//! Redox-specific system library.
#![no_std]

pub use syscall::error;
use syscall::error::{Error, Result};

pub mod flag {
    pub use libc::{
        O_ACCMODE, O_CLOEXEC, O_CREAT, O_DIRECTORY, O_NONBLOCK, O_RDONLY, O_RDWR, O_WRONLY,
    };

    pub use libc::{CLOCK_MONOTONIC, CLOCK_REALTIME};

    pub use libc::{SIG_BLOCK, SIG_SETMASK, SIG_UNBLOCK};

    pub use libc::{SIGUSR1, SIGUSR2};

    #[cfg(target_os = "redox")]
    pub use libc::{O_EXLOCK, O_SHLOCK};

    #[cfg(target_os = "redox")]
    pub const O_STAT: i32 = syscall::flag::O_STAT as i32;

    pub const MAP_SHARED: u32 = libc::MAP_SHARED as u32;
    pub const MAP_PRIVATE: u32 = libc::MAP_PRIVATE as u32;

    pub const PROT_NONE: u32 = libc::PROT_NONE as u32;
    pub const PROT_READ: u32 = libc::PROT_READ as u32;
    pub const PROT_WRITE: u32 = libc::PROT_WRITE as u32;
    pub const PROT_EXEC: u32 = libc::PROT_EXEC as u32;
}

pub mod errno {
    pub use libc::{
        EACCES, EAGAIN, EBADF, EBADFD, EBUSY, EINTR, ENODEV, EPERM, EPIPE, ESPIPE, ESRCH,
        EWOULDBLOCK,
    };
}
pub mod data {
    pub use libc::sigaction as SigAction;
    pub use libc::timespec as TimeSpec;

    #[cfg(target_os = "redox")]
    pub use libc::sigset_t as SigSet;

    // TODO: Should libredox compile on non-Redox platforms?
    #[cfg(not(target_os = "redox"))]
    pub type SigSet = u64;
}

type RawResult = usize;

extern "C" {
    // NOTE: Although there are version suffixes, there'd have to be strong reasons for adding new
    // version.
    fn redox_open_v1(path_base: *const u8, path_len: usize, flags: u32, mode: u16) -> RawResult;
    fn redox_dup_v1(fd: usize, buf: *const u8, len: usize) -> RawResult;
    fn redox_dup2_v1(old_fd: usize, new_fd: usize, buf: *const u8, len: usize) -> RawResult;
    fn redox_read_v1(fd: usize, dst_base: *mut u8, dst_len: usize) -> RawResult;
    fn redox_write_v1(fd: usize, src_base: *const u8, src_len: usize) -> RawResult;
    fn redox_fsync_v1(fd: usize) -> RawResult;
    fn redox_fdatasync_v1(fd: usize) -> RawResult;
    fn redox_fchmod_v1(fd: usize, new_mode: u16) -> RawResult;
    fn redox_fchown_v1(fd: usize, new_uid: u32, new_gid: u32) -> RawResult;
    fn redox_fpath_v1(fd: usize, dst_base: *mut u8, dst_len: usize) -> RawResult;
    fn redox_close_v1(fd: usize) -> RawResult;

    // NOTE: While the Redox kernel currently doesn't distinguish between threads and processes,
    // the return value of this function is expected to be treated as a process ID and not a thread
    // ID.
    fn redox_get_pid_v1() -> RawResult;

    fn redox_get_euid_v1() -> RawResult;
    fn redox_get_ruid_v1() -> RawResult;
    fn redox_get_egid_v1() -> RawResult;
    fn redox_get_rgid_v1() -> RawResult;
    fn redox_setrens_v1(rns: usize, ens: usize) -> RawResult;

    fn redox_kill_v1(pid: usize, signal: u32) -> RawResult;
    fn redox_waitpid_v1(pid: usize, status: *mut i32, options: u32) -> RawResult;

    fn redox_sigprocmask_v1(how: u32, new: *const u64, old: *mut u64) -> RawResult;
    fn redox_sigaction_v1(
        signal: u32,
        new: *const data::SigAction,
        old: *mut data::SigAction,
    ) -> RawResult;

    fn redox_clock_gettime_v1(clock: usize, ts: *mut data::TimeSpec) -> RawResult;

    fn redox_mmap_v1(
        addr: *mut (),
        unaligned_len: usize,
        prot: u32,
        flags: u32,
        fd: usize,
        offset: u64,
    ) -> RawResult;
    fn redox_munmap_v1(addr: *mut (), unaligned_len: usize) -> RawResult;
}

#[cfg(feature = "call")]
pub struct Fd(usize);

#[cfg(feature = "call")]
impl Fd {
    #[inline]
    pub fn open(path: &str, flags: i32, mode: u16) -> Result<Self> {
        Ok(Self(call::open(path, flags, mode)?))
    }
    #[inline]
    pub fn dup(&self, buf: &[u8]) -> Result<usize> {
        call::dup(self.raw(), buf)
    }
    #[inline]
    pub fn dup2(&self, new_fd: usize, buf: &[u8]) -> Result<usize> {
        call::dup2(self.raw(), new_fd, buf)
    }

    #[inline]
    pub const fn raw(&self) -> usize {
        self.0
    }

    #[inline]
    pub fn into_raw(self) -> usize {
        let raw = self.raw();
        core::mem::forget(self);
        raw
    }

    #[inline]
    pub fn read(&self, buf: &mut [u8]) -> Result<usize> {
        call::read(self.raw(), buf)
    }
    #[inline]
    pub fn write(&self, buf: &[u8]) -> Result<usize> {
        call::write(self.raw(), buf)
    }
    #[inline]
    pub fn fpath(&self, path: &mut [u8]) -> Result<usize> {
        call::fpath(self.raw(), path)
    }
    #[inline]
    pub fn fsync(&self) -> Result<()> {
        call::fsync(self.raw())
    }
    #[inline]
    pub fn fdatasync(&self) -> Result<()> {
        call::fdatasync(self.raw())
    }

    #[inline]
    pub fn chmod(&self, new_mode: u16) -> Result<()> {
        call::fchmod(self.raw(), new_mode)
    }
    #[inline]
    pub fn chown(&self, new_uid: u32, new_gid: u32) -> Result<()> {
        call::fchown(self.raw(), new_uid, new_gid)
    }
    #[inline]
    pub fn close(self) -> Result<()> {
        call::close(self.into_raw())
    }
}
#[cfg(feature = "call")]
impl Drop for Fd {
    fn drop(&mut self) {
        let _ = unsafe { redox_close_v1(self.0) };
    }
}

#[cfg(feature = "call")]
pub mod call {
    use super::*;

    /// flags and mode are binary compatible with libc
    #[inline]
    pub fn open(path: impl AsRef<str>, flags: i32, mode: u16) -> Result<usize> {
        let path = path.as_ref();
        Ok(Error::demux(unsafe {
            redox_open_v1(path.as_ptr(), path.len(), flags as u32, mode)
        })?)
    }
    #[inline]
    pub fn dup(fd: usize, buf: impl AsRef<[u8]>) -> Result<usize> {
        let buf = buf.as_ref();
        Ok(Error::demux(unsafe {
            redox_dup_v1(fd, buf.as_ptr(), buf.len())
        })?)
    }
    #[inline]
    pub fn dup2(old_fd: usize, new_fd: usize, buf: impl AsRef<[u8]>) -> Result<usize> {
        let buf = buf.as_ref();
        Ok(Error::demux(unsafe {
            redox_dup2_v1(old_fd, new_fd, buf.as_ptr(), buf.len())
        })?)
    }
    #[inline]
    pub fn read(raw_fd: usize, buf: &mut [u8]) -> Result<usize> {
        Ok(Error::demux(unsafe {
            redox_read_v1(raw_fd, buf.as_mut_ptr(), buf.len())
        })?)
    }
    #[inline]
    pub fn write(raw_fd: usize, buf: &[u8]) -> Result<usize> {
        Ok(Error::demux(unsafe {
            redox_write_v1(raw_fd, buf.as_ptr(), buf.len())
        })?)
    }
    #[inline]
    pub fn fsync(raw_fd: usize) -> Result<()> {
        Error::demux(unsafe { redox_fsync_v1(raw_fd) }).map(|_| ())
    }
    #[inline]
    pub fn fdatasync(raw_fd: usize) -> Result<()> {
        Ok(Error::demux(unsafe { redox_fdatasync_v1(raw_fd) })?).map(|_| ())
    }
    #[inline]
    pub fn fchmod(raw_fd: usize, new_mode: u16) -> Result<()> {
        Error::demux(unsafe { redox_fchmod_v1(raw_fd, new_mode) })?;
        Ok(())
    }
    #[inline]
    pub fn fchown(raw_fd: usize, new_uid: u32, new_gid: u32) -> Result<()> {
        Error::demux(unsafe { redox_fchown_v1(raw_fd, new_uid, new_gid) })?;
        Ok(())
    }
    #[inline]
    pub fn fpath(raw_fd: usize, buf: &mut [u8]) -> Result<usize> {
        Ok(Error::demux(unsafe {
            redox_fpath_v1(raw_fd, buf.as_mut_ptr(), buf.len())
        })?)
    }
    #[inline]
    pub fn close(raw_fd: usize) -> Result<()> {
        Error::demux(unsafe { redox_close_v1(raw_fd) })?;
        Ok(())
    }

    #[inline]
    pub fn geteuid() -> Result<usize> {
        Error::demux(unsafe { redox_get_euid_v1() })
    }

    #[inline]
    pub fn getruid() -> Result<usize> {
        Error::demux(unsafe { redox_get_ruid_v1() })
    }

    #[inline]
    pub fn getegid() -> Result<usize> {
        Error::demux(unsafe { redox_get_egid_v1() })
    }
    #[inline]
    pub fn getrgid() -> Result<usize> {
        Error::demux(unsafe { redox_get_rgid_v1() })
    }
    #[inline]
    pub fn getpid() -> Result<usize> {
        Error::demux(unsafe { redox_get_pid_v1() })
    }
    #[inline]
    pub fn setrens(rns: usize, ens: usize) -> Result<usize> {
        Error::demux(unsafe { redox_setrens_v1(rns, ens) })
    }
    #[inline]
    pub fn waitpid(pid: usize, status: &mut i32, options: i32) -> Result<usize> {
        Error::demux(unsafe { redox_waitpid_v1(pid, status as *mut i32, options as u32) })
    }
    #[inline]
    pub fn kill(pid: usize, signal: u32) -> Result<()> {
        Error::demux(unsafe { redox_kill_v1(pid, signal) }).map(|_| ())
    }
    #[inline]
    pub fn clock_gettime(clock: i32, ts: &mut data::TimeSpec) -> Result<()> {
        Error::demux(unsafe { redox_clock_gettime_v1(clock as usize, ts) }).map(|_| ())
    }
    #[inline]
    pub fn sigprocmask(
        how: i32,
        newmask: Option<&data::SigSet>,
        oldmask: Option<&mut data::SigSet>,
    ) -> Result<()> {
        Error::demux(unsafe {
            redox_sigprocmask_v1(
                how as u32,
                newmask.map_or(core::ptr::null(), |m| m),
                oldmask.map_or(core::ptr::null_mut(), |m| m),
            )
        })
        .map(|_| ())
    }
    #[inline]
    pub fn sigaction(
        signal: i32,
        newact: Option<&data::SigAction>,
        oldact: Option<&mut data::SigAction>,
    ) -> Result<()> {
        Error::demux(unsafe {
            redox_sigaction_v1(
                signal as u32,
                newact.map_or(core::ptr::null(), |m| m),
                oldact.map_or(core::ptr::null_mut(), |m| m),
            )
        })
        .map(|_| ())
    }

    #[derive(Clone, Copy, Debug)]
    pub struct MmapArgs {
        pub addr: *mut (),
        pub length: usize,
        pub prot: u32,
        pub flags: u32,
        pub fd: usize,
        pub offset: u64,
    }
    #[inline]
    pub unsafe fn mmap(args: MmapArgs) -> Result<*mut ()> {
        Error::demux(redox_mmap_v1(
            args.addr,
            args.length,
            args.prot,
            args.flags,
            args.fd,
            args.offset,
        ))
        .map(|addr| addr as *mut ())
    }
    #[inline]
    pub unsafe fn munmap(addr: *mut (), length: usize) -> Result<()> {
        Error::demux(redox_munmap_v1(addr, length)).map(|_| ())
    }
}

#[cfg(feature = "scheme")]
pub mod scheme {
    use super::*;

    use core::mem::size_of;

    use syscall::Packet;
    pub use syscall::{Scheme, SchemeBlock, SchemeBlockMut, SchemeMut};

    #[repr(transparent)]
    #[derive(Clone, Copy, Default)]
    pub struct Request(Packet);

    impl Request {
        pub fn handle_scheme(mut self, scheme: &impl Scheme) -> Response {
            scheme.handle(&mut self.0);
            Response(self.0)
        }
        pub fn handle_scheme_mut(mut self, scheme: &mut impl SchemeMut) -> Response {
            scheme.handle(&mut self.0);
            Response(self.0)
        }
        pub fn handle_scheme_block(
            mut self,
            scheme: &mut impl SchemeBlock,
        ) -> Result<Response, Request> {
            match scheme.handle(&mut self.0) {
                Some(code) => Ok(Response(Packet { a: code, ..self.0 })),
                None => Err(self),
            }
        }
        pub fn handle_scheme_block_mut(
            mut self,
            scheme: &mut impl SchemeBlockMut,
        ) -> Result<Response, Request> {
            match scheme.handle(&mut self.0) {
                Some(code) => Ok(Response(Packet { a: code, ..self.0 })),
                None => Err(self),
            }
        }
    }

    #[repr(transparent)]
    #[derive(Clone, Copy, Default)]
    pub struct Response(Packet);

    impl Response {
        pub fn new(req: &Request, status: Result<usize>) -> Self {
            Self(Packet {
                a: Error::mux(status),
                ..req.0
            })
        }
    }

    pub enum SignalBehavior {
        Interrupt,
        Restart,
    }

    // TODO: Support uninitialized memory
    #[inline]
    pub fn read_requests(
        socket: usize,
        buf: &mut [Request],
        behavior: SignalBehavior,
    ) -> Result<usize> {
        let len = buf.len().checked_mul(size_of::<Request>()).unwrap();

        let bytes_read = loop {
            match call::read(socket, unsafe {
                core::slice::from_raw_parts_mut(buf.as_mut_ptr().cast(), len)
            }) {
                Ok(n) => break n,
                error @ Err(Error {
                    errno: errno::EINTR,
                }) => match behavior {
                    SignalBehavior::Restart => continue,
                    SignalBehavior::Interrupt => return error,
                },
                Err(err) => return Err(err),
            }
        };

        debug_assert_eq!(bytes_read % size_of::<Request>(), 0);

        Ok(bytes_read / size_of::<Request>())
    }

    #[inline]
    pub fn write_responses(
        socket: usize,
        buf: &[Response],
        behavior: SignalBehavior,
    ) -> Result<usize> {
        let bytes = unsafe {
            core::slice::from_raw_parts(
                buf.as_ptr().cast(),
                buf.len().checked_mul(size_of::<Response>()).unwrap(),
            )
        };

        let bytes_written = loop {
            match call::write(socket, bytes) {
                Ok(n) => break n,
                error @ Err(Error {
                    errno: errno::EINTR,
                }) => match behavior {
                    SignalBehavior::Restart => continue,
                    SignalBehavior::Interrupt => return error,
                },
                Err(err) => return Err(err),
            }
        };
        debug_assert_eq!(bytes_written % size_of::<Response>(), 0);
        Ok(bytes_written / size_of::<Response>())
    }
}