// 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.

use async_trait::async_trait;

use std::io;

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

use std::os::unix::process::ExitStatusExt;

use std::process::Stdio;

use tokio;

use tokio::process::{Child, ChildStdin, Command};

use crate::message::CommandSpec;

use crate::procutil;

/// Callback to process shell command requests received from server.

#[async_trait]

pub trait SystemHandler {

    type PagerStdin: AsRawFd;

    /// Handles pager command request.

    ///

    /// Returns the pipe to be attached to the server if the pager is spawned.

    async fn spawn_pager(&mut self, spec: &CommandSpec) -> io::Result<Self::PagerStdin>;

    /// Handles system command request.

    ///

    /// Returns command exit code (positive) or signal number (negative).

    async fn run_system(&mut self, spec: &CommandSpec) -> io::Result<i32>;

}

/// Default cHg implementation to process requests received from server.

pub struct ChgUiHandler {

    pager: Option<Child>,

}

impl ChgUiHandler {

    pub fn new() -> ChgUiHandler {

        ChgUiHandler { pager: None }

    }

    /// Waits until the pager process exits.

    pub async fn wait_pager(&mut self) -> io::Result<()> {

        if let Some(p) = self.pager.take() {

            p.await?;

        }

        Ok(())

    }

}

#[async_trait]

impl SystemHandler for ChgUiHandler {

    type PagerStdin = ChildStdin;

    async fn spawn_pager(&mut self, spec: &CommandSpec) -> io::Result<Self::PagerStdin> {

        let mut pager = new_shell_command(&spec).stdin(Stdio::piped()).spawn()?;

        let pin = pager.stdin.take().unwrap();

        procutil::set_blocking_fd(pin.as_raw_fd())?;

        // TODO: if pager exits, notify the server with SIGPIPE immediately.

        // otherwise the server won't get SIGPIPE if it does not write

        // anything. (issue5278)

        // kill(peerpid, SIGPIPE);

        self.pager = Some(pager);

        Ok(pin)

    }

    async fn run_system(&mut self, spec: &CommandSpec) -> io::Result<i32> {

        let status = new_shell_command(&spec).spawn()?.await?;

    }

}

fn new_shell_command(spec: &CommandSpec) -> Command {

    let mut builder = Command::new("/bin/sh");

    builder

        .arg("-c")

        .arg(&spec.command)

        .current_dir(&spec.current_dir)

        .env_clear()

        .envs(spec.envs.iter().cloned());

    builder

}