//
// Created by Kirill Zhukov on 20.04.2025.
//

#include "Compactor.h"

namespace usub::utils
{
    Compactor::Compactor(VersionManager& vm) : version_manager(vm)
    {
        this->background_thread = std::thread([this] { this->run(); });
    }

    void Compactor::add_sstable_l0(const std::string& filename)

    {
        this->level0_files.push_back(filename);
        if (this->level0_files.size() >= 4)
        {
            compact_level0();
        }
    }

    void Compactor::compact_level0()
    {
        if (this->level0_files.size() < 2) return;

        std::string merged_filename = "L1_" + std::to_string(std::time(nullptr)) + ".dat";

        LFSkipList<Hash128, std::string> merged(this->version_manager);
        for (const auto& file : this->level0_files)
        {
            read_sstable_with_mmap(merged, file);
        }

        write_sstable_with_index(merged, merged_filename);

        this->level1_files.push_back(merged_filename);
        for (const auto& file : this->level0_files)
        {
            ::remove(file.c_str());
        }
        this->level0_files.clear();
    }

    void Compactor::compact_level1()
    {
        if (this->level1_files.size() < 4) return;

        std::string merged_filename = "L2_" + std::to_string(std::time(nullptr)) + ".dat";

        LFSkipList<Hash128, std::string> merged(this->version_manager);
        for (const auto& file : this->level1_files)
        {
            read_sstable_with_mmap(merged, file);
        }

        write_sstable_with_index(merged, merged_filename);

        this->level2_files.push_back(merged_filename);
        for (const auto& file : this->level1_files)
        {
            ::remove(file.c_str());
        }
        this->level1_files.clear();
    }

    void Compactor::run()
    {
        while (this->running.load())
        {
            compact_level0();
            std::this_thread::sleep_for(std::chrono::seconds(1));
        }
    }
} // utils
// usub