#!/usr/bin/env node
/**
 * @file systemd-service.js
 * @description Shared helper for installing/removing a systemd `--user`
 * service that keeps the AgentHub dashboard server running across reboots,
 * without needing Claude Code (or any other tool) to be started first.
 * Used by both `agenthub service install` (checkout installs) and
 * `plugin-bootstrap.js` (plugin installs) so the two paths stay in sync.
 * Linux/systemd only — callers fall back to their existing manual-start
 * path when `systemctlAvailable()` is false.
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

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

const MARKER = "# agenthub-managed-unit — regenerated on install, do not edit by hand";

function unitDir() {
  return path.join(os.homedir(), ".config", "systemd", "user");
}

function unitPath(name) {
  return path.join(unitDir(), `${name}.service`);
}

function systemctlAvailable() {
  if (process.platform !== "linux") return false;
  return spawnSync("systemctl", ["--user", "--version"], { stdio: "ignore" }).status === 0;
}

function unitContent({ description, workingDir, execStart, env }) {
  const envLines = Object.entries(env)
    .map(([k, v]) => `Environment=${k}=${v}`)
    .join("\n");
  return `[Unit]
${MARKER}
Description=${description}
After=network.target

[Service]
Type=simple
WorkingDirectory=${workingDir}
ExecStart=${execStart}
Restart=on-failure
RestartSec=3
${envLines}

[Install]
WantedBy=default.target
`;
}

function systemctl(args) {
  return spawnSync("systemctl", ["--user", ...args], { stdio: "inherit" });
}

/**
 * Writes (or refreshes) the unit file and enables + starts it. Idempotent:
 * an unchanged unit is left running as-is; a changed one (e.g. a plugin
 * cache path after an update) is reloaded and restarted.
 *
 * @returns {"written"|"unchanged"|"foreign"|"unavailable"|"failed"}
 */
function installUserService({ name, description, workingDir, execStart, env = {} }) {
  if (!systemctlAvailable()) return "unavailable";
  const body = unitContent({ description, workingDir, execStart, env });
  const target = unitPath(name);
  try {
    if (fs.existsSync(target)) {
      const current = fs.readFileSync(target, "utf8");
      if (!current.includes(MARKER)) return "foreign";
      if (current === body) {
        systemctl(["enable", "--now", `${name}.service`]);
        return "unchanged";
      }
    }
    fs.mkdirSync(unitDir(), { recursive: true });
    fs.writeFileSync(target, body, "utf8");
    systemctl(["daemon-reload"]);
    systemctl(["enable", "--now", `${name}.service`]);
    systemctl(["restart", `${name}.service`]);
    return "written";
  } catch {
    return "failed";
  }
}

/** @returns {"removed"|"absent"|"foreign"|"unavailable"} */
function uninstallUserService(name) {
  if (!systemctlAvailable()) return "unavailable";
  const target = unitPath(name);
  if (!fs.existsSync(target)) return "absent";
  if (!fs.readFileSync(target, "utf8").includes(MARKER)) return "foreign";
  systemctl(["disable", "--now", `${name}.service`]);
  fs.rmSync(target, { force: true });
  systemctl(["daemon-reload"]);
  return "removed";
}

/** Lets the user service start on cold boot, not just after login. Best
 *  effort — some setups require an admin to grant this, so a failure here
 *  is reported, never thrown. */
function enableLinger() {
  const user = os.userInfo().username;
  return spawnSync("loginctl", ["enable-linger", user], { stdio: "ignore" }).status === 0;
}

module.exports = {
  systemctlAvailable,
  installUserService,
  uninstallUserService,
  enableLinger,
  unitPath,
};