#pragma once

#include "envoy/config/core/v3/http_service.pb.h"

#include "envoy/formatter/substitution_formatter_base.h"

#include "envoy/http/header_map.h"

#include "envoy/server/factory_context.h"

#include "source/common/http/headers.h"

#include "source/common/stream_info/stream_info_impl.h"

namespace Envoy {

namespace Http {

/**

 * Parses and applies request_headers_to_add from an HTTP service configuration.

 *

 * Separates headers into static (plain string value) and formatted (substitution

 * formatter) groups. Static headers are evaluated once at construction time.

 * Formatted headers are re-evaluated on each apply() call, so that

 * runtime updates such as SDS secret rotation are reflected in outgoing requests.

 */

class HttpServiceHeadersApplicator {

public:

  HttpServiceHeadersApplicator(const envoy::config::core::v3::HttpService& http_service,

                               Server::Configuration::ServerFactoryContext& server_context,

                               absl::Status& creation_status);

  /**

   * Apply all parsed headers to the outgoing request message.

   */

  void apply(RequestHeaderMap& headers) const;

private:

  std::vector<std::pair<const LowerCaseString, std::string>> static_headers_;

  std::vector<std::pair<const LowerCaseString, Formatter::FormatterPtr>> formatted_headers_;

  // A `StreamInfo` is required, but in this context we don't have one, so create an empty one.

  // This allows formatters that don't require any stream info to succeed, such as extensions that

  // load data externally for API keys and similar.

  const StreamInfo::StreamInfoImpl stream_info_;

};

} // namespace Http

} // namespace Envoy