/**
 * @file tray.js — the AgentHub icon in the OS status area (GNOME top bar,
 * macOS menu bar, Windows notification area), like 9router's. The icon is its
 * own process (`scripts/tray.js`) so a server restart or a Quit never takes it
 * away — after a Quit it is how the user starts AgentHub again. A production
 * server keeps it alive (`startTrayWatch`): ON by default, OFF once the user
 * hides it (the flag `<data dir>/runtime/tray-off`, written by Settings →
 * System or the icon's own "Hide this icon"; nothing turns it back on but the
 * user). On Linux it waits for a graphical session — a server started at boot
 * has no DISPLAY until someone logs in. Never in server mode.
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

const fs = require("fs");
const path = require("path");
const { getDataDir } = require("./claude-home");

const ROOT = path.resolve(__dirname, "..", "..");
const CHECK_MS = 60_000;
const MAX_FAILED_STARTS = 3;
const HEARTBEAT_MS = 5_000;

const runtime = () => path.join(getDataDir(), "runtime");
const offPath = () => path.join(runtime(), "tray-off");
const pidPath = () => path.join(runtime(), "tray.json");

function isEnabled() {
  return !fs.existsSync(offPath());
}

/**
 * `{pid, root}` of the live tray process, or null. The icon touches its file
 * on every poll (`HEARTBEAT_MS`), so a file left by a crash or a reboot goes
 * stale and its pid — by then possibly another program's — is never signalled.
 */
function liveTray() {
  try {
    if (Date.now() - fs.statSync(pidPath()).mtimeMs > 6 * HEARTBEAT_MS) return null;
    const rec = JSON.parse(fs.readFileSync(pidPath(), "utf8"));
    process.kill(rec.pid, 0);
    return rec;
  } catch {
    return null;
  }
}

function writePid(pid, root = ROOT) {
  fs.mkdirSync(runtime(), { recursive: true });
  fs.writeFileSync(pidPath(), JSON.stringify({ pid, root }), "utf8");
}

function stopTray() {
  const rec = liveTray();
  if (!rec) return;
  try {
    process.kill(rec.pid, "SIGTERM");
  } catch {
    /* already gone */
  }
}

/** The environment the icon needs to reach the desktop, or null when there is none. */
function guiEnv() {
  if (process.platform !== "linux") return {};
  const env = require("./desktop-env").desktopEnv();
  return env.DISPLAY || env.WAYLAND_DISPLAY ? env : null;
}

function status() {
  const { isServerMode } = require("./auth");
  return {
    available: !isServerMode() && guiEnv() !== null,
    enabled: isEnabled(),
    running: liveTray() !== null,
  };
}

let failedStarts = 0;

/**
 * Starts the icon when it should be up and is not. `replace` (once, at server
 * start) retires an icon still running from another install root — the
 * previous plugin build, whose cache directory is about to be pruned.
 */
function ensureTray({ replace = false, spawn = require("child_process").spawn } = {}) {
  if (!isEnabled() || failedStarts >= MAX_FAILED_STARTS) return "skipped";
  const live = liveTray();
  if (live && !(replace && live.root !== ROOT)) return "running";
  const env = guiEnv();
  if (!env) return "no-gui";
  if (live) stopTray();
  const started = Date.now();
  const child = spawn(process.execPath, [path.join(ROOT, "scripts", "tray.js")], {
    cwd: ROOT,
    detached: true,
    stdio: "ignore",
    env: { ...process.env, ...env },
  });
  child.on("error", () => failedStarts++);
  // An icon that dies at once (no tray host, a binary the OS refuses) is not
  // retried forever: three quick deaths and this server leaves it alone.
  child.on("exit", () => {
    if (Date.now() - started < 10_000) failedStarts++;
  });
  child.unref();
  return "started";
}

function setEnabled(on, opts) {
  if (on) {
    fs.rmSync(offPath(), { force: true });
    failedStarts = 0;
    ensureTray(opts);
  } else {
    fs.mkdirSync(runtime(), { recursive: true });
    fs.writeFileSync(offPath(), `${new Date().toISOString()}\n`, "utf8");
    stopTray();
  }
  return status();
}

function startTrayWatch() {
  if (process.env.NODE_ENV !== "production" || require("./auth").isServerMode()) return;
  try {
    ensureTray({ replace: true });
  } catch {
    /* an icon is never worth a server crash */
  }
  setInterval(() => {
    try {
      ensureTray();
    } catch {
      /* same */
    }
  }, CHECK_MS).unref();
}

module.exports = {
  isEnabled,
  liveTray,
  writePid,
  stopTray,
  status,
  ensureTray,
  setEnabled,
  startTrayWatch,
  offPath,
  pidPath,
  HEARTBEAT_MS,
};