oauth_metadata_provider.h

#ifndef SOURCEMETA_CORE_OAUTH_METADATA_PROVIDER_H_
#define SOURCEMETA_CORE_OAUTH_METADATA_PROVIDER_H_
 
#ifndef SOURCEMETA_CORE_OAUTH_EXPORT
#include <sourcemeta/core/oauth_export.h>
#endif
 
#include <sourcemeta/core/oauth_metadata.h>
 
#include <chrono>      // std::chrono::seconds, std::chrono::system_clock
#include <functional>  // std::function
#include <memory>      // std::shared_ptr
#include <mutex>       // std::mutex
#include <optional>    // std::optional
#include <string>      // std::string
#include <string_view> // std::string_view
 
namespace sourcemeta::core {
 
#if defined(_MSC_VER)
#pragma warning(disable : 4251)
#endif

class SOURCEMETA_CORE_OAUTH_EXPORT OAuthMetadataProvider {
public:
  struct FetchResult {
    std::string body;
    std::optional<std::chrono::seconds> max_age;
  };

  using Fetcher =
      std::function<std::optional<FetchResult>(std::string_view url)>;

  using Clock = std::function<std::chrono::system_clock::time_point()>;

  struct Options {
    std::chrono::seconds fallback_ttl{std::chrono::hours{1}};
    std::chrono::seconds minimum_ttl{std::chrono::minutes{5}};
    std::chrono::seconds maximum_ttl{std::chrono::hours{24}};
  };

  OAuthMetadataProvider(std::string issuer, const OAuthWellKnownKind kind,
                        Fetcher fetcher);
  OAuthMetadataProvider(std::string issuer, const OAuthWellKnownKind kind,
                        Fetcher fetcher, Options options);
  OAuthMetadataProvider(std::string issuer, const OAuthWellKnownKind kind,
                        Fetcher fetcher, Options options, Clock clock);

  OAuthMetadataProvider(const OAuthMetadataProvider &) = delete;
  auto operator=(const OAuthMetadataProvider &)
      -> OAuthMetadataProvider & = delete;
  OAuthMetadataProvider(OAuthMetadataProvider &&) = delete;
  auto operator=(OAuthMetadataProvider &&) -> OAuthMetadataProvider & = delete;

  [[nodiscard]] auto metadata() -> std::shared_ptr<const OAuthServerMetadata>;

  [[nodiscard]] auto refresh() -> std::shared_ptr<const OAuthServerMetadata>;
 
private:
  auto install_locked(const OAuthWellKnownKind kind,
                      const std::chrono::system_clock::time_point now) -> bool;
  auto fetch_and_install_locked(const std::chrono::system_clock::time_point now)
      -> bool;
 
  const std::string issuer_;
  const OAuthWellKnownKind kind_;
  const Fetcher fetcher_;
  const Options options_;
  const Clock clock_;
  std::mutex mutex_;
  std::shared_ptr<const OAuthServerMetadata> metadata_;
  std::chrono::system_clock::time_point next_refresh_{};
};

class SOURCEMETA_CORE_OAUTH_EXPORT OAuthResourceMetadataProvider {
public:
  using FetchResult = OAuthMetadataProvider::FetchResult;

  using Fetcher = OAuthMetadataProvider::Fetcher;

  using Clock = OAuthMetadataProvider::Clock;

  using Options = OAuthMetadataProvider::Options;

  OAuthResourceMetadataProvider(std::string resource, Fetcher fetcher);
  OAuthResourceMetadataProvider(std::string resource, Fetcher fetcher,
                                Options options);
  OAuthResourceMetadataProvider(std::string resource, Fetcher fetcher,
                                Options options, Clock clock);

  OAuthResourceMetadataProvider(const OAuthResourceMetadataProvider &) = delete;
  auto operator=(const OAuthResourceMetadataProvider &)
      -> OAuthResourceMetadataProvider & = delete;
  OAuthResourceMetadataProvider(OAuthResourceMetadataProvider &&) = delete;
  auto operator=(OAuthResourceMetadataProvider &&)
      -> OAuthResourceMetadataProvider & = delete;

  [[nodiscard]] auto metadata() -> std::shared_ptr<const OAuthResourceMetadata>;

  [[nodiscard]] auto refresh() -> std::shared_ptr<const OAuthResourceMetadata>;
 
private:
  auto fetch_and_install_locked(const std::chrono::system_clock::time_point now)
      -> bool;
 
  const std::string resource_;
  const Fetcher fetcher_;
  const Options options_;
  const Clock clock_;
  std::mutex mutex_;
  std::shared_ptr<const OAuthResourceMetadata> metadata_;
  std::chrono::system_clock::time_point next_refresh_{};
};
 
#if defined(_MSC_VER)
#pragma warning(default : 4251)
#endif
 
} // namespace sourcemeta::core
 
#endif