// This file Copyright © Mnemosyne LLC.
// It may be used under GPLv2 (SPDX: GPL-2.0-only), GPLv3 (SPDX: GPL-3.0-only),
// or any future license endorsed by Mnemosyne LLC.
// License text can be found in the licenses/ folder.

#include <algorithm>
#include <array>
#include <iterator>
#include <list>
#include <string>
#include <string_view>
#include <utility>
#include <vector>

#ifdef __HAIKU__
#include <limits.h> /* PATH_MAX */
#endif

#ifdef _WIN32
#include <process.h> /* _beginthreadex(), _endthreadex() */
#include <windows.h>
#include <shlobj.h> /* SHGetKnownFolderPath(), FOLDERID_... */
#ifdef small // workaround name collision between libsmall and rpcndr.h
#undef small
#endif
#else
#include <pwd.h>
#include <unistd.h> /* getuid() */
#endif

#ifdef BUILD_MAC_CLIENT
#include <CoreFoundation/CoreFoundation.h>
#endif

#ifdef __HAIKU__
#include <FindDirectory.h>
#endif

#include <fmt/format.h>

#include "libtransmission/transmission.h"

#include "libtransmission/file.h"
#include "libtransmission/log.h"
#include "libtransmission/platform.h"
#include "libtransmission/session.h"
#include "libtransmission/tr-strbuf.h"
#include "libtransmission/utils.h"

using namespace std::literals;

namespace
{
#ifdef _WIN32
std::string win32_get_known_folder_ex(REFKNOWNFOLDERID folder_id, DWORD flags)
{
    if (PWSTR path = nullptr; SHGetKnownFolderPath(folder_id, flags | KF_FLAG_DONT_UNEXPAND, nullptr, &path) == S_OK)
    {
        auto ret = tr_win32_native_to_utf8(path);
        CoTaskMemFree(path);
        return ret;
    }

    return {};
}

auto win32_get_known_folder(REFKNOWNFOLDERID folder_id)
{
    return win32_get_known_folder_ex(folder_id, KF_FLAG_DONT_VERIFY);
}
#endif

std::string getHomeDir()
{
    if (auto dir = tr_env_get_string("HOME"sv); !std::empty(dir))
    {
        return dir;
    }

#ifdef _WIN32

    if (auto dir = win32_get_known_folder(FOLDERID_Profile); !std::empty(dir))
    {
        return dir;
    }

#else

    struct passwd pwent = {};
    struct passwd* pw = nullptr;
    auto buf = std::array<char, 4096>{};
    getpwuid_r(getuid(), &pwent, std::data(buf), std::size(buf), &pw);
    if (pw != nullptr)
    {
        return pw->pw_dir;
    }

#endif

    return {};
}

std::string xdgConfigHome()
{
    if (auto dir = tr_env_get_string("XDG_CONFIG_HOME"sv); !std::empty(dir))
    {
        return dir;
    }

    return fmt::format("{:s}/.config"sv, getHomeDir());
}

std::string getXdgEntryFromUserDirs(std::string_view key)
{
    auto content = std::vector<char>{};
    if (auto const filename = fmt::format("{:s}/{:s}"sv, xdgConfigHome(), "user-dirs.dirs"sv);
        !tr_sys_path_exists(filename) || !tr_file_read(filename, content) || std::empty(content))
    {
        return {};
    }

    // search for key="val" and extract val
    auto const search = fmt::format("{:s}=\"", key);
    auto begin = std::search(std::begin(content), std::end(content), std::begin(search), std::end(search));
    if (begin == std::end(content))
    {
        return {};
    }
    std::advance(begin, std::size(search));
    auto const end = std::find(begin, std::end(content), '"');
    if (end == std::end(content))
    {
        return {};
    }
    auto val = std::string{ begin, end };

    // if val contains "$HOME", replace that with getHomeDir()
    auto constexpr Home = "$HOME"sv;
    if (auto const it = std::search(std::begin(val), std::end(val), std::begin(Home), std::end(Home)); it != std::end(val))
    {
        val.replace(it, it + std::size(Home), getHomeDir());
    }

    return val;
}

[[nodiscard]] bool isWebClientDir(std::string_view path)
{
    auto const filename = tr_pathbuf{ path, '/', "index.html"sv };
    bool const found = tr_sys_path_exists(filename);
    tr_logAddTrace(fmt::format("Searching for web interface file '{:s}'", filename));
    return found;
}
} // namespace

// ---

std::string tr_getDefaultConfigDir(std::string_view appname)
{
    if (std::empty(appname))
    {
        appname = "Transmission"sv;
    }

    if (auto dir = tr_env_get_string("TRANSMISSION_HOME"sv); !std::empty(dir))
    {
        return dir;
    }

#ifdef __APPLE__

    return fmt::format("{:s}/Library/Application Support/{:s}"sv, getHomeDir(), appname);

#elif defined(_WIN32)

    auto const appdata = win32_get_known_folder(FOLDERID_LocalAppData);
    return fmt::format("{:s}/{:s}"sv, appdata, appname);

#elif defined(__HAIKU__)

    char buf[PATH_MAX];
    find_directory(B_USER_SETTINGS_DIRECTORY, -1, true, buf, sizeof(buf));
    return fmt::format("{:s}/{:s}"sv, buf, appname);

#else

    return fmt::format("{:s}/{:s}"sv, xdgConfigHome(), appname);

#endif
}

std::string tr_getDefaultDownloadDir()
{
    if (auto dir = getXdgEntryFromUserDirs("XDG_DOWNLOAD_DIR"sv); !std::empty(dir))
    {
        return dir;
    }

#ifdef _WIN32
    if (auto dir = win32_get_known_folder(FOLDERID_Downloads); !std::empty(dir))
    {
        return dir;
    }
#endif

#ifdef __HAIKU__
    return fmt::format("{:s}/Desktop"sv, getHomeDir());
#endif

    return fmt::format("{:s}/Downloads"sv, getHomeDir());
}

// ---

std::string tr_getWebClientDir([[maybe_unused]] tr_session const* session)
{
    if (auto dir = tr_env_get_string("CLUTCH_HOME"sv); !std::empty(dir))
    {
        return dir;
    }

    if (auto dir = tr_env_get_string("TRANSMISSION_WEB_HOME"sv); !std::empty(dir))
    {
        return dir;
    }

#ifdef BUILD_MAC_CLIENT

    // look in the Application Support folder
    if (auto path = tr_pathbuf{ session->configDir(), "/public_html"sv }; isWebClientDir(path))
    {
        return std::string{ path };
    }

    // look in the resource bundle
    auto app_url = CFBundleCopyBundleURL(CFBundleGetMainBundle());
    auto app_ref = CFURLCopyFileSystemPath(app_url, kCFURLPOSIXPathStyle);
    auto const buflen = CFStringGetMaximumSizeOfFileSystemRepresentation(app_ref);
    auto buf = std::vector<char>(buflen, '\0');
    bool const success = CFStringGetFileSystemRepresentation(app_ref, std::data(buf), std::size(buf));
    TR_ASSERT(success);
    CFRelease(app_url);
    CFRelease(app_ref);
    if (auto const path = tr_pathbuf{ std::string_view{ std::data(buf) }, "/Contents/Resources/public_html"sv };
        isWebClientDir(path))
    {
        return std::string{ path };
    }

#elif defined(_WIN32)

    /* Generally, Web interface should be stored in a Web subdir of
     * calling executable dir. */

    static auto constexpr KnownFolderIds = std::array<KNOWNFOLDERID const* const, 3>{
        &FOLDERID_LocalAppData,
        &FOLDERID_RoamingAppData,
        &FOLDERID_ProgramData,
    };

    for (auto const* const folder_id : KnownFolderIds)
    {
        auto const dir = win32_get_known_folder(*folder_id);

        if (auto const path = tr_pathbuf{ dir, "/Transmission/public_html"sv }; isWebClientDir(path))
        {
            return std::string{ path };
        }
    }

    /* check calling module place */
    auto wide_module_path = std::array<wchar_t, MAX_PATH>{};
    GetModuleFileNameW(nullptr, std::data(wide_module_path), std::size(wide_module_path));
    auto const module_path = tr_win32_native_to_utf8({ std::data(wide_module_path) });
    if (auto const dir = tr_sys_path_dirname(module_path); !std::empty(dir))
    {
        if (auto const path = tr_pathbuf{ dir, "/public_html"sv }; isWebClientDir(path))
        {
            return std::string{ path };
        }
    }

#else // everyone else, follow the XDG spec

    auto candidates = std::list<std::string>{};

    /* XDG_DATA_HOME should be the first in the list of candidates */
    if (auto tmp = tr_env_get_string("XDG_DATA_HOME"sv); !std::empty(tmp))
    {
        candidates.emplace_back(std::move(tmp));
    }
    else
    {
        candidates.emplace_back(fmt::format("{:s}/.local/share"sv, getHomeDir()));
    }

    /* XDG_DATA_DIRS are the backup directories */
    {
        char const* const pkg = PACKAGE_DATA_DIR;
        auto const xdg = tr_env_get_string("XDG_DATA_DIRS"sv);
        auto const buf = fmt::format("{:s}:{:s}:/usr/local/share:/usr/share", pkg, xdg);

        auto sv = std::string_view{ buf };
        auto token = std::string_view{};
        while (tr_strv_sep(&sv, &token, ':'))
        {
            token = tr_strv_strip(token);
            if (!std::empty(token))
            {
                candidates.emplace_back(token);
            }
        }
    }

    /* walk through the candidates & look for a match */
    for (auto const& dir : candidates)
    {
        if (auto const path = tr_pathbuf{ dir, "/transmission/public_html"sv }; isWebClientDir(path))
        {
            return std::string{ path };
        }
    }

#endif

    return {};
}

std::string tr_getSessionIdDir()
{
#ifndef _WIN32

    return std::string{ "/tmp"sv };

#else

    auto const program_data_dir = win32_get_known_folder_ex(FOLDERID_ProgramData, KF_FLAG_CREATE);
    auto result = fmt::format("{:s}/Transmission"sv, program_data_dir);
    tr_sys_dir_create(result, 0, 0);
    return result;

#endif
}
