import { useCallback, useState } from "react";
import { activeAccountId } from "./activeAccount";

// Central registry of every localStorage key the app uses. One place to see them all, rename
// safely, and avoid collisions — instead of `"siftlode.x"` string literals scattered across
// files. Parametric (per-user) keys are functions. All keys are namespaced `siftlode.*`.
export const LS = {
  theme: "siftlode.theme",
  sidebarLayout: "siftlode.sidebarLayout",
  plexLayout: "siftlode.plexLayout",
  playlistsLayout: "siftlode.playlistsLayout",
  playlistsCollapsed: "siftlode.playlistsCollapsed",
  filesLayout: "siftlode.filesLayout",
  filesCollapsed: "siftlode.filesCollapsed",
  // The Files view last open (every file, shared with me, or a folder id), per-account.
  filesView: "siftlode.filesView",
  // The Files table's rows-per-page and page (DataTable's persist blob), per-account.
  filesTable: "siftlode.filesTable",
  // List or grid per Files view (a `{ viewParam: layout }` map), the sort both paints share, and the
  // grid's cards per page — per-account mirrors of the server prefs (the last is local only).
  filesLayouts: "siftlode.filesLayouts",
  filesSort: "siftlode.filesSort",
  filesCardSize: "siftlode.filesCardSize",
  hints: "siftlode.hints",
  lang: "siftlode.lang",
  filters: "siftlode.filters",
  page: "siftlode.page",
  // Start every session on the Home surface rather than on the module you happened to leave
  // open. Per-account, "0" = opt out and go back to remembering the last module. Read by
  // `loadInitialPage` in NavigationProvider's initializer, which BootGate runs only once the tab's
  // account is pinned — so the landing is decided right before the first paint, never corrected after.
  startOnHome: "siftlode.startOnHome",
  perfMode: "siftlode.perfMode",
  // The feed's view mode (see lib/feedView.ts) — a local copy of the server pref, which usePref seeds
  // from only when the server has never stored the key.
  feedView: "siftlode.feedView",
  // The subscribed table's column filters (a FilterMap), lifted out of the table so the top status
  // chips, the Sync column funnel, and the card layout all share ONE state (per-account). Supersedes
  // the old single-string `channelFilter` sync chip.
  channelsFilterMap: "siftlode.channelsFilterMap",
  // DEPRECATED — the retired single-value sync chip; read once to migrate a pinned value into
  // `channelsFilterMap`, then inert. Do not write.
  legacyChannelFilter: "siftlode.channelFilter",
  channelsView: "siftlode.channelsView",
  // The channel manager's layout (table / cards — see lib/channelLayout.ts), per-account.
  channelLayout: "siftlode.channelLayout",
  // The manager's sort, lifted out of the table so the card layout shares it (per-account, per-tab).
  channelSort: "siftlode.channelSort",
  channelShow: "siftlode.channelShow",
  channelDiscoverySort: "siftlode.channelDiscoverySort",
  // Cards-per-page for the card layout (the table keeps its own rows-per-page in its persist blob).
  channelCardSize: "siftlode.channelCardSize",
  channelDiscoveryCardSize: "siftlode.channelDiscoveryCardSize",
  channelsTable: "siftlode.channelsTable",
  // Channel id → name as last seen (useChannelNames): names a channel filter's chips after a reload,
  // before the subscription list has landed. A cache, rewritten from the list on every load.
  channelNames: "siftlode.channelNames",
  channelDiscoveryTable: "siftlode.channelDiscoveryTable",
  // A page's sub-tab: sessionStorage, per browser tab (useTabPersistedState), like adminUsersTab and
  // statsTab below.
  settingsTab: "siftlode.settingsTab",
  configTab: "siftlode.configTab",
  auditTable: "siftlode.auditTable",
  statsTab: "siftlode.statsTab",
  adminUsersTab: "siftlode.adminUsersTab",
  filterCollapsed: "siftlode.filterCollapsed",
  playlist: "siftlode.playlist",
  plSort: "siftlode.plSort",
  plexLibrary: "siftlode.plexLibrary",
  plexShow: "siftlode.plexShow",
  plexSort: "siftlode.plexSort",
  plexFilters: "siftlode.plexFilters",
  plexQ: "siftlode.plexQ",
  plexField: "siftlode.plexField",
  plexPlaylistLayout: "siftlode.plexPlaylistLayout",
  plexPlayerPrefs: "siftlode.plexPlayerPrefs",
  // The YouTube modal player's volume (`{ volume: 0–100 }`; 0 IS muted — there is no separate
  // flag). A YT.Player instance is created per video and starts at full volume, so without this
  // every next video is loud again (same idea as plexPlayerPrefs).
  ytPlayerPrefs: "siftlode.ytPlayerPrefs",
  notifHistory: "siftlode.notifications",
  notifSettings: "siftlode.notifSettings",
  onboardingDismissed: "siftlode.onboarding.dismissed",
  seenVersion: "siftlode.seenVersion",
  // The public /watch page's repeat toggle (JSON boolean; on by default). Browser-wide, NOT per account:
  // that page runs outside the app, with no account at all.
  watchRepeat: "siftlode.watchRepeat",
  // Where this browser stopped in each shared /watch link (`lib/resume.ts`: token -> {at, t}). Same
  // reason as above: the viewer has no account to keep it in.
  watchResume: "siftlode.watchResume",
} as const;

// --- per-account scoping -----------------------------------------------------------------
// The active-account primitive (activeAccountId) lives in ./activeAccount
// so it can be shared without a cycle; the helpers below key localStorage on it.

/** Suffix a base localStorage key with an account id so per-account UI state (filters, selected
 * playlist, notifications, tab positions, cached prefs…) is NOT shared across the accounts signed
 * into one browser — a bare shared key leaks one account's state into another (and, with per-tab
 * accounts, two tabs would fight over it). Defaults to the current tab's active account; returns
 * null when no account is known yet, so callers fall back to defaults / skip persistence instead
 * of touching another account's data. */
export function accountKey(
  base: string,
  id: number | null | undefined = activeAccountId(),
): string | null {
  return id != null ? `${base}.${id}` : null;
}

/** Per-account variants of the read/write helpers: key by the current account, no-op / return the
 * fallback when the account isn't known (avoids reading or writing a shared/other-account key). */
export function readAccount<T>(base: string, fallback: T): T {
  const k = accountKey(base);
  return k ? readJSON(k, fallback) : fallback;
}
export function readAccountMerged<T extends object>(base: string, defaults: T): T {
  const k = accountKey(base);
  return k ? readMerged(k, defaults) : { ...defaults };
}
export function writeAccount(base: string, value: unknown): void {
  const k = accountKey(base);
  if (k) writeJSON(k, value);
}
export function getAccountRaw(base: string): string | null {
  const k = accountKey(base);
  return k ? localStorage.getItem(k) : null;
}
export function setAccountRaw(base: string, value: string): void {
  const k = accountKey(base);
  if (k) {
    try {
      localStorage.setItem(k, value);
    } catch {
      /* ignore */
    }
  }
}

// --- typed read/write helpers (do the JSON + try/catch once) ----------------------------

/** Read an object-shaped value merged over `defaults` (so missing/added keys are tolerated),
 * falling back to `defaults` on missing or corrupt data. Module-private: its only caller is
 * `readAccountMerged` above (exporting it makes knip flag it as an unused export). */
function readMerged<T extends object>(key: string, defaults: T): T {
  try {
    return { ...defaults, ...JSON.parse(localStorage.getItem(key) || "{}") };
  } catch {
    return { ...defaults };
  }
}

/** Read any JSON value (arrays/scalars), falling back on missing or corrupt data. */
export function readJSON<T>(key: string, fallback: T): T {
  try {
    const raw = localStorage.getItem(key);
    return raw == null ? fallback : (JSON.parse(raw) as T);
  } catch {
    return fallback;
  }
}

/** Persist a value as JSON, swallowing quota/serialization errors. */
export function writeJSON(key: string, value: unknown): void {
  try {
    localStorage.setItem(key, JSON.stringify(value));
  } catch {
    /* ignore quota / serialization errors */
  }
}

// --- reactive persisted string state ----------------------------------------------------

/** A `useState` whose string value is mirrored to localStorage, scoped to the current account (see
 * accountKey), so one account's persisted tab/view position doesn't carry over to another in the
 * same browser. Survives reload (F5); validation is deferred to the caller (clamp at render) so it
 * can be used before an async-loaded option list is known, keeping hook order stable. Read once, at
 * mount: BootGate mounts every consumer after the account is pinned. */
export function useAccountPersistedState(
  base: string,
  fallback = "",
): [string, (value: string) => void] {
  const [value, setValue] = useState<string>(() => getAccountRaw(base) ?? fallback);
  // Stable setter (base is stable) so a provider can build a stable action on top of it — e.g.
  // ChannelsProvider's setView, which must not change identity on every tab switch.
  const set = useCallback(
    (next: string) => {
      setValue(next);
      setAccountRaw(base, next);
    },
    [base],
  );
  return [value, set];
}

// --- a page's sub-tab, per browser tab ---------------------------------------------------------

// Which sub-tab a page was left on (Settings, Configuration, Statistics, Users) is kept for THIS browser
// tab only — sessionStorage, account-scoped: it survives a reload and a trip to another page, and a new
// tab opens the page on its first sub-tab (the owner's call: a position remembered forever in
// localStorage made Configuration open on "Plex" in every fresh tab, as if that were its home).

/** The sub-tab stored for this browser tab, or null. */
function getTabRaw(base: string): string | null {
  const k = accountKey(base);
  try {
    return k ? sessionStorage.getItem(k) : null;
  } catch {
    return null;
  }
}

/** Pre-select a page's sub-tab before navigating there (a "Review" link, the Google-link return). */
export function setTabRaw(base: string, value: string): void {
  const k = accountKey(base);
  if (!k) return;
  try {
    sessionStorage.setItem(k, value);
  } catch {
    /* ignore */
  }
}

/** `useAccountPersistedState` for a page's sub-tab, kept per browser tab (see above). */
export function useTabPersistedState(
  base: string,
  fallback = "",
): [string, (value: string) => void] {
  const [value, setValue] = useState<string>(() => {
    // The position used to live in localStorage; a value left there would never be read again.
    const old = accountKey(base);
    if (old) {
      try {
        localStorage.removeItem(old);
      } catch {
        /* ignore */
      }
    }
    return getTabRaw(base) ?? fallback;
  });
  const set = useCallback(
    (next: string) => {
      setValue(next);
      setTabRaw(base, next);
    },
    [base],
  );
  return [value, set];
}

/** A per-account persisted JSON OBJECT: `patch(partial)` merges + saves, unknown/missing keys fall
 * back to `defaults` (via readAccountMerged) so adding a field later is safe. Used for bundles of
 * related per-account settings (e.g. the Plex player prefs: volume, offsets, seek steps, sub style). */
export function useAccountPersistedObject<T extends object>(
  base: string,
  defaults: T,
): [T, (patch: Partial<T>) => void] {
  const [value, setValue] = useState<T>(() => readAccountMerged(base, defaults));
  const patch = useCallback(
    (p: Partial<T>) => {
      setValue((prev) => {
        const next = { ...prev, ...p };
        writeAccount(base, next);
        return next;
      });
    },
    [base],
  );
  return [value, patch];
}