// Copyright 2018 Yuya Nishihara <yuya@tcha.org>

//

// This software may be used and distributed according to the terms of the

// GNU General Public License version 2 or any later version.

//! Functions to run Mercurial command in cHg-aware command server.

use bytes::Bytes;

use futures::future::IntoFuture;

use futures::{Async, Future, Poll};

use std::io;

use std::mem;

use std::os::unix::io::AsRawFd;

use tokio_hglib::codec::ChannelMessage;

use tokio_hglib::protocol::MessageLoop;

use super::attachio::AttachIo;

use super::message::{self, CommandType};

use super::uihandler::SystemHandler;

enum AsyncS<R, S> {

    Ready(R),

    NotReady(S),

    PollAgain(S),

}

enum CommandState<C, H>

{

    Running(MessageLoop<C>, H),

    SpawningPager(Client<C>, <H::SpawnPagerResult as IntoFuture>::Future),

    AttachingPager(AttachIo<C, io::Stdin, H::PagerStdin, H::PagerStdin>, H),

    WaitingSystem(Client<C>, <H::RunSystemResult as IntoFuture>::Future),

    Finished,

}

type CommandPoll<C, H> = io::Result<(AsyncS<(Client<C>, H, i32), CommandState<C, H>>)>;

/// Future resolves to `(exit_code, client)`.

#[must_use = "futures do nothing unless polled"]

pub struct ChgRunCommand<C, H>

{

    state: CommandState<C, H>,

}

impl<C, H> ChgRunCommand<C, H>

{

        let msg_loop = MessageLoop::start_with_args(client, b"runcommand", packed_args);

        ChgRunCommand {

            state: CommandState::Running(msg_loop, handler),

        }

    }

}

impl<C, H> Future for ChgRunCommand<C, H>

{

    type Item = (Client<C>, H, i32);

    type Error = io::Error;

    fn poll(&mut self) -> Poll<Self::Item, Self::Error> {

        loop {

            let state = mem::replace(&mut self.state, CommandState::Finished);

            match state.poll()? {

                AsyncS::Ready((client, handler, code)) => {

                    return Ok(Async::Ready((client, handler, code)));

                }

                AsyncS::NotReady(newstate) => {

                    self.state = newstate;

                    return Ok(Async::NotReady);

                }

                AsyncS::PollAgain(newstate) => {

                    self.state = newstate;

                }

            }

        }

    }

}

impl<C, H> CommandState<C, H>

{

    fn poll(self) -> CommandPoll<C, H> {

        match self {

            CommandState::Running(mut msg_loop, handler) => {

                if let Async::Ready((client, msg)) = msg_loop.poll()? {

                    process_message(client, handler, msg)

                } else {

                    Ok(AsyncS::NotReady(CommandState::Running(msg_loop, handler)))

                }

            }

            CommandState::SpawningPager(client, mut fut) => {

                if let Async::Ready((handler, pin)) = fut.poll()? {

                    let fut = AttachIo::with_client(client, io::stdin(), pin, None);

                } else {

                    Ok(AsyncS::NotReady(CommandState::SpawningPager(client, fut)))

                }

            }

            CommandState::AttachingPager(mut fut, handler) => {

                if let Async::Ready(client) = fut.poll()? {

                    Ok(AsyncS::PollAgain(CommandState::Running(msg_loop, handler)))

                } else {

                    Ok(AsyncS::NotReady(CommandState::AttachingPager(fut, handler)))

                }

            }

            CommandState::WaitingSystem(client, mut fut) => {

                if let Async::Ready((handler, code)) = fut.poll()? {

                    let data = message::pack_result_code(code);

                    let msg_loop = MessageLoop::resume_with_data(client, data);

                    Ok(AsyncS::PollAgain(CommandState::Running(msg_loop, handler)))

                } else {

                    Ok(AsyncS::NotReady(CommandState::WaitingSystem(client, fut)))

                }

            }

        }

    }

}

fn process_message<C, H>(client: Client<C>, handler: H, msg: ChannelMessage) -> CommandPoll<C, H>

{

    match msg {

        ChannelMessage::Data(b'r', data) => {

            let code = message::parse_result_code(data)?;

            Ok(AsyncS::Ready((client, handler, code)))

        }

        ChannelMessage::Data(..) => {

            // just ignores data sent to optional channel

            let msg_loop = MessageLoop::resume(client);

            Ok(AsyncS::PollAgain(CommandState::Running(msg_loop, handler)))

        }

        ChannelMessage::SystemRequest(data) => {

            let (cmd_type, cmd_spec) = message::parse_command_spec(data)?;

            match cmd_type {

                CommandType::Pager => {

                    let fut = handler.spawn_pager(cmd_spec).into_future();

                    Ok(AsyncS::PollAgain(CommandState::SpawningPager(client, fut)))

                }

                CommandType::System => {

                    let fut = handler.run_system(cmd_spec).into_future();

                    Ok(AsyncS::PollAgain(CommandState::WaitingSystem(client, fut)))

                }

            }

        }

    }

}