idempotencyKeyInterceptor function

Interceptor idempotencyKeyInterceptor([ IdempotencyConfig config = const IdempotencyConfig() ])

Builds an Interceptor that injects an idempotency key into IDEMPOTENT unary calls.

Skips:

• Streaming RPCs (Connect-Dart cannot replay them).
• Methods without an idempotency_level annotation (the schema did not promise dedup; a key would be misleading).
• Methods that already carry the header (caller- or composed-op-supplied keys win, e.g. per-leg keys derived as {op_id}/{leg_index}).
• NO_SIDE_EFFECTS methods, unless includeNoSideEffects: true.

Implementation

Interceptor idempotencyKeyInterceptor([
  IdempotencyConfig config = const IdempotencyConfig(),
]) {
  final generator = config.keyGenerator ?? defaultIdempotencyKeyGenerator;
  return <I extends Object, O extends Object>(AnyFn<I, O> next) {
    return (Request<I, O> req) {
      if (req.spec.streamType != StreamType.unary) {
        return next(req);
      }
      final level = req.spec.idempotency;
      if (level == null) {
        return next(req);
      }
      if (level == Idempotency.noSideEffects && !config.includeNoSideEffects) {
        return next(req);
      }
      if (req.headers[config.headerName] != null) {
        return next(req);
      }
      req.headers[config.headerName] = generator();
      return next(req);
    };
  };
}