// Copyright 2017 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.

//! This module implements the virtio wayland used by the guest to access the host's wayland server.
//!
//! The virtio wayland protocol is done over two queues: `in` and `out`. The `in` queue is used for
//! sending commands to the guest that are generated by the host, usually messages from the wayland
//! server. The `out` queue is for commands from the guest, usually requests to allocate shared
//! memory, open a wayland server connection, or send data over an existing connection.
//!
//! Each `WlVfd` represents one virtual file descriptor created by either the guest or the host.
//! Virtual file descriptors contain actual file descriptors, either a shared memory file descriptor
//! or a unix domain socket to the wayland server. In the shared memory case, there is also an
//! associated slot that indicates which KVM memory slot the memory is installed into, as well as a
//! page frame number that the guest can access the memory from.
//!
//! The types starting with `Ctrl` are structures representing the virtio wayland protocol "on the
//! wire." They are decoded and executed in the `execute` function and encoded as some variant of
//! `WlResp` for responses.
//!
//! There is one `WlState` instance that contains every known vfd and the current state of `in`
//! queue. The `in` queue requires extra state to buffer messages to the guest in case the `in`
//! queue is already full. The `WlState` also has a control socket necessary to fulfill certain
//! requests, such as those registering guest memory.
//!
//! The `Worker` is responsible for the poll loop over all possible events, encoding/decoding from
//! the virtio queue, and routing messages in and out of `WlState`. Possible events include the kill
//! event, available descriptors on the `in` or `out` queue, and incoming data on any vfd's socket.

use std::collections::BTreeMap as Map;
use std::os::unix::io::{AsRawFd, RawFd};
use std::path::PathBuf;
use std::sync::Arc;
use std::thread;

use super::resource_bridge::*;
use super::{Interrupt, InterruptProxyEvent, Queue, VirtioDevice, TYPE_WL, VIRTIO_F_VERSION_1};
use crate::MemoryParams;
use vm_control::{MaybeOwnedFd, VmMemoryControlRequestSocket};

use msg_socket::{MsgOnSocket, MsgReceiver, MsgSocket};
use serde::{Deserialize, Serialize};
use sys_util::net::UnixSeqpacket;
use sys_util::{error, EventFd, GuestMemory, PollContext, PollToken, SharedMemory};

#[derive(Debug, MsgOnSocket)]
pub enum MsgOnSocketRequest {
    Create {
        // wayland_paths: Map<String, PathBuf>,
        vm_socket: MaybeOwnedFd<UnixSeqpacket>,
        // resource_bridge: Option<ResourceRequestSocket>,
        memory_params: MemoryParams,
    },
    Activate {
        shm: MaybeOwnedFd<SharedMemory>,
        interrupt: MaybeOwnedFd<UnixSeqpacket>,
        interrupt_resample_evt: MaybeOwnedFd<EventFd>,
        in_queue: Queue,
        out_queue: Queue,
        in_queue_evt: MaybeOwnedFd<EventFd>,
        out_queue_evt: MaybeOwnedFd<EventFd>,
    },
    Kill,
}

#[derive(Debug, Serialize, Deserialize)]
pub enum BincodeRequest {
    WriteConfig { offset: u64, data: Vec<u8> },
}

pub type Request = poly_msg_socket::Value<MsgOnSocketRequest, BincodeRequest>;

impl From<MsgOnSocketRequest> for Request {
    fn from(request: MsgOnSocketRequest) -> Self {
        Self::MsgOnSocket(request)
    }
}

impl From<BincodeRequest> for Request {
    fn from(request: BincodeRequest) -> Self {
        Self::Bincode(request)
    }
}

#[derive(Debug, MsgOnSocket)]
pub enum MsgOnSocketResponse {
    Kill,
}

#[derive(Debug, Deserialize, Serialize)]
pub struct BincodeResponse;

pub type Response = poly_msg_socket::Value<MsgOnSocketResponse, BincodeResponse>;

impl From<MsgOnSocketResponse> for Response {
    fn from(response: MsgOnSocketResponse) -> Self {
        Self::MsgOnSocket(response)
    }
}

impl From<BincodeResponse> for Response {
    fn from(response: BincodeResponse) -> Self {
        Self::Bincode(response)
    }
}

use poly_msg_socket::PolyMsgSocket;
type Socket =
    PolyMsgSocket<MsgOnSocketRequest, MsgOnSocketResponse, BincodeRequest, BincodeResponse>;

const VIRTIO_WL_F_TRANS_FLAGS: u32 = 0x01;

// TODO: support arbitrary number of queues
const QUEUE_SIZE: u16 = 16;
const QUEUE_SIZES: &[u16] = &[QUEUE_SIZE, QUEUE_SIZE];

struct Worker {
    device_socket: Arc<Socket>,
    interrupt: Interrupt,
    interrupt_socket: MsgSocket<(), InterruptProxyEvent>,

    shutdown: bool,
}

impl Worker {
    fn new(
        device_socket: Arc<Socket>,
        interrupt: Interrupt,
        interrupt_socket: MsgSocket<(), InterruptProxyEvent>,
    ) -> Self {
        Self {
            device_socket,
            interrupt,
            interrupt_socket,
            shutdown: false,
        }
    }

    fn handle_response(&mut self) {
        use poly_msg_socket::Value::*;
        match self.device_socket.recv() {
            Ok(MsgOnSocket(MsgOnSocketResponse::Kill)) => {
                self.shutdown = true;
            }

            Ok(Bincode(BincodeResponse)) => unreachable!(),

            Err(e) => {
                error!("recv failed: {:?}", e);
            }
        }
    }

    fn interrupt(&self) {
        use InterruptProxyEvent::*;
        match self.interrupt_socket.recv() {
            Ok(SignalUsedQueue(value)) => self.interrupt.signal_used_queue(value).unwrap(),
            Ok(SignalConfigChanged) => self.interrupt.signal_config_changed().unwrap(),
            Ok(InterruptResample) => self.interrupt.interrupt_resample().unwrap(),

            Err(e) => {
                eprintln!("recv error: {}", e);
                panic!("recv error: {}", e)
            }
        }
    }

    fn kill(&self) {
        if let Err(e) = self.device_socket.send(poly_msg_socket::Value::MsgOnSocket(
            MsgOnSocketRequest::Kill,
        )) {
            error!("failed to send Kill message: {}", e);
        }
    }

    fn run(mut self, kill_evt: EventFd) {
        #[derive(Debug, PollToken)]
        enum Token {
            Device,
            Interrupt,
            Kill,
        }

        let poll_ctx: PollContext<Token> = match PollContext::build_with(&[
            (&*self.device_socket, Token::Device),
            (&self.interrupt_socket, Token::Interrupt),
            (&kill_evt, Token::Kill),
        ]) {
            Ok(pc) => pc,
            Err(e) => {
                error!("failed creating PollContext: {}", e);
                return;
            }
        };

        while !self.shutdown {
            let events = match poll_ctx.wait() {
                Ok(v) => v,
                Err(e) => {
                    error!("failed polling for events: {}", e);
                    break;
                }
            };

            for event in &events {
                match event.token() {
                    Token::Device => self.handle_response(),
                    Token::Interrupt => self.interrupt(),
                    Token::Kill => self.kill(),
                }
            }
        }
    }
}

pub struct Controller {
    kill_evt: Option<EventFd>,
    worker_thread: Option<thread::JoinHandle<()>>,
    use_transition_flags: bool,
    socket: Arc<Socket>,
}

impl Controller {
    pub fn create(
        wayland_paths: Map<String, PathBuf>,
        vm_socket: VmMemoryControlRequestSocket,
        resource_bridge: Option<ResourceRequestSocket>,
        memory_params: MemoryParams,
        socket: Socket,
    ) -> Result<Controller, poly_msg_socket::Error> {
        socket.send(MsgOnSocketRequest::Create {
            // wayland_paths,
            vm_socket: MaybeOwnedFd::new_borrowed(&vm_socket),
            // resource_bridge,
            memory_params,
        })?;

        Ok(Controller {
            kill_evt: None,
            worker_thread: None,
            use_transition_flags: false,
            socket: Arc::new(socket),
        })
    }
}

impl Drop for Controller {
    fn drop(&mut self) {
        if let Some(kill_evt) = self.kill_evt.take() {
            // Ignore the result because there is nothing we can do about it.
            let _ = kill_evt.write(1);
        }

        if let Some(worker_thread) = self.worker_thread.take() {
            let _ = worker_thread.join();
        }
    }
}

impl VirtioDevice for Controller {
    fn keep_fds(&self) -> Vec<RawFd> {
        let mut keep_fds = Vec::new();

        if let Some(ref kill_evt) = self.kill_evt {
            keep_fds.push(kill_evt.as_raw_fd());
        }

        keep_fds.push(self.socket.as_raw_fd());

        keep_fds
    }

    fn device_type(&self) -> u32 {
        TYPE_WL
    }

    fn queue_max_sizes(&self) -> &[u16] {
        QUEUE_SIZES
    }

    fn features(&self) -> u64 {
        1 << VIRTIO_WL_F_TRANS_FLAGS | 1 << VIRTIO_F_VERSION_1
    }

    fn ack_features(&mut self, value: u64) {
        if value & (1 << VIRTIO_WL_F_TRANS_FLAGS) != 0 {
            self.use_transition_flags = true;
        }
    }

    fn activate(
        &mut self,
        mem: GuestMemory,
        interrupt: Interrupt,
        mut queues: Vec<Queue>,
        queue_evts: Vec<EventFd>,
    ) {
        if queues.len() != QUEUE_SIZES.len() || queue_evts.len() != QUEUE_SIZES.len() {
            return;
        }

        let (self_kill_evt, kill_evt) = match EventFd::new().and_then(|e| Ok((e.try_clone()?, e))) {
            Ok(v) => v,
            Err(e) => {
                error!("failed creating kill EventFd pair: {}", e);
                return;
            }
        };
        self.kill_evt = Some(self_kill_evt);

        let use_transition_flags = self.use_transition_flags;

        let (ours, theirs) = UnixSeqpacket::pair().expect("pair failed");

        if let Err(e) = self.socket.send(MsgOnSocketRequest::Activate {
            shm: MaybeOwnedFd::new_borrowed(&mem),
            interrupt: MaybeOwnedFd::new_borrowed(&theirs),
            interrupt_resample_evt: MaybeOwnedFd::new_borrowed(interrupt.get_resample_evt()),
            in_queue: queues.remove(0),
            out_queue: queues.remove(0),
            in_queue_evt: MaybeOwnedFd::new_borrowed(&queue_evts[0]),
            out_queue_evt: MaybeOwnedFd::new_borrowed(&queue_evts[1]),
        }) {
            error!("failed to send Activate: {}", e);
            return;
        }

        let socket = Arc::clone(&self.socket);
        let worker_result = thread::Builder::new()
            .name("virtio_wl".to_string())
            .spawn(move || {
                Worker::new(socket, interrupt, MsgSocket::new(ours)).run(kill_evt);
            });

        match worker_result {
            Err(e) => {
                error!("failed to spawn virtio_wl worker: {}", e);
                return;
            }
            Ok(join_handle) => {
                self.worker_thread = Some(join_handle);
            }
        }
    }
}