82 lines
2.2 KiB
TypeScript
82 lines
2.2 KiB
TypeScript
/**
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* Format an ISO timestamp for the brief/chat message label line.
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*
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* Display scales with age (like a messaging app):
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* - same day: "1:30 PM" or "13:30" (locale-dependent)
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* - within 6 days: "Sunday, 4:15 PM" (locale-dependent)
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* - older: "Sunday, Feb 20, 4:30 PM" (locale-dependent)
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*
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* Respects POSIX locale env vars (LC_ALL > LC_TIME > LANG) for time format
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* (12h/24h), weekday names, month names, and overall structure.
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* Bun/V8's `toLocaleString(undefined)` ignores these on macOS, so we
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* convert them to BCP 47 tags ourselves.
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*
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* `now` is injectable for tests.
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*/
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export function formatBriefTimestamp(
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isoString: string,
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now: Date = new Date(),
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): string {
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const d = new Date(isoString)
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if (Number.isNaN(d.getTime())) {
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return ''
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}
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const locale = getLocale()
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const dayDiff = startOfDay(now) - startOfDay(d)
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const daysAgo = Math.round(dayDiff / 86_400_000)
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if (daysAgo === 0) {
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return d.toLocaleTimeString(locale, {
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hour: 'numeric',
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minute: '2-digit',
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})
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}
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if (daysAgo > 0 && daysAgo < 7) {
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return d.toLocaleString(locale, {
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weekday: 'long',
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hour: 'numeric',
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minute: '2-digit',
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})
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}
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return d.toLocaleString(locale, {
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weekday: 'long',
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month: 'short',
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day: 'numeric',
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hour: 'numeric',
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minute: '2-digit',
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})
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}
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/**
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* Derive a BCP 47 locale tag from POSIX env vars.
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* LC_ALL > LC_TIME > LANG, falls back to undefined (system default).
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* Converts POSIX format (en_GB.UTF-8) to BCP 47 (en-GB).
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*/
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function getLocale(): string | undefined {
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const raw =
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process.env.LC_ALL || process.env.LC_TIME || process.env.LANG || ''
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if (!raw || raw === 'C' || raw === 'POSIX') {
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return undefined
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}
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// Strip codeset (.UTF-8) and modifier (@euro), replace _ with -
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const base = raw.split('.')[0]!.split('@')[0]!
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if (!base) {
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return undefined
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}
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const tag = base.replaceAll('_', '-')
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// Validate by trying to construct an Intl locale — invalid tags throw
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try {
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new Intl.DateTimeFormat(tag)
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return tag
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} catch {
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return undefined
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}
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}
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function startOfDay(d: Date): number {
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return new Date(d.getFullYear(), d.getMonth(), d.getDate()).getTime()
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}
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