#include <iostream>
#include <sstream>
#include <system_error>
#include <cerrno>
#include <boost/filesystem.hpp>
#include <boost/optional.hpp>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <fcntl.h>

namespace fs = boost::filesystem;

enum class SearchInPath { No, Yes };

void launch(SearchInPath search_in_path,
            const fs::path& path,
            const std::vector<std::string>& args,
            const boost::optional<fs::path>& log = boost::none) {
  std::vector<char*> exec_args;
  for (const std::string& arg : args) {
    exec_args.push_back(const_cast<char*>(arg.c_str()));
  }
  exec_args.push_back(nullptr);

  pid_t pid = fork();
  if (pid == -1) {
    throw std::system_error(errno, std::system_category());
  } else if (pid == 0) {
    int rc;

    if (log) {
      int fd = open(log.get().c_str(), O_WRONLY | O_CREAT | O_TRUNC, 0666);
      if (fd != -1) {
        close(STDERR_FILENO);
        dup2(fd, STDERR_FILENO);
      }
    }

    if (search_in_path == SearchInPath::Yes) {
      rc = execvp(path.c_str(), exec_args.data());
    } else {
      rc = execv(path.c_str(), exec_args.data());
    }
  } else {
    int status;
    int rc = waitpid(pid, &status, 0);
    if (rc == -1) {
      throw std::system_error(errno, std::system_category());
    }

    if (status != 0) {
      throw std::runtime_error("Process existed with return code: " + std::to_string(status));
    }
  }
}

int main(int argc, char **argv) {
  fs::path path;
  fs::path daemon;
  fs::path pakpath;
  fs::path log;

  try {
    path    = fs::read_symlink("/proc/self/exe").parent_path();
    daemon  = path / "linux64" / "daemon";
    pakpath = path / "pkg";
    log     = path / "Unvanquished.log";

    launch(SearchInPath::No, daemon.c_str(), {"daemon", "-pakpath", pakpath.string()}, log);
  } catch (const std::exception& e) {
    std::ostringstream msg;

    msg << "Unvanquished has failed to launch.\n";
    msg << "Visit <a href=\"http://forums.unvanquished.net/\">Unvanquished forums</a> for support.\n\n";

    msg << "Please include the following technical information in your post:\n\n";

    msg << "Error message: " << e.what() << ".";

    if (!path.empty()) {
      msg << "\n";
      msg << "Base path: " << path << ".\n";
      msg << "Daemon executable exists: " << (fs::exists(daemon) ? "yes" : "no") << ".\n";
      msg << "Package directory exists: " << (fs::exists(pakpath) ? "yes" : "no") << ".";
    }

    if (fs::exists(log)) {
      msg << "\n\n";
      msg << "Please also incude the contents of the log file.\n\n";
      msg << "Log file location: " << log.string();
    }

    try {
      launch(SearchInPath::Yes, "zenity", {"zenity", "--error", "--text", msg.str()});
    } catch (...) {}

    std::cout << msg.str() << std::endl;
  }

  return 0;
}