/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */

use anyhow::Result;
use crash_helper_common::ProcessHandle;
use nix::{
    libc::_exit,
    unistd::{fork, getpid, setsid, write, ForkResult},
};
use std::{ffi::CStr, io::stdout, os::fd::AsFd};

pub(crate) const PROXY_RENDEZ_VOUS: bool = false;

// Daemonize the current process by forking it and then immediately returning
// in the parent. This should have been done via a double fork() in the
// crash_helper_client crate, however the first fork() call causes issues to
// Thunderbird on macOS 10.15 (see bug 1977514). This is a known problem with
// macOS 10.15 implemenetation, not a flaw in our logic, and the only way to
// work around it is to use posix_spawn() instead, which forces use to move
// the step to reparent the crash helper to PID 1 here.
//
// Note that if this fails for some reason, the crash helper will still launch,
// but not as a daemon. Not ideal but still better to have a fallback.
//
// # Safety
//
// This calls fork() which can only be done safely in a non-multi-threaded
// environment. This is something that the caller must guarantee. If we have
// spawned any other threads before calling this function then things might
// break in unexpected ways.
pub(crate) unsafe fn daemonize() {
    // Create a new process group and a new session, this guarantees
    // that the crash helper process will be disconnected from the
    // signals of Firefox main process' controlling terminal. Killing
    // Firefox via the terminal shouldn't kill the crash helper which
    // has its own lifecycle management.
    //
    // We don't check for errors as there's nothing we can do to
    // handle one in this context.
    let _ = setsid();

    let pid = if let Ok(res) = fork() {
        match res {
            ForkResult::Child => {
                return;
            }
            ForkResult::Parent { child } => child,
        }
    } else {
        getpid()
    };

    // We're done, write the daemonized process pid to standard output if
    // forking succeeded, or write the current process pid if it failed.
    let raw_pid = pid.as_raw();
    let raw_pid_bytes: [u8; 4] = raw_pid.to_ne_bytes();
    let rv = write(stdout().as_fd(), &raw_pid_bytes);

    _exit(if rv.is_ok_and(|rv| rv == 4) { 0 } else { 1 });
}

pub(crate) fn get_client_handle(_handle: &CStr) -> Result<Option<ProcessHandle>> {
    Ok(None)
}