#pragma once

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

#include "source/extensions/filters/http/cache/http_cache.h"

#include "absl/base/thread_annotations.h"

#include "absl/container/flat_hash_map.h"

#include "absl/synchronization/mutex.h"

namespace Envoy {

namespace Extensions {

namespace HttpFilters {

namespace Cache {

// Example cache backend that never evicts. Not suitable for production use.

class SimpleHttpCache : public HttpCache, public Singleton::Instance {

private:

  struct Entry {

    Http::ResponseHeaderMapPtr response_headers_;

    ResponseMetadata metadata_;

    std::string body_;

    Http::ResponseTrailerMapPtr trailers_;

  };

  // Looks for a response that has been varied. Only called from lookup.

  Entry varyLookup(const LookupRequest& request,

                   const Http::ResponseHeaderMapPtr& response_headers);

  // A list of headers that we do not want to update upon validation

  // We skip these headers because either it's updated by other application logic

  // or they are fall into categories defined in the IETF doc below

  // https://www.ietf.org/archive/id/draft-ietf-httpbis-cache-18.html s3.2

  static const absl::flat_hash_set<Http::LowerCaseString> headersNotToUpdate();

public:

  // HttpCache

  LookupContextPtr makeLookupContext(LookupRequest&& request,

                                     Http::StreamFilterCallbacks& callbacks) override;

  InsertContextPtr makeInsertContext(LookupContextPtr&& lookup_context,

                                     Http::StreamFilterCallbacks& callbacks) override;

  void updateHeaders(const LookupContext& lookup_context,

                     const Http::ResponseHeaderMap& response_headers,

                     const ResponseMetadata& metadata, UpdateHeadersCallback on_complete) override;

  CacheInfo cacheInfo() const override;

  Entry lookup(const LookupRequest& request);

  bool insert(const Key& key, Http::ResponseHeaderMapPtr&& response_headers,

              ResponseMetadata&& metadata, std::string&& body,

              Http::ResponseTrailerMapPtr&& trailers);

  // Inserts a response that has been varied on certain headers.

  bool varyInsert(const Key& request_key, Http::ResponseHeaderMapPtr&& response_headers,

                  ResponseMetadata&& metadata, std::string&& body,

                  const Http::RequestHeaderMap& request_headers,

                  const VaryAllowList& vary_allow_list, Http::ResponseTrailerMapPtr&& trailers);

  absl::Mutex mutex_;

  absl::flat_hash_map<Key, Entry, MessageUtil, MessageUtil> map_ ABSL_GUARDED_BY(mutex_);

};

} // namespace Cache

} // namespace HttpFilters

} // namespace Extensions

} // namespace Envoy