#pragma once

#include "envoy/common/pure.h"

#include "envoy/http/message.h"

#include "envoy/upstream/cluster_manager.h"

namespace Envoy {

namespace Extensions {

namespace Common {

namespace Aws {

class MetadataFetcher;

using MetadataFetcherPtr = std::unique_ptr<MetadataFetcher>;

/**

 * MetadataFetcher interface can be used to retrieve AWS Metadata from various providers.

 * An instance of this interface is designed to retrieve one AWS Metadata at a time.

 * The implementation of AWS Metadata Fetcher is similar to JwksFetcher.

 */

class MetadataFetcher {

public:

  class MetadataReceiver {

  public:

    enum class Failure {

      /* A network error occurred causing AWS Metadata retrieval failure. */

      Network,

      /* A failure occurred when trying to parse the retrieved AWS Metadata data. */

      InvalidMetadata,

      /* A missing config causing AWS Metadata retrieval failure. */

      MissingConfig,

    };

    // Metadata fetcher begins in "FirstRefresh" and stays there until first success, then reverts

    // to standard cache duration timing. "FirstRefresh" state will cause credential refresh at 2

    // sec, doubling to a maximum of 30 sec until successful.

    enum class RefreshState {

      FirstRefresh,

      Ready,

    };

    /**

     * @brief Successful retrieval callback of returned AWS Metadata.

     * @param body Fetched AWS Metadata.

     */

    virtual void onMetadataSuccess(const std::string&& body) PURE;

    /**

     * @brief Retrieval error callback.

     * @param reason the failure reason.

     */

    virtual void onMetadataError(Failure reason) PURE;

  };

  /**

   * @brief Cancel any in-flight request.

   */

  virtual void cancel() PURE;

  /**

   * @brief Retrieve a AWS Metadata from a remote HTTP host.

   * At most one outstanding request may be in-flight.

   * i.e. from the invocation of `fetch()` until either

   * a callback or `cancel()` is invoked, no additional

   * `fetch()` may be issued. The URI to fetch is to pre

   * determined based on the credentials provider source.

   *

   * @param receiver the receiver of the fetched AWS Metadata or error

   */

  virtual void fetch(Http::RequestMessage& message, Tracing::Span& parent_span,

                     MetadataReceiver& receiver) PURE;

  /**

   * @brief Return MetadataReceiver Failure enum as a string.

   *

   * @return absl::string_view

   */

  virtual absl::string_view failureToString(MetadataReceiver::Failure) PURE;

  /**

   * @brief Factory method for creating a Metadata Fetcher.

   *

   * @param cm the cluster manager to use during AWS Metadata retrieval

   * @param provider the AWS Metadata provider

   * @return a MetadataFetcher instance

   */

  static MetadataFetcherPtr create(Upstream::ClusterManager& cm, absl::string_view cluster_name);

};

} // namespace Aws

} // namespace Common

} // namespace Extensions

} // namespace Envoy