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// *****************************************************************************
// * This file is part of the FreeFileSync project. It is distributed under    *
// * GNU General Public License: https://www.gnu.org/licenses/gpl-3.0          *
// * Copyright (C) Zenju (zenju AT freefilesync DOT org) - All Rights Reserved *
// *****************************************************************************

#ifndef DIR_EXIST_ASYNC_H_0817328167343215806734213
#define DIR_EXIST_ASYNC_H_0817328167343215806734213

#include <zen/thread.h>
#include <zen/file_error.h>
#include <zen/basic_math.h>
#include "process_callback.h"
#include "../fs/abstract.h"


namespace fff
{
namespace
{
//directory existence checking may hang for non-existent network drives => run asynchronously and update UI!
//- check existence of all directories in parallel! (avoid adding up search times if multiple network drives are not reachable)
//- add reasonable time-out time!
//- avoid checking duplicate entries => std::set
struct FolderStatus
{
    std::set<AbstractPath> existing;
    std::set<AbstractPath> notExisting;
    std::map<AbstractPath, zen::FileError> failedChecks;
};

FolderStatus getFolderStatusNonBlocking(const std::set<AbstractPath>& folderPaths, const std::map<AbstractPath, size_t>& deviceParallelOps,
                                        std::chrono::seconds folderAccessTimeout, bool allowUserInteraction,
                                        ProcessCallback& procCallback  /*throw X*/)
{
    using namespace zen;

    //aggregate folder paths that are on the same root device: see parallel_scan.h
    std::map<AbstractPath, std::set<AbstractPath>> perDevicePaths;

    for (const AbstractPath& folderPath : folderPaths)
        if (!AFS::isNullPath(folderPath)) //skip empty folders
            perDevicePaths[AFS::getRootPath(folderPath)].insert(folderPath);

    std::vector<std::pair<AbstractPath, std::future<bool>>> futureInfo;

    std::vector<ThreadGroup<std::packaged_task<bool()>>> perDeviceThreads;
    for (const auto& item : perDevicePaths)
    {
        const AbstractPath& rootPath = item.first;
        const size_t parallelOps = getDeviceParallelOps(deviceParallelOps, rootPath);

        perDeviceThreads.emplace_back(parallelOps, "DirExist: " + utfTo<std::string>(AFS::getDisplayPath(rootPath)));
        auto& threadGroup = perDeviceThreads.back();
        threadGroup.detach(); //don't wait on threads hanging longer than "folderAccessTimeout"

        for (const AbstractPath& folderPath : item.second)
        {
            std::packaged_task<bool()> pt([folderPath, allowUserInteraction] //AbstractPath is thread-safe like an int! :)
            {
                //1. login to network share, open FTP connection, ect.
                AFS::connectNetworkFolder(folderPath, allowUserInteraction); //throw FileError

                //2. check dir existence
                return static_cast<bool>(AFS::getItemTypeIfExists(folderPath)); //throw FileError
                //TODO: consider ItemType::FILE a failure instead? In any case: return "false" IFF nothing (of any type) exists
            });
            auto fut = pt.get_future();
            threadGroup.run(std::move(pt));

            futureInfo.emplace_back(folderPath, std::move(fut));
        }
    }

    //don't wait (almost) endlessly like Win32 would on non-existing network shares:
    const auto startTime = std::chrono::steady_clock::now();

    FolderStatus output;

    for (auto& fi : futureInfo)
    {
        const std::wstring& displayPathFmt = fmtPath(AFS::getDisplayPath(fi.first));

        procCallback.reportStatus(replaceCpy(_("Searching for folder %x..."), L"%x", displayPathFmt)); //throw X

        while (std::chrono::steady_clock::now() < startTime + folderAccessTimeout &&
               fi.second.wait_for(UI_UPDATE_INTERVAL / 2) != std::future_status::ready)
            procCallback.requestUiRefresh(); //throw X

        if (isReady(fi.second))
        {
            try
            {
                //call future::get() only *once*! otherwise: undefined behavior!
                if (fi.second.get()) //throw FileError
                    output.existing.insert(fi.first);
                else
                    output.notExisting.insert(fi.first);
            }
            catch (const FileError& e) { output.failedChecks.emplace(fi.first, e); }
        }
        else
            output.failedChecks.emplace(fi.first, FileError(replaceCpy(_("Timeout while searching for folder %x."), L"%x", displayPathFmt)));
    }
    return output;
}
}
}

#endif //DIR_EXIST_ASYNC_H_0817328167343215806734213
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