Add local decision log

internal/decision/engine.go

@@ -23,6 +23,12 @@ type Engine struct {
 	policy  *policy.Package
 	mu      sync.RWMutex
 	history map[string]api.DecisionEnvelope
+	log     DecisionRecorder
+}
+
+// DecisionRecorder persists decision envelopes.
+type DecisionRecorder interface {
+	Append(api.DecisionEnvelope) error
 }
 
 // ListAllowedRequest describes a deterministic list_allowed call.
@@ -69,6 +75,13 @@ func NewEngine(store *registry.Store, policyPackage *policy.Package) (*Engine, e
 	}, nil
 }
 
+// SetDecisionLog attaches a local decision recorder to the engine.
+func (e *Engine) SetDecisionLog(log DecisionRecorder) {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+	e.log = log
+}
+
 // Check evaluates one subject/action/resource request.
 func (e *Engine) Check(ctx context.Context, request api.CheckRequest) (api.DecisionEnvelope, error) {
 	normalized, facts := e.normalizeRequest(request)
@@ -79,7 +92,9 @@ func (e *Engine) Check(ctx context.Context, request api.CheckRequest) (api.Decis
 	}
 
 	decision := e.envelope(normalized, expectation, facts)
-	e.recordDecision(decision)
+	if err := e.recordDecision(decision); err != nil {
+		return api.DecisionEnvelope{}, err
+	}
 	return decision, nil
 }
 
@@ -286,10 +301,14 @@ func (e *Engine) envelope(request api.CheckRequest, expectation api.DecisionExpe
 	return envelope
 }
 
-func (e *Engine) recordDecision(decision api.DecisionEnvelope) {
+func (e *Engine) recordDecision(decision api.DecisionEnvelope) error {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 	e.history[decision.ID] = decision
+	if e.log != nil {
+		return e.log.Append(decision)
+	}
+	return nil
 }
 
 func (e *Engine) caringDecisionMetadata(descriptor *api.CaringAccessDescriptor, findings []api.CaringConformanceFinding) *api.CaringDecisionMetadata {

internal/decision/engine_test.go

@@ -9,6 +9,7 @@ import (
 
 	"gopkg.in/yaml.v3"
 
+	"github.com/netkingdom/flex-auth/internal/audit"
 	"github.com/netkingdom/flex-auth/internal/decision"
 	"github.com/netkingdom/flex-auth/internal/policy"
 	"github.com/netkingdom/flex-auth/internal/registry"
@@ -188,6 +189,40 @@ func TestExplainUsesRecordedDecision(t *testing.T) {
 	}
 }
 
+func TestCheckWritesDecisionLog(t *testing.T) {
+	engine := newTestEngine(t)
+	log := audit.NewJSONLDecisionLog(filepath.Join(t.TempDir(), "decisions.jsonl"))
+	engine.SetDecisionLog(log)
+
+	got, err := engine.Check(context.Background(), api.CheckRequest{
+		ID:      "check:logged-deny",
+		Subject: api.SubjectRef{ID: "user:alice"},
+		Action:  "read",
+		Resource: api.ResourceRef{
+			ID:     "document:missing",
+			Type:   "document",
+			System: "markitect-tool",
+		},
+	})
+	if err != nil {
+		t.Fatalf("Check: %v", err)
+	}
+	if got.Effect != api.DecisionEffectDeny {
+		t.Fatalf("got.Effect = %q; want deny", got.Effect)
+	}
+
+	decisions, err := log.ReadAll()
+	if err != nil {
+		t.Fatalf("ReadAll: %v", err)
+	}
+	if len(decisions) != 1 {
+		t.Fatalf("len(decisions) = %d; want 1", len(decisions))
+	}
+	if decisions[0].ID != got.ID || decisions[0].Effect != api.DecisionEffectDeny {
+		t.Fatalf("logged decision = %+v; want logged deny %s", decisions[0], got.ID)
+	}
+}
+
 func newTestEngine(t *testing.T) *decision.Engine {
 	t.Helper()