/**
 * @file nine-router-update.js
 * @description The **Update 9router** button of Settings → AI Proxy: one
 * in-memory job that shuts the host's 9router down, updates its npm package and
 * starts it again hidden — in that order, because 9router's own updater relaunches
 * through `npx` and kills by `ps aux | grep`, which neither respects a
 * `9router.service` user unit (`Restart=always` would fight it) nor leaves a
 * pane alone.
 *
 * Steps:
 *   1. **shutdown** — disconnect every client by stopping 9router: a running
 *      `9router.service` user unit is `systemctl --user stop`ped; otherwise the
 *      9router processes of THIS account (matched by the install's own path in
 *      their argv, never by name) get SIGTERM — its CLI kills its server and tray
 *      icon on that — then SIGKILL after a grace period, until the port is free.
 *   2. **update** — `npm install -g --prefix <its own prefix> 9router@latest`, so
 *      the copy that is updated is the one that runs. A prefix this account
 *      cannot write runs the same argv under `sudo -n`, and only when sudoers
 *      already allows that npm without a password (probed BEFORE step 1 with
 *      `sudo -n <npm> --version`, so a refused update never leaves 9router
 *      down); otherwise
 *      the start is refused with the command to run by hand.
 *   3. **relaunch** — only when 9router was running before step 1: the unit is
 *      started again, or `cli.js --tray --no-browser --skip-update -p <port>` is
 *      spawned detached (inside its own `systemd-run --user --scope` on Linux, so
 *      a dashboard restart never takes it along). A failed update still
 *      relaunches — the old version is better than none.
 *
 * Nothing here takes a command, path or package name from a request: the
 * package is always `9router`, its location comes from PATH.
 *
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

const fs = require("node:fs");
const net = require("node:net");
const path = require("node:path");
const { execFile, spawn } = require("node:child_process");

const aiTools = require("./ai-tools");
const versions = require("./ai-tool-versions");
const { compareVersions } = require("./update-check");
const { desktopEnv } = require("./desktop-env");

const PKG = "9router";
const UNIT = "9router.service";
const DEFAULT_PORT = 20128;
const LATEST_CACHE_MS = 10 * 60 * 1000;
const LOG_CAP = 128 * 1024;
const STEPS = ["shutdown", "update", "relaunch"];

const timing = {
  installTimeoutMs: 10 * 60 * 1000,
  termGraceMs: 5000,
  portFreeMs: 15000,
  portUpMs: 45000,
};

const makeErr = (code, message, extra = {}) => Object.assign(new Error(message), { code }, extra);

/** execFile as a promise that never rejects: `{code, stdout, stderr}`. */
const realExec = (file, args, opts = {}) =>
  new Promise((resolve) => {
    execFile(file, args, { encoding: "utf8", timeout: 10000, ...opts }, (err, stdout, stderr) =>
      resolve({
        code: err ? (typeof err.code === "number" ? err.code : 1) : 0,
        stdout: String(stdout || ""),
        stderr: String(stderr || err?.message || ""),
      })
    );
  });

// Seams (tests): command runner, the systemd user manager, the latest-version
// lookup, and whether a relaunch may use systemd-run.
let exec = realExec;
let useSystemd = process.platform === "linux";
let fetchLatestImpl = async () => {
  const r = await fetch(`https://registry.npmjs.org/${PKG}/latest`, {
    signal: AbortSignal.timeout(5000),
  });
  if (!r.ok) return null;
  const v = (await r.json())?.version;
  return typeof v === "string" ? v : null;
};

let job = null;
let latestCache = null; // { at, version }

/** The env a `systemctl --user` needs; a server started outside a login lacks XDG_RUNTIME_DIR. */
function userEnv() {
  const env = { ...process.env, PATH: versions.jobPath() };
  if (!env.XDG_RUNTIME_DIR && typeof process.getuid === "function") {
    const dir = `/run/user/${process.getuid()}`;
    if (fs.existsSync(dir)) env.XDG_RUNTIME_DIR = dir;
  }
  return env;
}

/**
 * Where 9router is installed: `{bin, cli, pkgDir, prefix, version}`, or null.
 * `prefix` is null for a layout that is not an npm global install
 * (`<prefix>/lib/node_modules/9router`), which this updater does not touch.
 */
function locate() {
  const bin = aiTools.which(PKG, versions.jobPath());
  if (!bin) return null;
  let cli;
  try {
    cli = fs.realpathSync(bin);
  } catch {
    return null;
  }
  const pkgDir = path.dirname(cli);
  let version = null;
  try {
    const pkg = JSON.parse(fs.readFileSync(path.join(pkgDir, "package.json"), "utf8"));
    if (pkg.name !== PKG) return null;
    version = typeof pkg.version === "string" ? pkg.version : null;
  } catch {
    return null;
  }
  const nm = path.dirname(pkgDir);
  const lib = path.dirname(nm);
  const prefix =
    path.basename(nm) === "node_modules" && path.basename(lib) === "lib" ? path.dirname(lib) : null;
  return { bin, cli, pkgDir, prefix, version };
}

/** Whether this account can write `dir`. */
function canWrite(dir) {
  try {
    fs.accessSync(dir, fs.constants.W_OK);
    return true;
  } catch {
    return false;
  }
}

// Root's npm cache for a sudo run. Never root's HOME: the AgentHub unit makes
// `/root` inaccessible (`InaccessiblePaths=`), so `mkdir /root/.npm` fails with
// ENOENT (npm exit 254). A root-owned path, never one in /tmp a user could plant.
const SUDO_NPM_CACHE = "/var/cache/agenthub-9router-npm";

const npmArgs = (prefix, sudo = false) => [
  "install",
  "-g",
  "--prefix",
  prefix,
  "--prefer-online",
  ...(sudo ? ["--cache", SUDO_NPM_CACHE] : []),
  `${PKG}@latest`,
];

/** `direct` (we can write the prefix), `sudo` (passwordless sudo allows it), or null. */
async function installMode(loc, npm) {
  if (
    canWrite(path.join(loc.prefix, "lib", "node_modules")) &&
    canWrite(path.join(loc.prefix, "bin"))
  )
    return "direct";
  // `sudo -l` would answer yes for a rule that still asks for a password, so
  // the probe is a harmless real run of the same npm.
  const r = await exec("sudo", ["-n", "--", npm, "--version"], { timeout: 10000 });
  return r.code === 0 ? "sudo" : null;
}

/** Whether the `9router.service` user unit is running. */
async function unitActive() {
  if (!useSystemd) return false;
  const r = await exec("systemctl", ["--user", "is-active", "--quiet", UNIT], {
    env: userEnv(),
    timeout: 5000,
  });
  return r.code === 0;
}

/**
 * This account's 9router processes — those whose argv names the install itself.
 * `roots` are its CLI (argv carries cli.js or the bin link): SIGTERM lets each
 * stop its own server and tray; `all` adds their descendants, for the SIGKILL.
 */
async function findProcesses(loc) {
  const uid = typeof process.getuid === "function" ? String(process.getuid()) : null;
  const r = await exec("ps", ["-ww", ...(uid ? ["-U", uid] : ["-e"]), "-o", "pid=,ppid=,args="], {
    timeout: 5000,
  });
  const rows = [];
  for (const line of r.stdout.split("\n")) {
    const m = line.trim().match(/^(\d+)\s+(\d+)\s+(.*)$/);
    if (m && Number(m[1]) !== process.pid)
      rows.push({ pid: Number(m[1]), ppid: Number(m[2]), argv: m[3].split(/\s+/) });
  }
  const roots = [];
  let port = null;
  let host = null;
  for (const { pid, argv } of rows) {
    if (!argv.some((a) => a === loc.cli || a === loc.bin)) continue;
    roots.push(pid);
    const pi = argv.findIndex((a) => a === "-p" || a === "--port");
    if (pi >= 0 && /^\d{2,5}$/.test(argv[pi + 1] || "")) port = Number(argv[pi + 1]);
    const hi = argv.findIndex((a) => a === "-H" || a === "--host");
    if (hi >= 0 && /^[\w.:-]+$/.test(argv[hi + 1] || "")) host = argv[hi + 1];
  }
  // Its server renames itself (`next-server`), so children are found by parent,
  // plus anything still running from inside the install.
  const all = new Set(roots);
  for (const { pid, argv } of rows)
    if (argv.some((a) => a.startsWith(loc.pkgDir + path.sep))) all.add(pid);
  for (let grew = true; grew;) {
    grew = false;
    for (const { pid, ppid } of rows)
      if (all.has(ppid) && !all.has(pid)) {
        all.add(pid);
        grew = true;
      }
  }
  return { roots, all: [...all], port, host };
}

/** Whether something answers on 127.0.0.1:`port`. */
const portOpen = (port) =>
  new Promise((resolve) => {
    const s = net.connect({ host: "127.0.0.1", port });
    const done = (v) => {
      s.destroy();
      resolve(v);
    };
    s.setTimeout(1000, () => done(false));
    s.once("connect", () => done(true));
    s.once("error", () => done(false));
  });

async function waitFor(check, ms) {
  const until = Date.now() + ms;
  for (;;) {
    if (await check()) return true;
    if (Date.now() >= until) return false;
    await new Promise((r) => setTimeout(r, 300));
  }
}

const alive = (pid) => {
  try {
    process.kill(pid, 0);
    return true;
  } catch {
    return false;
  }
};

const signal = (pids, sig) => {
  for (const pid of pids) {
    try {
      process.kill(pid, sig);
    } catch {
      /* gone already */
    }
  }
};

async function latestVersion({ fresh = false } = {}) {
  if (!fresh && latestCache && Date.now() - latestCache.at < LATEST_CACHE_MS)
    return latestCache.version;
  let version = null;
  try {
    version = await fetchLatestImpl();
  } catch {
    version = null;
  }
  latestCache = { at: Date.now(), version };
  return version;
}

/** The public view of the job (a copy). */
const view = (j) => (j ? JSON.parse(JSON.stringify(j)) : null);

/**
 * What the page shows: `{installed, version, latest, updateAvailable, running,
 * managedBy, blocker, job}`. `blocker` (`{code, message, command?}`) is why a
 * start would be refused right now; `command` is the one to run by hand.
 */
async function status({ fresh = false } = {}) {
  const loc = locate();
  if (!loc) {
    return {
      installed: false,
      version: null,
      latest: null,
      updateAvailable: false,
      running: false,
      managedBy: null,
      blocker: { code: "ENOTINSTALLED", message: "9router is not installed on this machine" },
      job: view(job),
    };
  }
  const [latest, unit, procs] = await Promise.all([
    latestVersion({ fresh }),
    unitActive(),
    findProcesses(loc),
  ]);
  const updateAvailable = Boolean(
    latest && loc.version && compareVersions(latest, loc.version) > 0
  );
  const manual = `sudo npm install -g ${PKG}@latest`;
  let blocker = null;
  if (process.platform === "win32") {
    blocker = {
      code: "EUNSUPPORTED",
      message: "updating 9router from AgentHub is not supported on Windows",
    };
  } else if (!loc.prefix) {
    blocker = {
      code: "EUNSUPPORTED",
      message: `9router at ${loc.pkgDir} is not an npm global install`,
    };
  } else if (!updateAvailable) {
    blocker = latest
      ? { code: "EUPTODATE", message: `9router ${loc.version} is the latest version` }
      : { code: "ENOLATEST", message: "the npm registry could not be reached" };
  } else {
    const npm = versions.npmBin();
    if (!npm) blocker = { code: "ENONPM", message: "npm was not found on the login shell's PATH" };
    else if (!(await installMode(loc, npm)))
      blocker = {
        code: "ENOPERM",
        message: `${loc.prefix} is not writable by this account and sudo needs a password`,
        command: manual,
      };
  }
  return {
    installed: true,
    version: loc.version,
    latest,
    updateAvailable,
    running: unit || procs.roots.length > 0,
    managedBy: unit ? "systemd" : procs.roots.length ? "process" : null,
    blocker,
    job: view(job),
  };
}

function step(id) {
  return job.steps.find((s) => s.id === id);
}

function log(text) {
  job.log = (job.log + text).slice(-LOG_CAP);
}

function setStep(id, state, message) {
  const s = step(id);
  s.status = state;
  if (message !== undefined) s.message = message;
}

async function doShutdown(loc, unit, procs) {
  if (unit) {
    const r = await exec("systemctl", ["--user", "stop", UNIT], { env: userEnv(), timeout: 30000 });
    if (r.code !== 0) throw makeErr("ESTOP", `systemctl --user stop ${UNIT}: ${r.stderr.trim()}`);
  } else {
    signal(procs.roots, "SIGTERM");
    await waitFor(async () => !procs.roots.some(alive), timing.termGraceMs);
    // Whatever survived (and any child the CLI did not take down), by force.
    const left = (await findProcesses(loc)).all;
    signal([...new Set([...procs.all, ...left])].filter(alive), "SIGKILL");
  }
  const port = procs.port || DEFAULT_PORT;
  if (!(await waitFor(async () => !(await portOpen(port)), timing.portFreeMs)))
    throw makeErr("EPORTBUSY", `port ${port} is still in use after 9router stopped`);
}

/** Run npm, streaming its output into the job log. Resolves its exit code. */
function runInstall(argv) {
  return new Promise((resolve) => {
    log(`$ ${argv.join(" ")}\n`);
    const child = spawn(argv[0], argv.slice(1), {
      stdio: ["ignore", "pipe", "pipe"],
      env: { ...process.env, PATH: versions.jobPath() },
      detached: true,
    });
    const timer = setTimeout(() => {
      log("\n[agenthub] npm timed out\n");
      try {
        process.kill(-child.pid, "SIGKILL");
      } catch {
        /* gone */
      }
    }, timing.installTimeoutMs);
    child.stdout.on("data", (d) => log(String(d)));
    child.stderr.on("data", (d) => log(String(d)));
    child.on("error", (e) => {
      clearTimeout(timer);
      log(`\n${e.message}\n`);
      resolve(1);
    });
    child.on("close", (code) => {
      clearTimeout(timer);
      resolve(code ?? 1);
    });
  });
}

/** Start 9router hidden, detached from this server. */
async function launchHidden(loc, procs) {
  const node = aiTools.which("node", versions.jobPath()) || process.execPath;
  const port = procs.port || DEFAULT_PORT;
  const args = [
    "--dns-result-order=ipv4first",
    loc.cli,
    "--tray",
    "--no-browser",
    "--skip-update",
    "-p",
    String(port),
  ];
  if (procs.host) args.push("-H", procs.host);
  const env = { ...userEnv(), ...desktopEnv() };
  delete env.TRAY_MODE;
  const spawnDetached = (file, argv) => {
    const child = spawn(file, argv, { detached: true, stdio: "ignore", env, cwd: loc.pkgDir });
    child.unref();
    return child;
  };
  const systemdRun = useSystemd && env.XDG_RUNTIME_DIR && aiTools.which("systemd-run", env.PATH);
  if (systemdRun) {
    const child = spawnDetached(systemdRun, [
      "--user",
      "--scope",
      "--quiet",
      "--collect",
      "--description=9Router",
      "--",
      node,
      ...args,
    ]);
    // A scope that cannot be created exits at once; anything else is 9router running.
    const failed = await new Promise((resolve) => {
      const t = setTimeout(() => resolve(false), 1500);
      child.once("exit", (code) => {
        clearTimeout(t);
        resolve(code !== 0);
      });
      child.once("error", () => {
        clearTimeout(t);
        resolve(true);
      });
    });
    if (!failed) return port;
    log("[agenthub] systemd-run --user --scope failed; starting 9router directly\n");
  }
  spawnDetached(node, args);
  return port;
}

async function doRelaunch(loc, unit, procs) {
  let port = procs.port || DEFAULT_PORT;
  if (unit) {
    const r = await exec("systemctl", ["--user", "start", UNIT], {
      env: userEnv(),
      timeout: 30000,
    });
    if (r.code !== 0) throw makeErr("ESTART", `systemctl --user start ${UNIT}: ${r.stderr.trim()}`);
  } else {
    port = await launchHidden(loc, procs);
  }
  if (!(await waitFor(() => portOpen(port), timing.portUpMs)))
    throw makeErr("ENOTUP", `9router did not answer on port ${port}`);
}

async function runJob(loc, npm, mode, unit, procs) {
  const wasRunning = unit || procs.roots.length > 0;
  let failed = false;
  if (!wasRunning) setStep("shutdown", "skipped", "9router was not running");
  else {
    setStep("shutdown", "running");
    try {
      await doShutdown(loc, unit, procs);
      setStep("shutdown", "done");
    } catch (e) {
      // Still running (or unknown): updating underneath it is not safe.
      setStep("shutdown", "failed", e.message);
      setStep("update", "skipped");
      failed = true;
    }
  }
  if (!failed) {
    setStep("update", "running");
    const argv = [npm, ...npmArgs(loc.prefix, mode === "sudo")];
    const code = await runInstall(mode === "sudo" ? ["sudo", "-n", "--", ...argv] : argv);
    const after = locate();
    job.to = after?.version || null;
    if (code === 0) setStep("update", "done", job.to ? `${job.from} → ${job.to}` : undefined);
    else {
      setStep("update", "failed", `npm exited with code ${code}`);
      failed = true;
    }
  }
  if (!wasRunning) setStep("relaunch", "skipped", "9router was not running before the update");
  else {
    setStep("relaunch", "running");
    try {
      await doRelaunch(locate() || loc, unit, procs);
      setStep("relaunch", "done");
    } catch (e) {
      setStep("relaunch", "failed", e.message);
      failed = true;
    }
  }
  job.status = failed ? "failed" : "done";
  job.finishedAt = new Date().toISOString();
  latestCache = null;
}

/** Start the update; refuses (with the status blocker's code) when it cannot run. */
async function start() {
  if (job?.status === "running") throw makeErr("EBUSY", "a 9router update is already running");
  const s = await status({ fresh: true });
  if (job?.status === "running") throw makeErr("EBUSY", "a 9router update is already running");
  if (s.blocker)
    throw makeErr(
      s.blocker.code,
      s.blocker.message,
      s.blocker.command ? { command: s.blocker.command } : {}
    );
  const loc = locate();
  const npm = versions.npmBin();
  const mode = await installMode(loc, npm);
  if (!mode) throw makeErr("ENOPERM", "the npm prefix is not writable and sudo needs a password");
  const unit = await unitActive();
  const procs = await findProcesses(loc);
  job = {
    status: "running",
    startedAt: new Date().toISOString(),
    finishedAt: null,
    from: loc.version,
    to: null,
    managedBy: unit ? "systemd" : procs.roots.length ? "process" : null,
    install: mode,
    steps: STEPS.map((id) => ({ id, status: "pending", message: null })),
    log: "",
  };
  runJob(loc, npm, mode, unit, procs).catch((e) => {
    job.status = "failed";
    job.finishedAt = new Date().toISOString();
    log(`\n${e.message}\n`);
  });
  return view(job);
}

const current = () => view(job);

function __setSeams({ exec: e, useSystemd: u, fetchLatest, timing: t } = {}) {
  if (e) exec = e;
  if (u !== undefined) useSystemd = u;
  if (fetchLatest) fetchLatestImpl = fetchLatest;
  if (t) Object.assign(timing, t);
  latestCache = null;
}

function __reset() {
  job = null;
  latestCache = null;
  exec = realExec;
}

module.exports = { status, start, current, locate, STEPS, __setSeams, __reset };