/**
 * @file linux-accounts.js
 * @description Server mode, one Linux user per account (S3 plan, P2). Each
 * AgentHub user `alice` maps to the Linux user `ah-alice`, whose home is
 * `<USERS_ROOT>/alice` — the same folder `scope.folderAllowed` keeps her
 * workspaces in.
 *
 * S3 is ON when server mode is on AND `/etc/agenthub/server.conf` exists
 * (written by `sudo agenthub server install-system`, root-owned). Without it
 * everything here is a no-op and server mode behaves as in S2.
 *
 * `provision` is the dashboard's only way to create, disable or enable a Linux
 * account: `sudo -n /opt/agenthub/sbin/agenthub-provision <action> <name>`,
 * the one root command sudoers lets the host run. Only an action from a fixed
 * set and a name that passed `LINUX_NAME_RE` ever reach its argv.
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

const fs = require("node:fs");
const path = require("node:path");
const { execFileSync } = require("node:child_process");

/** Lower case, a letter first, ≤ 29 so `ah-<name>` fits Linux's 32. */
const LINUX_NAME_RE = /^[a-z][a-z0-9_-]{0,28}$/;
const PROVISION = "/opt/agenthub/sbin/agenthub-provision";
const ACTIONS = new Set(["create", "disable", "enable", "delete"]);

const confPath = () => process.env.AGENTHUB_SERVER_CONF || "/etc/agenthub/server.conf";

// server.conf is read on every tmux call's account lookup — keep it 5 s.
let confCache = { at: 0, path: null, value: null };
// The last server.conf that read well, per path. A server that started with
// S3 keeps it if the file later fails to read (a transient error, an edit in
// progress): falling back to "no S3" would run a member's pane as the HOST
// account in their folder. Removing S3 for good is followed by a restart.
let lastGood = { path: null, value: null };

/** `{hostUser, hostUid, usersRoot, port, bins}` from server.conf, or null. */
function serverConf() {
  const file = confPath();
  if (confCache.path === file && Date.now() - confCache.at < 5000) return confCache.value;
  let value = readConf(file);
  if (value) lastGood = { path: file, value };
  else if (lastGood.path === file && require("./auth").isServerMode()) value = lastGood.value;
  confCache = { at: Date.now(), path: file, value };
  return confCache.value;
}

let TMUX_MEMBER = "/opt/agenthub/libexec/tmux-member";
/** Test seam: where tmux-member is looked for. */
function __setTmuxMember(p) {
  TMUX_MEMBER = p;
  confCache = { at: 0, path: null, value: null };
}

function readConf(file) {
  let text;
  try {
    text = fs.readFileSync(file, "utf8");
  } catch {
    return null;
  }
  const get = (k) => new RegExp(`^${k}=(.*)$`, "m").exec(text)?.[1]?.trim() || "";
  const usersRoot = get("USERS_ROOT");
  if (!path.isAbsolute(usersRoot)) return null;
  // A member's tmux runs through tmux-member once install-system put it there
  // (and in sudoers): it picks their RUNNING server's own binary, so a tmux
  // upgrade never mixes a new client with an old server. Before that, TMUX_BIN.
  let tmuxBin = get("TMUX_BIN");
  try {
    fs.accessSync(TMUX_MEMBER, fs.constants.X_OK);
    if (path.isAbsolute(tmuxBin)) tmuxBin = TMUX_MEMBER;
  } catch {
    /* not installed yet */
  }
  return {
    hostUser: get("HOST_USER"),
    hostUid: Number(get("HOST_UID")),
    usersRoot,
    port: Number(get("PORT")) || null,
    // The installed tmux (a new member server starts on it).
    tmuxInstalled: path.isAbsolute(get("TMUX_BIN")) ? get("TMUX_BIN") : null,
    // The absolute paths sudoers lists (sudo would resolve a bare name on its
    // own secure_path, which may not be them).
    bins: Object.fromEntries(
      [
        ["tmux", tmuxBin],
        ["git", get("GIT_BIN")],
        ["gh", get("GH_BIN")],
      ].filter(([, v]) => path.isAbsolute(v))
    ),
  };
}

/** Is S3 on: server mode plus an installed system layout. */
function s3Enabled() {
  return require("./auth").isServerMode() && serverConf() !== null;
}

/**
 * A member's folder (under this machine's S3 users root) while THIS server
 * runs without S3 — a local-mode or dev dashboard on the same database. Its
 * panes live on the member's own tmux server, which such a server cannot
 * ask, so it must never judge them dead.
 */
function unseenMemberFolder(cwd) {
  if (typeof cwd !== "string" || !cwd || s3Enabled()) return false;
  const conf = serverConf();
  if (!conf) return false;
  const rel = path.relative(conf.usersRoot, path.resolve(cwd));
  return !!rel && !rel.startsWith("..") && !path.isAbsolute(rel);
}

const loginFor = (username) => `ah-${username}`;

/** The Linux side of an AgentHub user, or null outside S3. */
function accountFor(username) {
  const conf = s3Enabled() ? serverConf() : null;
  if (!conf || !LINUX_NAME_RE.test(String(username || ""))) return null;
  return { login: loginFor(username), home: path.join(conf.usersRoot, username) };
}

/** Throws EBADUSER unless `username` can be a Linux account (S3 only). */
function assertLinuxName(username) {
  if (s3Enabled() && !LINUX_NAME_RE.test(String(username || ""))) {
    throw Object.assign(
      new Error(
        "username: with one Linux user per account it must be lower case — a letter, then up to 28 letters, digits, '_' or '-'"
      ),
      { code: "EBADUSER" }
    );
  }
}

// Test seam: the sudo call itself.
let runImpl = (argv) =>
  execFileSync("sudo", ["-n", ...argv], { encoding: "utf8", stdio: ["ignore", "pipe", "pipe"] });
function __setRunImpl(fn) {
  runImpl = fn;
}

/**
 * Create / disable / enable / delete (account AND home) the Linux account of
 * `username`. A no-op outside
 * S3 (returns null). Throws EPROVISION with the helper's own words on failure.
 */
function provision(action, username) {
  if (!s3Enabled()) return null;
  if (!ACTIONS.has(action)) throw new Error(`unknown provision action: ${action}`);
  assertLinuxName(username);
  try {
    return String(runImpl([PROVISION, action, username]) || "").trim();
  } catch (e) {
    const why = String(e.stderr || e.message || "")
      .trim()
      .split("\n")
      .pop();
    // An installed helper older than this build (root's copy is refreshed
    // only by install-system) does not know the action yet.
    const hint = /unknown action/.test(why)
      ? " — the server helper is older than this AgentHub: run `sudo agenthub server install-system` once"
      : "";
    throw Object.assign(new Error(`could not ${action} the Linux account: ${why}${hint}`), {
      code: "EPROVISION",
    });
  }
}

function __resetConfCache() {
  confCache = { at: 0, path: null, value: null };
  lastGood = { path: null, value: null };
}

module.exports = {
  __resetConfCache,
  __setTmuxMember,
  confPath,
  LINUX_NAME_RE,
  serverConf,
  s3Enabled,
  unseenMemberFolder,
  accountFor,
  assertLinuxName,
  provision,
  loginFor,
  __setRunImpl,
};