/*
Start official upstream Jupyter(Lab) server if necessary, then send a message
to the hub with the port the server is serving on.

This is used by the proxy server to route a certain URL to jupyter(lab).

- socket -- TCP connection between project and hub
- mesg -- the message from the hub requesting the jupyter port.
*/

import { promisify } from "util";
import { exec as fs_exec } from "child_process";
import { getLogger } from "@cocalc/project/logger";

const exec = promisify(fs_exec);
const winston = getLogger("upstream-jupyter");

export default async function getPort(lab: boolean = false): Promise<number> {
  let s: { port?: number; status?: string } = await status(lab);
  winston.debug(`jupyter_port, lab=${lab}, status = ${JSON.stringify(s)}`);
  if (!s.port || s.status != "running") {
    winston.debug("getPort: not running so start");
    s = await start(lab);
  }
  if (!s.port || s.status != "running") {
    throw Error(`unable to start jupyter ${lab ? "lab" : "classic"}`);
  }

  winston.debug(
    `getPort: started jupyter ${lab ? "lab" : "classic"} at port ${s.port}`
  );
  return s.port;
}

async function cmd(arg: string, lab: boolean) {
  const command = `cc-jupyter${lab ? "lab" : ""} ${arg}`;
  winston.debug(command);
  return await exec(command);
}

async function start(
  lab: boolean
): Promise<{ base: string; pid: number; port: number }> {
  const { stdout } = await cmd("start", lab);
  return JSON.parse(stdout);
}

async function status(
  lab: boolean
): Promise<{ status: "stopped" | "running"; port?: number }> {
  try {
    const { stdout } = await cmd("status", lab);
    return JSON.parse(stdout);
  } catch (err) {
    return { status: "stopped" };
  }
}