wehub-resource-sync
99 lines
2.9 KiB
JavaScript
99 lines
2.9 KiB
JavaScript
/**
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* UserMetaCache
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*
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* Singleton in-memory cache for per-user browser metadata (timezone, language).
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* Keyed by numeric user ID in multi-user mode, or the string 'primary' in
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* single-user mode. Populated from the X-Timezone / X-Language request headers
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* on every authenticated HTTP request via the validatedRequest middleware.
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*
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* Because every request repopulates the cache from headers, the data stays
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* fresh within a session without any database writes.
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*
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* Usage:
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* const { UserMetaCache } = require("../userLocale");
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* UserMetaCache.set(userId, { timezone, lang });
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* const { timezone, lang } = UserMetaCache.get(userId);
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*/
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const DEFAULT_TIMEZONE = "UTC";
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const DEFAULT_LANG = "en";
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class _UserMetaCache {
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#cache = new Map();
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/**
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* Validate that a string is a recognised IANA timezone identifier.
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* @param {string} tz
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* @returns {boolean}
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*/
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#isValidTimezone(tz) {
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if (!tz || typeof tz !== "string") return false;
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try {
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Intl.DateTimeFormat(undefined, { timeZone: tz });
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return true;
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} catch {
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return false;
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}
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}
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/**
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* Normalise a user ID to a cache key.
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* @param {number|null|undefined} userId
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* @returns {number|'primary'}
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*/
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#key(userId) {
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return userId ?? "primary";
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}
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/**
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* Store or update locale metadata for a user.
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* Invalid timezone strings are silently ignored (existing/default value kept).
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*
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* @param {number|null} userId - Numeric user ID, or null for single-user mode.
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* @param {{ timezone?: string, lang?: string }} meta
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*/
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set(userId, { timezone, lang } = {}) {
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const key = this.#key(userId);
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const current = this.#cache.get(key) || {};
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this.#cache.set(key, {
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timezone:
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timezone && this.#isValidTimezone(timezone)
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? timezone
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: current.timezone || DEFAULT_TIMEZONE,
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lang: lang || current.lang || DEFAULT_LANG,
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});
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}
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/**
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* Retrieve locale metadata for a user.
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* Returns defaults if nothing has been cached yet.
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*
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* @param {number|null} userId - Numeric user ID, or null for single-user mode.
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* @returns {{ timezone: string, lang: string }}
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*/
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get(userId) {
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return (
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this.#cache.get(this.#key(userId)) || {
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timezone: DEFAULT_TIMEZONE,
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lang: DEFAULT_LANG,
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}
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);
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}
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/**
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* Read X-Timezone and X-Language from an Express request and store them.
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* Intended to be called from the validatedRequest middleware after auth.
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*
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* @param {import('express').Request} request
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* @param {number|null} userId - null for single-user mode (stored under 'primary')
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*/
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setFromRequest(request, userId = null) {
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const timezone = request.header("X-Timezone");
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const lang = request.header("X-Language");
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if (timezone || lang) this.set(userId, { timezone, lang });
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}
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}
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const UserMetaCache = new _UserMetaCache();
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module.exports = { UserMetaCache };
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