Cookie Manager

CookieManager.ts

/** Flags we put at the start of each cookie value so we know how to parse them. */
enum CookieTypeMap {
    Boolean = `b`,
    Number = `n`,
    Object = `o`,
    String = `s`,
}

/**
 * Options when setting this cookie.
 *
 * {@link https://developer.mozilla.org/en-US/docs/Web/API/Document/cookie#write_a_new_cookie API Reference}
 */
interface CookieOptions {
    /**
     * How long until this cookie expires, in seconds.
     *
     * This get's applied as the `max-age` property, and defaults to the end of
     * the session if omitted.
     *
     * @example 60 * 60 * 24 * 365 (1 year)
     */
    expiresIn?: number;

    /**
     * Whether this cookie should only be transmitted over HTTPS.
     *
     * @default false
     */
    secure?: boolean;

    /**
     * Whether to prevent the browser from sending this cookie along cross-site requests.
     *
     * - `lax` - Send in same-site and and top-level navigation `GET` requests.
     * - `strict` - Send in same-site only.
     * - `none` - Send in same-site and cross-site.
     *
     * @default `none` (In modern browsers)
     */
    sameSite?: `lax` | `strict` | `none`;
}

/**
 * Manages geting and setting typed cookie values.
 *
 * Works with boolean, number, string, and JSON objects.
 *
 * {@link https://developer.mozilla.org/en-US/docs/Web/API/Document/cookie API Reference}
 */
export default class CookieManager<T = Record<string, unknown>> {
    public set<K extends keyof T>(key: K, value: T[K], options?: CookieOptions): void {
        let finalVal: string;
        let finalType: CookieTypeMap;

        switch (typeof value) {
            case `boolean`:
                finalVal = String(value);
                finalType = CookieTypeMap.Boolean;
                break;
            case `number`:
                finalVal = value.toString();
                finalType = CookieTypeMap.Number;
                break;
            case `object`:
                finalVal = JSON.stringify(value);
                finalType = CookieTypeMap.Object;
                break;
            case `string`:
                finalVal = value;
                finalType = CookieTypeMap.String;
                break;
            default:
                throw new Error(`Unsupported value type for ${String(key)}: ${typeof value}`);
        }

        const optionArray = new Array<string>();
        if (options?.expiresIn !== undefined) {
            optionArray.push(`;max-age=${options.expiresIn}`);
        }
        if (options?.secure === true) {
            optionArray.push(`;secure`);
        }
        if (options?.sameSite !== undefined) {
            if (options.sameSite === `none` && options.secure !== true) {
                throw new Error(
                    `Cannot set 'sameSite=None' without also setting 'Secure'. See https://web.dev/samesite-cookies-explained/#samesite=none-must-be-secure for more info`,
                );
            }
            optionArray.push(`;samesite=${options.sameSite}`);
        }

        finalVal = encodeURIComponent(finalType + finalVal);

        document.cookie = `${String(key)}=${finalVal}${optionArray.join(``)}`;
    }

    public get<K extends keyof T>(key: K): T[K] | undefined {
        let row = document.cookie
            .split(`; `)
            .find((row) => row.startsWith(`${String(key)}=`))
            ?.slice(`${String(key)}=`.length);
        if (row === undefined) return undefined;

        let output: boolean | string | number;

        row = decodeURIComponent(row);

        switch (row[0] as CookieTypeMap) {
            case CookieTypeMap.Boolean:
                if (row.slice(1) === `true`) output = true;
                else if (row.slice(1) === `false`) output = false;
                else
                    throw new Error(
                        `Unrecognized value for ${String(key)} (expected 'true' or 'false'): ${row.slice(1)}`,
                    );
                break;
            case CookieTypeMap.Number:
                output = Number(row.slice(1));
                if (Number.isNaN(output)) {
                    throw new Error(`Unrecognized value for ${String(key)} (expected valid number): ${row.slice(1)}`);
                }
                break;
            case CookieTypeMap.Object:
                try {
                    output = JSON.parse(row.slice(1));
                } catch (error) {
                    throw new Error(`Unrecognized value for ${String(key)} (expected JSON object): ${row.slice(1)}`);
                }
                break;
            case CookieTypeMap.String:
                output = row.slice(1);
                break;
            default:
                throw new Error(`Unrecognized value type for ${String(key)}: ${row[0]}`);
        }

        return output as T[K];
    }
}