#!/usr/bin/env node
/**
 * @file systemd-system-service.js
 * @description Server mode with one Linux user per account (S3): the dashboard
 * runs as a SYSTEM unit, `/etc/systemd/system/agenthub.service`, written once
 * by `agenthub server install-system` (scripts/server/install-system.sh).
 * The unit runs as the host account with group `agenthub` and
 * CAP_DAC_READ_SEARCH — the two things a `systemd --user` unit cannot give.
 *
 * Same API as `systemd-service.js`, so the bootstrap, Quit, the autostart
 * switch and the doctor keep their rules unchanged (`service-manager.js`
 * picks this module while that unit exists and is ours). The difference is who
 * may write what:
 *  - the unit file is root's and never rewritten here. It reads the plugin
 *    root, node and env from `<runtime dir>/agenthub.system.env`, a file the
 *    HOST owns — so `writeUserService` (the bootstrap's repoint after a plugin
 *    update) is a plain file write, no root;
 *  - start, stop, restart, enable and disable go through
 *    `sudo -n systemctl …`, allowed for exactly those commands by the
 *    sudoers file the installer wrote. `--no-block` everywhere it matters,
 *    for the same cgroup reason as the user unit (CLAUDE.md).
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

const fs = require("fs");
const path = require("path");
const { spawnSync } = require("child_process");

const MARKER = "# agenthub-managed-system-unit";
const UNIT_DIR = "/etc/systemd/system";

function unitPath(name) {
  return path.join(process.env.AGENTHUB_SYSTEM_UNIT_DIR || UNIT_DIR, `${name}.service`);
}

/** The host-owned env file the unit's `EnvironmentFile=` names. */
function envPath() {
  const { getDataDir } = require("../server/lib/claude-home");
  return path.join(getDataDir(), "runtime", "agenthub.system.env");
}

// Test seams: `systemctl` itself (reads) and `sudo -n systemctl` (writes).
const defaultExec = (args, opts) => spawnSync("systemctl", args, opts);
const defaultSudo = (args, opts) => spawnSync("sudo", ["-n", "systemctl", ...args], opts);
let execImpl = defaultExec;
let sudoImpl = defaultSudo;
function __setExecImpl(fn, sudoFn) {
  execImpl = fn;
  sudoImpl = sudoFn || fn;
}
function __reset() {
  execImpl = defaultExec;
  sudoImpl = defaultSudo;
}

/** Is there a system unit by this name, written by the installer? Pure fs. */
function unitIsOurs(name) {
  try {
    return fs.readFileSync(unitPath(name), "utf8").includes(MARKER);
  } catch {
    return false;
  }
}

function systemctlAvailable() {
  if (process.platform !== "linux" || !unitIsOurs("agenthub")) return false;
  return execImpl(["--version"], { stdio: "ignore" }).status === 0;
}

function readEnv() {
  try {
    return Object.fromEntries(
      fs
        .readFileSync(envPath(), "utf8")
        .split("\n")
        .map((l) => /^([A-Z_][A-Z0-9_]*)=(.*)$/.exec(l))
        .filter(Boolean)
        .map((m) => [m[1], m[2]])
    );
  } catch {
    return null;
  }
}

/** The plugin root the unit runs from (env file), or null. Pure fs. */
function unitRoot(name) {
  if (!fs.existsSync(unitPath(name))) return null;
  return readEnv()?.AGENTHUB_ROOT || null;
}

/** Does the env file still name `root`? Pure fs, like the user unit's. */
function unitIsStale(name, root) {
  if (!unitIsOurs(name)) return false;
  return unitRoot(name) !== root;
}

function unitIsEnabled(name) {
  if (!systemctlAvailable()) return false;
  const res = execImpl(["is-enabled", `${name}.service`], { encoding: "utf8", stdio: "pipe" });
  return String(res.stdout || "").trim() === "enabled";
}

function unitIsActive(name) {
  if (!systemctlAvailable()) return false;
  const res = execImpl(["is-active", `${name}.service`], { encoding: "utf8", stdio: "pipe" });
  return String(res.stdout || "").trim() === "active";
}

function setUnitEnabled(name, on) {
  if (!systemctlAvailable()) return "unavailable";
  const res = sudoImpl([on ? "enable" : "disable", `${name}.service`], { stdio: "ignore" });
  return res.status === 0 ? "ok" : "failed";
}

/**
 * Point the unit at this plugin version: rewrite the host-owned env file the
 * unit reads. Starts nothing, enables nothing (the unit file is root's).
 * @returns {"written"|"unchanged"|"unavailable"|"failed"}
 */
function writeUserService({ argv, env = {} }) {
  if (!systemctlAvailable()) return "unavailable";
  const root = path.dirname(path.dirname(argv[1])); // <root>/server/index.js
  // The port install-system chose outlives a bootstrap that does not pass one
  // (server.conf and the member hook still name it).
  // ponytail: only DASHBOARD_PORT is carried over; others if they ever matter.
  let kept = {};
  try {
    const m = /^DASHBOARD_PORT=(\d+)$/m.exec(fs.readFileSync(envPath(), "utf8"));
    if (m) kept = { DASHBOARD_PORT: m[1] };
  } catch {
    /* no file yet */
  }
  const body =
    Object.entries({ AGENTHUB_NODE: argv[0], AGENTHUB_ROOT: root, ...kept, ...env })
      .map(([k, v]) => `${k}=${String(v).replace(/\n/g, "")}`)
      .join("\n") + "\n";
  try {
    const file = envPath();
    if (fs.existsSync(file) && fs.readFileSync(file, "utf8") === body) return "unchanged";
    fs.mkdirSync(path.dirname(file), { recursive: true });
    fs.writeFileSync(`${file}.tmp`, body, { mode: 0o600 });
    fs.renameSync(`${file}.tmp`, file);
    return "written";
  } catch {
    return "failed";
  }
}

/** `--no-block`: the caller may sit in this unit's cgroup (CLAUDE.md). */
function restartUserService(name) {
  if (!systemctlAvailable()) return "unavailable";
  const res = sudoImpl(["restart", "--no-block", `${name}.service`], { stdio: "ignore" });
  return res.status === 0 ? "restarted" : "failed";
}

/** Point the unit here, then start it (without blocking). */
function installUserService(opts) {
  const result = writeUserService(opts);
  if (result === "written" || result === "unchanged") {
    sudoImpl(["start", "--no-block", `${opts.name}.service`], { stdio: "ignore" });
  }
  return result;
}

/** Removing the system unit is root's: `agenthub server install-system --uninstall`. */
function uninstallUserService() {
  return "foreign";
}

/** A system unit starts at boot; there is no linger to enable. */
function enableLinger() {
  return true;
}

/** The argv that stops the unit without waiting (Quit, server/lib/quit.js). */
function stopArgv(name) {
  return ["sudo", ["-n", "systemctl", "stop", "--no-block", `${name}.service`]];
}

module.exports = {
  kind: "systemd-system",
  label: "systemd system service",
  MARKER,
  systemctlAvailable,
  unitIsOurs,
  unitIsStale,
  unitRoot,
  unitIsActive,
  unitIsEnabled,
  setUnitEnabled,
  writeUserService,
  restartUserService,
  installUserService,
  uninstallUserService,
  enableLinger,
  stopArgv,
  unitPath,
  envPath,
  __setExecImpl,
  __reset,
};