/**
 * @file Which HOME folder a user's File Explorer opens (`/api/homes/*`):
 *  - S3: their own Linux account's home (`/srv/agenthub/users/<name>`);
 *  - server mode without S3: their own folder under AGENTHUB_USERS_ROOT;
 *  - local mode, or an admin with no Linux account of their own: the host
 *    account's home.
 * `me` is always the caller's. An admin may also open another user's home —
 * read-only (the routes refuse every write, `EREADONLY`) and written to the
 * audit log — the "view other users' homes" option. A home is never a
 * workspace (the S3 rule stands); it is browsed with `file-explorer.js`'s
 * `inHome`, which keeps every dot entry at its top out of reach.
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

const fs = require("node:fs");
const os = require("node:os");
const path = require("node:path");

const auth = require("./auth");
const linux = require("./linux-accounts");
const runAs = require("./run-as");
const { ownFolder } = require("./scope");

const isDir = (p) => {
  try {
    return fs.statSync(p).isDirectory();
  } catch {
    return false;
  }
};

/** The home of AgentHub user `user` (a users row or req.user), or null. */
function homeOf(user) {
  if (!auth.isServerMode()) return os.homedir();
  if (!user) return null;
  if (linux.s3Enabled()) {
    let acct = null;
    try {
      acct = runAs.accountForUser(user.username);
    } catch {
      acct = null; // disabled or not provisioned: no home to open
    }
    if (acct) return acct.home;
    return user.role === "admin" ? os.homedir() : null;
  }
  const own = ownFolder({ user });
  if (own) return isDir(own) ? own : null;
  return user.role === "admin" ? os.homedir() : null;
}

/**
 * The homes `req` may open: `{ id: "me" | <username>, label, readOnly }`.
 * Others' only for an admin, and only those that resolve to a folder.
 */
function listHomes(req) {
  const out = [];
  const me = req.user || null;
  if (homeOf(me))
    out.push({ id: "me", label: me?.displayName || me?.username || "", readOnly: false });
  if (me?.role === "admin" && auth.isServerMode()) {
    for (const u of auth.listUsers()) {
      if (u.id === me.id || u.disabled) continue;
      const home = homeOf(u);
      if (home && home !== homeOf(me)) {
        out.push({ id: u.username, label: u.displayName || u.username, readOnly: true });
      }
    }
  }
  return out;
}

/**
 * `{ dir, readOnly, ownerId }` for home `who` of `req`, or a thrown ENOHOME
 * (404) — never another user's for a non-admin.
 */
function resolveHome(req, who) {
  const none = () => Object.assign(new Error("no such home"), { code: "ENOHOME" });
  const me = req.user || null;
  if (who === "me") {
    const dir = homeOf(me);
    if (!dir) throw none();
    return { dir: path.resolve(dir), readOnly: false, ownerId: me?.id ?? null };
  }
  if (me?.role !== "admin" || !auth.isServerMode()) throw none();
  const u = auth.listUsers().find((x) => x.username === String(who) && !x.disabled);
  const dir = u && homeOf(u);
  if (!dir) throw none();
  return { dir: path.resolve(dir), readOnly: true, ownerId: u.id };
}

module.exports = { homeOf, listHomes, resolveHome };