use std::{
	ffi::CString,
	fs::{DirBuilder, File},
	io,
	os::unix::ffi::OsStrExt,
	path::Path,
};

use nix::{
	mount::{self, MsFlags},
	sched::{self, CloneFlags},
};
use serde::{Deserialize, Serialize};

use crate::util::ToIOResult;

fn prepare_buildtmp() -> io::Result<()> {
	mount::mount::<_, _, _, str>(
		Some("buildtmp"),
		"build/tmp",
		Some("tmpfs"),
		MsFlags::empty(),
		None,
	)
	.to_io_result()?;

	DirBuilder::new().create("build/tmp/rootfs")?;

	{
		let file = File::open("build/rootfs.tar")?;
		let mut archive = tar::Archive::new(file);
		archive.set_preserve_permissions(true);
		archive.set_preserve_mtime(true);
		archive.set_unpack_xattrs(true);

		let dst = Path::new("build/tmp/rootfs");

		for entry_r in archive.entries()? {
			let mut entry = entry_r?;
			if entry.unpack_in(dst)? {
				let header = entry.header();
				let uid = header.uid()? as libc::uid_t;
				let gid = header.gid()? as libc::gid_t;

				let path = CString::new(dst.join(entry.path()?).as_os_str().as_bytes())
					.map_err(|e| io::Error::new(io::ErrorKind::Other, e))?;
				if unsafe { libc::lchown(path.as_ptr(), uid, gid) } < 0 {
					return Err(io::Error::last_os_error());
				}
			}
		}
	}

	DirBuilder::new().create("build/tmp/runc")?;
	DirBuilder::new().create("build/tmp/runc/rootfs")?;

	mount::mount::<_, _, str, str>(
		Some("build/tmp/rootfs"),
		"build/tmp/runc/rootfs",
		None,
		MsFlags::MS_BIND,
		None,
	)
	.to_io_result()?;
	mount::mount::<str, _, str, str>(
		None,
		"build/tmp/runc/rootfs",
		None,
		MsFlags::MS_BIND | MsFlags::MS_REMOUNT | MsFlags::MS_RDONLY,
		None,
	)
	.to_io_result()?;

	Ok(())
}

#[derive(Debug, Deserialize, Serialize)]
pub enum Error {
	Code(i32),
	String(String),
}

impl From<io::Error> for Error {
	fn from(error: io::Error) -> Self {
		match error.raw_os_error() {
			Some(code) => Error::Code(code),
			None => Error::String(error.to_string()),
		}
	}
}

impl From<Error> for io::Error {
	fn from(error: Error) -> Self {
		match error {
			Error::Code(code) => io::Error::from_raw_os_error(code),
			Error::String(string) => io::Error::new(io::ErrorKind::Other, string),
		}
	}
}

pub fn runc_unshare() -> Result<(), Error> {
	sched::unshare(CloneFlags::CLONE_NEWUSER | CloneFlags::CLONE_NEWNS).to_io_result()?;
	Ok(())
}

pub fn runc_initialize() -> Result<(), Error> {
	prepare_buildtmp()?;
	Ok(())
}