hermit/fs/

virtio_fs.rs

use alloc::borrow::ToOwned;
use alloc::boxed::Box;
use alloc::ffi::CString;
use alloc::string::String;
use alloc::sync::Arc;
use alloc::vec::Vec;
use core::marker::PhantomData;
use core::mem::MaybeUninit;
use core::sync::atomic::{AtomicU64, Ordering};
use core::task::Poll;
use core::{future, mem, ptr, slice};

use align_address::Align;
use async_lock::Mutex;
use embedded_io::{ErrorType, Read, Write};
use fuse_abi::linux::*;

#[cfg(not(feature = "pci"))]
use crate::arch::kernel::mmio::get_filesystem_driver;
#[cfg(feature = "pci")]
use crate::drivers::pci::get_filesystem_driver;
use crate::drivers::virtio::virtqueue::error::VirtqError;
use crate::errno::Errno;
use crate::executor::block_on;
use crate::fd::{Fd, PollEvent};
use crate::fs::virtio_fs::ops::SetAttrValidFields;
use crate::fs::{
	self, AccessPermission, DirectoryEntry, FileAttr, NodeKind, ObjectInterface, OpenOption,
	SeekWhence, VfsNode,
};
use crate::mm::device_alloc::DeviceAlloc;
use crate::syscalls::Dirent64;
use crate::time::{time_t, timespec};
use crate::{arch, io};

// response out layout eg @ https://github.com/zargony/fuse-rs/blob/bf6d1cf03f3277e35b580f3c7b9999255d72ecf3/src/ll/request.rs#L44
// op in/out sizes/layout: https://github.com/hanwen/go-fuse/blob/204b45dba899dfa147235c255908236d5fde2d32/fuse/opcode.go#L439
// possible responses for command: qemu/tools/virtiofsd/fuse_lowlevel.h

const MAX_READ_LEN: usize = 1024 * 64;
const MAX_WRITE_LEN: usize = 1024 * 64;

const U64_SIZE: usize = size_of::<u64>();

const S_IFLNK: u32 = 0o120_000;
const S_IFMT: u32 = 0o170_000;

pub(crate) trait VirtioFsInterface {
	fn send_command<O: ops::Op + 'static>(
		&mut self,
		cmd: Cmd<O>,
		rsp_payload_len: u32,
	) -> Result<Rsp<O>, VirtioFsError>
	where
		<O as ops::Op>::InStruct: Send,
		<O as ops::Op>::OutStruct: Send;

	fn get_mount_point(&self) -> String;
}

pub(crate) mod ops {
	#![allow(clippy::type_complexity)]
	use alloc::boxed::Box;
	use alloc::ffi::CString;
	use core::fmt;

	use fuse_abi::linux::*;

	use super::Cmd;
	use crate::fd::PollEvent;
	use crate::fs::{FileAttr, SeekWhence};

	#[repr(C)]
	#[derive(Debug, Default, Copy, Clone, Hash, PartialEq, Eq)]
	pub(crate) struct CreateOut {
		pub entry: fuse_entry_out,
		pub open: fuse_open_out,
	}

	pub(crate) trait Op {
		const OP_CODE: fuse_opcode;

		type InStruct: fmt::Debug;
		type InPayload: ?Sized;
		type OutStruct: fmt::Debug;
		type OutPayload: ?Sized;
	}

	#[derive(Debug)]
	pub(crate) struct Init;

	impl Op for Init {
		const OP_CODE: fuse_opcode = fuse_opcode::FUSE_INIT;
		type InStruct = fuse_init_in;
		type InPayload = ();
		type OutStruct = fuse_init_out;
		type OutPayload = ();
	}

	impl Init {
		pub(crate) fn create() -> (Cmd<Self>, u32) {
			let cmd = Cmd::new(
				FUSE_ROOT_ID,
				fuse_init_in {
					major: 7,
					minor: 31,
					..Default::default()
				},
			);
			(cmd, 0)
		}
	}

	#[derive(Debug)]
	pub(crate) struct Create;

	impl Op for Create {
		const OP_CODE: fuse_opcode = fuse_opcode::FUSE_CREATE;
		type InStruct = fuse_create_in;
		type InPayload = CString;
		type OutStruct = CreateOut;
		type OutPayload = ();
	}

	impl Create {
		#[allow(clippy::self_named_constructors)]
		pub(crate) fn create(path: CString, flags: u32, mode: u32) -> (Cmd<Self>, u32) {
			let cmd = Cmd::with_cstring(
				FUSE_ROOT_ID,
				fuse_create_in {
					flags,
					mode,
					..Default::default()
				},
				path,
			);
			(cmd, 0)
		}
	}

	#[derive(Debug)]
	pub(crate) struct Open;

	impl Op for Open {
		const OP_CODE: fuse_opcode = fuse_opcode::FUSE_OPEN;
		type InStruct = fuse_open_in;
		type InPayload = ();
		type OutStruct = fuse_open_out;
		type OutPayload = ();
	}

	impl Open {
		pub(crate) fn create(nid: u64, flags: u32) -> (Cmd<Self>, u32) {
			let cmd = Cmd::new(
				nid,
				fuse_open_in {
					flags,
					..Default::default()
				},
			);
			(cmd, 0)
		}
	}

	#[derive(Debug)]
	pub(crate) struct Write;

	impl Op for Write {
		const OP_CODE: fuse_opcode = fuse_opcode::FUSE_WRITE;
		type InStruct = fuse_write_in;
		type InPayload = [u8];
		type OutStruct = fuse_write_out;
		type OutPayload = ();
	}

	impl Write {
		pub(crate) fn create(nid: u64, fh: u64, buf: Box<[u8]>, offset: u64) -> (Cmd<Self>, u32) {
			let cmd = Cmd::with_boxed_slice(
				nid,
				fuse_write_in {
					fh,
					offset,
					size: buf.len().try_into().unwrap(),
					..Default::default()
				},
				buf,
			);
			(cmd, 0)
		}
	}

	#[derive(Debug)]
	pub(crate) struct Read;

	impl Op for Read {
		const OP_CODE: fuse_opcode = fuse_opcode::FUSE_READ;
		type InStruct = fuse_read_in;
		type InPayload = ();
		type OutStruct = ();
		type OutPayload = [u8];
	}

	impl Read {
		pub(crate) fn create(nid: u64, fh: u64, size: u32, offset: u64) -> (Cmd<Self>, u32) {
			let cmd = Cmd::new(
				nid,
				fuse_read_in {
					fh,
					offset,
					size,
					..Default::default()
				},
			);
			(cmd, size)
		}
	}

	#[derive(Debug)]
	pub(crate) struct Lseek;

	impl Op for Lseek {
		const OP_CODE: fuse_opcode = fuse_opcode::FUSE_LSEEK;
		type InStruct = fuse_lseek_in;
		type InPayload = ();
		type OutStruct = fuse_lseek_out;
		type OutPayload = ();
	}

	impl Lseek {
		pub(crate) fn create(
			nid: u64,
			fh: u64,
			offset: isize,
			whence: SeekWhence,
		) -> (Cmd<Self>, u32) {
			let cmd = Cmd::new(
				nid,
				fuse_lseek_in {
					fh,
					offset: i64::try_from(offset).unwrap() as u64,
					whence: u8::from(whence).into(),
					..Default::default()
				},
			);
			(cmd, 0)
		}
	}

	#[derive(Debug)]
	pub(crate) struct Getattr;

	impl Op for Getattr {
		const OP_CODE: fuse_opcode = fuse_opcode::FUSE_GETATTR;
		type InStruct = fuse_getattr_in;
		type InPayload = ();
		type OutStruct = fuse_attr_out;
		type OutPayload = ();
	}

	impl Getattr {
		pub(crate) fn create(nid: u64, fh: u64, getattr_flags: u32) -> (Cmd<Self>, u32) {
			let cmd = Cmd::new(
				nid,
				fuse_getattr_in {
					getattr_flags,
					fh,
					..Default::default()
				},
			);
			(cmd, 0)
		}
	}

	#[derive(Debug)]
	pub(crate) struct Setattr;

	impl Op for Setattr {
		const OP_CODE: fuse_opcode = fuse_opcode::FUSE_SETATTR;
		type InStruct = fuse_setattr_in;
		type InPayload = ();
		type OutStruct = fuse_attr_out;
		type OutPayload = ();
	}

	bitflags! {
		#[derive(Debug, Copy, Clone, Default)]
		pub struct SetAttrValidFields: u32 {
			const FATTR_MODE = FATTR_MODE;
			const FATTR_UID = FATTR_UID;
			const FATTR_GID = FATTR_GID;
			const FATTR_SIZE = FATTR_SIZE;
			const FATTR_ATIME = FATTR_ATIME;
			const FATTR_MTIME = FATTR_MTIME;
			const FATTR_FH = FATTR_FH;
			const FATTR_ATIME_NOW = FATTR_ATIME_NOW;
			const FATTR_MTIME_NOW = FATTR_MTIME_NOW;
			const FATTR_LOCKOWNER = FATTR_LOCKOWNER;
			const FATTR_CTIME = FATTR_CTIME;
			const FATTR_KILL_SUIDGID = FATTR_KILL_SUIDGID;
		}
	}

	impl Setattr {
		pub(crate) fn create(
			nid: u64,
			fh: u64,
			attr: FileAttr,
			valid_attr: SetAttrValidFields,
		) -> (Cmd<Self>, u32) {
			let cmd = Cmd::new(
				nid,
				fuse_setattr_in {
					valid: valid_attr
						.difference(
							// Remove unsupported attributes
							SetAttrValidFields::FATTR_LOCKOWNER,
						)
						.bits(),
					padding: 0,
					fh,

					// FUSE attributes mapping: https://github.com/libfuse/libfuse/blob/fc1c8da0cf8a18d222cb1feed0057ba44ea4d18f/lib/fuse_lowlevel.c#L105
					size: attr.st_size as u64,
					atime: attr.st_atim.tv_sec as u64,
					atimensec: attr.st_atim.tv_nsec as u32,
					mtime: attr.st_ctim.tv_sec as u64,
					mtimensec: attr.st_ctim.tv_nsec as u32,
					ctime: attr.st_ctim.tv_sec as u64,
					ctimensec: attr.st_ctim.tv_nsec as u32,
					mode: attr.st_mode.bits(),
					unused4: 0,
					uid: attr.st_uid,
					gid: attr.st_gid,
					unused5: 0,

					lock_owner: 0, // unsupported
				},
			);

			(cmd, 0)
		}
	}

	#[derive(Debug)]
	pub(crate) struct Readlink;

	impl Op for Readlink {
		const OP_CODE: fuse_opcode = fuse_opcode::FUSE_READLINK;
		type InStruct = ();
		type InPayload = ();
		type OutStruct = ();
		type OutPayload = [u8];
	}

	impl Readlink {
		pub(crate) fn create(nid: u64, size: u32) -> (Cmd<Self>, u32) {
			let cmd = Cmd::new(nid, ());
			(cmd, size)
		}
	}

	#[derive(Debug)]
	pub(crate) struct Release;

	impl Op for Release {
		const OP_CODE: fuse_opcode = fuse_opcode::FUSE_RELEASE;
		type InStruct = fuse_release_in;
		type InPayload = ();
		type OutStruct = ();
		type OutPayload = ();
	}

	impl Release {
		pub(crate) fn create(nid: u64, fh: u64) -> (Cmd<Self>, u32) {
			let cmd = Cmd::new(
				nid,
				fuse_release_in {
					fh,
					..Default::default()
				},
			);
			(cmd, 0)
		}
	}

	#[derive(Debug)]
	pub(crate) struct Poll;

	impl Op for Poll {
		const OP_CODE: fuse_opcode = fuse_opcode::FUSE_POLL;
		type InStruct = fuse_poll_in;
		type InPayload = ();
		type OutStruct = fuse_poll_out;
		type OutPayload = ();
	}

	impl Poll {
		pub(crate) fn create(nid: u64, fh: u64, kh: u64, event: PollEvent) -> (Cmd<Self>, u32) {
			let cmd = Cmd::new(
				nid,
				fuse_poll_in {
					fh,
					kh,
					events: event.bits() as u32,
					..Default::default()
				},
			);
			(cmd, 0)
		}
	}

	#[derive(Debug)]
	pub(crate) struct Mkdir;

	impl Op for Mkdir {
		const OP_CODE: fuse_opcode = fuse_opcode::FUSE_MKDIR;
		type InStruct = fuse_mkdir_in;
		type InPayload = CString;
		type OutStruct = fuse_entry_out;
		type OutPayload = ();
	}

	impl Mkdir {
		pub(crate) fn create(path: CString, mode: u32) -> (Cmd<Self>, u32) {
			let cmd = Cmd::with_cstring(
				FUSE_ROOT_ID,
				fuse_mkdir_in {
					mode,
					..Default::default()
				},
				path,
			);
			(cmd, 0)
		}
	}

	#[derive(Debug)]
	pub(crate) struct Unlink;

	impl Op for Unlink {
		const OP_CODE: fuse_opcode = fuse_opcode::FUSE_UNLINK;
		type InStruct = ();
		type InPayload = CString;
		type OutStruct = ();
		type OutPayload = ();
	}

	impl Unlink {
		pub(crate) fn create(name: CString) -> (Cmd<Self>, u32) {
			let cmd = Cmd::with_cstring(FUSE_ROOT_ID, (), name);
			(cmd, 0)
		}
	}

	#[derive(Debug)]
	pub(crate) struct Rmdir;

	impl Op for Rmdir {
		const OP_CODE: fuse_opcode = fuse_opcode::FUSE_RMDIR;
		type InStruct = ();
		type InPayload = CString;
		type OutStruct = ();
		type OutPayload = ();
	}

	impl Rmdir {
		pub(crate) fn create(name: CString) -> (Cmd<Self>, u32) {
			let cmd = Cmd::with_cstring(FUSE_ROOT_ID, (), name);
			(cmd, 0)
		}
	}

	#[derive(Debug)]
	pub(crate) struct Lookup;

	impl Op for Lookup {
		const OP_CODE: fuse_opcode = fuse_opcode::FUSE_LOOKUP;
		type InStruct = ();
		type InPayload = CString;
		type OutStruct = fuse_entry_out;
		type OutPayload = ();
	}

	impl Lookup {
		pub(crate) fn create(name: CString) -> (Cmd<Self>, u32) {
			let cmd = Cmd::with_cstring(FUSE_ROOT_ID, (), name);
			(cmd, 0)
		}
	}
}

impl From<fuse_attr> for FileAttr {
	fn from(attr: fuse_attr) -> FileAttr {
		FileAttr {
			st_ino: attr.ino,
			st_nlink: attr.nlink.into(),
			st_mode: AccessPermission::from_bits_retain(attr.mode),
			st_uid: attr.uid,
			st_gid: attr.gid,
			st_rdev: attr.rdev.into(),
			st_size: attr.size.try_into().unwrap(),
			st_blksize: attr.blksize.into(),
			st_blocks: attr.blocks.try_into().unwrap(),
			st_atim: timespec {
				tv_sec: attr.atime as time_t,
				tv_nsec: attr.atimensec as i32,
			},
			st_mtim: timespec {
				tv_sec: attr.mtime as time_t,
				tv_nsec: attr.mtimensec as i32,
			},
			st_ctim: timespec {
				tv_sec: attr.ctime as time_t,
				tv_nsec: attr.ctimensec as i32,
			},
			..Default::default()
		}
	}
}

#[repr(C)]
#[derive(Debug)]
pub(crate) struct CmdHeader<O: ops::Op> {
	pub in_header: fuse_in_header,
	op_header: O::InStruct,
}

impl<O: ops::Op> CmdHeader<O>
where
	O: ops::Op<InPayload = ()>,
{
	fn new(nodeid: u64, op_header: O::InStruct) -> Self {
		Self::with_payload_size(nodeid, op_header, 0)
	}
}

impl<O: ops::Op> CmdHeader<O> {
	fn with_payload_size(nodeid: u64, op_header: O::InStruct, len: usize) -> CmdHeader<O> {
		CmdHeader {
			in_header: fuse_in_header {
				// The length we need the provide in the header is not the same as the size of the struct because of padding, so we need to calculate it manually.
				len: (size_of::<fuse_in_header>() + size_of::<O::InStruct>() + len)
					.try_into()
					.expect("The command is too large"),
				opcode: O::OP_CODE.into(),
				nodeid,
				unique: 1,
				..Default::default()
			},
			op_header,
		}
	}
}

pub(crate) struct Cmd<O: ops::Op> {
	pub headers: Box<CmdHeader<O>, DeviceAlloc>,
	pub payload: Option<Vec<u8, DeviceAlloc>>,
}

impl<O: ops::Op> Cmd<O>
where
	O: ops::Op<InPayload = ()>,
{
	fn new(nodeid: u64, op_header: O::InStruct) -> Self {
		Self {
			headers: Box::new_in(CmdHeader::new(nodeid, op_header), DeviceAlloc),
			payload: None,
		}
	}
}

impl<O: ops::Op> Cmd<O>
where
	O: ops::Op<InPayload = CString>,
{
	fn with_cstring(nodeid: u64, op_header: O::InStruct, cstring: CString) -> Self {
		let cstring_bytes = cstring.into_bytes_with_nul().to_vec_in(DeviceAlloc);
		Self {
			headers: Box::new_in(
				CmdHeader::with_payload_size(nodeid, op_header, cstring_bytes.len()),
				DeviceAlloc,
			),
			payload: Some(cstring_bytes),
		}
	}
}

impl<O: ops::Op> Cmd<O>
where
	O: ops::Op<InPayload = [u8]>,
{
	fn with_boxed_slice(nodeid: u64, op_header: O::InStruct, slice: Box<[u8]>) -> Self {
		let mut device_slice = Vec::with_capacity_in(slice.len(), DeviceAlloc);
		device_slice.extend_from_slice(&slice);
		Self {
			headers: Box::new_in(
				CmdHeader::with_payload_size(nodeid, op_header, slice.len()),
				DeviceAlloc,
			),
			payload: Some(device_slice),
		}
	}
}

#[repr(C)]
#[derive(Debug)]
// The generic H parameter allows us to handle RspHeaders with their op_header
// potenitally uninitialized. After checking for the error code in the out_header,
// the object can be transmuted to one with an initialized op_header.
pub(crate) struct RspHeader<O: ops::Op, H = <O as ops::Op>::OutStruct> {
	pub out_header: fuse_out_header,
	op_header: H,
	_phantom: PhantomData<O::OutStruct>,
}

#[derive(Debug)]
pub(crate) struct Rsp<O: ops::Op> {
	pub headers: Box<RspHeader<O>, DeviceAlloc>,
	pub payload: Option<Vec<u8, DeviceAlloc>>,
}

#[derive(Debug)]
pub(crate) enum VirtioFsError {
	VirtqError(VirtqError),
	IOError(Errno),
}

impl From<VirtqError> for VirtioFsError {
	fn from(value: VirtqError) -> Self {
		Self::VirtqError(value)
	}
}

impl From<VirtioFsError> for Errno {
	fn from(value: VirtioFsError) -> Self {
		match value {
			VirtioFsError::VirtqError(virtq_error) => virtq_error.into(),
			VirtioFsError::IOError(io_error) => io_error,
		}
	}
}

fn lookup(name: CString) -> Option<u64> {
	let (cmd, rsp_payload_len) = ops::Lookup::create(name);
	let rsp = get_filesystem_driver()
		.unwrap()
		.lock()
		.send_command(cmd, rsp_payload_len)
		.ok()?;
	Some(rsp.headers.op_header.nodeid)
}

fn readlink(nid: u64) -> io::Result<String> {
	let len = MAX_READ_LEN as u32;
	let (cmd, rsp_payload_len) = ops::Readlink::create(nid, len);
	let rsp = get_filesystem_driver()
		.unwrap()
		.lock()
		.send_command(cmd, rsp_payload_len)?;
	let len: usize = if rsp.headers.out_header.len as usize - size_of::<fuse_out_header>()
		>= usize::try_from(len).unwrap()
	{
		len.try_into().unwrap()
	} else {
		(rsp.headers.out_header.len as usize) - size_of::<fuse_out_header>()
	};

	Ok(String::from_utf8(rsp.payload.unwrap()[..len].to_vec()).unwrap())
}

#[derive(Debug)]
struct VirtioFsFileHandleInner {
	fuse_nid: Option<u64>,
	fuse_fh: Option<u64>,
	offset: usize,
}

impl VirtioFsFileHandleInner {
	pub fn new() -> Self {
		Self {
			fuse_nid: None,
			fuse_fh: None,
			offset: 0,
		}
	}

	async fn poll(&self, events: PollEvent) -> io::Result<PollEvent> {
		static KH: AtomicU64 = AtomicU64::new(0);
		let kh = KH.fetch_add(1, Ordering::SeqCst);

		future::poll_fn(|cx| {
			let Some(nid) = self.fuse_nid else {
				return Poll::Ready(Ok(PollEvent::POLLERR));
			};

			let Some(fh) = self.fuse_fh else {
				return Poll::Ready(Ok(PollEvent::POLLERR));
			};

			let (cmd, rsp_payload_len) = ops::Poll::create(nid, fh, kh, events);
			let rsp = get_filesystem_driver()
				.ok_or(Errno::Nosys)?
				.lock()
				.send_command(cmd, rsp_payload_len)?;

			if rsp.headers.out_header.error < 0 {
				return Poll::Ready(Err(Errno::Io));
			}

			let revents =
				PollEvent::from_bits(i16::try_from(rsp.headers.op_header.revents).unwrap())
					.unwrap();
			if !revents.intersects(events)
				&& !revents
					.intersects(PollEvent::POLLERR | PollEvent::POLLNVAL | PollEvent::POLLHUP)
			{
				// the current implementation use polling to wait for an event
				// consequently, we have to wakeup the waker, if the the event doesn't arrive
				cx.waker().wake_by_ref();
			}
			Poll::Ready(Ok(revents))
		})
		.await
	}

	fn lseek(&mut self, offset: isize, whence: SeekWhence) -> io::Result<isize> {
		debug!("virtio-fs lseek: offset: {offset}, whence: {whence:?}");

		// Seek on FUSE file systems seems to be a little odd: All reads are referenced from the
		// beginning of the file, thus we have to track the offset ourself. Also, a read doesn't
		// move the read pointer on the remote side, so we can't get the current position using
		// remote lseek when referencing from `Cur` and we have to use the internally tracked
		// position instead.
		match whence {
			SeekWhence::End | SeekWhence::Data | SeekWhence::Hole => {
				let nid = self.fuse_nid.ok_or(Errno::Io)?;
				let fh = self.fuse_fh.ok_or(Errno::Io)?;

				let (cmd, rsp_payload_len) = ops::Lseek::create(nid, fh, offset, whence);
				let rsp = get_filesystem_driver()
					.ok_or(Errno::Nosys)?
					.lock()
					.send_command(cmd, rsp_payload_len)?;

				if rsp.headers.out_header.error < 0 {
					return Err(Errno::Io);
				}

				let rsp_offset = rsp.headers.op_header.offset;
				self.offset = rsp.headers.op_header.offset.try_into().unwrap();

				Ok(rsp_offset.try_into().unwrap())
			}
			SeekWhence::Set => {
				self.offset = offset.try_into().map_err(|_e| Errno::Inval)?;
				Ok(self.offset as isize)
			}
			SeekWhence::Cur => {
				self.offset = (self.offset as isize + offset)
					.try_into()
					.map_err(|_e| Errno::Inval)?;
				Ok(self.offset as isize)
			}
		}
	}

	fn fstat(&mut self) -> io::Result<FileAttr> {
		debug!("virtio-fs getattr");

		let nid = self.fuse_nid.ok_or(Errno::Io)?;
		let fh = self.fuse_fh.ok_or(Errno::Io)?;

		let (cmd, rsp_payload_len) = ops::Getattr::create(nid, fh, FUSE_GETATTR_FH);
		let rsp = get_filesystem_driver()
			.ok_or(Errno::Nosys)?
			.lock()
			.send_command(cmd, rsp_payload_len)?;

		if rsp.headers.out_header.error < 0 {
			return Err(Errno::Io);
		}

		Ok(rsp.headers.op_header.attr.into())
	}

	fn set_attr(&mut self, attr: FileAttr, valid: SetAttrValidFields) -> io::Result<FileAttr> {
		debug!("virtio-fs setattr");

		let nid = self.fuse_nid.ok_or(Errno::Io)?;
		let fh = self.fuse_fh.ok_or(Errno::Io)?;

		let (cmd, rsp_payload_len) = ops::Setattr::create(nid, fh, attr, valid);
		let rsp = get_filesystem_driver()
			.ok_or(Errno::Nosys)?
			.lock()
			.send_command(cmd, rsp_payload_len)?;

		if rsp.headers.out_header.error < 0 {
			return Err(Errno::Io);
		}

		Ok(rsp.headers.op_header.attr.into())
	}
}

impl ErrorType for VirtioFsFileHandleInner {
	type Error = Errno;
}

impl Read for VirtioFsFileHandleInner {
	fn read(&mut self, buf: &mut [u8]) -> Result<usize, Self::Error> {
		let mut len = buf.len();
		if len > MAX_READ_LEN {
			debug!("Reading longer than max_read_len: {len}");
			len = MAX_READ_LEN;
		}

		let nid = self.fuse_nid.ok_or(Errno::Io)?;
		let fh = self.fuse_fh.ok_or(Errno::Io)?;

		let (cmd, rsp_payload_len) =
			ops::Read::create(nid, fh, len.try_into().unwrap(), self.offset as u64);
		let rsp = get_filesystem_driver()
			.ok_or(Errno::Nosys)?
			.lock()
			.send_command(cmd, rsp_payload_len)?;
		let len: usize =
			if (rsp.headers.out_header.len as usize) - size_of::<fuse_out_header>() >= len {
				len
			} else {
				(rsp.headers.out_header.len as usize) - size_of::<fuse_out_header>()
			};
		self.offset += len;

		buf[..len].copy_from_slice(&rsp.payload.unwrap()[..len]);

		Ok(len)
	}
}

impl Write for VirtioFsFileHandleInner {
	fn write(&mut self, buf: &[u8]) -> Result<usize, Self::Error> {
		debug!("virtio-fs write!");
		let mut truncated_len = buf.len();
		if truncated_len > MAX_WRITE_LEN {
			debug!(
				"Writing longer than max_write_len: {} > {}",
				buf.len(),
				MAX_WRITE_LEN
			);
			truncated_len = MAX_WRITE_LEN;
		}

		let nid = self.fuse_nid.ok_or(Errno::Io)?;
		let fh = self.fuse_fh.ok_or(Errno::Io)?;

		let truncated_buf = Box::<[u8]>::from(&buf[..truncated_len]);
		let (cmd, rsp_payload_len) = ops::Write::create(nid, fh, truncated_buf, self.offset as u64);
		let rsp = get_filesystem_driver()
			.ok_or(Errno::Nosys)?
			.lock()
			.send_command(cmd, rsp_payload_len)?;

		if rsp.headers.out_header.error < 0 {
			return Err(Errno::Io);
		}

		let rsp_size = rsp.headers.op_header.size;
		let rsp_len: usize = if rsp_size > u32::try_from(truncated_len).unwrap() {
			truncated_len
		} else {
			rsp_size.try_into().unwrap()
		};
		self.offset += rsp_len;
		Ok(rsp_len)
	}

	fn flush(&mut self) -> Result<(), Self::Error> {
		Ok(())
	}
}

impl Drop for VirtioFsFileHandleInner {
	fn drop(&mut self) {
		let Some(fuse_nid) = self.fuse_nid else {
			return;
		};

		let Some(fuse_fh) = self.fuse_fh else {
			return;
		};

		let (cmd, rsp_payload_len) = ops::Release::create(fuse_nid, fuse_fh);
		get_filesystem_driver()
			.unwrap()
			.lock()
			.send_command(cmd, rsp_payload_len)
			.unwrap();
	}
}

pub struct VirtioFsFileHandle(Arc<Mutex<VirtioFsFileHandleInner>>);

impl VirtioFsFileHandle {
	pub fn new() -> Self {
		Self(Arc::new(Mutex::new(VirtioFsFileHandleInner::new())))
	}
}

impl ObjectInterface for VirtioFsFileHandle {
	async fn poll(&self, event: PollEvent) -> io::Result<PollEvent> {
		self.0.lock().await.poll(event).await
	}

	async fn read(&self, buf: &mut [u8]) -> io::Result<usize> {
		self.0.lock().await.read(buf)
	}

	async fn write(&self, buf: &[u8]) -> io::Result<usize> {
		self.0.lock().await.write(buf)
	}

	async fn lseek(&self, offset: isize, whence: SeekWhence) -> io::Result<isize> {
		self.0.lock().await.lseek(offset, whence)
	}

	async fn fstat(&self) -> io::Result<FileAttr> {
		self.0.lock().await.fstat()
	}

	async fn truncate(&self, size: usize) -> io::Result<()> {
		let attr = FileAttr {
			st_size: size.try_into().unwrap(),
			..FileAttr::default()
		};

		self.0
			.lock()
			.await
			.set_attr(attr, SetAttrValidFields::FATTR_SIZE)
			.map(|_| ())
	}

	async fn chmod(&self, access_permission: AccessPermission) -> io::Result<()> {
		let attr = FileAttr {
			st_mode: access_permission,
			..FileAttr::default()
		};

		self.0
			.lock()
			.await
			.set_attr(attr, SetAttrValidFields::FATTR_MODE)
			.map(|_| ())
	}
}

impl Clone for VirtioFsFileHandle {
	fn clone(&self) -> Self {
		warn!("VirtioFsFileHandle: clone not tested");
		Self(self.0.clone())
	}
}

pub struct VirtioFsDirectoryHandle {
	name: String,
	read_position: Mutex<usize>,
}

impl VirtioFsDirectoryHandle {
	pub fn new(name: String) -> Self {
		Self {
			name,
			read_position: Mutex::new(0),
		}
	}
}

impl ObjectInterface for VirtioFsDirectoryHandle {
	async fn getdents(&self, buf: &mut [MaybeUninit<u8>]) -> io::Result<usize> {
		let path = if self.name.is_empty() {
			CString::new("/").unwrap()
		} else {
			let path = ["/", &self.name].join("");
			CString::new(path).unwrap()
		};

		debug!("virtio-fs opendir: {path:#?}");

		let fuse_nid = lookup(path.clone()).ok_or(Errno::Noent)?;

		// Opendir
		// Flag 0x10000 for O_DIRECTORY might not be necessary
		let (mut cmd, rsp_payload_len) = ops::Open::create(fuse_nid, 0x10000);
		cmd.headers.in_header.opcode = fuse_opcode::FUSE_OPENDIR as u32;
		let rsp = get_filesystem_driver()
			.ok_or(Errno::Nosys)?
			.lock()
			.send_command(cmd, rsp_payload_len)?;
		let fuse_fh = rsp.headers.op_header.fh;

		debug!("virtio-fs readdir: {path:#?}");

		// Linux seems to allocate a single page to store the dirfile
		let len = MAX_READ_LEN as u32;
		let rsp_offset: &mut usize = &mut *self.read_position.lock().await;
		let mut buf_offset: usize = 0;

		// read content of the directory
		let (mut cmd, rsp_payload_len) = ops::Read::create(fuse_nid, fuse_fh, len, 0);
		cmd.headers.in_header.opcode = fuse_opcode::FUSE_READDIR as u32;
		let rsp = get_filesystem_driver()
			.ok_or(Errno::Nosys)?
			.lock()
			.send_command(cmd, rsp_payload_len)?;

		let len = usize::min(
			MAX_READ_LEN,
			rsp.headers.out_header.len as usize - size_of::<fuse_out_header>(),
		);

		if len <= size_of::<fuse_dirent>() {
			debug!("virtio-fs no new dirs");
			return Err(Errno::Noent);
		}

		let mut ret = 0;

		while (rsp.headers.out_header.len as usize) - *rsp_offset > size_of::<fuse_dirent>() {
			let dirent = unsafe {
				&*rsp
					.payload
					.as_ref()
					.unwrap()
					.as_ptr()
					.byte_add(*rsp_offset)
					.cast::<fuse_dirent>()
			};

			let dirent_len = mem::offset_of!(Dirent64, d_name) + dirent.namelen as usize + 1;
			let next_dirent = (buf_offset + dirent_len).align_up(align_of::<Dirent64>());

			if next_dirent > buf.len() {
				if ret == 0 {
					// Buffer too small to hold even one entry
					return Err(Errno::Inval);
				}
				// Buffer full -> return bytes written so far; caller retries from rsp_offset
				break;
			}

			// could be replaced with slice_as_ptr once maybe_uninit_slice is stabilized.
			let target_dirent = buf[buf_offset].as_mut_ptr().cast::<Dirent64>();
			unsafe {
				target_dirent.write(Dirent64 {
					d_ino: dirent.ino,
					d_off: 0,
					d_reclen: (dirent_len.align_up(align_of::<Dirent64>()))
						.try_into()
						.unwrap(),
					d_type: (dirent.type_ as u8).try_into().unwrap(),
					d_name: PhantomData {},
				});
				let nameptr = ptr::from_mut(&mut (*(target_dirent)).d_name).cast::<u8>();
				nameptr.copy_from_nonoverlapping(
					dirent.name.as_ptr().cast::<u8>(),
					dirent.namelen as usize,
				);
				nameptr.add(dirent.namelen as usize).write(0); // zero termination
			}

			*rsp_offset += size_of::<fuse_dirent>() + dirent.namelen as usize;
			// Align to dirent struct
			*rsp_offset = ((*rsp_offset) + U64_SIZE - 1) & (!(U64_SIZE - 1));
			buf_offset = next_dirent;
			ret = buf_offset;
		}

		let (cmd, rsp_payload_len) = ops::Release::create(fuse_nid, fuse_fh);
		get_filesystem_driver()
			.unwrap()
			.lock()
			.send_command(cmd, rsp_payload_len)?;

		Ok(ret)
	}

	/// lseek for a directory entry is the equivalent for seekdir on linux. But on Hermit this is
	/// logically the same operation, so we can just use the same fn in the backend.
	/// Any other offset than 0 is not supported. (Mostly because it doesn't make any sense, as
	/// userspace applications have no way of knowing valid offsets)
	async fn lseek(&self, offset: isize, whence: SeekWhence) -> io::Result<isize> {
		if whence != SeekWhence::Set && offset != 0 {
			error!("Invalid offset for directory lseek ({offset})");
			return Err(Errno::Inval);
		}
		*self.read_position.lock().await = offset as usize;
		Ok(offset)
	}
}

#[derive(Debug)]
pub(crate) struct VirtioFsDirectory {
	/// The external path of this directory.
	///
	/// Before talking to virtio-fs, the relative path inside this directory is
	/// adjoined with this prefix.
	prefix: String,
	attr: FileAttr,
}

impl VirtioFsDirectory {
	pub fn new(prefix: String) -> Self {
		let microseconds = arch::kernel::systemtime::now_micros();
		let t = timespec::from_usec(microseconds as i64);

		VirtioFsDirectory {
			prefix,
			attr: FileAttr {
				st_mode: AccessPermission::from_bits(0o777).unwrap() | AccessPermission::S_IFDIR,
				st_atim: t,
				st_mtim: t,
				st_ctim: t,
				..Default::default()
			},
		}
	}

	fn traversal_path(&self, path: &str) -> CString {
		let prefix = self.prefix.as_str();
		let prefix = prefix.strip_suffix("/").unwrap_or(prefix);
		let path = [prefix, path].join("/");
		CString::new(path).unwrap()
	}
}

impl VfsNode for VirtioFsDirectory {
	/// Returns the node type
	fn get_kind(&self) -> NodeKind {
		NodeKind::Directory
	}

	fn get_file_attributes(&self) -> io::Result<FileAttr> {
		Ok(self.attr)
	}

	fn get_object(&self) -> io::Result<Arc<async_lock::RwLock<Fd>>> {
		Ok(Arc::new(async_lock::RwLock::new(
			VirtioFsDirectoryHandle::new(self.prefix.clone()).into(),
		)))
	}

	fn traverse_readdir(&self, path: &str) -> io::Result<Vec<DirectoryEntry>> {
		let path = self.traversal_path(path);

		debug!("virtio-fs opendir: {path:#?}");

		let fuse_nid = lookup(path.clone()).ok_or(Errno::Noent)?;

		// Opendir
		// Flag 0x10000 for O_DIRECTORY might not be necessary
		let (mut cmd, rsp_payload_len) = ops::Open::create(fuse_nid, 0x10000);
		cmd.headers.in_header.opcode = fuse_opcode::FUSE_OPENDIR as u32;
		let rsp = get_filesystem_driver()
			.ok_or(Errno::Nosys)?
			.lock()
			.send_command(cmd, rsp_payload_len)?;
		let fuse_fh = rsp.headers.op_header.fh;

		debug!("virtio-fs readdir: {path:#?}");

		// Linux seems to allocate a single page to store the dirfile
		let len = MAX_READ_LEN as u32;
		let mut offset: usize = 0;

		// read content of the directory
		let (mut cmd, rsp_payload_len) = ops::Read::create(fuse_nid, fuse_fh, len, 0);
		cmd.headers.in_header.opcode = fuse_opcode::FUSE_READDIR as u32;
		let rsp = get_filesystem_driver()
			.ok_or(Errno::Nosys)?
			.lock()
			.send_command(cmd, rsp_payload_len)?;

		let len: usize = if rsp.headers.out_header.len as usize - size_of::<fuse_out_header>()
			>= usize::try_from(len).unwrap()
		{
			len.try_into().unwrap()
		} else {
			(rsp.headers.out_header.len as usize) - size_of::<fuse_out_header>()
		};

		if len <= size_of::<fuse_dirent>() {
			debug!("virtio-fs no new dirs");
			return Err(Errno::Noent);
		}

		let mut entries: Vec<DirectoryEntry> = Vec::new();
		while (rsp.headers.out_header.len as usize) - offset > size_of::<fuse_dirent>() {
			let dirent = unsafe {
				&*rsp
					.payload
					.as_ref()
					.unwrap()
					.as_ptr()
					.byte_add(offset)
					.cast::<fuse_dirent>()
			};

			offset += size_of::<fuse_dirent>() + dirent.namelen as usize;
			// Align to dirent struct
			offset = ((offset) + U64_SIZE - 1) & (!(U64_SIZE - 1));

			let name: &'static [u8] = unsafe {
				slice::from_raw_parts(
					dirent.name.as_ptr().cast(),
					dirent.namelen.try_into().unwrap(),
				)
			};
			entries.push(DirectoryEntry::new(unsafe {
				core::str::from_utf8_unchecked(name).to_owned()
			}));
		}

		let (cmd, rsp_payload_len) = ops::Release::create(fuse_nid, fuse_fh);
		get_filesystem_driver()
			.unwrap()
			.lock()
			.send_command(cmd, rsp_payload_len)?;

		Ok(entries)
	}

	fn traverse_stat(&self, path: &str) -> io::Result<FileAttr> {
		let path = self.traversal_path(path);

		debug!("virtio-fs stat: {path:#?}");

		// Is there a better way to implement this?
		let (cmd, rsp_payload_len) = ops::Lookup::create(path);
		let rsp = get_filesystem_driver()
			.unwrap()
			.lock()
			.send_command(cmd, rsp_payload_len)?;

		if rsp.headers.out_header.error != 0 {
			return Err(Errno::try_from(-rsp.headers.out_header.error).unwrap());
		}

		let entry_out = rsp.headers.op_header;
		let attr = entry_out.attr;

		if attr.mode & S_IFMT != S_IFLNK {
			return Ok(FileAttr::from(attr));
		}

		let path = readlink(entry_out.nodeid)?;
		self.traverse_stat(&path)
	}

	fn traverse_lstat(&self, path: &str) -> io::Result<FileAttr> {
		let path = self.traversal_path(path);

		debug!("virtio-fs lstat: {path:#?}");

		let (cmd, rsp_payload_len) = ops::Lookup::create(path);
		let rsp = get_filesystem_driver()
			.unwrap()
			.lock()
			.send_command(cmd, rsp_payload_len)?;
		Ok(FileAttr::from(rsp.headers.op_header.attr))
	}

	fn traverse_open(
		&self,
		path: &str,
		opt: OpenOption,
		mode: AccessPermission,
	) -> io::Result<Arc<async_lock::RwLock<Fd>>> {
		let path = self.traversal_path(path);

		debug!("virtio-fs open: {path:#?}, {opt:?} {mode:?}");

		if opt.contains(OpenOption::O_DIRECTORY) {
			if opt.contains(OpenOption::O_CREAT) {
				// See https://lwn.net/Articles/926782/
				warn!("O_DIRECTORY and O_CREAT are together invalid as open options.");
				return Err(Errno::Inval);
			}

			let (cmd, rsp_payload_len) = ops::Lookup::create(path.clone());
			let rsp = get_filesystem_driver()
				.unwrap()
				.lock()
				.send_command(cmd, rsp_payload_len)?;

			let attr = FileAttr::from(rsp.headers.op_header.attr);
			if !attr.st_mode.contains(AccessPermission::S_IFDIR) {
				return Err(Errno::Notdir);
			}

			let mut path = path.into_string().unwrap();
			path.remove(0);
			return Ok(Arc::new(async_lock::RwLock::new(
				VirtioFsDirectoryHandle::new(path).into(),
			)));
		}

		let file = VirtioFsFileHandle::new();

		// 1.FUSE_INIT to create session
		// Already done
		let mut file_guard = block_on(async { Ok(file.0.lock().await) }, None)?;

		// Differentiate between opening and creating new file, since FUSE does not support O_CREAT on open.
		if opt.contains(OpenOption::O_CREAT) {
			// Create file (opens implicitly, returns results from both lookup and open calls)
			let (cmd, rsp_payload_len) =
				ops::Create::create(path, opt.bits().try_into().unwrap(), mode.bits());
			let rsp = get_filesystem_driver()
				.ok_or(Errno::Nosys)?
				.lock()
				.send_command(cmd, rsp_payload_len)?;

			let inner = rsp.headers.op_header;
			file_guard.fuse_nid = Some(inner.entry.nodeid);
			file_guard.fuse_fh = Some(inner.open.fh);
		} else {
			// 2.FUSE_LOOKUP(FUSE_ROOT_ID, “foo”) -> nodeid
			file_guard.fuse_nid = lookup(path);

			if file_guard.fuse_nid.is_none() {
				warn!("virtio-fs lookup seems to have failed!");
				return Err(Errno::Noent);
			}

			// 3.FUSE_OPEN(nodeid, O_RDONLY) -> fh
			let (cmd, rsp_payload_len) =
				ops::Open::create(file_guard.fuse_nid.unwrap(), opt.bits().try_into().unwrap());
			let rsp = get_filesystem_driver()
				.ok_or(Errno::Nosys)?
				.lock()
				.send_command(cmd, rsp_payload_len)?;
			file_guard.fuse_fh = Some(rsp.headers.op_header.fh);
		}

		drop(file_guard);

		Ok(Arc::new(async_lock::RwLock::new(file.into())))
	}

	fn traverse_unlink(&self, path: &str) -> io::Result<()> {
		let path = self.traversal_path(path);

		let (cmd, rsp_payload_len) = ops::Unlink::create(path);
		let rsp = get_filesystem_driver()
			.ok_or(Errno::Nosys)?
			.lock()
			.send_command(cmd, rsp_payload_len)?;
		trace!("unlink answer {rsp:?}");

		Ok(())
	}

	fn traverse_rmdir(&self, path: &str) -> io::Result<()> {
		let path = self.traversal_path(path);

		let (cmd, rsp_payload_len) = ops::Rmdir::create(path);
		let rsp = get_filesystem_driver()
			.ok_or(Errno::Nosys)?
			.lock()
			.send_command(cmd, rsp_payload_len)?;
		trace!("rmdir answer {rsp:?}");

		Ok(())
	}

	fn traverse_mkdir(&self, path: &str, mode: AccessPermission) -> io::Result<()> {
		let path = self.traversal_path(path);
		let (cmd, rsp_payload_len) = ops::Mkdir::create(path, mode.bits());

		let rsp = get_filesystem_driver()
			.ok_or(Errno::Nosys)?
			.lock()
			.send_command(cmd, rsp_payload_len)?;
		if rsp.headers.out_header.error != 0 {
			return Err(Errno::try_from(-rsp.headers.out_header.error).unwrap());
		}

		Ok(())
	}
}

pub(crate) fn init() {
	debug!("Try to initialize virtio-fs filesystem");

	let Some(driver) = get_filesystem_driver() else {
		return;
	};

	let (cmd, rsp_payload_len) = ops::Init::create();
	let rsp = driver.lock().send_command(cmd, rsp_payload_len).unwrap();
	trace!("virtio-fs init answer: {rsp:?}");

	let mount_point = driver.lock().get_mount_point();
	if mount_point != "/" {
		let mount_point = if mount_point.starts_with('/') {
			mount_point
		} else {
			["/", &mount_point].join("")
		};

		info!("Mounting virtio-fs at {mount_point}");
		fs::FILESYSTEM
			.get()
			.unwrap()
			.mount(
				mount_point.as_str(),
				Box::new(VirtioFsDirectory::new("/".to_owned())),
			)
			.expect("Mount failed. Invalid mount_point?");
		return;
	}

	let fuse_nid = lookup(c"/".to_owned()).unwrap();
	// Opendir
	// Flag 0x10000 for O_DIRECTORY might not be necessary
	let (mut cmd, rsp_payload_len) = ops::Open::create(fuse_nid, 0x10000);
	cmd.headers.in_header.opcode = fuse_opcode::FUSE_OPENDIR as u32;
	let rsp = get_filesystem_driver()
		.unwrap()
		.lock()
		.send_command(cmd, rsp_payload_len)
		.unwrap();
	let fuse_fh = rsp.headers.op_header.fh;

	// Linux seems to allocate a single page to store the dirfile
	let len = MAX_READ_LEN as u32;
	let mut offset: usize = 0;

	// read content of the directory
	let (mut cmd, rsp_payload_len) = ops::Read::create(fuse_nid, fuse_fh, len, 0);
	cmd.headers.in_header.opcode = fuse_opcode::FUSE_READDIR as u32;
	let rsp = get_filesystem_driver()
		.unwrap()
		.lock()
		.send_command(cmd, rsp_payload_len)
		.unwrap();

	let len: usize = if rsp.headers.out_header.len as usize - size_of::<fuse_out_header>()
		>= usize::try_from(len).unwrap()
	{
		len.try_into().unwrap()
	} else {
		(rsp.headers.out_header.len as usize) - size_of::<fuse_out_header>()
	};

	assert!(len > size_of::<fuse_dirent>(), "virtio-fs no new dirs");

	let mut entries: Vec<String> = Vec::new();
	while (rsp.headers.out_header.len as usize) - offset > size_of::<fuse_dirent>() {
		let dirent = unsafe {
			&*rsp
				.payload
				.as_ref()
				.unwrap()
				.as_ptr()
				.byte_add(offset)
				.cast::<fuse_dirent>()
		};

		offset += size_of::<fuse_dirent>() + dirent.namelen as usize;
		// Align to dirent struct
		offset = ((offset) + U64_SIZE - 1) & (!(U64_SIZE - 1));

		let name: &'static [u8] = unsafe {
			slice::from_raw_parts(
				dirent.name.as_ptr().cast(),
				dirent.namelen.try_into().unwrap(),
			)
		};
		entries.push(unsafe { core::str::from_utf8_unchecked(name).to_owned() });
	}

	let (cmd, rsp_payload_len) = ops::Release::create(fuse_nid, fuse_fh);
	get_filesystem_driver()
		.unwrap()
		.lock()
		.send_command(cmd, rsp_payload_len)
		.unwrap();

	// remove predefined directories
	entries.retain(|x| x != ".");
	entries.retain(|x| x != "..");
	entries.retain(|x| x != "tmp");
	entries.retain(|x| x != "proc");
	warn!(
		"virtio-fs don't mount the host directories 'tmp' and 'proc' into the guest file system!"
	);

	for entry in entries {
		let i_cstr = CString::new(entry.as_str()).unwrap();
		let (cmd, rsp_payload_len) = ops::Lookup::create(i_cstr);
		let rsp = get_filesystem_driver()
			.unwrap()
			.lock()
			.send_command(cmd, rsp_payload_len)
			.unwrap();

		let attr = FileAttr::from(rsp.headers.op_header.attr);
		if attr.st_mode.contains(AccessPermission::S_IFDIR) {
			let path = ["/", &entry].join("");
			info!("virtio-fs mount {entry} to {path}");
			fs::FILESYSTEM
				.get()
				.unwrap()
				.mount(&path, Box::new(VirtioFsDirectory::new(path.clone())))
				.expect("Mount failed. Invalid mount_point?");
		} else {
			warn!("virtio-fs don't mount {entry}. It isn't a directory!");
		}
	}
}