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#ifndef __GRPCPP_CREDENTIALS_H_
#define __GRPCPP_CREDENTIALS_H_

#include <chrono>
#include <memory>

#include <grpc++/config.h>

struct grpc_credentials;

namespace grpc {

// grpc_credentials wrapper class. Typical use in C++ applications is limited
// to creating an instance using CredentialsFactory, and passing it down
// during channel construction.

class Credentials final {
 public:
  ~Credentials();

  // TODO(abhikumar): Specify a plugin API here to be implemented by
  // credentials that do not have a corresponding implementation in C.

 private:
  explicit Credentials(grpc_credentials*);
  grpc_credentials* GetRawCreds();

  friend class Channel;
  friend class CredentialsFactory;

  grpc_credentials* creds_;
};

// Options used to build SslCredentials
// pem_roots_cert is the buffer containing the PEM encoding of the server root
// certificates. If this parameter is empty, the default roots will be used.
// pem_private_key is the buffer containing the PEM encoding of the client's
// private key. This parameter can be empty if the client does not have a
// private key.
// pem_cert_chain is the buffer containing the PEM encoding of the client's
// certificate chain. This parameter can be empty if the client does not have
// a certificate chain.
struct SslCredentialsOptions {
  grpc::string pem_root_certs;
  grpc::string pem_private_key;
  grpc::string pem_cert_chain;
};

// Factory for building different types of Credentials
// The methods may return empty unique_ptr when credentials cannot be created.
// If a Credentials pointer is returned, it can still be invalid when used to
// create a channel. A lame channel will be created then and all rpcs will
// fail on it.
class CredentialsFactory {
 public:
  // Builds credentials with reasonable defaults.
  static std::unique_ptr<Credentials> DefaultCredentials();

  // Builds SSL Credentials given SSL specific options
  static std::unique_ptr<Credentials> SslCredentials(
      const SslCredentialsOptions& options);

  // Builds credentials for use when running in GCE
  static std::unique_ptr<Credentials> ComputeEngineCredentials();

  // Builds service account credentials.
  // json_key is the JSON key string containing the client's private key.
  // scope is a space-delimited list of the requested permissions.
  // token_lifetime is the lifetime of each token acquired through this service
  // account credentials. It should be positive and should not exceed
  // grpc_max_auth_token_lifetime or will be cropped to this value.
  static std::unique_ptr<Credentials> ServiceAccountCredentials(
      const grpc::string& json_key, const grpc::string& scope,
      std::chrono::seconds token_lifetime);

  // Builds IAM credentials.
  static std::unique_ptr<Credentials> IAMCredentials(
      const grpc::string& authorization_token,
      const grpc::string& authority_selector);

  // Combines two credentials objects into a composite credentials
  static std::unique_ptr<Credentials> ComposeCredentials(
      const std::unique_ptr<Credentials>& creds1,
      const std::unique_ptr<Credentials>& creds2);
};

}  // namespace grpc

#endif  // __GRPCPP_CREDENTIALS_H_