Add local decision log

internal/audit/doc.go

@@ -1,6 +1,3 @@
 // Package audit persists compact decision envelopes. Denies, redactions,
-// exports, and emergency actions are always recorded; allows may be
-// sampled.
-//
-// Implementation lands in FLEX-WP-0002 P2.6.
+// exports, and emergency actions are always recorded; allows may be sampled.
 package audit

internal/audit/log.go

@@ -0,0 +1,94 @@
+package audit
+
+import (
+	"bufio"
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"sync"
+
+	"github.com/netkingdom/flex-auth/pkg/api"
+)
+
+// JSONLDecisionLog persists compact decision envelopes for local development.
+type JSONLDecisionLog struct {
+	path string
+	mu   sync.Mutex
+}
+
+// NewJSONLDecisionLog returns a JSONL-backed decision log.
+func NewJSONLDecisionLog(path string) *JSONLDecisionLog {
+	return &JSONLDecisionLog{path: path}
+}
+
+// Append writes one decision envelope as one JSON line.
+func (l *JSONLDecisionLog) Append(decision api.DecisionEnvelope) error {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+
+	if err := os.MkdirAll(filepath.Dir(l.path), 0o755); err != nil {
+		return fmt.Errorf("create decision log directory: %w", err)
+	}
+
+	file, err := os.OpenFile(l.path, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0o644)
+	if err != nil {
+		return fmt.Errorf("open decision log: %w", err)
+	}
+	defer file.Close()
+
+	data, err := json.Marshal(decision)
+	if err != nil {
+		return fmt.Errorf("marshal decision envelope: %w", err)
+	}
+	if _, err := file.Write(append(data, '\n')); err != nil {
+		return fmt.Errorf("write decision log: %w", err)
+	}
+	return nil
+}
+
+// ReadAll returns every decision envelope from the log in file order.
+func (l *JSONLDecisionLog) ReadAll() ([]api.DecisionEnvelope, error) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+
+	file, err := os.Open(l.path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil, nil
+		}
+		return nil, fmt.Errorf("open decision log: %w", err)
+	}
+	defer file.Close()
+
+	var decisions []api.DecisionEnvelope
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		if scanner.Text() == "" {
+			continue
+		}
+		var decision api.DecisionEnvelope
+		if err := json.Unmarshal(scanner.Bytes(), &decision); err != nil {
+			return nil, fmt.Errorf("unmarshal decision log line %d: %w", len(decisions)+1, err)
+		}
+		decisions = append(decisions, decision)
+	}
+	if err := scanner.Err(); err != nil {
+		return nil, fmt.Errorf("read decision log: %w", err)
+	}
+	return decisions, nil
+}
+
+// Find returns one decision envelope by id.
+func (l *JSONLDecisionLog) Find(id string) (api.DecisionEnvelope, bool, error) {
+	decisions, err := l.ReadAll()
+	if err != nil {
+		return api.DecisionEnvelope{}, false, err
+	}
+	for _, decision := range decisions {
+		if decision.ID == id {
+			return decision, true, nil
+		}
+	}
+	return api.DecisionEnvelope{}, false, nil
+}

internal/audit/log_test.go

@@ -0,0 +1,59 @@
+package audit_test
+
+import (
+	"path/filepath"
+	"testing"
+
+	"github.com/netkingdom/flex-auth/internal/audit"
+	"github.com/netkingdom/flex-auth/pkg/api"
+)
+
+func TestJSONLDecisionLogRoundTripsDecisions(t *testing.T) {
+	log := audit.NewJSONLDecisionLog(filepath.Join(t.TempDir(), "decisions.jsonl"))
+
+	first := api.DecisionEnvelope{
+		ID:     "decision:allow",
+		Effect: api.DecisionEffectAllow,
+		Reason: "reader_relation",
+		Subject: api.SubjectRef{
+			ID: "user:alice",
+		},
+		Resource: api.ResourceRef{
+			ID: "document:internal-note",
+		},
+		Provenance: api.DecisionProvenance{
+			Evaluator: "flex-auth/local",
+			Mode:      "standalone",
+		},
+	}
+	second := first
+	second.ID = "decision:deny"
+	second.Effect = api.DecisionEffectDeny
+	second.Reason = "no_matching_rule"
+
+	if err := log.Append(first); err != nil {
+		t.Fatalf("Append first: %v", err)
+	}
+	if err := log.Append(second); err != nil {
+		t.Fatalf("Append second: %v", err)
+	}
+
+	got, err := log.ReadAll()
+	if err != nil {
+		t.Fatalf("ReadAll: %v", err)
+	}
+	if len(got) != 2 {
+		t.Fatalf("len(got) = %d; want 2", len(got))
+	}
+	if got[0].ID != first.ID || got[1].ID != second.ID {
+		t.Fatalf("ids = %q/%q; want %q/%q", got[0].ID, got[1].ID, first.ID, second.ID)
+	}
+
+	found, ok, err := log.Find("decision:deny")
+	if err != nil {
+		t.Fatalf("Find: %v", err)
+	}
+	if !ok || found.Effect != api.DecisionEffectDeny {
+		t.Fatalf("Find decision:deny = %+v, %v; want deny", found, ok)
+	}
+}