"use client";

/**
 * Kiosk / wall-display support for the live wall (server-26#234).
 *
 * Kiosk is URL-driven only — `?kiosk=1` or `#…&kiosk` — never remembered in
 * storage, so a normal viewer can't get stuck without the nav. A wall PC's
 * startup URL carries it, which is what makes it survive a browser restart.
 *
 * Everything here degrades silently: no Fullscreen API, no Screen Wake Lock,
 * blocked sessionStorage — the wall still renders and still updates.
 */
import { useCallback, useEffect, useRef, useState } from "react";

/** Fired on window whenever kiosk is switched in-page (replaceState fires no hashchange). */
export const KIOSK_EVENT = "drb:kiosk-change";

function queryKiosk(search: string): boolean {
  const v = new URLSearchParams(search).get("kiosk");
  return v != null && v !== "0" && v !== "false";
}

function hashKiosk(hash: string): boolean {
  const p = new URLSearchParams(hash.replace(/^#/, ""));
  return p.has("kiosk") && p.get("kiosk") !== "0";
}

/** True when the current URL asks for kiosk mode (query or hash). Client-side only. */
export function readKioskFlag(): boolean {
  if (typeof window === "undefined") return false;
  return queryKiosk(window.location.search) || hashKiosk(window.location.hash);
}

/** Whether `?kiosk=` is in the query (the hash part is LiveView's to manage). */
export function kioskInQuery(): boolean {
  return typeof window !== "undefined" && queryKiosk(window.location.search);
}

/** Drops `?kiosk` from the query string in place; the caller clears the hash flag. */
export function stripKioskQuery(): void {
  try {
    const url = new URL(window.location.href);
    url.searchParams.delete("kiosk");
    window.history.replaceState(window.history.state, "", url.pathname + url.search + url.hash);
  } catch { /* nothing to strip */ }
}

export function announceKioskChange(): void {
  window.dispatchEvent(new Event(KIOSK_EVENT));
}

/** Live view of the URL's kiosk flag, for chrome outside LiveView (ChromeSwitcher). */
export function useKioskFlag(): boolean {
  const [on, setOn] = useState(false);
  useEffect(() => {
    const read = () => setOn(readKioskFlag());
    read();
    window.addEventListener("hashchange", read);
    window.addEventListener("popstate", read);
    window.addEventListener(KIOSK_EVENT, read);
    return () => {
      window.removeEventListener("hashchange", read);
      window.removeEventListener("popstate", read);
      window.removeEventListener(KIOSK_EVENT, read);
    };
  }, []);
  return on;
}

// ── Screen Wake Lock (typed locally; not in every TS lib.dom) ────────────────
interface WakeLockSentinelLike extends EventTarget { released: boolean; release(): Promise<void> }
interface WakeLockLike { request(type: "screen"): Promise<WakeLockSentinelLike> }

export type WakeState = "on" | "off" | "unsupported";

const RETRY_KEY = "drb.wall.retryAttempts";
const RETRY_BASE_MS = 30_000;
const RETRY_MAX_MS = 10 * 60_000;
/** Healthy this long after a load → the retry backoff resets. */
const HEALTHY_RESET_MS = 2 * 60_000;
/** Offline at least this long → a kiosk reloads on reconnect for fresh listeners. */
const OFFLINE_RELOAD_MS = 60_000;

function readAttempts(): number {
  try { return Math.max(0, Number(window.sessionStorage.getItem(RETRY_KEY)) || 0); } catch { return 0; }
}
function writeAttempts(n: number): void {
  try {
    if (n > 0) window.sessionStorage.setItem(RETRY_KEY, String(n));
    else window.sessionStorage.removeItem(RETRY_KEY);
  } catch { /* storage blocked — backoff restarts at the base delay */ }
}

export interface KioskBanner { tone: "offline" | "error"; message: string; retryAt: number | null }

export interface KioskState {
  fullscreen: boolean;
  canFullscreen: boolean;
  toggleFullscreen: () => void;
  wake: WakeState;
  online: boolean;
  banner: KioskBanner | null;
  retryNow: () => void;
}

/**
 * @param kiosk     kiosk presentation is on (wake lock, auto-fullscreen, auto-reload)
 * @param dataError the live-data listener's error (e.g. useCalls().error) — a
 *                  Firestore snapshot error is terminal for that listener, so
 *                  the recovery is a reload; the hooks themselves are untouched.
 */
export function useKiosk(kiosk: boolean, dataError: string | null): KioskState {
  // ── Fullscreen ──────────────────────────────────────────────────────────
  const [fullscreen, setFullscreen] = useState(false);
  const [canFullscreen, setCanFullscreen] = useState(false);
  useEffect(() => {
    setCanFullscreen(typeof document !== "undefined" && !!document.fullscreenEnabled);
    const on = () => setFullscreen(!!document.fullscreenElement);
    on();
    document.addEventListener("fullscreenchange", on);
    return () => document.removeEventListener("fullscreenchange", on);
  }, []);
  const toggleFullscreen = useCallback(() => {
    try {
      if (document.fullscreenElement) void document.exitFullscreen().catch(() => undefined);
      else void document.documentElement.requestFullscreen().catch(() => undefined);
    } catch { /* unsupported */ }
  }, []);
  // Browsers only allow fullscreen from a user gesture, so in kiosk the first
  // touch/key anywhere enters it. A wall PC launched with the browser's own
  // kiosk flag is already fullscreen and needs no click at all.
  useEffect(() => {
    if (!kiosk || !document.fullscreenEnabled) return;
    const arm = () => {
      if (!document.fullscreenElement) void document.documentElement.requestFullscreen().catch(() => undefined);
    };
    window.addEventListener("pointerdown", arm, { once: true });
    window.addEventListener("keydown", arm, { once: true });
    return () => {
      window.removeEventListener("pointerdown", arm);
      window.removeEventListener("keydown", arm);
    };
  }, [kiosk]);

  // ── Screen Wake Lock — held while kiosk is on, re-acquired when visible again ──
  const [wake, setWake] = useState<WakeState>("off");
  useEffect(() => {
    const wl = (navigator as Navigator & { wakeLock?: WakeLockLike }).wakeLock;
    if (!kiosk) { setWake("off"); return; }
    if (!wl) { setWake("unsupported"); return; }
    let sentinel: WakeLockSentinelLike | null = null;
    let cancelled = false;
    const onRelease = () => { if (!cancelled) setWake("off"); };
    const acquire = async () => {
      if (cancelled || document.visibilityState !== "visible" || (sentinel && !sentinel.released)) return;
      try {
        const s = await wl.request("screen");
        if (cancelled) { void s.release().catch(() => undefined); return; }
        sentinel = s;
        s.addEventListener("release", onRelease);
        setWake("on");
      } catch {
        setWake("off");   // denied (battery saver, policy) — the wall still works
      }
    };
    void acquire();
    const onVis = () => { void acquire(); };
    document.addEventListener("visibilitychange", onVis);
    return () => {
      cancelled = true;
      document.removeEventListener("visibilitychange", onVis);
      if (sentinel) {
        sentinel.removeEventListener("release", onRelease);
        void sentinel.release().catch(() => undefined);
      }
    };
  }, [kiosk]);

  // ── Reconnect watchdog ─────────────────────────────────────────────────
  const [online, setOnline] = useState(true);
  const offlineSince = useRef<number | null>(null);
  const kioskRef = useRef(kiosk);
  kioskRef.current = kiosk;
  useEffect(() => {
    const sync = () => {
      const now = navigator.onLine;
      setOnline(now);
      if (!now) {
        if (offlineSince.current == null) offlineSince.current = Date.now();
        return;
      }
      const since = offlineSince.current;
      offlineSince.current = null;
      // Firestore resumes its listeners on its own after a blip; after a long
      // outage an unattended wall reloads rather than trust that it did.
      if (kioskRef.current && since != null && Date.now() - since >= OFFLINE_RELOAD_MS) window.location.reload();
    };
    sync();
    window.addEventListener("online", sync);
    window.addEventListener("offline", sync);
    return () => {
      window.removeEventListener("online", sync);
      window.removeEventListener("offline", sync);
    };
  }, []);

  const retryNow = useCallback(() => {
    writeAttempts(readAttempts() + 1);
    window.location.reload();
  }, []);

  // Healthy for a while → forget earlier failures.
  useEffect(() => {
    if (dataError) return;
    const id = setTimeout(() => writeAttempts(0), HEALTHY_RESET_MS);
    return () => clearTimeout(id);
  }, [dataError]);

  // Data error in kiosk → reload after an exponential backoff (30 s → 10 min).
  const [retryAt, setRetryAt] = useState<number | null>(null);
  useEffect(() => {
    if (!dataError || !kiosk || !online) { setRetryAt(null); return; }
    const delay = Math.min(RETRY_MAX_MS, RETRY_BASE_MS * 2 ** readAttempts());
    setRetryAt(Date.now() + delay);
    const id = setTimeout(retryNow, delay);
    return () => clearTimeout(id);
  }, [dataError, kiosk, online, retryNow]);

  let banner: KioskBanner | null = null;
  if (!online) {
    banner = { tone: "offline", message: "Offline — showing the last data received. Reconnects automatically.", retryAt: null };
  } else if (dataError) {
    banner = { tone: "error", message: "Live data stopped updating.", retryAt };
  }

  return { fullscreen, canFullscreen, toggleFullscreen, wake, online, banner, retryNow };
}