// Client-side notification store. Surfaces transient toasts AND keeps a history that
// the Notification Center shows (info events, actions awaiting interaction, and app
// errors). History is persisted to localStorage so it survives reloads; action
// callbacks are live-only and dropped on reload.

export type NotifLevel = "info" | "success" | "warning" | "error" | "fatal";

export interface NotifAction {
  label: string;
  onClick: () => void;
}

// Structured payload that lets the Notification Center offer in-app actions even
// after a reload (when live `action` callbacks are gone).
export type VideoHiddenMeta = {
  kind: "video-hidden";
  videoId: string;
  title: string;
  channelId: string;
  channelName: string;
};
export type VideoWatchedMeta = {
  kind: "video-watched";
  videoId: string;
  title: string;
  channelId: string;
  channelName: string;
};
export type ChannelSubscribedMeta = {
  kind: "channel-subscribed";
  channelId: string;
  channelName: string;
};
export type NotifMeta = VideoHiddenMeta | VideoWatchedMeta | ChannelSubscribedMeta;

export interface Notification {
  id: number;
  level: NotifLevel;
  title?: string;
  message: string;
  action?: NotifAction;
  meta?: NotifMeta;
  requiresInteraction: boolean;
  duration?: number; // auto-dismiss ms (undefined when it stays until acted on)
  ts: number;
  read: boolean;
  dismissed: boolean; // transient toast surface closed (still kept in history)
  // Live session-only status (e.g. "connection lost"): sticky toast (no auto-dismiss
  // timer) that the producer removes itself when the condition resolves. Never persisted
  // to history, so a reload can't orphan it with no live handle to clear it.
  transient: boolean;
}

export interface NotifyInput {
  message: string;
  level?: NotifLevel;
  title?: string;
  action?: NotifAction;
  meta?: NotifMeta;
  requiresInteraction?: boolean;
  sound?: boolean; // force the alert tone (when sound is enabled) even for an info toast
  transient?: boolean; // live status: sticky toast, not persisted (see Notification.transient)
}

const HISTORY_KEY = "subfeed.notifications";
const SETTINGS_KEY = "subfeed.notifSettings";
const MAX_HISTORY = 100;
const ERROR_TTL = 15000;

// 6b: per-account notification settings (persisted by the Settings panel into the
// server `preferences`, mirrored to localStorage so they apply before login).
export interface NotifSettings {
  sound: boolean; // play a short tone on attention-needing notifications
  durationMs: number; // auto-dismiss time for info/success toasts
}
const DEFAULT_SETTINGS: NotifSettings = { sound: false, durationMs: 6000 };
let config: NotifSettings = loadSettings();

function loadSettings(): NotifSettings {
  try {
    return { ...DEFAULT_SETTINGS, ...JSON.parse(localStorage.getItem(SETTINGS_KEY) || "{}") };
  } catch {
    return DEFAULT_SETTINGS;
  }
}

export function getNotifSettings(): NotifSettings {
  return config;
}

export function configureNotifications(p: Partial<NotifSettings>): void {
  config = { ...config, ...p };
  try {
    localStorage.setItem(SETTINGS_KEY, JSON.stringify(config));
  } catch {
    /* ignore */
  }
}

let audioCtx: AudioContext | null = null;
function beep(): void {
  try {
    const Ctx = window.AudioContext || (window as unknown as { webkitAudioContext: typeof AudioContext }).webkitAudioContext;
    audioCtx = audioCtx || new Ctx();
    if (audioCtx.state === "suspended") void audioCtx.resume();
    const osc = audioCtx.createOscillator();
    const gain = audioCtx.createGain();
    osc.connect(gain);
    gain.connect(audioCtx.destination);
    osc.frequency.value = 660;
    gain.gain.value = 0.04;
    osc.start();
    osc.stop(audioCtx.currentTime + 0.12);
  } catch {
    /* autoplay blocked or unsupported — ignore */
  }
}

let items: Notification[] = load();
let listeners: Array<() => void> = [];
let counter = items.reduce((m, n) => Math.max(m, n.id), 0) + 1;

// Cached derived snapshots — useSyncExternalStore needs stable references between
// emits, so we recompute these only when `items` changes.
let cachedActive: Notification[] = [];
let cachedReversed: Notification[] = [];
let cachedUnread = 0;

function load(): Notification[] {
  try {
    const raw = JSON.parse(localStorage.getItem(HISTORY_KEY) || "[]");
    if (!Array.isArray(raw)) return [];
    // Restored entries are history only. Mark them dismissed so they don't
    // resurrect as active toasts on reload — their auto-dismiss timers aren't
    // re-armed across a reload, so otherwise they'd stick forever. Also drop the
    // live `action` callback, which can't survive serialization.
    return raw.map((n) => ({ ...n, action: undefined, dismissed: true, transient: false }) as Notification);
  } catch {
    return [];
  }
}

function persist() {
  try {
    // Transient status notices are live-session only — never write them to history,
    // so a reload can't leave one stranded with no producer left to clear it.
    const slim = items.filter((n) => !n.transient).map(({ action: _action, ...n }) => n);
    localStorage.setItem(HISTORY_KEY, JSON.stringify(slim));
  } catch {
    /* ignore quota / serialization errors */
  }
}

function recompute() {
  cachedActive = items.filter((n) => !n.dismissed);
  cachedReversed = [...items].reverse();
  cachedUnread = items.reduce((c, n) => c + (n.read ? 0 : 1), 0);
}

function emit() {
  items = items.slice(-MAX_HISTORY);
  recompute();
  persist();
  listeners.forEach((l) => l());
}

recompute();

export function subscribe(listener: () => void): () => void {
  listeners.push(listener);
  return () => {
    listeners = listeners.filter((l) => l !== listener);
  };
}

export function notify(input: NotifyInput): number {
  const id = counter++;
  const requiresInteraction = input.requiresInteraction ?? false;
  const level = input.level ?? "info";
  // config.durationMs === 0 means "don't auto-dismiss" (toast stays until dismissed).
  // A transient status stays put until its producer clears it (no auto-dismiss timer),
  // same as an interaction-awaiting notice.
  const duration = requiresInteraction || input.transient
    ? undefined
    : level === "error" || level === "fatal"
      ? ERROR_TTL
      : config.durationMs > 0
        ? config.durationMs
        : undefined;
  items = [
    ...items,
    {
      id,
      level,
      title: input.title,
      message: input.message,
      action: input.action,
      meta: input.meta,
      requiresInteraction,
      duration,
      ts: Date.now(),
      read: false,
      dismissed: false,
      transient: input.transient ?? false,
    },
  ];
  emit();
  if (config.sound && (input.sound || requiresInteraction || level === "error" || level === "fatal")) {
    beep();
  }
  if (duration) setTimeout(() => dismiss(id), duration);
  return id;
}

/** Back-compat: a simple info toast with an optional inline action (e.g. Undo). */
export function toast(message: string, action?: NotifAction): number {
  return notify({ message, action });
}

/** Close the transient toast surface; the entry stays in the center's history. */
export function dismiss(id: number): void {
  items = items.map((n) => (n.id === id ? { ...n, dismissed: true } : n));
  emit();
}

export function markAllRead(): void {
  if (items.every((n) => n.read)) return;
  items = items.map((n) => (n.read ? n : { ...n, read: true }));
  emit();
}

export function clearAll(): void {
  if (items.length === 0) return;
  items = [];
  emit();
}

/** Remove a single history entry entirely (per-item clear in the notification center). */
export function remove(id: number): void {
  const before = items.length;
  items = items.filter((n) => n.id !== id);
  if (items.length !== before) emit();
}

/** Resolve any history entries tied to a video — called when it's unhidden/unwatched so the
 * now-stale "Hidden/Watched X" notice disappears instead of lingering with a dead action. */
export function resolveVideo(videoId: string): void {
  const before = items.length;
  items = items.filter(
    (n) =>
      !(
        (n.meta?.kind === "video-hidden" || n.meta?.kind === "video-watched") &&
        n.meta.videoId === videoId
      )
  );
  if (items.length !== before) emit();
}

export const getActiveToasts = (): Notification[] => cachedActive;
export const getNotifications = (): Notification[] => cachedReversed;
export const getUnreadCount = (): number => cachedUnread;