lorentz
2ac2db7a23
- New lib/hooks/use-user-timezone.ts exporting useUserTimezone() and formatInUserTimezone()
- Reads user.timezone from Better Auth useSession() additionalField (Plan 01)
- Validates against Intl.supportedValuesOf('timeZone') with safe fallback to NEXT_PUBLIC_DEFAULT_TIMEZONE || 'UTC'
- Pure formatInUserTimezone helper safe to call inside loops (not a hook)
- Resolves TZ-04
61 lines
2.2 KiB
TypeScript
61 lines
2.2 KiB
TypeScript
"use client";
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import { useSession } from "@/lib/auth-client";
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// Public-readable default (Next.js exposes NEXT_PUBLIC_* to the browser).
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// Operators can set this in .env.local to match the server-side
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// DEFAULT_TIMEZONE. If unset, both server and client default to 'UTC'.
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function getClientDefaultTimezone(): string {
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return process.env.NEXT_PUBLIC_DEFAULT_TIMEZONE || "UTC";
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}
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function isValidIanaTimezone(tz: unknown): tz is string {
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if (typeof tz !== "string" || tz.length === 0 || tz.length > 64) return false;
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try {
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return Intl.supportedValuesOf("timeZone").includes(tz);
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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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* useUserTimezone — TZ-04.
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*
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* Returns the calling user's IANA timezone string, sourced from the
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* Better Auth additionalField on `useSession()`. Falls back to
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* `process.env.NEXT_PUBLIC_DEFAULT_TIMEZONE || 'UTC'` while the session
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* is loading, when the field is missing, or when the stored value is
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* not a recognized IANA zone.
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*
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* This is the ONLY supported way to read the user's tz on the client.
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* Do NOT call `Intl.DateTimeFormat()` with a hardcoded zone or rely on
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* the browser's local zone — the user may have travelled or set a
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* preference that differs from the device.
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*/
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export function useUserTimezone(): string {
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const { data } = useSession();
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// Better Auth additionalField is typed `string` post-Plan-01; defence
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// in depth: validate before returning.
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const raw = (data?.user as { timezone?: unknown } | undefined)?.timezone;
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if (isValidIanaTimezone(raw)) return raw;
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return getClientDefaultTimezone();
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}
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/**
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* formatInUserTimezone — convenience wrapper for the common case of
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* "format an ISO string in the user's tz". Equivalent to
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* `new Date(iso).toLocaleString(locale, { ...options, timeZone: tz })`.
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*
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* Pass `tz` from `useUserTimezone()` and the same options object you'd
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* pass to toLocaleString / toLocaleDateString — this helper keeps
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* existing format strings working without rewrites.
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*/
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export function formatInUserTimezone(
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input: string | number | Date,
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tz: string,
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options?: Intl.DateTimeFormatOptions,
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locale: string = "en-US",
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): string {
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const date = input instanceof Date ? input : new Date(input);
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return date.toLocaleString(locale, { ...options, timeZone: tz });
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}
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