package logging

import "context"

// requestIDKey is the unexported context key under which the HTTP layer
// stores the request id propagated from the X-Request-Id header.
type requestIDKey struct{}

// WithRequestID returns a child context that carries requestID. An empty
// requestID returns ctx unchanged so callers do not have to branch.
func WithRequestID(ctx context.Context, requestID string) context.Context {
	if ctx == nil || requestID == "" {
		return ctx
	}
	return context.WithValue(ctx, requestIDKey{}, requestID)
}

// RequestIDFromContext returns the request id stored on ctx by
// WithRequestID, or an empty string when no value is present.
func RequestIDFromContext(ctx context.Context) string {
	if ctx == nil {
		return ""
	}
	value, _ := ctx.Value(requestIDKey{}).(string)
	return value
}

// ContextAttrs returns slog key-value pairs that materialise the frozen
// `rtmanager/README.md` §Observability log fields `request_id`,
// `trace_id`, and `span_id` from ctx. Pairs whose value is empty are
// omitted so logs stay tight.
func ContextAttrs(ctx context.Context) []any {
	if ctx == nil {
		return nil
	}

	var attrs []any
	if requestID := RequestIDFromContext(ctx); requestID != "" {
		attrs = append(attrs, "request_id", requestID)
	}
	attrs = append(attrs, TraceAttrsFromContext(ctx)...)
	return attrs
}