#pragma once

#include <string>

#include <vector>

#include "envoy/access_log/access_log.h"

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

#include "envoy/http/header_evaluator.h"

#include "envoy/http/header_map.h"

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

#include "source/common/protobuf/protobuf.h"

namespace Envoy {

namespace Router {

class HeaderParser;

using HeaderParserPtr = std::unique_ptr<HeaderParser>;

using HeaderAppendAction = envoy::config::core::v3::HeaderValueOption::HeaderAppendAction;

using HeaderValueOption = envoy::config::core::v3::HeaderValueOption;

using HeaderValue = envoy::config::core::v3::HeaderValue;

struct HeadersToAddEntry {

  HeadersToAddEntry(const HeaderValue& header_value, HeaderAppendAction append_action);

  HeadersToAddEntry(const HeaderValueOption& header_value_option);

  std::string original_value_;

  bool add_if_empty_ = false;

  Formatter::FormatterPtr formatter_;

  HeaderAppendAction append_action_;

};

/**

 * HeaderParser manipulates Http::HeaderMap instances. Headers to be added are pre-parsed to select

 * between a constant value implementation and a dynamic value implementation based on

 * StreamInfo::StreamInfo fields.

 */

class HeaderParser : public Http::HeaderEvaluator {

public:

  /*

   * @param headers_to_add defines the headers to add during calls to evaluateHeaders

   * @return HeaderParserPtr a configured HeaderParserPtr

   */

  static HeaderParserPtr

  configure(const Protobuf::RepeatedPtrField<HeaderValueOption>& headers_to_add);

  /*

   * @param headers_to_add defines headers to add during calls to evaluateHeaders.

   * @param append_action defines action taken to append/overwrite the given value for an existing

   * header or to only add this header if it's absent.

   * @return HeaderParserPtr a configured HeaderParserPtr.

   */

  static HeaderParserPtr

  configure(const Protobuf::RepeatedPtrField<envoy::config::core::v3::HeaderValue>& headers_to_add,

            HeaderAppendAction append_action);

  /*

   * @param headers_to_add defines headers to add during calls to evaluateHeaders

   * @param headers_to_remove defines headers to remove during calls to evaluateHeaders

   * @return HeaderParserPtr a configured HeaderParserPtr

   */

  static HeaderParserPtr

  configure(const Protobuf::RepeatedPtrField<HeaderValueOption>& headers_to_add,

            const Protobuf::RepeatedPtrField<std::string>& headers_to_remove);

  static const HeaderParser& defaultParser() {

    static HeaderParser* instance = new HeaderParser();

    return *instance;

  }

  void evaluateHeaders(Http::HeaderMap& headers, const Formatter::HttpFormatterContext& context,

                       const StreamInfo::StreamInfo& stream_info) const override;

  void evaluateHeaders(Http::HeaderMap& headers, const Formatter::HttpFormatterContext& context,

                       const StreamInfo::StreamInfo* stream_info) const;

  /**

   * Helper methods to evaluate methods without explicitly passing request and response headers.

   * The method will try to fetch request headers from steam_info. Response headers will always be

   * empty.

   */

  void evaluateHeaders(Http::HeaderMap& headers, const StreamInfo::StreamInfo& stream_info) const {

    evaluateHeaders(headers, {stream_info.getRequestHeaders()}, &stream_info);

  }

  void evaluateHeaders(Http::HeaderMap& headers, const StreamInfo::StreamInfo* stream_info) const {

    evaluateHeaders(headers,

                    Formatter::HttpFormatterContext{

                        stream_info == nullptr ? nullptr : stream_info->getRequestHeaders()},

                    stream_info);

  }

  /*

   * Same as evaluateHeaders, but returns the modifications that would have been made rather than

   * modifying an existing HeaderMap.

   * @param stream_info contains additional information about the request.

   * @param do_formatting whether or not to evaluate configured transformations; if false, returns

   * original values instead.

   */

  Http::HeaderTransforms getHeaderTransforms(const StreamInfo::StreamInfo& stream_info,

                                             bool do_formatting = true) const;

  static std::string translateMetadataFormat(const std::string& header_value);

  static std::string translatePerRequestState(const std::string& header_value);

protected:

  HeaderParser() = default;

private:

  std::vector<std::pair<Http::LowerCaseString, HeadersToAddEntry>> headers_to_add_;

  std::vector<Http::LowerCaseString> headers_to_remove_;

};

} // namespace Router

} // namespace Envoy