/*******************************************************************************
 * Copyright (c) 2026, Jan Koester jan.koester@gmx.net
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 * Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 * Neither the name of the <organization> nor the
 *      names of its contributors may be used to endorse or promote products
 *      derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
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 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 *******************************************************************************/

#pragma once

#include <vector>
#include <cstdint>
#include <atomic>
#include <chrono>
#include <future>
#include <mutex>
#include <map>
#include <set>
#include <shared_mutex>
#include <memory>

#include "../backend.h"
#include "../authdb.h"

#ifdef Windows
#define VISIBILITY __declspec(dllexport)
#else
#define VISIBILITY __attribute__((visibility("default")))
#endif

namespace authdb {

    // Shared per-domain cache: avoids redundant cluster fetches when multiple
    // ClusterBackend instances exist for the same domain (e.g. AD plugin).
    struct DomainCache {
        std::vector<uint8_t> buffer;
        std::chrono::steady_clock::time_point last_fetch{};
        uint64_t recovery_epoch{0};
        std::mutex fetch_mutex;
        std::future<std::vector<uint8_t>> pending_retrieve;
    };

    class VISIBILITY ClusterBackend : public AuthBackendApi {
    public:
        ClusterBackend(const char *domain, size_t version, const char *filepath = nullptr);
        virtual ~ClusterBackend();

        void write(const unsigned char *dest, size_t destsize);
        void read(unsigned char *src, size_t srcsize);

        void prefetch() override;
        void lock();
        void unlock();

        void setPos(size_t pos);
        size_t getPos();

        size_t end();

        size_t getRevesion();
        void newRevesion();

        void vacuum();
        void purge();
        void flushSync() override;

        bool clusterDataExists() const override { return _ClusterDataExists.load(); }

        // Force next fetchFromCluster to bypass the 30s throttle
        void forceRefresh();

        // Returns the set of domain group IDs from all known cached domains
        static std::set<uint64_t> knownDomainGroupIds();

    private:
        struct EntityKey {
            unsigned char ruid[16] = {0};
            int type = 0;
            bool operator<(const EntityKey &o) const {
                int cmp = std::memcmp(ruid, o.ruid, 16);
                if (cmp != 0) return cmp < 0;
                return type < o.type;
            }
            bool operator==(const EntityKey &o) const {
                return std::memcmp(ruid, o.ruid, 16) == 0 && type == o.type;
            }
        };

        uint64_t domainGroupId() const;
        uint64_t entityGroupId(const EntityKey &ek) const;
        void fetchFromCluster();
        void pushToCluster();

        std::map<EntityKey, std::vector<uint8_t>> parseEntities() const;
        void pushManifest(const std::set<EntityKey> &keys);
        void pushManifestSync(const std::set<EntityKey> &keys);

        static std::shared_mutex s_cache_mutex_;
        static std::map<std::string, std::shared_ptr<DomainCache>> s_domain_cache_;
        std::shared_ptr<DomainCache> getDomainCache();

        std::string              _Domain;
        std::vector<uint8_t>     _Buffer;
        size_t                   _Pos;
        std::atomic<bool>        _Dirty;
        std::atomic<bool>        _ClusterDataExists{false};
        std::map<EntityKey, uint64_t> entity_hashes_; // per-entity content hashes
    };
};
