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

export interface AttachPtyOptions {
  sessionName: 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;
}

// v1.10.8c: no `-d` (multi-attach friendly — boolab pattern). With per-pane
// tmux sessions, dropping `-d` means multiple browser tabs viewing the same
// pane share one tmux session as N clients; tmux fans I/O at the session
// layer just like boolab's backend. The earlier `-d` flag detached EVERY
// other client of the session — across windows — which caused the
// "[detached] from session" bug whenever a new pane attached to a chat
// session that already had another pane open.
//
// Tmux server + session persist across PTY exits, so a refresh resumes with
// full scrollback. Explicit destroy happens via the /kill route (called from
// the frontend when the user closes a pane).
export function attachPty(opts: AttachPtyOptions): IPty {
  return pty.spawn(
    'tmux',
    [
      '-f', opts.tmuxConfPath,
      'attach-session',
      '-t', opts.sessionName,
    ],
    {
      name: 'xterm-256color',
      cols: opts.cols,
      rows: opts.rows,
      cwd: opts.projectRoot,
      env: cleanEnv(),
    },
  );
}