proxy_builder.h

#ifndef THIRD_PARTY_MILOTIC_INTERNAL_CC_PROXY_PROXY_BUILDER_H_
#define THIRD_PARTY_MILOTIC_INTERNAL_CC_PROXY_PROXY_BUILDER_H_

#include <cstddef>
#include <functional>
#include <list>
#include <memory>
#include <string>
#include <utility>
#include <vector>

#include "absl/functional/any_invocable.h"
#include "absl/status/status.h"
#include "absl/status/statusor.h"
#include "redfish_query_engine/file/uds.h"
#include "grpcpp/security/authorization_policy_provider.h"
#include "proxy.h"
#include "proxy_config.pb.h"
#include "redfish_plugin.h"
#include "resource_authz.h"
#include "ssh_client.h"
#include "voyager/deferrable_priority_queue.hpp"
#include "voyager/priority_queue.hpp"

namespace milotic {

namespace internal {
absl::StatusOr<milotic_grpc_proxy::Configuration> LoadConfig(
    const std::string& config_file_path);
}  // namespace internal

// A PluginFactory is a wrapper to register factory functions for plugins so
// that they can be linked to configuration items. Each plugin should have a
// corresponding configuration field in the milotic_grpc_proxy.Plugin message.
// The plugin should also create a static PluginFactory with a function that
// creates an instance of the plugin using the `Plugin` configuration proto.
// Usually, this is done using REGISTER_REDFISH_PLUGIN with the appropriate
// template parameters indicating the proto field and plugin type. See
// test_plugin.cc for an example.
class PluginFactory {
 public:
  using FactoryFn = std::function<std::unique_ptr<RedfishPlugin>(
      const milotic_grpc_proxy::Plugin&)>;
  // The constructor is not thread-safe. PluginFactory objects should usually be
  // global statics, so they are initialized in the same thread.
  explicit PluginFactory(FactoryFn&& f) {
    GetFunctionList().push_back(std::move(f));
  }

  PluginFactory(const PluginFactory&) = delete;

  static std::unique_ptr<RedfishPlugin> CreatePlugin(
      const milotic_grpc_proxy::Plugin& plugin);

  // TODO(shounak): This is much cleaner with static proto reflection, but that
  // is not yet available in OSS.
  template <auto Get, auto Has, typename PluginType>
  static std::unique_ptr<RedfishPlugin> Default(
      const milotic_grpc_proxy::Plugin& plugin_conf) {
    if (!(plugin_conf.*Has)()) return nullptr;
    return std::make_unique<PluginType>((plugin_conf.*Get)());
  }

 private:
  static std::vector<FactoryFn>& GetFunctionList() {
    static std::vector<FactoryFn> list;
    return list;
  }
};

#define REGISTER_REDFISH_PLUGIN(_name, _type)      \
  ::milotic::PluginFactory _name##_plugin_factory( \
      ::milotic::PluginFactory::Default<           \
          &::milotic_grpc_proxy::Plugin::_name,    \
          &::milotic_grpc_proxy::Plugin::has_##_name, _type>)

class ProxyBuilder {
 public:
  struct Options {
    using ExecutorFactory =
        absl::AnyInvocable<std::unique_ptr<voyager::Executor>(
            const milotic_grpc_proxy::QueueOptions& options) const>;
    using PermissionCheckerFactory =
        absl::AnyInvocable<std::unique_ptr<PermissionChecker>() const>;
    Options() : is_safe_uds_root(ecclesia::IsSafeUnixDomainSocketRoot) {}
    Options& SafeUdsRoot(
        std::function<bool(const std::string&)> new_is_safe_uds_root) {
      is_safe_uds_root = new_is_safe_uds_root;
      return *this;
    }
    Options& AddCredentials(Proxy::GrpcCredentials creds) {
      credentials.push_back(std::move(creds));
      return *this;
    }
    Options& AddAuthorizationPolicy(
        std::shared_ptr<
            grpc::experimental::AuthorizationPolicyProviderInterface>
            provider) {
      authorization_providers.push_back(std::move(provider));
      return *this;
    }
    template <typename SshClientType>
    Options& SetSshClientType() {
      ssh_client_factory = SshClientType::Create;
      return *this;
    }
    Options& SetExecutorFactory(ExecutorFactory new_executor_factory) {
      executor_factory = std::move(new_executor_factory);
      return *this;
    }
    Options& SetPermissionCheckerFactory(
        PermissionCheckerFactory new_permission_checker_factory) {
      permission_checker_factory = std::move(new_permission_checker_factory);
      return *this;
    }
    std::function<bool(const std::string&)> is_safe_uds_root;
    std::vector<Proxy::GrpcCredentials> credentials;
    std::vector<std::shared_ptr<
        grpc::experimental::AuthorizationPolicyProviderInterface>>
        authorization_providers;
    absl::AnyInvocable<absl::StatusOr<std::unique_ptr<SshClient>>(
        SshClient::CreationOptions options) const>
        ssh_client_factory;
    ExecutorFactory executor_factory =
        [](const milotic_grpc_proxy::QueueOptions& options) {
          return std::make_unique<voyager::DefaultExecutor>();
        };
    PermissionCheckerFactory permission_checker_factory;
  };

  ProxyBuilder(const ProxyBuilder&) = delete;
  ProxyBuilder& operator=(const ProxyBuilder&) = delete;
  // Movable to support factory functions
  ProxyBuilder(ProxyBuilder&&) = default;

  static absl::StatusOr<ProxyBuilder> CreateAndStart(
      const milotic_grpc_proxy::Configuration& config,
      const Options& options = Options());

  static absl::StatusOr<ProxyBuilder> CreateAndStart(
      const std::string& config_file_path, const Options& options = Options());

  ~ProxyBuilder();
  absl::Status Wait();
  void Shutdown();

  const voyager::DeferrablePriorityQueue& queue() const { return *queue_; }

 private:
  ProxyBuilder(size_t queue_size, int quantum,
               std::unique_ptr<voyager::Executor> executor)
      : queue_(std::make_unique<voyager::DeferrablePriorityQueue>(
            queue_size, std::move(executor))),
        quantum_(quantum) {}

  absl::Status AddProxy(
      const milotic_grpc_proxy::ProxyConfiguration& proxy_config,
      const Options& options);

  std::list<Proxy> proxies_;
  std::unique_ptr<voyager::DeferrablePriorityQueue> queue_;
  int quantum_;
};

}  // namespace milotic
#endif  // THIRD_PARTY_MILOTIC_INTERNAL_CC_PROXY_PROXY_BUILDER_H_