// Copyright Epic Games, Inc. All Rights Reserved.

#pragma once

#include <zencore/httpserver.h>

#include <spdlog/spdlog.h>
#include <memory>

class ZenCacheStore;

namespace zen {

class CasStore;
class CidStore;
class UpstreamCache;

/**
 * Structured cache service. Imposes constraints on keys, supports blobs and
 * structured values
 *
 * Keys are structured as:
 *
 *   {BucketId}/{KeyHash}
 *
 * Where BucketId is an alphanumeric string, and KeyHash is a 40-character hexadecimal
 * sequence. The hash value may be derived in any number of ways, it's up to the
 * application to pick an approach.
 *
 * Values may be structured or unstructured. Structured values are encoded using Unreal
 * Engine's compact binary encoding
 *
 * Additionally, attachments may be addressed as:
 *
 *   {BucketId}/{KeyHash}/{PayloadHash}
 *
 * Where the two initial components are the same as for the main endpoint
 *
 * The storage strategy is as follows:
 *
 *  - Structured values are stored in a dedicated backing store per bucket
 *  - Unstructured values and attachments are stored in the CAS pool
 *
 */

class HttpStructuredCacheService : public zen::HttpService
{
public:
	HttpStructuredCacheService(ZenCacheStore&				  InCacheStore,
							   zen::CasStore&				  InCasStore,
							   zen::CidStore&				  InCidStore,
							   std::unique_ptr<UpstreamCache> UpstreamCache);
	~HttpStructuredCacheService();

	virtual const char* BaseUri() const override;

	virtual void HandleRequest(zen::HttpServerRequest& Request) override;

	void Flush();

private:
	struct CacheRef
	{
		std::string BucketSegment;
		IoHash		HashKey;
		IoHash		PayloadId;
	};

	[[nodiscard]] bool ValidateKeyUri(zen::HttpServerRequest& Request, CacheRef& OutRef);
	void			   HandleCacheRecordRequest(zen::HttpServerRequest& Request, CacheRef& Ref);
	void			   HandleCachePayloadRequest(zen::HttpServerRequest& Request, CacheRef& Ref);
	void			   HandleCacheBucketRequest(zen::HttpServerRequest& Request, std::string_view Bucket);

	spdlog::logger				   m_Log;
	ZenCacheStore&				   m_CacheStore;
	zen::CasStore&				   m_CasStore;
	zen::CidStore&				   m_CidStore;
	std::unique_ptr<UpstreamCache> m_UpstreamCache;
};

}  // namespace zen