#include <iostream>
#include <filesystem>
#include <optional>
#include <boost/program_options.hpp>
#include <Common/filesystemHelpers.h>

#include <csignal>
#include <sys/stat.h>

#if defined(OS_LINUX)
    #include <syscall.h>
    #include <linux/capability.h>
#endif

#if defined(OS_DARWIN)
    #include <mach-o/dyld.h>
#endif

#include <Common/Exception.h>
#include <Common/ErrnoException.h>
#include <Common/ShellCommand.h>
#include <Common/formatReadable.h>
#include <Common/shellQuote.h>
#include <Common/Config/ConfigProcessor.h>
#include <Common/OpenSSLHelpers.h>
#include <base/sleep.h>
#include <IO/WriteBufferFromFileDescriptor.h>
#include <IO/ReadBufferFromFile.h>
#include <IO/WriteBufferFromFile.h>
#include <IO/MMapReadBufferFromFile.h>
#include <IO/ReadBufferFromMemory.h>
#include <IO/copyData.h>
#include <IO/Operators.h>
#include <IO/Ask.h>
#include <IO/ReadHelpers.h>
#include <Access/AccessEntityIO.h>
#include <Access/User.h>
#include <Access/Common/AccessEntityType.h>
#include <Common/StringUtils.h>
#include <base/range.h>
#include <readpassphrase.h>

#include <Poco/Util/XMLConfiguration.h>

#include "config.h"

/// Embedded configuration files used inside the install program
constexpr unsigned char resource_config_xml[] =
{
#embed "../server/config.xml"
};

constexpr unsigned char resource_users_xml[] =
{
#embed "../server/users.xml"
};

constexpr unsigned char resource_users_yaml[] =
{
#embed "../server/users.yaml.example"
};


/** This tool can be used to install ClickHouse without a deb/rpm/tgz package, having only "clickhouse" binary.
  * It also allows to avoid dependency on systemd, upstart, SysV init.
  *
  * The following steps are performed:
  *
  * - copying the binary to binary directory (/usr/bin/)
  * - creation of symlinks for tools.
  * - creation of clickhouse user and group.
  * - creation of config directory (/etc/clickhouse-server/).
  * - creation of default configuration files.
  * - creation of a directory for logs (/var/log/clickhouse-server/).
  * - creation of a data directory if not exists.
  * - setting a password for default user.
  * - choose an option to listen connections.
  * - changing the ownership and mode of the directories.
  * - setting capabilities for binary.
  * - setting ulimits for the user.
  * - (todo) put service in cron.
  *
  * It does not install clickhouse-odbc-bridge.
  */

namespace DB
{

namespace ErrorCodes
{
    extern const int FILE_DOESNT_EXIST;
    extern const int CANNOT_OPEN_FILE;
    extern const int SYSTEM_ERROR;
    extern const int NOT_ENOUGH_SPACE;
    extern const int NOT_IMPLEMENTED;
    extern const int CANNOT_KILL;
    extern const int BAD_ARGUMENTS;
}

}

#if defined(OS_DARWIN)
/// Until createUser() and createGroup() are implemented, only sudo-less installations are supported/default for macOS.
static constexpr auto DEFAULT_CLICKHOUSE_SERVER_USER = "";
static constexpr auto DEFAULT_CLICKHOUSE_SERVER_GROUP = "";
static constexpr auto DEFAULT_CLICKHOUSE_BRIDGE_USER = "";
static constexpr auto DEFAULT_CLICKHOUSE_BRIDGE_GROUP = "";
#else
static constexpr auto DEFAULT_CLICKHOUSE_SERVER_USER = "clickhouse";
static constexpr auto DEFAULT_CLICKHOUSE_SERVER_GROUP = "clickhouse";
static constexpr auto DEFAULT_CLICKHOUSE_BRIDGE_USER = "clickhouse-bridge";
static constexpr auto DEFAULT_CLICKHOUSE_BRIDGE_GROUP = "clickhouse-bridge";
#endif

using namespace DB;
namespace po = boost::program_options;
namespace fs = std::filesystem;


static auto executeScript(const std::string & command, bool throw_on_error = false)
{
    auto sh = ShellCommand::execute(command);

    WriteBufferFromFileDescriptor wb_stdout(STDOUT_FILENO);
    copyData(sh->out, wb_stdout);
    wb_stdout.finalize();

    WriteBufferFromFileDescriptor wb_stderr(STDERR_FILENO);
    copyData(sh->err, wb_stderr);
    wb_stderr.finalize();

    if (throw_on_error)
    {
        sh->wait();
        return 0;
    }

    return sh->tryWait();
}

static bool filesEqual(std::string path1, std::string path2)
{
    MMapReadBufferFromFile in1(path1, 0);
    MMapReadBufferFromFile in2(path2, 0);

    /// memcmp is faster than hashing and comparing hashes
    return in1.buffer().size() == in2.buffer().size()
        && 0 == memcmp(in1.buffer().begin(), in2.buffer().begin(), in1.buffer().size());
}

static void changeOwnership(const String & file_name, const String & user_name, const String & group_name = {}, bool recursive = true)
{
    if (!user_name.empty() || !group_name.empty())
    {
        std::string command = fmt::format("chown {} {}:{} {}",
            (recursive ? "-R" : ""), shellQuote(user_name), shellQuote(group_name), shellQuote(file_name));
        fmt::print(" {}\n", command);
        executeScript(command);
    }
}

/// Whether the authentication of the user at `user_path` in a users config is configured with anything but an empty flat `password`.
/// The installer sets up a password by replacing the flat `password` with `password_sha256_hex`, which is valid only if
/// the user has no other authentication method: `UsersConfigParser` allows only one flat method, rejects flat methods together
/// with `auth_methods`, and allows `time_based_one_time_password` at the user level. Like `UsersConfigParser`, a method counts
/// if it is present, even if its value is empty.
static bool hasAuthentication(const Poco::Util::AbstractConfiguration & config, const std::string & user_path)
{
    if (!config.getString(user_path + ".password", "").empty())
        return true;

    for (const auto * key : {"no_password", "password_sha256_hex", "password_scram_sha256_hex", "password_double_sha1_hex",
             "ldap", "kerberos", "ssl_certificates", "ssh_keys", "http_authentication", "auth_methods", "time_based_one_time_password"})
        if (config.has(user_path + "." + key))
            return true;

    return false;
}

/// Whether a flat authentication method at `path` in a users config is a non-empty password.
static bool hasPasswordAt(const Poco::Util::AbstractConfiguration & config, const std::string & path)
{
    for (const auto * key : {"password", "password_sha256_hex", "password_scram_sha256_hex", "password_double_sha1_hex"})
        if (!config.getString(path + "." + key, "").empty())
            return true;
    return false;
}

/// Whether the user at `user_path` in a users config has a non-empty password among its authentication methods,
/// either as a flat field or as an entry of `auth_methods`, so that it can connect with `clickhouse-client --password`.
static bool hasPassword(const Poco::Util::AbstractConfiguration & config, const std::string & user_path)
{
    const std::string auth_methods_path = user_path + ".auth_methods";
    if (!config.has(auth_methods_path))
        return hasPasswordAt(config, user_path);

    Poco::Util::AbstractConfiguration::Keys auth_methods;
    config.keys(auth_methods_path, auth_methods);
    for (const auto & auth_method : auth_methods)
        if (hasPasswordAt(config, auth_methods_path + "." + auth_method))
            return true;
    return false;
}

/// Whether the user at `user_path` in a users config can authenticate only with credentials, i.e. not with an empty password
/// or `no_password`. Checks the same carriers as `UsersConfigParser`: the flat fields of the user and every entry of `auth_methods`.
/// Any entry of `auth_methods` that needs no credentials makes the user accessible without them, unless the user has
/// `time_based_one_time_password`: it applies to every authentication method, even `no_password` or an empty password
/// (see `checkBasicAuthentication`).
static bool hasCredentials(const Poco::Util::AbstractConfiguration & config, const std::string & user_path)
{
    if (config.has(user_path + ".time_based_one_time_password"))
        return true;

    auto has_credentials_at = [&](const std::string & path)
    {
        if (hasPasswordAt(config, path))
            return true;
        for (const auto * key : {"ldap", "kerberos", "ssl_certificates", "ssh_keys", "http_authentication"})
            if (config.has(path + "." + key))
                return true;
        return false;
    };

    const std::string auth_methods_path = user_path + ".auth_methods";
    if (!config.has(auth_methods_path))
        return has_credentials_at(user_path);

    Poco::Util::AbstractConfiguration::Keys auth_methods;
    config.keys(auth_methods_path, auth_methods);
    if (auth_methods.empty())
        return false;
    for (const auto & auth_method : auth_methods)
        if (!has_credentials_at(auth_methods_path + "." + auth_method))
            return false;
    return true;
}

/// Whether a `DiskAccessStorage` at `directory_path` is known not to define the default user.
/// Mirrors how it loads entities at startup: if there is no `need_rebuild_lists.mark` and all `*.list` files can be read,
/// it trusts them and ignores `<id>.sql` files not listed there; otherwise it rebuilds the lists from all `<id>.sql` files.
/// Empty lists and entities of other types (roles, settings profiles, etc.) don't define the default user.
/// A relative path is resolved against the working directory of the server, which is not known here.
/// A directory or a file that cannot be inspected (e.g. without permissions, or corrupted) is not known to be without the default user.
static bool isKnownWithoutDefaultUserDiskAccessStorage(const fs::path & directory_path)
{
    if (directory_path.is_relative())
        return false;

    std::error_code ec;
    if (!fs::exists(directory_path, ec))
        return !ec;

    try
    {
        /// Same as `DiskAccessStorage::readLists`: if any list file is missing or cannot be parsed, the lists are rebuilt.
        bool lists_are_used = !fs::exists(directory_path / "need_rebuild_lists.mark");
        bool has_default_user_in_lists = false;
        for (auto type : collections::range(AccessEntityType::MAX))
        {
            if (!lists_are_used)
                break;

            String list_file_name = AccessEntityTypeInfo::get(type).plural_raw_name;
            toLowerASCII(list_file_name);
            const fs::path list_path = directory_path / (list_file_name + ".list");
            if (!fs::exists(list_path))
            {
                lists_are_used = false;
                break;
            }

            try
            {
                /// Same format as `writeListFile` in `DiskAccessStorage`.
                ReadBufferFromFile in(list_path.string());
                size_t num = 0;
                readVarUInt(num, in);
                for (size_t i = 0; i != num; ++i)
                {
                    String name;
                    readStringBinary(name, in);
                    UUID id;
                    readUUIDText(id, in);
                    if (type == AccessEntityType::USER && name == "default")
                        has_default_user_in_lists = true;
                }
            }
            catch (...)
            {
                /// Ok: same as `DiskAccessStorage::readLists`, a list file that cannot be read means the lists are rebuilt from the `.sql` files.
                lists_are_used = false;
            }
        }

        if (lists_are_used)
            return !has_default_user_in_lists;

        /// Same as `DiskAccessStorage::reloadAllAndRebuildLists`: only regular `<uuid>.sql` files are entities,
        /// and a file that cannot be read or parsed is skipped.
        for (const auto & entry : fs::directory_iterator(directory_path))
        {
            UUID id;
            if (!entry.is_regular_file() || entry.path().extension() != ".sql" || !tryParse(id, entry.path().stem().string()))
                continue;

            AccessEntityPtr entity;
            try
            {
                String definition;
                {
                    ReadBufferFromFile in(entry.path().string());
                    readStringUntilEOF(definition, in);
                }
                entity = deserializeAccessEntity(definition, entry.path().string());
            }
            catch (...)
            {
                /// Ok: the server skips such a file too.
                continue;
            }

            if (entity->isTypeOf<User>() && entity->getName() == "default")
                return false;
        }
    }
    catch (...)
    {
        std::cerr << "Cannot check whether " << directory_path.string() << " defines the default user: "
            << getCurrentExceptionMessage(false) << "\n";
        return false;
    }

    return true;
}

/// The merge directory of a users config that is applied last: `ConfigProcessor::getConfigMergeFiles` merges the files
/// from both `<name>.d` and `conf.d` sorted by their full paths, so all files of one directory precede all files of the other.
static fs::path getLastConfigMergeDir(const fs::path & config_path)
{
    fs::path own_merge_dir = fs::path(config_path).replace_extension("d");
    fs::path conf_d = fs::path(config_path).replace_filename("conf.d");
    /// Compare with a trailing separator, like the paths of the files inside.
    if ((conf_d / "").string() > (own_merge_dir / "").string())
        return conf_d;
    return own_merge_dir;
}

static void createGroup(const String & group_name)
{
    if (!group_name.empty())
    {
#if defined(OS_DARWIN)
        // TODO: implement.
        throw Exception(ErrorCodes::NOT_IMPLEMENTED, "Unable to create a group in macOS");
#elif defined(OS_FREEBSD)
        std::string command = fmt::format("pw groupadd {}", shellQuote(group_name));
        fmt::print(" {}\n", command);
        executeScript(command);
#else
        std::string command = fmt::format("groupadd -r {}", shellQuote(group_name));
        fmt::print(" {}\n", command);
        executeScript(command);
#endif
    }
}

static void createUser(const String & user_name, [[maybe_unused]] const String & group_name)
{
    if (!user_name.empty())
    {
#if defined(OS_DARWIN)
        // TODO: implement.
        throw Exception(ErrorCodes::NOT_IMPLEMENTED, "Unable to create a user in macOS");
#elif defined(OS_FREEBSD)
        std::string command = group_name.empty()
            ? fmt::format("pw useradd -s /bin/false -d /nonexistent -n {}", shellQuote(user_name))
            : fmt::format("pw useradd -s /bin/false -d /nonexistent -g {} -n {}", shellQuote(group_name), shellQuote(user_name));
        fmt::print(" {}\n", command);
        executeScript(command);
#else
        std::string command = group_name.empty()
            ? fmt::format("useradd -r --shell /bin/false --home-dir /nonexistent --user-group {}", shellQuote(user_name))
            : fmt::format("useradd -r --shell /bin/false --home-dir /nonexistent -g {} {}", shellQuote(group_name), shellQuote(user_name));
        fmt::print(" {}\n", command);
        executeScript(command);
#endif
    }
}


static std::string formatWithSudo(std::string command, bool needed = true)
{
    if (!needed)
        return command;

#if defined(OS_FREEBSD)
    /// FreeBSD does not have 'sudo' installed.
    /// `su -c` takes a single shell command string, so quote the whole command
    /// to keep embedded shell metacharacters from breaking the wrapper.
    return fmt::format("su -m root -c {}", shellQuote(command));
#else
    return fmt::format("sudo {}", command);
#endif
}


int mainEntryClickHouseInstall(int argc, char ** argv);
int mainEntryClickHouseInstall(int argc, char ** argv)
{
    try
    {
        const char * start_hilite = "";
        const char * end_hilite = "";

        if (isatty(STDOUT_FILENO))
        {
            /// ANSI escape sequence for intense color in terminal.
            start_hilite = "\033[1m";
            end_hilite = "\033[0m";
        }

        po::options_description desc;
        desc.add_options()
            ("help,h", "produce help message")
            ("prefix", po::value<std::string>()->default_value("/"), "prefix for all paths")
#if defined (OS_DARWIN)
            /// https://stackoverflow.com/a/36734569/22422288
            ("binary-path", po::value<std::string>()->default_value("usr/local/bin"), "where to install binaries")
#else
            ("binary-path", po::value<std::string>()->default_value("usr/bin"), "where to install binaries")
#endif
            ("config-path", po::value<std::string>()->default_value("etc/clickhouse-server"), "where to install configs")
            ("log-path", po::value<std::string>()->default_value("var/log/clickhouse-server"), "where to create log directory")
            ("data-path", po::value<std::string>()->default_value("var/lib/clickhouse"), "directory for data")
            ("pid-path", po::value<std::string>()->default_value("var/run/clickhouse-server"), "directory for pid file")
            ("user", po::value<std::string>()->default_value(DEFAULT_CLICKHOUSE_SERVER_USER), "clickhouse user to create")
            ("group", po::value<std::string>()->default_value(DEFAULT_CLICKHOUSE_SERVER_GROUP), "clickhouse group to create")
            ("noninteractive,y", "run non-interactively")
            ("link", "create symlink to the binary instead of copying to binary-path")
        ;

        po::variables_map options;
        po::store(po::parse_command_line(argc, argv, desc), options);

        if (options.contains("help"))
        {
            std::cout << "Install ClickHouse without .deb/.rpm/.tgz packages (having the binary only)\n\n";
            std::cout << "Usage: " << formatWithSudo("clickhouse install", getuid() != 0) << " [options]\n";
            std::cout << desc << '\n';
            return 0;
        }

        /// We need to copy binary to the binary directory.
        /// The binary is currently run. We need to obtain its path from procfs (on Linux).

#if defined(OS_DARWIN)
        uint32_t path_length = 0;
        _NSGetExecutablePath(nullptr, &path_length);
        if (path_length <= 1)
            throw Exception(ErrorCodes::FILE_DOESNT_EXIST, "Cannot obtain path to the binary");

        std::string path(path_length, std::string::value_type());
        auto res = _NSGetExecutablePath(&path[0], &path_length);
        if (res != 0)
            throw Exception(ErrorCodes::FILE_DOESNT_EXIST, "Cannot obtain path to the binary");

        if (path.back() == '\0')
            path.pop_back();

        fs::path binary_self_path(path);
#elif defined(OS_FREEBSD)
        /// https://stackoverflow.com/questions/1023306/finding-current-executables-path-without-proc-self-exe
        fs::path binary_self_path = argc >= 1 ? argv[0] : "/proc/curproc/file";
#else
        fs::path binary_self_path = "/proc/self/exe";
#endif

        if (!fs::exists(binary_self_path))
            throw Exception(ErrorCodes::FILE_DOESNT_EXIST, "Cannot obtain path to the binary from {}, file doesn't exist",
                            binary_self_path.string());

        fs::path binary_self_canonical_path = fs::canonical(binary_self_path);

        /// Copy binary to the destination directory.

        fs::path prefix = options["prefix"].as<std::string>();
        fs::path bin_dir = prefix / options["binary-path"].as<std::string>();

        fs::path main_bin_path = bin_dir / "clickhouse";
        fs::path main_bin_tmp_path = bin_dir / "clickhouse.new";
        fs::path main_bin_old_path = bin_dir / "clickhouse.old";

        size_t binary_size = fs::file_size(binary_self_path);

        bool old_binary_exists = fs::exists(main_bin_path);
        bool already_installed = false;

        if (options.contains("link"))
        {
            if (old_binary_exists)
            {
                bool is_symlink = FS::isSymlink(main_bin_path);
                fs::path points_to;
                if (is_symlink)
                    points_to = fs::weakly_canonical(FS::readSymlink(main_bin_path));

                if (is_symlink && points_to == binary_self_canonical_path)
                {
                    already_installed = true;
                }
                else
                {
                    if (!is_symlink)
                    {
                        fmt::print("File {} already exists but it's not a symlink. Will rename to {}.\n",
                                   main_bin_path.string(), main_bin_old_path.string());
                        fs::rename(main_bin_path, main_bin_old_path);
                    }
                    else if (points_to != main_bin_path)
                    {
                        fmt::print("Symlink {} already exists but it points to {}. Will replace the old symlink to {}.\n",
                                   main_bin_path.string(), points_to.string(), binary_self_canonical_path.string());
                        (void)fs::remove(main_bin_path);
                    }
                }
            }

            if (!already_installed)
            {
                if (!fs::exists(bin_dir))
                {
                    fmt::print("Creating binary directory {}.\n", bin_dir.string());
                    fs::create_directories(bin_dir);
                }

                fmt::print("Creating symlink {} to {}.\n", main_bin_path.string(), binary_self_canonical_path.string());
                fs::create_symlink(binary_self_canonical_path, main_bin_path);

                if (0 != chmod(binary_self_canonical_path.string().c_str(), S_IRUSR | S_IRGRP | S_IROTH | S_IXUSR | S_IXGRP | S_IXOTH))
                    throw ErrnoException(ErrorCodes::SYSTEM_ERROR, "Cannot chmod {}", binary_self_canonical_path.string());
            }
        }
        else
        {
            bool is_symlink = FS::isSymlink(main_bin_path);

            if (!is_symlink)
            {
                /// Check if the binary is the same file (already installed).
                if (old_binary_exists && binary_self_canonical_path == fs::canonical(main_bin_path))
                {
                    already_installed = true;
                    fmt::print("ClickHouse binary is already located at {}\n", main_bin_path.string());
                }
                /// Check if binary has the same content.
                else if (old_binary_exists && binary_size == fs::file_size(main_bin_path))
                {
                    fmt::print("Found already existing ClickHouse binary at {} having the same size. Will check its contents.\n",
                        main_bin_path.string());

                    if (filesEqual(binary_self_path.string(), main_bin_path.string()))
                    {
                        already_installed = true;
                        fmt::print("ClickHouse binary is already located at {} and it has the same content as {}\n",
                            main_bin_path.string(), binary_self_canonical_path.string());
                    }
                }
            }

            if (already_installed)
            {
                if (0 != chmod(main_bin_path.string().c_str(), S_IRUSR | S_IRGRP | S_IROTH | S_IXUSR | S_IXGRP | S_IXOTH))
                    throw ErrnoException(ErrorCodes::SYSTEM_ERROR, "Cannot chmod {}", main_bin_path.string());
            }
            else
            {
                if (!fs::exists(bin_dir))
                {
                    fmt::print("Creating binary directory {}.\n", bin_dir.string());
                    fs::create_directories(bin_dir);
                }

                size_t available_space = fs::space(bin_dir).available;
                if (available_space < binary_size)
                    throw Exception(ErrorCodes::NOT_ENOUGH_SPACE, "Not enough space for clickhouse binary in {}, required {}, available {}.",
                        bin_dir.string(), ReadableSize(binary_size), ReadableSize(available_space));

                fmt::print("Copying ClickHouse binary to {}\n", main_bin_tmp_path.string());

                try
                {
                    String source = binary_self_path.string();
                    String destination = main_bin_tmp_path.string();

                    /// Try to make a hard link first, as an optimization.
                    /// It is possible if the source and the destination are on the same filesystems.
                    if (0 != link(source.c_str(), destination.c_str()))
                    {
                        ReadBufferFromFile in(binary_self_path.string());
                        WriteBufferFromFile out(main_bin_tmp_path.string());
                        copyData(in, out);
                        out.sync();
                        out.finalize();
                    }

                    if (0 != chmod(destination.c_str(), S_IRUSR | S_IRGRP | S_IROTH | S_IXUSR | S_IXGRP | S_IXOTH))
                        throw ErrnoException(ErrorCodes::SYSTEM_ERROR, "Cannot chmod {}", main_bin_tmp_path.string());
                }
                catch (const Exception & e)
                {
                    if (e.code() == ErrorCodes::CANNOT_OPEN_FILE && geteuid() != 0)
                        std::cerr << "Install must be run as root: " << formatWithSudo("./clickhouse install") << '\n';
                    throw;
                }

                if (old_binary_exists)
                {
                    fmt::print("{} already exists, will rename existing binary to {} and put the new binary in place\n",
                            main_bin_path.string(), main_bin_old_path.string());

                    /// There is file exchange operation in Linux but it's not portable.
                    fs::rename(main_bin_path, main_bin_old_path);
                }

                fmt::print("Renaming {} to {}.\n", main_bin_tmp_path.string(), main_bin_path.string());
                fs::rename(main_bin_tmp_path, main_bin_path);
            }
        }

        /// Create symlinks.

        std::initializer_list<std::string_view> tools
        {
            "clickhouse-server",
            "clickhouse-client",
            "clickhouse-local",
            "clickhouse-benchmark",
            "clickhouse-obfuscator",
            "clickhouse-git-import",
            "clickhouse-compressor",
            "clickhouse-format",
            "clickhouse-extract-from-config",
            "clickhouse-keeper",
            "clickhouse-keeper-converter",
            "clickhouse-disks",
#if USE_CHDIG
            "clickhouse-chdig",
            "chdig",
#endif
            "ch",
            "chl",
            "chc",
        };

        for (const auto & tool : tools)
        {
            bool need_to_create = true;
            fs::path symlink_path = bin_dir / tool;

            if (fs::exists(symlink_path))
            {
                /// Do not replace short named symlinks if they are already present in the system
                /// to avoid collision with other tools.
                if (!tool.starts_with("clickhouse"))
                {
                    fmt::print("Symlink {} already exists. Will keep it.\n", symlink_path.string());
                    need_to_create = false;
                }
                else
                {
                    bool is_symlink = FS::isSymlink(symlink_path);
                    fs::path points_to;
                    if (is_symlink)
                        points_to = fs::weakly_canonical(FS::readSymlink(symlink_path));

                    if (is_symlink && (points_to == main_bin_path || (options.contains("link") && points_to == binary_self_canonical_path)))
                    {
                        need_to_create = false;
                    }
                    else
                    {
                        if (!is_symlink)
                        {
                            fs::path rename_path = symlink_path.replace_extension(".old");
                            fmt::print("File {} already exists but it's not a symlink. Will rename to {}.\n",
                                       symlink_path.string(), rename_path.string());
                            fs::rename(symlink_path, rename_path);
                        }
                        else if (points_to != main_bin_path)
                        {
                            fmt::print("Symlink {} already exists but it points to {}. Will replace the old symlink to {}.\n",
                                       symlink_path.string(), points_to.string(), main_bin_path.string());
                            (void)fs::remove(symlink_path);
                        }
                    }
                }
            }

            if (need_to_create)
            {
                fmt::print("Creating symlink {} to {}.\n", symlink_path.string(), main_bin_path.string());
                fs::create_symlink(main_bin_path, symlink_path);
            }
        }

        /// Creation of clickhouse user and group.

        std::string user = options["user"].as<std::string>();
        std::string group = options["group"].as<std::string>();

        if (!group.empty())
        {
            fmt::print("Creating clickhouse group if it does not exist.\n");
            createGroup(group);
        }
        else
            fmt::print("Will not create a dedicated clickhouse group.\n");

        if (!user.empty())
        {
            fmt::print("Creating clickhouse user if it does not exist.\n");
            createUser(user, group);

            if (group.empty())
                group = user;

            /// Setting ulimits.
            try
            {
#if defined(OS_DARWIN)

                /// TODO Set ulimits on macOS.

#else
                fs::path ulimits_dir = "/etc/security/limits.d";
                fs::path ulimits_file = ulimits_dir / fmt::format("{}.conf", user);
                fmt::print("Will set ulimits for {} user in {}.\n", user, ulimits_file.string());
                std::string ulimits_content = fmt::format(
                    "{0}\tsoft\tnofile\t1048576\n"
                    "{0}\thard\tnofile\t1048576\n", user);

                fs::create_directories(ulimits_dir);

                WriteBufferFromFile out(ulimits_file.string());
                out.write(ulimits_content.data(), ulimits_content.size());
                out.sync();
                out.finalize();
#endif
            }
            catch (...)
            {
                std::cerr << "Cannot set ulimits: " << getCurrentExceptionMessage(false) << "\n";
            }
        }
        else
            fmt::print("Will not create a dedicated clickhouse user.\n");

        /// Creating configuration files and directories.

        fs::path config_dir = prefix / options["config-path"].as<std::string>();

        if (!fs::exists(config_dir))
        {
            fmt::print("Creating config directory {}.\n", config_dir.string());
            fs::create_directories(config_dir);
        }

        fs::path main_config_file = config_dir / "config.xml";
        fs::path users_config_file = config_dir / "users.xml";
        fs::path config_d = config_dir / "config.d";
        fs::path users_d = config_dir / "users.d";

        fs::path log_path = prefix / options["log-path"].as<std::string>();
        fs::path data_path = prefix / options["data-path"].as<std::string>();
        fs::path pid_path = prefix / options["pid-path"].as<std::string>();

        /// True if the authentication of the default user is configured with anything but an empty flat `password`,
        /// so the installer does not set up a password for it.
        bool has_authentication_for_default_user = false;
        /// True if the default user cannot log in without credentials, so it is reasonable to accept connections from the network.
        bool has_credentials_for_default_user = false;
        /// True if the default user has a password, so it can connect with `clickhouse-client --password`.
        bool has_password_for_default_user = false;
        bool is_default_user_removed = false;
        /// True if no XML users config preceding `shadowing_access_storage` defines the default user,
        /// so the effective default user is not known.
        bool is_default_user_maybe_shadowed = false;
        /// False if the main config has `user_directories` without `users_xml` and no `users_config`,
        /// so the server does not read users from any XML file.
        bool has_users_xml_config = true;
        /// Set if the first XML users config is a relative path that does not exist in the config directory,
        /// other than the stock `users.xml`. The server resolves it against its working directory, which is not known here,
        /// so the installer neither creates it nor sets up a password in it.
        std::optional<fs::path> unresolved_users_config_file;
        /// All XML users configs the server reads users from, in the order it looks up users in them.
        std::vector<fs::path> users_config_files;
        /// The first access storage that is not an XML users config and may store the default user (e.g. `local_directory`),
        /// and the number of XML users configs preceding it. The server looks up users in all storages in order,
        /// so if no preceding XML users config defines the default user, the installer cannot know the effective one.
        std::string shadowing_access_storage;
        size_t num_users_configs_before_shadowing_access_storage = 0;
        /// Set if the default user may instead be defined in a later XML users config with a relative path
        /// that is resolved against the working directory of the server, which is not known here.
        std::optional<fs::path> unresolved_later_users_config_file;

        if (!fs::exists(config_d))
        {
            fmt::print("Creating config directory {} that is used for tweaks of main server configuration.\n", config_d.string());
            fs::create_directory(config_d);
        }

        if (!fs::exists(main_config_file))
        {
            std::string_view main_config_content(reinterpret_cast<const char *>(resource_config_xml), std::size(resource_config_xml));
            if (main_config_content.empty())
            {
                fmt::print("There is no default config.xml, you have to download it and place to {}.\n", main_config_file.string());
            }
            else
            {
                {
                    WriteBufferFromFile out(main_config_file.string());
                    out.write(main_config_content.data(), main_config_content.size());
                    out.sync();
                    out.finalize();
                }

                /// Override the default paths.

                /// Data paths.
                const std::string data_file = config_d / "data-paths.xml";
                if (!fs::exists(data_file))
                {
                    WriteBufferFromFile out(data_file);
                    out << "<clickhouse>\n"
                    "    <path>" << data_path.string() << "</path>\n"
                    "    <tmp_path>" << (data_path / "tmp").string() << "</tmp_path>\n"
                    "    <user_files_path>" << (data_path / "user_files").string() << "</user_files_path>\n"
                    "    <format_schema_path>" << (data_path / "format_schemas").string() << "</format_schema_path>\n"
                    "</clickhouse>\n";
                    out.sync();
                    out.finalize();
                    fs::permissions(data_file, fs::perms::owner_read, fs::perm_options::replace);
                    fmt::print("Data path configuration override is saved to file {}.\n", data_file);
                }

                /// Logger.
                const std::string logger_file = config_d / "logger.xml";
                if (!fs::exists(logger_file))
                {
                    WriteBufferFromFile out(logger_file);
                    out << "<clickhouse>\n"
                    "    <logger>\n"
                    "        <log>" << (log_path / "clickhouse-server.log").string() << "</log>\n"
                    "        <errorlog>" << (log_path / "clickhouse-server.err.log").string() << "</errorlog>\n"
                    "    </logger>\n"
                    "</clickhouse>\n";
                    out.sync();
                    out.finalize();
                    fs::permissions(logger_file, fs::perms::owner_read, fs::perm_options::replace);
                    fmt::print("Log path configuration override is saved to file {}.\n", logger_file);
                }

                /// User directories.
                const std::string user_directories_file = config_d / "user-directories.xml";
                if (!fs::exists(user_directories_file))
                {
                    WriteBufferFromFile out(user_directories_file);
                    out << "<clickhouse>\n"
                    "    <user_directories>\n"
                    "        <local_directory>\n"
                    "            <path>" << (data_path / "access").string() << "</path>\n"
                    "        </local_directory>\n"
                    "    </user_directories>\n"
                    "</clickhouse>\n";
                    out.sync();
                    out.finalize();
                    fs::permissions(user_directories_file, fs::perms::owner_read, fs::perm_options::replace);
                    fmt::print("User directory path configuration override is saved to file {}.\n", user_directories_file);
                }

                /// OpenSSL.
                const std::string openssl_file = config_d / "openssl.xml";
                if (!fs::exists(openssl_file))
                {
                    WriteBufferFromFile out(openssl_file);
                    out << "<clickhouse>\n"
                    "    <openSSL>\n"
                    "        <server>\n"
                    "            <certificateFile>" << (config_dir / "server.crt").string() << "</certificateFile>\n"
                    "            <privateKeyFile>" << (config_dir / "server.key").string() << "</privateKeyFile>\n"
                    "        </server>\n"
                    "    </openSSL>\n"
                    "</clickhouse>\n";
                    out.sync();
                    out.finalize();
                    fs::permissions(openssl_file, fs::perms::owner_read, fs::perm_options::replace);
                    fmt::print("OpenSSL path configuration override is saved to file {}.\n", openssl_file);
                }
            }
        }
        else
        {
            fmt::print("Config file {} already exists, will keep it and extract path info from it.\n", main_config_file.string());

            ConfigProcessor processor(main_config_file.string(), /* throw_on_bad_incl = */ false, /* log_to_console = */ false);
            ConfigurationPtr configuration(new Poco::Util::XMLConfiguration(processor.processConfig()));

            if (configuration->has("path"))
            {
                data_path = configuration->getString("path");
                fmt::print("{} has {} as data path.\n", main_config_file.string(), data_path.string());
            }

            if (configuration->has("logger.log"))
            {
                log_path = fs::path(configuration->getString("logger.log")).remove_filename();
                fmt::print("{} has {} as log path.\n", main_config_file.string(), log_path.string());
            }

            /// Find the XML users configs in the same order as `AccessControl::addStoragesFromMainConfig` adds them.
            /// The first one is where the password for the default user is written to.
            /// Like `AccessControl`, a relative path is resolved against the config directory only if the file exists there.
            /// Otherwise the server resolves it against its working directory, which is not known here.
            auto resolve_users_config_path = [&](fs::path users_config_path)
            {
                if (users_config_path.is_relative() && fs::exists(config_dir / users_config_path))
                    users_config_path = (config_dir / users_config_path).lexically_normal();
                return users_config_path;
            };

            auto add_users_config = [&](const fs::path & users_config_path)
            {
                if (std::find(users_config_files.begin(), users_config_files.end(), users_config_path) == users_config_files.end())
                    users_config_files.push_back(users_config_path);
            };

            /// `disk_storage_path` is set for a local directory storage, which shadows the users configs only if it may define the default user.
            auto add_shadowing_access_storage = [&](const std::string & description, const std::optional<fs::path> & disk_storage_path = {})
            {
                if (shadowing_access_storage.empty() && !(disk_storage_path && isKnownWithoutDefaultUserDiskAccessStorage(*disk_storage_path)))
                {
                    shadowing_access_storage = description;
                    num_users_configs_before_shadowing_access_storage = users_config_files.size();
                }
            };

            /// `AccessControl::addStoragesFromMainConfig` adds the storage from `access_control_path` before all others.
            std::string access_control_path = configuration->getString("access_control_path", "");
            if (!access_control_path.empty())
                add_shadowing_access_storage("access_control_path", fs::path(access_control_path));

            bool has_user_directories = configuration->has("user_directories");
            std::string configured_users_config = configuration->getString("users_config", "");
            if (!configured_users_config.empty())
                add_users_config(resolve_users_config_path(configured_users_config));
            else if (!has_user_directories)
                add_users_config(main_config_file);

            if (has_user_directories)
            {
                Poco::Util::AbstractConfiguration::Keys keys_in_user_directories;
                configuration->keys("user_directories", keys_in_user_directories);
                for (const auto & key_in_user_directories : keys_in_user_directories)
                {
                    /// Same type names as in `AccessControl::addStoragesFromUserDirectoriesConfig`.
                    std::string type = key_in_user_directories;
                    if (size_t bracket_pos = type.find('['); bracket_pos != std::string::npos)
                        type.resize(bracket_pos);
                    if (type == "users_xml" || type == "users.xml" || type == "users_config")
                        add_users_config(resolve_users_config_path(
                            configuration->getString("user_directories." + key_in_user_directories + ".path")));
                    else if (type == "local" || type == "local_directory")
                        add_shadowing_access_storage("user_directories." + key_in_user_directories,
                            fs::path(configuration->getString("user_directories." + key_in_user_directories + ".path", "")));
                    else if (type != "memory")
                        /// `replicated` or `ldap`: the default user may be stored or authenticated there.
                        /// A `memory` storage is empty when the server starts.
                        add_shadowing_access_storage("user_directories." + key_in_user_directories);
                }
            }

            if (users_config_files.empty())
            {
                has_users_xml_config = false;
                fmt::print("{} does not use an XML users config.\n", main_config_file.string());
            }
            else
            {
                /// The first XML users config is a relative path only if it does not exist in the config directory.
                /// For the stock `users.xml` it is created there below, as `clickhouse install` always did,
                /// and then the server resolves the path to it the same way as above, as it checks the config directory first.
                /// This keeps the stock layout working.
                /// Any other relative path (including `users.yaml` and `users.yml`) may intentionally point to a file
                /// in the working directory of the server, and creating it in the config directory would silently switch
                /// the server to the new file.
                if (users_config_files.front().is_relative())
                {
                    const fs::path first_users_config = users_config_files.front().lexically_normal();
                    if (first_users_config == "users.xml")
                        users_config_files.front() = (config_dir / first_users_config).lexically_normal();
                    else
                        unresolved_users_config_file = users_config_files.front();
                }

                if (unresolved_users_config_file)
                {
                    has_users_xml_config = false;
                    fmt::print("{} has {} as users config, which is resolved against the working directory of the server.\n",
                        main_config_file.string(), unresolved_users_config_file->string());
                }
                else if (users_config_files.front() != users_config_file)
                {
                    users_config_file = users_config_files.front();
                    users_d = fs::path(users_config_file).replace_extension("d");
                    fmt::print("{} has {} as users config.\n", main_config_file.string(), users_config_file.string());
                }

                if (!shadowing_access_storage.empty() && num_users_configs_before_shadowing_access_storage == 0)
                {
                    /// The server still reads the users config, so it is created if missing, but the default user it defines may be shadowed.
                    is_default_user_maybe_shadowed = true;
                    fmt::print("{} has {} before any XML users config.\n", main_config_file.string(), shadowing_access_storage);
                }
            }
        }

        if (users_config_files.empty() && has_users_xml_config)
            users_config_files.push_back(users_config_file);

        if (has_users_xml_config && !fs::exists(users_d))
        {
            fmt::print("Creating config directory {} that is used for tweaks of users configuration.\n", users_d.string());
            fs::create_directories(users_d);
        }

        /// The XML users config that defines the effective default user, and the directory for its tweaks,
        /// where the password for the default user is written to. It is the first XML users config unless the default user
        /// is removed from it and defined in a later one: overriding it in the first one would create a new default user there,
        /// which would shadow the later definition entirely. The tweaks directory is the merge directory that is applied last,
        /// so the password written there overrides the authentication from other merged files.
        fs::path default_user_config_file = users_config_file;
        fs::path default_user_users_d = getLastConfigMergeDir(users_config_file);

        if (!has_users_xml_config)
        {
            /// Nothing to create or check: users are not configured in XML files.
        }
        else if (!fs::exists(users_config_file))
        {
            /// The server parses the users config according to its extension, case-insensitively, like `ConfigProcessor::parseConfig`.
            std::string users_config_extension = users_config_file.extension().string();
            toLowerASCII(users_config_extension);
            const bool is_yaml_users_config = users_config_extension == ".yaml" || users_config_extension == ".yml";
            std::string_view users_config_content = is_yaml_users_config
                ? std::string_view(reinterpret_cast<const char *>(resource_users_yaml), std::size(resource_users_yaml))
                : std::string_view(reinterpret_cast<const char *>(resource_users_xml), std::size(resource_users_xml));
            if (users_config_content.empty())
            {
                fmt::print("There is no default users config, you have to download it and place to {}.\n", users_config_file.string());
            }
            else
            {
                WriteBufferFromFile out(users_config_file.string());
                out.write(users_config_content.data(), users_config_content.size());
                out.sync();
                out.finalize();
            }
        }
        else
        {
            fmt::print("Users config file {} already exists, will keep it and extract users info from it.\n", users_config_file.string());
        }

        /// Also check a just created users config: the existing fragments in its companion `users.d` directory
        /// may remove the default user or set up its authentication.
        if (has_users_xml_config && fs::exists(users_config_file))
        {
            /// The server looks up the default user in the XML users configs in order and uses the first one that defines it,
            /// so check whether it is defined anywhere and whether its first definition has a password.
            is_default_user_removed = true;
            for (size_t i = 0; i < users_config_files.size(); ++i)
            {
                if (!shadowing_access_storage.empty() && i == num_users_configs_before_shadowing_access_storage)
                {
                    /// The default user may be defined in a storage that is not an XML users config.
                    is_default_user_removed = false;
                    is_default_user_maybe_shadowed = true;
                    break;
                }

                const auto & users_config_path = users_config_files[i];
                /// A relative path here is resolved against the working directory of the server, which is not known,
                /// so the default user may be defined in that file.
                if (users_config_path.is_relative())
                {
                    is_default_user_removed = false;
                    unresolved_later_users_config_file = users_config_path;
                    break;
                }

                if (!fs::exists(users_config_path))
                    continue;

                ConfigProcessor processor(users_config_path.string(), /* throw_on_bad_incl = */ false, /* log_to_console = */ false);
                ConfigurationPtr configuration(new Poco::Util::XMLConfiguration(processor.processConfig()));

                /// The default user may be explicitly removed, e.g. via `<default remove="1" />` in users.d.
                if (!configuration->has("users.default"))
                    continue;

                is_default_user_removed = false;
                has_authentication_for_default_user = hasAuthentication(*configuration, "users.default");
                has_credentials_for_default_user = hasCredentials(*configuration, "users.default");
                has_password_for_default_user = hasPassword(*configuration, "users.default");
                if (i != 0)
                {
                    default_user_config_file = users_config_path;
                    default_user_users_d = getLastConfigMergeDir(users_config_path);
                    fmt::print("The default user is defined in {}.\n", default_user_config_file.string());
                }
                break;
            }

            /// No XML users config defines the default user, but the server continues looking it up in the later
            /// storage that is not an XML users config.
            if (is_default_user_removed && !shadowing_access_storage.empty())
            {
                is_default_user_removed = false;
                is_default_user_maybe_shadowed = true;
            }
        }

        /// Don't allow relative paths because install script may cd to / when installing
        /// And having path=./ may break the system
        if (log_path.is_relative())
            throw Exception(ErrorCodes::BAD_ARGUMENTS, "Log path is relative: {}", log_path.string());
        if (data_path.is_relative())
            throw Exception(ErrorCodes::BAD_ARGUMENTS, "Data path is relative: {}", data_path.string());
        if (pid_path.is_relative())
            throw Exception(ErrorCodes::BAD_ARGUMENTS, "Pid path is relative: {}", pid_path.string());

        /// Create directories for data and log.

        if (fs::exists(log_path))
        {
            fmt::print("Log directory {} already exists.\n", log_path.string());
        }
        else
        {
            fmt::print("Creating log directory {}.\n", log_path.string());
            fs::create_directories(log_path);
        }

        if (fs::exists(data_path))
        {
            fmt::print("Data directory {} already exists.\n", data_path.string());
        }
        else
        {
            fmt::print("Creating data directory {}.\n", data_path.string());
            fs::create_directories(data_path);
        }

        if (fs::exists(pid_path))
        {
            fmt::print("Pid directory {} already exists.\n", pid_path.string());
        }
        else
        {
            fmt::print("Creating pid directory {}.\n", pid_path.string());
            fs::create_directories(pid_path);
        }

        /// Chmod and chown data and log directories
        changeOwnership(log_path, user, group);
        changeOwnership(pid_path, user, group);

        /// Not recursive, because there can be a huge number of files and it will be slow.
        changeOwnership(data_path, user, group, /* recursive= */ false);

        /// All users are allowed to read pid file (for clickhouse status command).
        fs::permissions(pid_path, fs::perms::owner_all | fs::perms::group_read | fs::perms::others_read, fs::perm_options::replace);

        /// Other users in clickhouse group are allowed to read and even delete logs.
        fs::permissions(log_path, fs::perms::owner_all | fs::perms::group_all, fs::perm_options::replace);

        /// Data directory is not accessible to anyone except clickhouse.
        fs::permissions(data_path, fs::perms::owner_all, fs::perm_options::replace);

        fs::path odbc_bridge_path = bin_dir / "clickhouse-odbc-bridge";
        fs::path library_bridge_path = bin_dir / "clickhouse-library-bridge";

        if (fs::exists(odbc_bridge_path) || fs::exists(library_bridge_path))
        {
            createGroup(DEFAULT_CLICKHOUSE_BRIDGE_GROUP);
            createUser(DEFAULT_CLICKHOUSE_BRIDGE_USER, DEFAULT_CLICKHOUSE_BRIDGE_GROUP);

            if (fs::exists(odbc_bridge_path))
                changeOwnership(odbc_bridge_path, DEFAULT_CLICKHOUSE_BRIDGE_USER, DEFAULT_CLICKHOUSE_BRIDGE_GROUP);
            if (fs::exists(library_bridge_path))
                changeOwnership(library_bridge_path, DEFAULT_CLICKHOUSE_BRIDGE_USER, DEFAULT_CLICKHOUSE_BRIDGE_GROUP);
        }

        bool stdin_is_a_tty = isatty(STDIN_FILENO);
        bool stdout_is_a_tty = isatty(STDOUT_FILENO);

        /// dpkg or apt installers can ask for non-interactive work explicitly.

        const char * debian_frontend_var = getenv("DEBIAN_FRONTEND"); // NOLINT(concurrency-mt-unsafe)
        bool noninteractive = (debian_frontend_var && debian_frontend_var == std::string_view("noninteractive"))
                              || options.contains("noninteractive");


        bool is_interactive = !noninteractive && stdin_is_a_tty && stdout_is_a_tty;

        /// We can ask password even if stdin is closed/redirected but /dev/tty is available.
        bool can_ask_password = !noninteractive && stdout_is_a_tty;

        /// Set up password for default user.
        if (unresolved_users_config_file)
        {
            fmt::print("{}The users config {} from {} is not in {}. Not setting up a password for the default user.{}\n",
                start_hilite, unresolved_users_config_file->string(), main_config_file.string(), config_dir.string(), end_hilite);
        }
        else if (unresolved_later_users_config_file)
        {
            fmt::print("{}The default user may be defined in the users config {} from {}, which is resolved against the working directory of the server. Not setting up a password for it.{}\n",
                start_hilite, unresolved_later_users_config_file->string(), main_config_file.string(), end_hilite);
        }
        else if (is_default_user_maybe_shadowed)
        {
            fmt::print("{}The default user may be defined in {} from {}, which is not an XML users config. Not setting up a password for it.{}\n",
                start_hilite, shadowing_access_storage, main_config_file.string(), end_hilite);
        }
        else if (!has_users_xml_config)
        {
            fmt::print("{}There is no XML users config in {}. Not setting up a password for the default user.{}\n",
                start_hilite, main_config_file.string(), end_hilite);
        }
        else if (is_default_user_removed)
        {
            fmt::print("{}The default user is removed from {} and {}. Not setting up a password for it.{}\n",
                start_hilite, users_config_file.string(), users_d.string(), end_hilite);
        }
        else if (has_credentials_for_default_user && has_password_for_default_user)
        {
            fmt::print("{}Password for the default user is already specified. To remind or reset, see {} and {}.{}\n",
                start_hilite, default_user_config_file.string(), default_user_users_d.string(), end_hilite);
        }
        else if (has_credentials_for_default_user)
        {
            fmt::print("{}The default user is configured to authenticate with credentials other than a password. See {} and {} to change it.{}\n",
                start_hilite, default_user_config_file.string(), default_user_users_d.string(), end_hilite);
        }
        else if (has_authentication_for_default_user)
        {
            fmt::print("{}The default user is configured to be accessible without a password. See {} and {} to change it.{}\n",
                start_hilite, default_user_config_file.string(), default_user_users_d.string(), end_hilite);
        }
        else if (!can_ask_password)
        {
            fmt::print("{}Password for the default user is an empty string. See {} and {} to change it.{}\n",
                start_hilite, default_user_config_file.string(), default_user_users_d.string(), end_hilite);
        }
        else
        {
            /// NOTE: When installing debian package with dpkg -i, stdin is not a terminal but we are still being able to enter password.
            /// More sophisticated method with /dev/tty is used inside the `readpassphrase` function.

            char buf[1000] = {};
            std::string password;
            if (auto * result = readpassphrase("Set up the password for the default user: ", buf, sizeof(buf), 0))
                password = result;

            if (!password.empty())
            {
                if (!fs::exists(default_user_users_d))
                {
                    fmt::print("Creating config directory {} that is used for tweaks of users configuration.\n", default_user_users_d.string());
                    fs::create_directories(default_user_users_d);
                }
                std::string password_file = default_user_users_d / "default-password.xml";
                WriteBufferFromFile out(password_file);
#if USE_SSL
                std::vector<uint8_t> hash;
                hash.resize(32);
                encodeSHA256(password, hash.data());
                std::string hash_hex;
                hash_hex.resize(64);
                for (size_t i = 0; i < 32; ++i)
                    writeHexByteLowercase(hash[i], &hash_hex[2 * i]);
                out << "<clickhouse>\n"
                    "    <users>\n"
                    "        <default>\n"
                    "            <password remove='1' />\n"
                    "            <password_sha256_hex>" << hash_hex << "</password_sha256_hex>\n"
                    "        </default>\n"
                    "    </users>\n"
                    "</clickhouse>\n";
                out.sync();
                out.finalize();
                fmt::print("{}Password for the default user is saved in file {}.{}\n", start_hilite, password_file, end_hilite);
#else
                out << "<clickhouse>\n"
                    "    <users>\n"
                    "        <default>\n"
                    "            <password><![CDATA[" << password << "]]></password>\n"
                    "        </default>\n"
                    "    </users>\n"
                    "</clickhouse>\n";
                out.sync();
                out.finalize();
                fmt::print("{}Password for the default user is saved in plaintext in file {}.{}\n", start_hilite, password_file, end_hilite);
#endif
                has_credentials_for_default_user = true;
                has_password_for_default_user = true;
            }
            else
                fmt::print("{}Password for the default user is an empty string. See {} and {} to change it.{}\n",
                    start_hilite, default_user_config_file.string(), default_user_users_d.string(), end_hilite);
        }

        /** Set capabilities for the binary.
          *
          * 1. Check that "setcap" tool exists.
          * 2. Check that an arbitrary program with installed capabilities can run.
          * 3. Set the capabilities.
          *
          * The second is important for Docker and systemd-nspawn.
          * When the container has no capabilities,
          * but the executable file inside the container has capabilities,
          *  then attempt to run this file will end up with a cryptic "Operation not permitted" message.
          */

#if defined(OS_LINUX)
        fmt::print("Setting capabilities for clickhouse binary. This is optional.\n");
        std::string command = fmt::format("command -v setcap >/dev/null"
            " && command -v capsh >/dev/null"
            " && capsh --has-p=cap_net_admin,cap_ipc_lock,cap_sys_nice,cap_net_bind_service+ep >/dev/null 2>&1"
            " && setcap 'cap_net_admin,cap_ipc_lock,cap_sys_nice,cap_net_bind_service+ep' {0}"
            " || echo \"Cannot set 'net_admin' or 'ipc_lock' or 'sys_nice' or 'net_bind_service' capability for clickhouse binary."
                " This is optional. Taskstats accounting will be disabled."
                " To enable taskstats accounting you may add the required capability later manually.\"",
            shellQuote(fs::canonical(main_bin_path).string()));
        executeScript(command);
#endif

        /// If the default user cannot log in without credentials, ask for open for connections.
        if (is_interactive && has_credentials_for_default_user)
        {
            if (ask("Allow server to accept connections from the network (default is localhost only), [y/N]: "))
            {
                std::string listen_file = config_d / "listen.xml";
                WriteBufferFromFile out(listen_file);
                out << "<clickhouse>\n"
                    "    <listen_host>::</listen_host>\n"
                    "</clickhouse>\n";
                out.sync();
                out.finalize();
                fmt::print("The choice is saved in file {}.\n", listen_file);
            }
        }

        /// Chmod and chown configs
        changeOwnership(config_dir, user, group);

        /// The server reads every XML users config together with its merge directories (`<name>.d` and `conf.d`, like `ConfigProcessor`),
        /// and they may live outside the config directory, so it needs to read them as well.
        std::vector<fs::path> users_config_files_to_fix;
        std::vector<fs::path> users_config_dirs_to_fix;
        if (has_users_xml_config)
        {
            auto add_unique = [](std::vector<fs::path> & paths, const fs::path & added_path)
            {
                fs::path normal_path = added_path.lexically_normal();
                if (std::find(paths.begin(), paths.end(), normal_path) == paths.end())
                    paths.push_back(std::move(normal_path));
            };

            auto add_users_config = [&](const fs::path & users_config_path)
            {
                /// A relative path is resolved against the working directory of the server, which is not known here.
                if (users_config_path.is_relative())
                    return;
                if (fs::exists(users_config_path))
                    add_unique(users_config_files_to_fix, users_config_path);
                for (const auto & merge_dir : {fs::path(users_config_path).replace_extension("d"), fs::path(users_config_path).replace_filename("conf.d")})
                    if (fs::is_directory(merge_dir))
                        add_unique(users_config_dirs_to_fix, merge_dir);
            };

            add_users_config(users_config_file);
            /// This also covers the `.d` directory of the users config that defines the default user, which may have been just created.
            for (const auto & users_config_path : users_config_files)
                add_users_config(users_config_path);

            auto is_outside_config_dir = [&](const fs::path & checked_path)
            {
                auto relative = checked_path.lexically_normal().lexically_relative(config_dir.lexically_normal());
                return relative.empty() || *relative.begin() == "..";
            };

            for (const auto & users_config_path : users_config_files_to_fix)
                if (is_outside_config_dir(users_config_path))
                    changeOwnership(users_config_path, user, group, /* recursive= */ false);
            for (const auto & merge_dir : users_config_dirs_to_fix)
                if (is_outside_config_dir(merge_dir))
                    changeOwnership(merge_dir, user, group);
        }

        /// Symlink "preprocessed_configs" is created by the server, so "write" is needed.
        fs::permissions(config_dir, fs::perms::owner_all, fs::perm_options::replace);

        /// Subdirectories, so "execute" is needed.
        if (fs::exists(config_d))
            fs::permissions(config_d, fs::perms::owner_read | fs::perms::owner_exec, fs::perm_options::replace);
        for (const auto & merge_dir : users_config_dirs_to_fix)
            fs::permissions(merge_dir, fs::perms::owner_read | fs::perms::owner_exec, fs::perm_options::replace);

        /// Readonly.
        if (fs::exists(main_config_file))
            fs::permissions(main_config_file, fs::perms::owner_read, fs::perm_options::replace);
        for (const auto & users_config_path : users_config_files_to_fix)
            fs::permissions(users_config_path, fs::perms::owner_read, fs::perm_options::replace);


        std::string maybe_password;
        if (has_credentials_for_default_user && has_password_for_default_user)
            maybe_password = " --password";

        /// If user specified --prefix, --pid-path, --config-path, --binary-path, --user, --group
        /// in install args we need to pass them to start command
        std::string maybe_prefix;
        if (options.contains("prefix") && !options["prefix"].defaulted() && prefix != "/")
            maybe_prefix = " --prefix " + prefix.string();

        std::string maybe_pid_path;
        if (options.contains("pid-path") && !options["pid-path"].defaulted())
            maybe_pid_path = " --pid-path " + options["pid-path"].as<std::string>();

        std::string maybe_config_path;
        if (options.contains("config-path") && !options["config-path"].defaulted())
            maybe_config_path = " --config-path " + options["config-path"].as<std::string>();

        std::string maybe_binary_path;
        if (options.contains("binary-path") && !options["binary-path"].defaulted())
            maybe_binary_path = " --binary-path " + options["binary-path"].as<std::string>();

        std::string maybe_user;
        if (options.contains("user") && !options["user"].defaulted() && user != DEFAULT_CLICKHOUSE_SERVER_USER)
            maybe_user = " --user " + user;

        std::string maybe_group;
        if (options.contains("group") && !options["group"].defaulted() && group != DEFAULT_CLICKHOUSE_SERVER_GROUP)
            maybe_group = " --group " + group;

        std::string start_options = maybe_prefix + maybe_pid_path + maybe_config_path + maybe_binary_path + maybe_user + maybe_group;

        fs::path pid_file = pid_path / "clickhouse-server.pid";
        if (fs::exists(pid_file))
        {
            fmt::print(
                "\nClickHouse has been successfully installed.\n"
                "\nRestart clickhouse-server with:\n"
                " {}{}\n"
                "\nStart clickhouse-client with:\n"
                " clickhouse-client{}\n\n",
                formatWithSudo("clickhouse restart"),
                start_options,
                maybe_password);
        }
        else
        {
            fmt::print(
                "\nClickHouse has been successfully installed.\n"
                "\nStart clickhouse-server with:\n"
                " {}{}\n"
                "\nStart clickhouse-client with:\n"
                " clickhouse-client{}\n\n",
                formatWithSudo("clickhouse start"),
                start_options,
                maybe_password);
        }
    }
    catch (const fs::filesystem_error &)
    {
        std::cerr << getCurrentExceptionMessage(false) << '\n';

        if (getuid() != 0)
            std::cerr << "\nRun with " << formatWithSudo("...") << "\n";

        return getCurrentExceptionCode();
    }
    catch (...)
    {
        std::cerr << getCurrentExceptionMessage(false) << '\n';
        return getCurrentExceptionCode();
    }

    return 0;
}


namespace
{
    int start(const std::string & user, const std::string & group, const fs::path & binary, const fs::path & executable, const fs::path & config, const fs::path & pid_file, unsigned max_tries, bool no_sudo)
    {
        if (fs::exists(pid_file))
        {
            ReadBufferFromFile in(pid_file.string());
            Int32 pid = {};
            if (tryReadIntText(pid, in))
            {
                fmt::print("{} file exists and contains pid = {}.\n", pid_file.string(), pid);

                if (0 == kill(pid, 0))
                {
                    fmt::print("The process with pid = {} is already running.\n", pid);
                    return 2;
                }
            }
            else
            {
                fmt::print("{} file exists but damaged, ignoring.\n", pid_file.string());
                (void)fs::remove(pid_file);
            }
        }
        else
        {
            /// Create a directory for pid file.
            /// It's created by "install" but we also support cases when ClickHouse is already installed different way.
            fs::path pid_path = pid_file;
            pid_path = pid_path.remove_filename();
            fs::create_directories(pid_path);
            /// All users are allowed to read pid file (for clickhouse status command).
            fs::permissions(pid_path, fs::perms::owner_all | fs::perms::group_read | fs::perms::others_read, fs::perm_options::replace);

            changeOwnership(pid_path, user);
        }

        std::string command = fmt::format("{} --config-file {} --pid-file {} --daemon",
            shellQuote(executable.string()), shellQuote(config.string()), shellQuote(pid_file.string()));

        if (!user.empty())
        {
            if (no_sudo)
            {
                /// Sometimes there is no sudo available like in some Docker images.
                /// We will use clickhouse su instead.
                command = fmt::format("{} su {} {}",
                    shellQuote(binary.string()), shellQuote(user + ":" + group), command);
            }
            else
            {
                /// sudo respects limits in /etc/security/limits.conf e.g. open files,
                /// that's why we are using it instead of the 'clickhouse su' tool.
                /// by default, sudo resets all the ENV variables, but we should preserve
                /// the values /etc/default/clickhouse in /etc/init.d/clickhouse file
                if (!group.empty())
                    command = fmt::format("sudo --preserve-env -u {} -g {} {}", shellQuote(user), shellQuote(group), command);
                else
                    command = fmt::format("sudo --preserve-env -u {} {}", shellQuote(user), command);
            }
        }

        fmt::print("Will run {}\n", command);
        executeScript(command, true);

        /// Wait to start.

        size_t try_num = 0;
        for (; try_num < max_tries; ++try_num)
        {
            fmt::print("Waiting for server to start\n");
            if (fs::exists(pid_file))
            {
                fmt::print("Server started\n");
                break;
            }
            sleepForSeconds(1);
        }

        if (try_num == max_tries)
        {
            fmt::print("Cannot start server. You can execute {} without --daemon option to run manually.\n", command);

            fs::path log_path;

            {
                ConfigProcessor processor(config.string(), /* throw_on_bad_incl = */ false, /* log_to_console = */ false);
                ConfigurationPtr configuration(new Poco::Util::XMLConfiguration(processor.processConfig()));

                if (configuration->has("logger.log"))
                    log_path = fs::path(configuration->getString("logger.log")).remove_filename();
            }

            if (log_path.empty())
            {
                fmt::print("Cannot obtain path to logs (logger.log) from config file {}.\n", config.string());
            }
            else
            {
                fs::path stderr_path = log_path;
                stderr_path.replace_filename("stderr.log");
                fmt::print("Look for logs at {} and for {}.\n", log_path.string(), stderr_path.string());
            }

            return 3;
        }

        return 0;
    }

    int isRunning(const fs::path & pid_file, bool ignore_file_does_not_exist)
    {
        int pid = 0;

        try
        {
            ReadBufferFromFile in(pid_file.string());
            if (tryReadIntText(pid, in))
            {
                fmt::print("{} file exists and contains pid = {}.\n", pid_file.string(), pid);
            }
            else
            {
                fmt::print("{} file exists but damaged, ignoring (the file will be removed).\n", pid_file.string());
                (void)fs::remove(pid_file);
            }
        }
        catch (const Exception & e)
        {
            if (!ignore_file_does_not_exist || e.code() != ErrorCodes::FILE_DOESNT_EXIST)
                throw;
        }

        if (pid)
        {
            if (0 == kill(pid, 0))
            {
                fmt::print("The process with pid = {} is running.\n", pid);
            }
            else if (errno == ESRCH)
            {
                fmt::print("The process with pid = {} does not exist.\n", pid);
                return 0;
            }
            else
                throw ErrnoException(ErrorCodes::CANNOT_KILL, "Cannot obtain the status of pid {} with `kill`", pid);
        }

        if (!pid)
        {
            fmt::print("Now there is no clickhouse-server process.\n");
        }

        return pid;
    }

    bool sendSignalAndWaitForStop(const fs::path & pid_file, int signal, unsigned max_tries, unsigned wait_ms, const char * signal_name)
    {
        int pid = isRunning(pid_file, /*ignore_file_does_not_exist=*/ false);

        if (!pid)
            return true;

        if (0 == kill(pid, signal))
            fmt::print("Sent {} signal to process with pid {}.\n", signal_name, pid);
        else
            throw ErrnoException(ErrorCodes::SYSTEM_ERROR, "Cannot send {} signal", signal_name);

        size_t try_num = 0;
        for (; try_num < max_tries; ++try_num)
        {
            fmt::print("Waiting for server to stop\n");
            if (!isRunning(pid_file, /*ignore_file_does_not_exist=*/ true))
            {
                fmt::print("Server stopped\n");
                break;
            }
            sleepForMilliseconds(wait_ms);
        }

        return try_num < max_tries;
    }

    int stop(const fs::path & pid_file, bool force, bool do_not_kill, unsigned max_tries)
    {
        if (force && do_not_kill)
            throw Exception(ErrorCodes::BAD_ARGUMENTS, "Specified flags are incompatible");

        int signal = force ? SIGKILL : SIGTERM;
        const char * signal_name = force ? "kill" : "terminate";

        if (sendSignalAndWaitForStop(pid_file, signal, max_tries, 1000, signal_name))
            return 0;

        int pid = isRunning(pid_file, /*ignore_file_does_not_exist=*/ false);
        if (!pid)
            return 0;

        if (do_not_kill)
        {
            fmt::print("Process (pid = {}) is still running. Will not try to kill it.\n", pid);
            return 1;
        }

        /// Send termination signal again, the server will receive it and immediately terminate.
        fmt::print("Will send the termination signal again to force the termination (pid = {}).\n", pid);
        if (sendSignalAndWaitForStop(pid_file, signal, std::min(10U, max_tries), 1000, signal_name))
            return 0;

        /// Send kill signal. Total wait is 100 seconds.
        constexpr size_t num_kill_check_tries = 1000;
        constexpr size_t kill_check_delay_ms = 100;
        fmt::print("Will terminate forcefully (pid = {}).\n", pid);
        if (sendSignalAndWaitForStop(pid_file, SIGKILL, num_kill_check_tries, kill_check_delay_ms, "kill"))
            return 0;

        if (!isRunning(pid_file, /*ignore_file_does_not_exist=*/ true))
            return 0;

        throw Exception(ErrorCodes::CANNOT_KILL,
            "The server process still exists after {} tries (delay: {} ms)",
            num_kill_check_tries, kill_check_delay_ms);
    }
}


int mainEntryClickHouseStart(int argc, char ** argv);
int mainEntryClickHouseStart(int argc, char ** argv)
{
    try
    {
        po::options_description desc;
        desc.add_options()
            ("help,h", "produce help message")
            ("prefix", po::value<std::string>()->default_value("/"), "prefix for all paths")
#if defined (OS_DARWIN)
            /// https://stackoverflow.com/a/36734569/22422288
            ("binary-path", po::value<std::string>()->default_value("usr/local/bin"), "directory with binary")
#else
            ("binary-path", po::value<std::string>()->default_value("usr/bin"), "directory with binary")
#endif
            ("config-path", po::value<std::string>()->default_value("etc/clickhouse-server"), "directory with configs")
            ("pid-path", po::value<std::string>()->default_value("var/run/clickhouse-server"), "directory for pid file")
            ("user", po::value<std::string>()->default_value(DEFAULT_CLICKHOUSE_SERVER_USER), "clickhouse user")
            ("group", po::value<std::string>()->default_value(DEFAULT_CLICKHOUSE_SERVER_GROUP), "clickhouse group")
            ("no-sudo", po::bool_switch(), "use clickhouse su instead of sudo (useful when running in a Docker container)")
            ("max-tries", po::value<unsigned>()->default_value(60), "Max number of tries for waiting the server (with 1 second delay)")
        ;

        po::variables_map options;
        po::store(po::parse_command_line(argc, argv, desc), options);

        bool no_sudo = options["no-sudo"].as<bool>();

        if (options.contains("help"))
        {
            std::cout << "Usage: " << formatWithSudo("clickhouse start", !no_sudo && getuid() != 0) << " [options]\n";
            std::cout << desc << "\n";
            return 0;
        }

        std::string user = options["user"].as<std::string>();
        std::string group = options["group"].as<std::string>();
        /// `--group` has a default for help/documentation purposes only.
        /// It should be applied to the launched server only when the user
        /// explicitly requested it. Otherwise `clickhouse start --user alice`
        /// would force `-g clickhouse` (or `alice:clickhouse` on the no-sudo
        /// path), which fails when the user is not a member of `clickhouse`.
        if (options["group"].defaulted())
            group.clear();

        fs::path prefix = options["prefix"].as<std::string>();
        fs::path binary = prefix / options["binary-path"].as<std::string>() / "clickhouse";
        fs::path executable = prefix / options["binary-path"].as<std::string>() / "clickhouse-server";
        fs::path config = prefix / options["config-path"].as<std::string>() / "config.xml";
        fs::path pid_file = prefix / options["pid-path"].as<std::string>() / "clickhouse-server.pid";
        unsigned max_tries = options["max-tries"].as<unsigned>();

        return start(user, group, binary, executable, config, pid_file, max_tries, no_sudo);
    }
    catch (...)
    {
        std::cerr << getCurrentExceptionMessage(false) << '\n';
        return getCurrentExceptionCode();
    }
}


int mainEntryClickHouseStop(int argc, char ** argv);
int mainEntryClickHouseStop(int argc, char ** argv)
{
    try
    {
        po::options_description desc;
        desc.add_options()
            ("help,h", "produce help message")
            ("prefix", po::value<std::string>()->default_value("/"), "prefix for all paths")
            ("pid-path", po::value<std::string>()->default_value("var/run/clickhouse-server"), "directory for pid file")
            ("force", po::bool_switch(), "Stop with KILL signal instead of TERM")
            ("do-not-kill", po::bool_switch(), "Do not send KILL even if TERM did not help")
            ("max-tries", po::value<unsigned>()->default_value(60), "Max number of tries for waiting the server to finish after sending TERM (with 1 second delay)")
        ;

        po::variables_map options;
        po::store(po::parse_command_line(argc, argv, desc), options);

        if (options.contains("help"))
        {
            std::cout << "Usage: " << formatWithSudo("clickhouse stop", getuid() != 0) << " [options]\n";
            std::cout << desc << "\n";
            return 0;
        }

        fs::path prefix = options["prefix"].as<std::string>();
        fs::path pid_file = prefix / options["pid-path"].as<std::string>() / "clickhouse-server.pid";

        bool force = options["force"].as<bool>();
        bool do_not_kill = options["do-not-kill"].as<bool>();
        unsigned max_tries = options["max-tries"].as<unsigned>();
        return stop(pid_file, force, do_not_kill, max_tries);
    }
    catch (...)
    {
        std::cerr << getCurrentExceptionMessage(false) << '\n';
        return getCurrentExceptionCode();
    }
}


int mainEntryClickHouseStatus(int argc, char ** argv);
int mainEntryClickHouseStatus(int argc, char ** argv)
{
    try
    {
        po::options_description desc;
        desc.add_options()
            ("help,h", "produce help message")
            ("prefix", po::value<std::string>()->default_value("/"), "prefix for all paths")
            ("pid-path", po::value<std::string>()->default_value("var/run/clickhouse-server"), "directory for pid file")
        ;

        po::variables_map options;
        po::store(po::parse_command_line(argc, argv, desc), options);

        if (options.contains("help"))
        {
            std::cout << "Usage: " << formatWithSudo("clickhouse status", getuid() != 0) << " [options]\n";
            std::cout << desc << "\n";
            return 0;
        }

        fs::path prefix = options["prefix"].as<std::string>();
        fs::path pid_file = prefix / options["pid-path"].as<std::string>() / "clickhouse-server.pid";

        isRunning(pid_file, /*ignore_file_does_not_exist=*/ false);
    }
    catch (...)
    {
        std::cerr << getCurrentExceptionMessage(false) << '\n';
        return getCurrentExceptionCode();
    }

    return 0;
}


int mainEntryClickHouseRestart(int argc, char ** argv);
int mainEntryClickHouseRestart(int argc, char ** argv)
{
    try
    {
        po::options_description desc;
        desc.add_options()
            ("help,h", "produce help message")
            ("prefix", po::value<std::string>()->default_value("/"), "prefix for all paths")
#if defined (OS_DARWIN)
            /// https://stackoverflow.com/a/36734569/22422288
            ("binary-path", po::value<std::string>()->default_value("usr/local/bin"), "directory with binary")
#else
            ("binary-path", po::value<std::string>()->default_value("usr/bin"), "directory with binary")
#endif
            ("config-path", po::value<std::string>()->default_value("etc/clickhouse-server"), "directory with configs")
            ("pid-path", po::value<std::string>()->default_value("var/run/clickhouse-server"), "directory for pid file")
            ("user", po::value<std::string>()->default_value(DEFAULT_CLICKHOUSE_SERVER_USER), "clickhouse user")
            ("group", po::value<std::string>()->default_value(DEFAULT_CLICKHOUSE_SERVER_GROUP), "clickhouse group")
            ("no-sudo", po::bool_switch(), "use clickhouse su instead of sudo (useful when running in a Docker container)")
            ("force", po::value<bool>()->default_value(false), "Stop with KILL signal instead of TERM")
            ("do-not-kill", po::bool_switch(), "Do not send KILL even if TERM did not help")
            ("max-tries", po::value<unsigned>()->default_value(60), "Max number of tries for waiting the server (with 1 second delay)")
        ;

        po::variables_map options;
        po::store(po::parse_command_line(argc, argv, desc), options);

        bool no_sudo = options["no-sudo"].as<bool>();

        if (options.contains("help"))
        {
            std::cout << "Usage: " << formatWithSudo("clickhouse restart", !no_sudo && getuid() != 0) << " [options]\n";
            std::cout << desc << "\n";
            return 0;
        }

        std::string user = options["user"].as<std::string>();
        std::string group = options["group"].as<std::string>();
        /// See the comment in `mainEntryClickHouseStart`: only apply `--group`
        /// when the user explicitly provided it.
        if (options["group"].defaulted())
            group.clear();

        fs::path prefix = options["prefix"].as<std::string>();
        fs::path binary = prefix / options["binary-path"].as<std::string>() / "clickhouse";
        fs::path executable = prefix / options["binary-path"].as<std::string>() / "clickhouse-server";
        fs::path config = prefix / options["config-path"].as<std::string>() / "config.xml";
        fs::path pid_file = prefix / options["pid-path"].as<std::string>() / "clickhouse-server.pid";

        bool force = options["force"].as<bool>();
        bool do_not_kill = options["do-not-kill"].as<bool>();
        unsigned max_tries = options["max-tries"].as<unsigned>();

        if (int res = stop(pid_file, force, do_not_kill, max_tries))
            return res;
        return start(user, group, binary, executable, config, pid_file, max_tries, no_sudo);
    }
    catch (...)
    {
        std::cerr << getCurrentExceptionMessage(false) << '\n';
        return getCurrentExceptionCode();
    }
}