/**
 * @file member-tmux.js
 * @description Server mode, one Linux user per account (S3): each member's
 * own tmux server as the Users page shows it — the version it runs next to
 * the installed one (`TMUX_BIN`), how many sessions it holds and whether an
 * agent of theirs is working — and an admin's restart of it. A tmux server
 * keeps the version it started with until its last session closes, so after
 * a tmux upgrade an old server lingers; `tmux-member` (install-system) keeps
 * every call on it matched to its own binary, and this is how an admin moves
 * a member onto the new version on purpose. A restart ends every pane of
 * theirs (their Claude sessions resume from the workspace).
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

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

const { db } = require("../db");
const linux = require("./linux-accounts");
const tmux = require("./tmux");

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

// The installed tmux's version (`3.8`), re-read at most once a minute.
let installed = { at: 0, bin: null, version: null };
function installedVersion() {
  const bin = linux.serverConf()?.tmuxInstalled || null;
  if (installed.bin === bin && Date.now() - installed.at < 60_000) return installed.version;
  let version = null;
  if (bin) {
    try {
      version =
        String(execFileSync(bin, ["-V"], { encoding: "utf8", timeout: 3000, stdio: "pipe" }))
          .trim()
          .replace(/^tmux\s+/, "") || null;
    } catch {
      /* missing or broken: unknown */
    }
  }
  installed = { at: Date.now(), bin, version };
  return version;
}

/** How many of `userId`'s workspaces have an agent working right now. */
function busyCount(userId) {
  return db
    .prepare("SELECT COUNT(*) AS n FROM lanes WHERE owner_id = ? AND status = 'running'")
    .get(userId).n;
}

/** One user's row; null for an account with no Linux side. */
function rowFor(user, installedV) {
  const acct = linux.accountFor(user.username);
  if (!acct) return null;
  const info = tmux.memberServerInfo(acct);
  return {
    id: user.id,
    username: user.username,
    ...info,
    busy: busyCount(user.id),
    outdated: !!(info.running && info.version && installedV && info.version !== installedV),
  };
}

/** `{available, installed, matched, users: [...]}` for the Users page. */
function overview(users) {
  if (!linux.s3Enabled()) return { available: false, users: [] };
  const conf = linux.serverConf();
  const v = installedVersion();
  return {
    available: true,
    installed: v,
    // Whether calls on an older server already use its own binary.
    matched: conf?.bins?.tmux !== conf?.tmuxInstalled,
    users: users.map((u) => rowFor(u, v)).filter(Boolean),
  };
}

/**
 * Restart `user`'s tmux server. `{restarted: false}` when none ran; throws
 * ETMUXSTUCK (with the pid) when it would not stop — root has to kill it.
 */
function restart(user) {
  const acct = linux.accountFor(user.username);
  if (!acct) throw err("ENOS3", "this account has no Linux user (S3 is not installed)");
  const before = tmux.memberServerInfo(acct);
  if (!before.running) return { restarted: false, before };
  try {
    tmux.killMemberServer(acct);
  } catch {
    /* judged by what is left below */
  }
  const after = tmux.memberServerInfo(acct);
  if (after.running) {
    const pid = before.pid || after.pid;
    throw err(
      "ETMUXSTUCK",
      `${user.username}'s tmux server did not stop — run \`sudo kill -9 ${pid || "<pid>"}\` on the server`
    );
  }
  return { restarted: true, before };
}

module.exports = { overview, restart, installedVersion };