text: /*
   *
   * Copyright 2016 gRPC authors.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   *
   */
  
  #ifndef GRPC_CORE_LIB_SECURITY_CREDENTIALS_JWT_JWT_CREDENTIALS_H
  #define GRPC_CORE_LIB_SECURITY_CREDENTIALS_JWT_JWT_CREDENTIALS_H
  
  #include <grpc/support/port_platform.h>
  
  #include "src/core/lib/security/credentials/credentials.h"
  #include "src/core/lib/security/credentials/jwt/json_token.h"
  
  class grpc_service_account_jwt_access_credentials
      : public grpc_call_credentials {
   public:
    grpc_service_account_jwt_access_credentials(grpc_auth_json_key key,
                                                gpr_timespec token_lifetime);
    ~grpc_service_account_jwt_access_credentials() override;
  
    bool get_request_metadata(grpc_polling_entity* pollent,
                              grpc_auth_metadata_context context,
                              grpc_credentials_mdelem_array* md_array,
                              grpc_closure* on_request_metadata,
                              grpc_error** error) override;
  
    void cancel_get_request_metadata(grpc_credentials_mdelem_array* md_array,
                                     grpc_error* error) override;
  
    const gpr_timespec& jwt_lifetime() const { return jwt_lifetime_; }
    const grpc_auth_json_key& key() const { return key_; }
  
   private:
    void reset_cache();
  
    // Have a simple cache for now with just 1 entry. We could have a map based on
    // the service_url for a more sophisticated one.
    gpr_mu cache_mu_;
    struct {
      grpc_mdelem jwt_md = GRPC_MDNULL;
      char* service_url = nullptr;
      gpr_timespec jwt_expiration;
    } cached_;
  
    grpc_auth_json_key key_;
    gpr_timespec jwt_lifetime_;
  };
  
  // Private constructor for jwt credentials from an already parsed json key.
  // Takes ownership of the key.
  grpc_core::RefCountedPtr<grpc_call_credentials>
  grpc_service_account_jwt_access_credentials_create_from_auth_json_key(
      grpc_auth_json_key key, gpr_timespec token_lifetime);
  
  #endif /* GRPC_CORE_LIB_SECURITY_CREDENTIALS_JWT_JWT_CREDENTIALS_H */
  