import * as pty from 'node-pty';
import type { IPty } from 'node-pty';

export interface AttachPtyOptions {
  sessionName: string;
  windowName: string;
  projectRoot: string;
  cols: number;
  rows: number;
  tmuxConfPath: string;
}

function cleanEnv(): { [key: string]: string } {
  const out: { [key: string]: string } = {};
  for (const [k, v] of Object.entries(process.env)) {
    if (typeof v === 'string') out[k] = v;
  }
  out['TERM'] = 'screen-256color';
  return out;
}

// Spawns a tmux client attached to the given session+window. `-d` detaches any
// other client so a browser refresh takes over the same window without
// duplicate input. tmux server (and the window) persists across PTY exits.
export function attachPty(opts: AttachPtyOptions): IPty {
  return pty.spawn(
    'tmux',
    [
      '-f', opts.tmuxConfPath,
      'attach-session', '-d',
      '-t', `${opts.sessionName}:${opts.windowName}`,
    ],
    {
      name: 'xterm-256color',
      cols: opts.cols,
      rows: opts.rows,
      cwd: opts.projectRoot,
      env: cleanEnv(),
    },
  );
}