// Copyright 2016 Joe Wilm, The Alacritty Project Contributors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use std::io::{self, Read, Write};
use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::mpsc::TryRecvError;

use mio::{self, Evented, Poll, PollOpt, Ready, Token};
use mio_anonymous_pipes::{EventedAnonRead, EventedAnonWrite};
use mio_named_pipes::NamedPipe;

use log::info;

use crate::config::Config;
use crate::event::OnResize;
use crate::term::SizeInfo;
use crate::tty::windows::child::ChildExitWatcher;
use crate::tty::{ChildEvent, EventedPty, EventedReadWrite};

mod child;
mod conpty;
mod winpty;

static IS_CONPTY: AtomicBool = AtomicBool::new(false);

pub fn is_conpty() -> bool {
    IS_CONPTY.load(Ordering::Relaxed)
}

#[derive(Clone)]
pub enum PtyHandle {
    Winpty(winpty::WinptyHandle),
    Conpty(conpty::ConptyHandle),
}

pub struct Pty {
    // XXX: Handle is required to be the first field, to ensure correct drop order. Dropping
    // `conout` before `handle` will cause a deadlock.
    handle: PtyHandle,
    // TODO: It's on the roadmap for the Conpty API to support Overlapped I/O.
    // See https://github.com/Microsoft/console/issues/262
    // When support for that lands then it should be possible to use
    // NamedPipe for the conout and conin handles
    conout: EventedReadablePipe,
    conin: EventedWritablePipe,
    read_token: mio::Token,
    write_token: mio::Token,
    child_event_token: mio::Token,
    child_watcher: ChildExitWatcher,
}

impl Pty {
    pub fn resize_handle(&self) -> impl OnResize {
        self.handle.clone()
    }
}

pub fn new<C>(config: &Config<C>, size: &SizeInfo, window_id: Option<usize>) -> Pty {
    if let Some(pty) = conpty::new(config, size, window_id) {
        info!("Using Conpty agent");
        IS_CONPTY.store(true, Ordering::Relaxed);
        pty
    } else {
        info!("Using Winpty agent");
        winpty::new(config, size, window_id)
    }
}

// TODO: The ConPTY API currently must use synchronous pipes as the input
// and output handles. This has led to the need to support two different
// types of pipe.
//
// When https://github.com/Microsoft/console/issues/262 lands then the
// Anonymous variant of this enum can be removed from the codebase and
// everything can just use NamedPipe.
pub enum EventedReadablePipe {
    Anonymous(EventedAnonRead),
    Named(NamedPipe),
}

pub enum EventedWritablePipe {
    Anonymous(EventedAnonWrite),
    Named(NamedPipe),
}

impl Evented for EventedReadablePipe {
    fn register(
        &self,
        poll: &Poll,
        token: Token,
        interest: Ready,
        opts: PollOpt,
    ) -> io::Result<()> {
        match self {
            EventedReadablePipe::Anonymous(p) => p.register(poll, token, interest, opts),
            EventedReadablePipe::Named(p) => p.register(poll, token, interest, opts),
        }
    }

    fn reregister(
        &self,
        poll: &Poll,
        token: Token,
        interest: Ready,
        opts: PollOpt,
    ) -> io::Result<()> {
        match self {
            EventedReadablePipe::Anonymous(p) => p.reregister(poll, token, interest, opts),
            EventedReadablePipe::Named(p) => p.reregister(poll, token, interest, opts),
        }
    }

    fn deregister(&self, poll: &Poll) -> io::Result<()> {
        match self {
            EventedReadablePipe::Anonymous(p) => p.deregister(poll),
            EventedReadablePipe::Named(p) => p.deregister(poll),
        }
    }
}

impl Read for EventedReadablePipe {
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        match self {
            EventedReadablePipe::Anonymous(p) => p.read(buf),
            EventedReadablePipe::Named(p) => p.read(buf),
        }
    }
}

impl Evented for EventedWritablePipe {
    fn register(
        &self,
        poll: &Poll,
        token: Token,
        interest: Ready,
        opts: PollOpt,
    ) -> io::Result<()> {
        match self {
            EventedWritablePipe::Anonymous(p) => p.register(poll, token, interest, opts),
            EventedWritablePipe::Named(p) => p.register(poll, token, interest, opts),
        }
    }

    fn reregister(
        &self,
        poll: &Poll,
        token: Token,
        interest: Ready,
        opts: PollOpt,
    ) -> io::Result<()> {
        match self {
            EventedWritablePipe::Anonymous(p) => p.reregister(poll, token, interest, opts),
            EventedWritablePipe::Named(p) => p.reregister(poll, token, interest, opts),
        }
    }

    fn deregister(&self, poll: &Poll) -> io::Result<()> {
        match self {
            EventedWritablePipe::Anonymous(p) => p.deregister(poll),
            EventedWritablePipe::Named(p) => p.deregister(poll),
        }
    }
}

impl Write for EventedWritablePipe {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        match self {
            EventedWritablePipe::Anonymous(p) => p.write(buf),
            EventedWritablePipe::Named(p) => p.write(buf),
        }
    }

    fn flush(&mut self) -> io::Result<()> {
        match self {
            EventedWritablePipe::Anonymous(p) => p.flush(),
            EventedWritablePipe::Named(p) => p.flush(),
        }
    }
}

impl OnResize for PtyHandle {
    fn on_resize(&mut self, sizeinfo: &SizeInfo) {
        match self {
            PtyHandle::Winpty(w) => w.resize(sizeinfo),
            PtyHandle::Conpty(c) => {
                let mut handle = c.clone();
                handle.on_resize(sizeinfo)
            },
        }
    }
}

impl EventedReadWrite for Pty {
    type Reader = EventedReadablePipe;
    type Writer = EventedWritablePipe;

    #[inline]
    fn register(
        &mut self,
        poll: &mio::Poll,
        token: &mut dyn Iterator<Item = mio::Token>,
        interest: mio::Ready,
        poll_opts: mio::PollOpt,
    ) -> io::Result<()> {
        self.read_token = token.next().unwrap();
        self.write_token = token.next().unwrap();

        if interest.is_readable() {
            poll.register(&self.conout, self.read_token, mio::Ready::readable(), poll_opts)?
        } else {
            poll.register(&self.conout, self.read_token, mio::Ready::empty(), poll_opts)?
        }
        if interest.is_writable() {
            poll.register(&self.conin, self.write_token, mio::Ready::writable(), poll_opts)?
        } else {
            poll.register(&self.conin, self.write_token, mio::Ready::empty(), poll_opts)?
        }

        self.child_event_token = token.next().unwrap();
        poll.register(
            self.child_watcher.event_rx(),
            self.child_event_token,
            mio::Ready::readable(),
            poll_opts,
        )?;

        Ok(())
    }

    #[inline]
    fn reregister(
        &mut self,
        poll: &mio::Poll,
        interest: mio::Ready,
        poll_opts: mio::PollOpt,
    ) -> io::Result<()> {
        if interest.is_readable() {
            poll.reregister(&self.conout, self.read_token, mio::Ready::readable(), poll_opts)?;
        } else {
            poll.reregister(&self.conout, self.read_token, mio::Ready::empty(), poll_opts)?;
        }
        if interest.is_writable() {
            poll.reregister(&self.conin, self.write_token, mio::Ready::writable(), poll_opts)?;
        } else {
            poll.reregister(&self.conin, self.write_token, mio::Ready::empty(), poll_opts)?;
        }

        poll.reregister(
            self.child_watcher.event_rx(),
            self.child_event_token,
            mio::Ready::readable(),
            poll_opts,
        )?;

        Ok(())
    }

    #[inline]
    fn deregister(&mut self, poll: &mio::Poll) -> io::Result<()> {
        poll.deregister(&self.conout)?;
        poll.deregister(&self.conin)?;
        poll.deregister(self.child_watcher.event_rx())?;
        Ok(())
    }

    #[inline]
    fn reader(&mut self) -> &mut Self::Reader {
        &mut self.conout
    }

    #[inline]
    fn read_token(&self) -> mio::Token {
        self.read_token
    }

    #[inline]
    fn writer(&mut self) -> &mut Self::Writer {
        &mut self.conin
    }

    #[inline]
    fn write_token(&self) -> mio::Token {
        self.write_token
    }
}

impl EventedPty for Pty {
    fn child_event_token(&self) -> mio::Token {
        self.child_event_token
    }

    fn next_child_event(&mut self) -> Option<ChildEvent> {
        match self.child_watcher.event_rx().try_recv() {
            Ok(ev) => Some(ev),
            Err(TryRecvError::Empty) => None,
            Err(TryRecvError::Disconnected) => Some(ChildEvent::Exited),
        }
    }
}