absl::Status DependencyManager::validDecodeDependencies() {

  using DependencyTuple = std::tuple<const std::string&, int>;

  absl::flat_hash_set<DependencyTuple> satisfied;

  for (const auto& [name, dependencies] : filter_chain_) {

    for (const auto& requirement : dependencies.decode_required()) {

      if (!satisfied.contains({requirement.name(), requirement.type()})) {

        return absl::NotFoundError(absl::Substitute(

            "Dependency violation: filter '$0' requires a $1 named '$2'", name,

            Dependency::DependencyType_Name(requirement.type()), requirement.name()));

      }

    }

    for (const auto& provided : dependencies.decode_provided()) {

      satisfied.insert({provided.name(), provided.type()});

    }

  }

  return absl::OkStatus();

}