base.hpp

#pragma once
 
/// @file userver/ugrpc/client/middlewares/middleware_base.hpp
/// @brief @copybrief ugrpc::client::MiddlewareBase
 
#include <memory>
#include <optional>
#include <vector>
 
#include <userver/components/loggable_component_base.hpp>
#include <userver/utils/function_ref.hpp>
 
#include <userver/ugrpc/client/middlewares/fwd.hpp>
#include <userver/ugrpc/client/rpc.hpp>
 
USERVER_NAMESPACE_BEGIN
 
namespace ugrpc::client {
 
/// @brief Context for middleware-specific data during gRPC call
///
/// It is created for each gRPC Call and it stores aux. data
/// used by middlewares. Each registered middleware is called by
/// `Middleware::Handle` with the context passed as an argument.
/// A middleware may access Call and initial request (if any) using the context.
class MiddlewareCallContext final {
 public:
  /// @cond
  MiddlewareCallContext(const Middlewares& middlewares, CallAnyBase& call,
                        utils::function_ref<void()> user_call,
                        const ::google::protobuf::Message* request);
  /// @endcond
 
  /// @brief Call next plugin, or gRPC handler if none
  void Next();
 
  /// @brief Get original gRPC Call
  CallAnyBase& GetCall();
 
  /// @brief Get initial gRPC request. For RPC w/o initial request
  /// returns nullptr.
  const ::google::protobuf::Message* GetInitialRequest();
 
 private:
  Middlewares::const_iterator middleware_;
  Middlewares::const_iterator middleware_end_;
  std::optional<utils::function_ref<void()>> user_call_;
 
  CallAnyBase& call_;
  const ::google::protobuf::Message* request_;
};
 
/// @ingroup userver_base_classes
///
/// @brief Base class for server gRPC middleware
class MiddlewareBase {
 public:
  MiddlewareBase();
  MiddlewareBase(const MiddlewareBase&) = delete;
  MiddlewareBase& operator=(const MiddlewareBase&) = delete;
  MiddlewareBase& operator=(MiddlewareBase&&) = delete;
 
  virtual ~MiddlewareBase();
 
  /// @brief Handles the gRPC request
  /// @note You MUST call context.Next() inside eventually, otherwise it will
  /// assert
  virtual void Handle(MiddlewareCallContext& context) const = 0;
};
 
/// @ingroup userver_base_classes
///
/// @brief Factory that creates specific client middlewares for clients
class MiddlewareFactoryBase {
 public:
  virtual ~MiddlewareFactoryBase();
 
  virtual std::shared_ptr<const MiddlewareBase> GetMiddleware(
      std::string_view client_name) const = 0;
};
 
using MiddlewareFactories =
    std::vector<std::shared_ptr<const MiddlewareFactoryBase>>;
 
/// @ingroup userver_base_classes
///
/// @brief Base class for client middleware component
class MiddlewareComponentBase : public components::LoggableComponentBase {
  using components::LoggableComponentBase::LoggableComponentBase;
 
 public:
  /// @brief Returns a middleware according to the component's settings
  virtual std::shared_ptr<const MiddlewareFactoryBase>
  GetMiddlewareFactory() = 0;
};
 
}  // namespace ugrpc::client
 
USERVER_NAMESPACE_END