Code sync, security fixes

internal/observability/logging.go

@@ -0,0 +1,88 @@
+// Package observability provides structured logging, request/job correlation
+// IDs, and Prometheus-compatible application metrics.
+//
+// Logging policy: never log passwords, session tokens, API credentials, whole
+// uploaded documents or embedding vectors. Content fields are recorded as
+// lengths and hashes, not values.
+package observability
+
+import (
+	"context"
+	"log/slog"
+	"os"
+	"strings"
+)
+
+type ctxKey int
+
+const (
+	ctxKeyRequestID ctxKey = iota
+	ctxKeyJobID
+	ctxKeyLogger
+)
+
+// NewLogger builds the application logger.
+func NewLogger(level string, asJSON bool) *slog.Logger {
+	var lv slog.Level
+	switch strings.ToLower(level) {
+	case "debug":
+		lv = slog.LevelDebug
+	case "warn":
+		lv = slog.LevelWarn
+	case "error":
+		lv = slog.LevelError
+	default:
+		lv = slog.LevelInfo
+	}
+	opts := &slog.HandlerOptions{Level: lv}
+	var h slog.Handler
+	if asJSON {
+		h = slog.NewJSONHandler(os.Stdout, opts)
+	} else {
+		h = slog.NewTextHandler(os.Stdout, opts)
+	}
+	return slog.New(h)
+}
+
+// WithRequestID attaches a request correlation ID to ctx.
+func WithRequestID(ctx context.Context, id string) context.Context {
+	return context.WithValue(ctx, ctxKeyRequestID, id)
+}
+
+// RequestID returns the correlation ID attached to ctx, if any.
+func RequestID(ctx context.Context) string {
+	v, _ := ctx.Value(ctxKeyRequestID).(string)
+	return v
+}
+
+// WithJobID attaches a job correlation ID to ctx.
+func WithJobID(ctx context.Context, id string) context.Context {
+	return context.WithValue(ctx, ctxKeyJobID, id)
+}
+
+// JobID returns the job ID attached to ctx, if any.
+func JobID(ctx context.Context) string {
+	v, _ := ctx.Value(ctxKeyJobID).(string)
+	return v
+}
+
+// WithLogger attaches a logger to ctx.
+func WithLogger(ctx context.Context, l *slog.Logger) context.Context {
+	return context.WithValue(ctx, ctxKeyLogger, l)
+}
+
+// LoggerFrom returns the context logger, enriched with any correlation IDs.
+// It never returns nil.
+func LoggerFrom(ctx context.Context) *slog.Logger {
+	l, _ := ctx.Value(ctxKeyLogger).(*slog.Logger)
+	if l == nil {
+		l = slog.Default()
+	}
+	if id := RequestID(ctx); id != "" {
+		l = l.With("request_id", id)
+	}
+	if id := JobID(ctx); id != "" {
+		l = l.With("job_id", id)
+	}
+	return l
+}