridden by existing obligation'
+        END
+    FROM morbac.rules r
+    WHERE r.org_id     = p_org_id
+      AND r.role_id    = p_role_id
+      AND r.activity   = p_activity
+      AND r.view       = p_view
+      AND r.context_id = p_context_id
+      AND r.modality  != p_modality
+      AND (p_exclude_id IS NULL OR r.id != p_exclude_id)
+      AND (
+          (p_modality = 'prohibition'    AND r.modality IN ('permission', 'obligation', 'recommendation'))
+          OR (r.modality = 'prohibition' AND p_modality IN ('permission', 'obligation', 'recommendation'))
+          OR (p_modality = 'obligation'     AND r.modality = 'recommendation')
+          OR (p_modality = 'recommendation' AND r.modality = 'obligation')
+      );
+END;
+$$;
+
+COMMENT ON FUNCTION morbac.detect_rule_conflicts(UUID, UUID, TEXT, TEXT, UUID, morbac.modality, UUID) IS
+'Returns rules that directly conflict with the given tuple due to modality precedence (prohibition > obligation > recommendation > permission).';
+
+-- Trigger: warn (non-blocking) when a new/updated rule conflicts with an existing one
+CREATE OR REPLACE FUNCTION morbac.trg_warn_rule_conflicts()
+RETURNS TRIGGER
+LANGUAGE plpgsql
+AS $$
+DECLARE
+    v_conflict RECORD;
+BEGIN
+    FOR v_conflict IN
+        SELECT * FROM morbac.detect_rule_conflicts(
+            NEW.org_id, NEW.role_id, NEW.activity, NEW.view, NEW.context_id, NEW.modality,
+            CASE WHEN TG_OP = 'UPDATE' THEN NEW.id ELSE NULL END
+        )
+    LOOP
+        RAISE WARNING 'Rule conflict: % (conflicts with rule %)',
+            v_conflict.description, v_conflict.conflicting_rule_id;
+    END LOOP;
+    RETURN NEW;
+END;
+$$;
+
+DROP TRIGGER IF EXISTS trg_rules_conflict_check ON morbac.rules;
+CREATE TRIGGER trg_rules_conflict_check
+BEFORE INSERT OR UPDATE ON morbac.rules
+FOR EACH ROW EXECUTE FUNCTION morbac.trg_warn_rule_conflicts();
+
+COMMENT ON FUNCTION morbac.trg_warn_rule_conflicts() IS
+'Trigger function: emits a WARNING (non-blocking) when a rule conflicts with an existing rule due to modality precedence.';