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mod init;
mod jobserver;
mod ns;
mod tar;
mod task;
mod util;

use capctl::prctl;
use ipc_channel::ipc;
use nix::{
	sched::CloneFlags,
	sys::{signal, stat, wait},
	unistd::{self, Gid, Uid},
};
use serde::{Deserialize, Serialize};

use self::{
	jobserver::Jobserver,
	util::{clone, unix},
};
use crate::{runner, util::error::*};

#[derive(Debug, Deserialize, Serialize)]
enum Message {
	Request(runner::Task, ipc::IpcSender<Result<runner::TaskOutput>>),
}

fn handle_request(
	jobserver: Jobserver,
	channel: ipc::IpcReceiver<Message>,
	task: runner::Task,
	reply_channel: ipc::IpcSender<Result<runner::TaskOutput>>,
) -> (Jobserver, ipc::IpcReceiver<Message>) {
	let child = |(mut jobserver, channel): (Jobserver, ipc::IpcReceiver<Message>)| {
		drop(channel);
		unsafe { signal::signal(signal::Signal::SIGCHLD, signal::SigHandler::SigDfl) }.unwrap();

		prctl::set_name(&task.label).expect("prctl(PR_SET_NAME)");

		let token = jobserver.wait();
		let (pid, mut jobserver) = unsafe {
			clone::spawn(None, jobserver, |jobserver| {
				let result = task::handle(task, jobserver);
				reply_channel.send(result).expect("IPC send() failed");
			})
		}
		.expect("fork()");
		let wait_res = wait::waitpid(pid, None);
		jobserver.post(token);
		wait_res.expect("waitpid()");
	};

	unsafe { clone::spawn(None, (jobserver, channel), child) }
		.expect("fork()")
		.1
}

fn runner_loop(mut channel: ipc::IpcReceiver<Message>) {
	let nproc = unix::nproc().expect("Failed to get number of available CPUs");
	let mut jobserver = Jobserver::new(nproc).expect("Failed to initialize jobserver pipe");

	while let Ok(msg) = channel.recv() {
		match msg {
			Message::Request(task, reply_channel) => {
				let ret = handle_request(jobserver, channel, task, reply_channel);
				jobserver = ret.0;
				channel = ret.1;
			}
		}
	}
}

fn runner(uid: Uid, gid: Gid, channel: ipc::IpcReceiver<Message>) {
	ns::mount_proc();
	ns::setup_userns(Uid::from_raw(0), Gid::from_raw(0), uid, gid);

	stat::umask(stat::Mode::from_bits_truncate(0o022));

	init::init_runner().unwrap();

	let msg_handler = unsafe {
		clone::spawn(None, (), |()| {
			signal::signal(signal::Signal::SIGCHLD, signal::SigHandler::SigIgn).unwrap();
			runner_loop(channel);
		})
	}
	.expect("fork()")
	.0;

	loop {
		let status = wait::wait().expect("wait()");
		if status.pid() == Some(msg_handler) {
			break;
		}
	}
}

pub struct ContainerRunner {
	channel: ipc::IpcSender<Message>,
}

impl ContainerRunner {
	/// Creates a new container runner
	///
	/// Unsafe: Do not call in multithreaded processes
	pub unsafe fn new() -> Result<Self> {
		let uid = unistd::geteuid();
		let gid = unistd::getegid();

		let (tx, rx) = ipc::channel().expect("IPC channel creation failed");

		let (tx, _rx) = clone::spawn(
			Some(CloneFlags::CLONE_NEWUSER | CloneFlags::CLONE_NEWNS | CloneFlags::CLONE_NEWPID),
			(tx, rx),
			|(tx, rx)| {
				drop(tx);
				runner(uid, gid, rx);
			},
		)
		.expect("clone()")
		.1;

		Ok(ContainerRunner { channel: tx })
	}
}

impl super::Runner for ContainerRunner {
	fn spawn(&self, task: &runner::Task) -> ipc::IpcReceiver<Result<runner::TaskOutput>> {
		let (reply_tx, reply_rx) = ipc::channel().expect("IPC channel creation failed");

		self.channel
			.send(Message::Request(task.clone(), reply_tx))
			.expect("ContainerRunner task submission failed");

		reply_rx
	}
}