CREATE TABLE audit_log (
  id bigserial PRIMARY KEY,
  table_name text,
  row_id bigint,
  action text,
  changed_at timestamptz DEFAULT now(),
  old_data jsonb,
  new_data jsonb
);

CREATE OR REPLACE FUNCTION audit_orders()
RETURNS trigger
LANGUAGE plpgsql
AS $$
BEGIN
  INSERT INTO audit_log (table_name, row_id, action, old_data, new_data)
  VALUES (
    TG_TABLE_NAME,
    COALESCE(NEW.id, OLD.id),
    TG_OP,
    CASE WHEN TG_OP IN ('UPDATE','DELETE') THEN to_jsonb(OLD) END,
    CASE WHEN TG_OP IN ('INSERT','UPDATE') THEN to_jsonb(NEW) END
  );
  RETURN COALESCE(NEW, OLD);
END;
$$;

CREATE TRIGGER trg_orders_audit
  AFTER INSERT OR UPDATE OR DELETE ON orders
  FOR EACH ROW EXECUTE FUNCTION audit_orders();