38 lines
1.5 KiB
TypeScript
38 lines
1.5 KiB
TypeScript
/** ISO-shaped time-context timestamp formatting shared by production and replay validation. */
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type TimestampPart = 'day' | 'hour' | 'minute' | 'month' | 'second' | 'timeZoneName' | 'year'
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/**
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* Create the exact formatter used by durable time-context readings.
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* @param timeZone - Explicit display zone, or `undefined` for the process fallback.
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* @returns A formatter with stable numeric local fields and long numeric offset.
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*/
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export function createTimestampFormatter(timeZone?: string): Intl.DateTimeFormat {
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return new Intl.DateTimeFormat('en-US', {
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...(timeZone === undefined ? {} : { timeZone }),
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year: 'numeric',
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month: '2-digit',
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day: '2-digit',
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hour: '2-digit',
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minute: '2-digit',
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second: '2-digit',
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hourCycle: 'h23',
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timeZoneName: 'longOffset',
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})
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}
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/**
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* Format an epoch millisecond value as an ISO-shaped timestamp with offset and IANA zone.
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* @param now - Epoch milliseconds to display.
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* @param formatter - Formatter created for `timeZone`.
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* @param timeZone - Canonical zone label carried in brackets.
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* @returns The durable timestamp text.
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*/
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export function formatTimestamp(now: number, formatter: Intl.DateTimeFormat, timeZone: string): string {
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const parts = Object.fromEntries(
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formatter.formatToParts(now).map(part => [part.type, part.value]),
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) as Record<TimestampPart, string>
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const offset = parts.timeZoneName.replace(/^GMT$/, 'GMT+00:00').slice(3)
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return `${parts['year']}-${parts['month']}-${parts['day']}T${parts['hour']}:${parts['minute']}:${parts['second']}${offset}[${timeZone}]`
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}
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