fake "nautilus" binary to make SmartGit able to open folders on non-nautilus-powered desktop envs (like KDE or XFCE or MATE or Budgie)

fake_nautilus.cpp

// compile invocation:
// prod: g++ -static -s -Os -Wall -Wextra -Wpedantic -Werror -o fake_nautilus fake_nautilus.cpp
// dev: g++ -D__DEV__ -O0 -Wall -Wextra -Wpedantic -Werror -o fake_nautilus fake_nautilus.cpp
#include <iostream>
#include <string>
#include <fstream>
#include <algorithm>

// https://github.com/divinity76/phpcpp
namespace php
{
    // https://www.php.net/manual/en/function.escapeshellarg.php
    std::string escapeshellarg(const std::string &$arg)
    {
        std::string ret;
        ret.reserve($arg.length() + 100); // should be enough to avoid realloc() in most cases.
        ret += "'";
        for (size_t i = 0; i < $arg.length(); ++i)
        {
            if ($arg[i] == '\00')
            {
                throw std::runtime_error("argument contains null bytes, it's literally impossible to escape null bytes in bash!");
            }
            else if ($arg[i] == '\'')
            {
                ret += "'\\''";
            }
            else
            {
                ret += $arg[i];
            }
        }
        ret += "'";
        return ret;
    }
    // on Windows one should use std::filesystem::operator/ which would make it compatible with Windows
    // https://bugs.php.net/bug.php?id=80155
    // https://www.php.net/manual/en/function.basename
    std::string basename(std::string $path, const std::string &$suffix = "")
    {
        const size_t last_pos = $path.find_last_of('/');
        if (last_pos != std::string::npos)
        {
            $path = $path.substr(last_pos + sizeof('/'));
        }
        if ($suffix.size() > 0)
        {
            const size_t suffix_pos = $path.rfind($suffix);
            if (suffix_pos != std::string::npos)
            {
                if ((suffix_pos + $suffix.size()) == $path.size())
                {
                    $path.resize(suffix_pos);
                }
            }
        }
        return $path;
    }
    // https://www.php.net/manual/en/function.rtrim.php
    std::string rtrim(std::string $str, const std::string &$character_mask = std::string("\x20\x09\x0A\x0D\x00\x0B", 6))
    {
        // optimizeme: can this be optimized to a single erase() call? probably.
        while ($str.size() > 0 && $character_mask.find_first_of($str.back()) != std::string::npos)
        {
            $str.pop_back();
        }
        return $str;
    }
    // https://www.php.net/manual/en/function.ltrim.php
    std::string ltrim(std::string $str, const std::string &$character_mask = std::string("\x20\x09\x0A\x0D\x00\x0B", 6))
    {
        // optimizeme: can this be optimized to a single erase() call? probably.
        while ($str.size() > 0 && $character_mask.find_first_of($str.front()) != std::string::npos)
        {
            $str.erase(0, 1);
        }
        return $str;
    }
    // https://www.php.net/manual/en/function.rtrim.php
    std::string trim(std::string $str, const std::string &$character_mask = std::string("\x20\x09\x0A\x0D\x00\x0B", 6))
    {
        return rtrim(ltrim($str, $character_mask), $character_mask);
    }
    // https://www.php.net/manual/en/function.strtolower.php
    std::string strtolower(std::string $string)
    {
        std::transform($string.begin(), $string.end(), $string.begin(), ::tolower);
        return $string;
    }

} // namespace php

void log(
    const std::string &str_to_log,
    const std::string &logfile = "/tmp/fake_nautilus_logfile.log",
    const std::string &log_prepend = "----------\n",
    const std::string &log_append = "\n----------\n")
{
    std::ofstream file(logfile, std::ofstream::binary | std::ofstream::app | std::ofstream::out | std::ofstream::ate);
    file.exceptions(std::ofstream::failbit | std::ofstream::badbit);
    file << log_prepend << str_to_log << log_append;
}

int main(int argc, char *argv[])
{
#ifdef __DEV__
    for (int i = 0; i < argc; ++i)
    {
        log("argv[" + std::to_string(i) + "]: " + argv[i]);
    }
#endif
    if (argc != 2)
    {
        std::cerr << "error: invalid number of arguments\n"
                     "usage: "
                  << php::escapeshellarg(argv[0]) << " " << php::escapeshellarg("file:///absolute/path/to/file") << std::endl;
        exit(EXIT_FAILURE);
    }
    const std::string in_raw(argv[1]);
    std::string in(in_raw);
    if (in_raw.find("file:///") != 0)
    {
        std::cerr << "error: filepath argument did not start with file:/// \n"
                  << "(PS, unlike the real nautilus, i don't support relative paths, you MUST supply absolute paths, like SmartGit does)\n"
                  << "usage: " << php::escapeshellarg(argv[0]) << " " << php::escapeshellarg("file:///absolute/path/to/file") << std::endl;
        exit(EXIT_FAILURE);
    }
    in = in.substr(sizeof("file://") - sizeof("")); // - null terminator
    const std::string target_file = php::basename(in);
    const std::string target_dir = in.substr(0, in.size() - target_file.size());
    const std::string xdg_current_desktop = php::strtolower(php::trim(getenv("XDG_CURRENT_DESKTOP")));
    const auto xdg_match = [xdg_current_desktop](const std::string &search) -> bool {
        return (xdg_current_desktop.find(php::trim(php::strtolower(search))) != std::string::npos);
    };
#if __DEV__
    log("in_raw: " + in_raw);
    log("in: " + in);
    log("target_file: " + target_file);
    log("target_dir: " + target_dir);
    log("xdg_current_desktop: " + xdg_current_desktop);
#endif
    if (xdg_match("XFCE"))
    {
        // XFCE desktop
        // tested on Xubuntu 18.04
        // tested on Xubuntu 20.04
        // this should work on XFCE since 2006, here is the commit adding support: https://github.com/xfce-mirror/thunar/commit/6342c7d582421a7c473ff5289a650e2894a316cd
        std::string cmd = "dbus-send ";
        cmd += "--type=method_call ";
        cmd += "--dest=org.xfce.Thunar ";
        cmd += "/org/xfce/FileManager ";
        cmd += "org.xfce.FileManager.DisplayFolderAndSelect ";
        cmd += "string:" + php::escapeshellarg(target_dir) + " ";
        std::string tmp = target_file;
        if(target_file.length() < 1){
            // important for XFCE: when you want to select a folder rather than a file in a folder,
            // the target must apparently be .
            tmp = ".";
        }
        cmd += "string:" + php::escapeshellarg(tmp) + " ";
        cmd += "string:" + php::escapeshellarg("") + " "; // ???
        cmd += "string:" + php::escapeshellarg("");       // ???
#ifdef __DEV__
        // should now look like:
        // dbus-send --type=method_call --dest=org.xfce.Thunar /org/xfce/FileManager org.xfce.FileManager.DisplayFolderAndSelect string:"/path/to/parent/folder" string:"Filename_to_focus" string:"" string:""
        log("cmd: " + cmd);
#endif
        const int ret = system(cmd.c_str());
        exit(ret);
    }
    else if (
        xdg_match("Budgie")   // Budgie desktop, tested on Ubuntu Budgie 20.04
        || xdg_match("GNOME") // GNOME desktop, tested on Ubuntu 20.04
        || xdg_match("MATE")  // MATE desktop, tested on Ubuntu Mate 20.04
        || xdg_match("KDE")   // KDE desktop, tested on Kubuntu 20.04
    )
    {
        // specifications: https://www.freedesktop.org/wiki/Specifications/file-manager-interface/
        std::string cmd = "dbus-send ";
        cmd += "--type=method_call ";
        cmd += "--dest=org.freedesktop.FileManager1 ";
        cmd += "/org/freedesktop/FileManager1 ";
        cmd += "org.freedesktop.FileManager1.ShowItems ";
        std::string tmp = "file://" + target_dir + "/" + target_file;
        cmd += "array:string:" + php::escapeshellarg(tmp) + " ";
        cmd += "string:" + php::escapeshellarg(""); // ???
#ifdef __DEV__
        // now it should look something like:
        // dbus-send --type=method_call --dest=org.freedesktop.FileManager1 /org/freedesktop/FileManager1 org.freedesktop.FileManager1.ShowItems array:string:"file://$1/$2" string:""
        log("cmd: " + cmd);
#endif
        const int ret = system(cmd.c_str());
        exit(ret);
    }
    else if (xdg_match("LXQt"))
    {
        std::cerr << "Sorry, LXQt is not supported (i have no idea how to make this work on lxqt)" << std::endl;
        exit(EXIT_FAILURE);
    }
    else
    {
        // unknown desktop enviorment..
        // using a fallback that "seems to work most places"
        //
        // specifications: https://www.freedesktop.org/wiki/Specifications/file-manager-interface/
        std::string cmd = "dbus-send ";
        cmd += "--type=method_call ";
        cmd += "--dest=org.freedesktop.FileManager1 ";
        cmd += "/org/freedesktop/FileManager1 ";
        cmd += "org.freedesktop.FileManager1.ShowItems ";
        std::string tmp = "file://" + target_dir + "/" + target_file;
        cmd += "array:string:" + php::escapeshellarg(tmp) + " ";
        cmd += "string:" + php::escapeshellarg(""); // ???
#ifdef __DEV__
        // now it should look something like:
        // dbus-send --type=method_call --dest=org.freedesktop.FileManager1 /org/freedesktop/FileManager1 org.freedesktop.FileManager1.ShowItems array:string:"file://$1/$2" string:""
        log("cmd: " + cmd);
#endif
        const int ret = system(cmd.c_str());
        exit(ret);
    }
}