//! PTY bridge — spawns a shell and bridges I/O to the SSH channel.

use anyhow::{Context, Result};
use portable_pty::{native_pty_system, CommandBuilder, PtySize};
use std::io::{Read, Write};

/// Spawn a PTY with the given command and return the bridge.
pub fn spawn_pty(
    command: &str,
    args: &[String],
    env: Vec<(String, String)>,
    cols: u16,
    rows: u16,
) -> Result<PtyBridge> {
    let pty_system = native_pty_system();

    let pair = pty_system
        .openpty(PtySize {
            rows,
            cols,
            pixel_width: 0,
            pixel_height: 0,
        })
        .context("Failed to open PTY")?;

    let mut cmd = CommandBuilder::new(command);
    for arg in args {
        cmd.arg(arg);
    }
    for (key, val) in &env {
        cmd.env(key, val);
    }

    let child = pair
        .slave
        .spawn_command(cmd)
        .context("Failed to spawn shell")?;

    let reader = pair
        .master
        .try_clone_reader()
        .context("Failed to clone PTY reader")?;
    let writer = pair
        .master
        .take_writer()
        .context("Failed to take PTY writer")?;

    Ok(PtyBridge {
        master: pair.master,
        child,
        reader: Some(reader),
        writer,
    })
}

/// A running PTY session with I/O handles.
pub struct PtyBridge {
    pub master: Box<dyn portable_pty::MasterPty + Send>,
    pub child: Box<dyn portable_pty::Child + Send + Sync>,
    /// PTY reader — `take()` this to move it into a dedicated read thread.
    pub reader: Option<Box<dyn Read + Send>>,
    pub writer: Box<dyn Write + Send>,
}

impl PtyBridge {
    /// Take the reader out of this bridge for use on a dedicated thread.
    /// Returns None if already taken.
    pub fn take_reader(&mut self) -> Option<Box<dyn Read + Send>> {
        self.reader.take()
    }

    /// Resize the PTY.
    pub fn resize(&self, cols: u16, rows: u16) -> Result<()> {
        self.master
            .resize(PtySize {
                rows,
                cols,
                pixel_width: 0,
                pixel_height: 0,
            })
            .context("Failed to resize PTY")?;
        Ok(())
    }
}