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import { subscribe, notifyListeners } from "./store";
import {
buildCookieString,
buildRemovalCookieString,
defaultDeserializer,
defaultSerializer,
isDocumentAvailable,
readRawCookie,
type CookieAttributes,
} from "./utils";
export type { CookieAttributes, SameSite } from "./utils";
/**
* Type for the initial value that can be a value or a function returning a value
* (lazy initialization).
*/
export type InitialValue<T> = T | (() => T);
/**
* Options for the {@link useCookie} hook. Combines serialization/lifecycle
* options (aligned with `@usefy/use-local-storage`) with the cookie-specific
* write attributes from {@link CookieAttributes}.
*/
export interface UseCookieOptions<T> extends CookieAttributes {
/**
* Initial value used when the cookie is absent (or on the server). Supports a
* lazy initializer function. This is also the value the state resets to when
* {@link UseCookieReturn} `remove()` is called.
*/
initialValue?: InitialValue<T>;
/**
* Custom serializer for converting the value to the stored cookie string.
* @default JSON.stringify
*/
serializer?: (value: T) => string;
/**
* Custom deserializer for parsing the stored cookie string back to a value.
* The default tries `JSON.parse` and **falls back to the raw string** for
* non-JSON cookies (so a plain `foo=bar` cookie never throws).
* @default (value) => { try { return JSON.parse(value) } catch { return value } }
*/
deserializer?: (value: string) => T;
/** Callback invoked when a serialization/deserialization error occurs. */
onError?: (error: Error) => void;
}
/**
* Return type for {@link useCookie} — a tuple similar to `useState`.
*/
export type UseCookieReturn<T> = readonly [
/** Current cookie value (`undefined` when the cookie is absent and no `initialValue` was given). */
T | undefined,
/** Update the cookie value. Accepts a value or a functional updater `(prev) => next`. */
React.Dispatch<React.SetStateAction<T | undefined>>,
/** Delete the cookie and reset state to `initialValue` (or `undefined`). */
() => void
];
/**
* Resolve an initial value, supporting a lazy initializer function.
*/
function resolveInitialValue<T>(
initialValue: InitialValue<T> | undefined
): T | undefined {
return typeof initialValue === "function"
? (initialValue as () => T)()
: initialValue;
}
/**
* A hook for reading and writing a browser **cookie** as React state — the
* cookie sibling of `@usefy/use-local-storage` and `@usefy/use-session-storage`.
* Works like `useState` but the value is persisted in `document.cookie`.
*
* Features:
* - **`useState`-like tuple**: `[value, setValue, remove]`.
* - **Same-document sync**: multiple `useCookie(key)` instances stay in sync.
* - **SSR-safe**: guards all `document` access and returns `initialValue` on the
* server (uses `useSyncExternalStore`, identical to its storage siblings, to
* avoid hydration mismatches).
* - **Cookie attributes**: `expires`, `maxAge`, `path`, `domain`, `secure`,
* `sameSite`.
* - **Safe (de)serialization**: JSON by default, with a graceful fallback to the
* raw string for plain (non-JSON) cookies.
*
* > **Cross-tab note:** cookies have no `storage` event, so writes in *other*
* > tabs are not observed without polling. Same-document instances always sync.
*
* @template T - The type of the stored value
* @param key - The cookie name
* @param options - Serialization, initial value, and cookie write attributes
* @returns A tuple of `[value, setValue, remove]`
*
* @example
* ```tsx
* // Basic usage — a string cookie
* function ThemeToggle() {
* const [theme, setTheme, removeTheme] = useCookie("theme", {
* initialValue: "light",
* });
*
* return (
* <div>
* <p>Current theme: {theme}</p>
* <button onClick={() => setTheme("dark")}>Dark</button>
* <button onClick={removeTheme}>Reset</button>
* </div>
* );
* }
* ```
*
* @example
* ```tsx
* // With cookie attributes — persist for a week over HTTPS only
* const [token, setToken] = useCookie<string>("token", {
* expires: 7, // days (or a Date)
* path: "/",
* secure: true,
* sameSite: "strict",
* });
* ```
*
* @example
* ```tsx
* // Object value with a functional update (JSON serialized)
* interface Prefs { lang: string; compact: boolean }
* const [prefs, setPrefs] = useCookie<Prefs>("prefs", {
* initialValue: { lang: "en", compact: false },
* });
* setPrefs((prev) => ({ ...prev!, compact: true }));
* ```
*/
export function useCookie<T = string>(
key: string,
options: UseCookieOptions<T> = {}
): UseCookieReturn<T> {
const {
initialValue,
serializer = defaultSerializer,
deserializer = defaultDeserializer,
onError,
expires,
maxAge,
path,
domain,
secure,
sameSite,
} = options;
// Store options in refs for stable references and access to the latest values.
const serializerRef = useRef(serializer);
const deserializerRef = useRef(deserializer);
const onErrorRef = useRef(onError);
const initialValueRef = useRef(initialValue);
serializerRef.current = serializer;
deserializerRef.current = deserializer;
onErrorRef.current = onError;
initialValueRef.current = initialValue;
// Latest cookie write attributes, so setValue/remove stay stable across renders.
const attributesRef = useRef<CookieAttributes>({});
attributesRef.current = { expires, maxAge, path, domain, secure, sameSite };
// Cache for getSnapshot so it returns a stable reference when the raw cookie
// value is unchanged — required by useSyncExternalStore to avoid loops.
const cacheRef = useRef<{
rawValue: string | undefined;
parsedValue: T | undefined;
} | null>(null);
const isClient = isDocumentAvailable();
// Subscribe to same-document changes via the internal store.
const subscribeToStore = useCallback(
(onStoreChange: () => void) => {
return subscribe(key, onStoreChange);
},
[key]
);
// getSnapshot: read the current value from document.cookie with caching.
const getSnapshot = useCallback((): T | undefined => {
Iif (!isClient) {
return resolveInitialValue(initialValueRef.current);
}
try {
const rawValue = readRawCookie(key);
if (cacheRef.current && cacheRef.current.rawValue === rawValue) {
return cacheRef.current.parsedValue;
}
let parsedValue: T | undefined;
if (rawValue !== undefined) {
parsedValue = deserializerRef.current(rawValue);
} else {
parsedValue = resolveInitialValue(initialValueRef.current);
}
cacheRef.current = { rawValue, parsedValue };
return parsedValue;
} catch (error) {
onErrorRef.current?.(error as Error);
const fallbackValue = resolveInitialValue(initialValueRef.current);
cacheRef.current = { rawValue: undefined, parsedValue: fallbackValue };
return fallbackValue;
}
}, [key, isClient]);
// getServerSnapshot: return the initial value for SSR.
const getServerSnapshot = useCallback((): T | undefined => {
return resolveInitialValue(initialValueRef.current);
}, []);
const storedValue = useSyncExternalStore(
subscribeToStore,
getSnapshot,
getServerSnapshot
);
// setValue — stable reference that writes the cookie and notifies listeners.
const setValue = useCallback<React.Dispatch<React.SetStateAction<T | undefined>>>(
(value) => {
try {
if (!isDocumentAvailable()) return;
// Resolve the current value for functional updates.
const currentValue = (() => {
try {
const raw = readRawCookie(key);
Iif (raw !== undefined) {
return deserializerRef.current(raw);
}
return resolveInitialValue(initialValueRef.current);
} catch {
return resolveInitialValue(initialValueRef.current);
}
})();
const valueToStore =
value instanceof Function ? value(currentValue) : value;
const serialized = serializerRef.current(valueToStore as T);
document.cookie = buildCookieString(
key,
serialized,
attributesRef.current
);
// Invalidate cache so the next getSnapshot reads the fresh value.
cacheRef.current = { rawValue: serialized, parsedValue: valueToStore };
notifyListeners(key);
} catch (error) {
onErrorRef.current?.(error as Error);
}
},
[key]
);
// remove — stable reference that deletes the cookie and resets to initial.
const removeValue = useCallback(() => {
try {
if (!isDocumentAvailable()) return;
document.cookie = buildRemovalCookieString(key, attributesRef.current);
const initialVal = resolveInitialValue(initialValueRef.current);
cacheRef.current = { rawValue: undefined, parsedValue: initialVal };
notifyListeners(key);
} catch (error) {
onErrorRef.current?.(error as Error);
}
}, [key]);
return [storedValue, setValue, removeValue] as const;
}
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