// Copyright 2018 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

mod msg_on_socket;

use std::io::Result;
use std::marker::PhantomData;
use std::os::unix::io::{AsRawFd, RawFd};

use sys_util::{handle_eintr, net::UnixSeqpacket, Error as SysError, ScmSocket};

pub use crate::msg_on_socket::*;
pub use msg_on_socket_derive::*;

/// Create a pair of socket. Request is send in one direction while response is in the other
/// direction.
pub fn pair<Request: MsgOnSocket, Response: MsgOnSocket>(
) -> Result<(MsgSocket<Request, Response>, MsgSocket<Response, Request>)> {
    let (sock1, sock2) = UnixSeqpacket::pair()?;
    let requester = MsgSocket {
        sock: sock1,
        _i: PhantomData,
        _o: PhantomData,
    };
    let responder = MsgSocket {
        sock: sock2,
        _i: PhantomData,
        _o: PhantomData,
    };
    Ok((requester, responder))
}

/// Bidirection sock that support both send and recv.
pub struct MsgSocket<I: MsgOnSocket, O: MsgOnSocket> {
    sock: UnixSeqpacket,
    _i: PhantomData<I>,
    _o: PhantomData<O>,
}

impl<I: MsgOnSocket, O: MsgOnSocket> MsgSocket<I, O> {
    // Create a new MsgSocket.
    pub fn new(s: UnixSeqpacket) -> MsgSocket<I, O> {
        MsgSocket {
            sock: s,
            _i: PhantomData,
            _o: PhantomData,
        }
    }
}

/// One direction socket that only supports sending.
pub struct Sender<M: MsgOnSocket> {
    sock: UnixSeqpacket,
    _m: PhantomData<M>,
}

impl<M: MsgOnSocket> Sender<M> {
    /// Create a new sender sock.
    pub fn new(s: UnixSeqpacket) -> Sender<M> {
        Sender {
            sock: s,
            _m: PhantomData,
        }
    }
}

/// One direction socket that only supports receiving.
pub struct Receiver<M: MsgOnSocket> {
    sock: UnixSeqpacket,
    _m: PhantomData<M>,
}

impl<M: MsgOnSocket> Receiver<M> {
    /// Create a new receiver sock.
    pub fn new(s: UnixSeqpacket) -> Receiver<M> {
        Receiver {
            sock: s,
            _m: PhantomData,
        }
    }
}

impl<I: MsgOnSocket, O: MsgOnSocket> AsRef<UnixSeqpacket> for MsgSocket<I, O> {
    fn as_ref(&self) -> &UnixSeqpacket {
        &self.sock
    }
}

impl<I: MsgOnSocket, O: MsgOnSocket> AsRawFd for MsgSocket<I, O> {
    fn as_raw_fd(&self) -> RawFd {
        self.sock.as_raw_fd()
    }
}

impl<M: MsgOnSocket> AsRef<UnixSeqpacket> for Sender<M> {
    fn as_ref(&self) -> &UnixSeqpacket {
        &self.sock
    }
}

impl<M: MsgOnSocket> AsRawFd for Sender<M> {
    fn as_raw_fd(&self) -> RawFd {
        self.sock.as_raw_fd()
    }
}

impl<M: MsgOnSocket> AsRef<UnixSeqpacket> for Receiver<M> {
    fn as_ref(&self) -> &UnixSeqpacket {
        &self.sock
    }
}

impl<M: MsgOnSocket> AsRawFd for Receiver<M> {
    fn as_raw_fd(&self) -> RawFd {
        self.sock.as_raw_fd()
    }
}

/// Types that could send a message.
pub trait MsgSender: AsRef<UnixSeqpacket> {
    type M: MsgOnSocket;
    fn send(&self, msg: &Self::M) -> MsgResult<()> {
        let msg_size = Self::M::msg_size();
        let fd_size = Self::M::max_fd_count();
        let mut msg_buffer: Vec<u8> = vec![0; msg_size];
        let mut fd_buffer: Vec<RawFd> = vec![0; fd_size];

        let fd_size = msg.write_to_buffer(&mut msg_buffer, &mut fd_buffer)?;
        let sock: &UnixSeqpacket = self.as_ref();
        if fd_size == 0 {
            handle_eintr!(sock.send(&msg_buffer))
                .map_err(|e| MsgError::Send(SysError::new(e.raw_os_error().unwrap_or(0))))?;
        } else {
            sock.send_with_fds(&msg_buffer[..], &fd_buffer[0..fd_size])
                .map_err(MsgError::Send)?;
        }
        Ok(())
    }
}

/// Types that could receive a message.
pub trait MsgReceiver: AsRef<UnixSeqpacket> {
    type M: MsgOnSocket;
    fn recv(&self) -> MsgResult<Self::M> {
        let msg_size = Self::M::msg_size();
        let fd_size = Self::M::max_fd_count();
        let mut msg_buffer: Vec<u8> = vec![0; msg_size];
        let mut fd_buffer: Vec<RawFd> = vec![0; fd_size];

        let sock: &UnixSeqpacket = self.as_ref();

        let (recv_msg_size, recv_fd_size) = {
            if fd_size == 0 {
                let size = sock
                    .recv(&mut msg_buffer)
                    .map_err(|e| MsgError::Recv(SysError::new(e.raw_os_error().unwrap_or(0))))?;
                (size, 0)
            } else {
                sock.recv_with_fds(&mut msg_buffer, &mut fd_buffer)
                    .map_err(MsgError::Recv)?
            }
        };
        if msg_size != recv_msg_size {
            return Err(MsgError::BadRecvSize {
                expected: msg_size,
                actual: recv_msg_size,
            });
        }
        // Safe because fd buffer is read from socket.
        let (v, read_fd_size) = unsafe {
            Self::M::read_from_buffer(&msg_buffer[0..recv_msg_size], &fd_buffer[0..recv_fd_size])?
        };
        if recv_fd_size != read_fd_size {
            return Err(MsgError::NotExpectFd);
        }
        Ok(v)
    }
}

impl<I: MsgOnSocket, O: MsgOnSocket> MsgSender for MsgSocket<I, O> {
    type M = I;
}
impl<I: MsgOnSocket, O: MsgOnSocket> MsgReceiver for MsgSocket<I, O> {
    type M = O;
}

impl<I: MsgOnSocket> MsgSender for Sender<I> {
    type M = I;
}
impl<O: MsgOnSocket> MsgReceiver for Receiver<O> {
    type M = O;
}