dev_agent
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Co-authored-by: dev_agent <dev_agent@cubecraftlabs.com>
47 lines
2.1 KiB
TypeScript
47 lines
2.1 KiB
TypeScript
// The IANA time zones the browser knows, with their current UTC offsets, for
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// the household time zone picker.
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export type TimeZoneOption = {
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zone: string
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// "UTC-04:00"; "UTC+00:00" for UTC itself.
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offset: string
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}
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// utcOffset is zone's offset from UTC at instant, as "UTC+05:30".
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export function utcOffset(zone: string, instant: Date): string {
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const name = new Intl.DateTimeFormat('en-US', { timeZone: zone, timeZoneName: 'longOffset' })
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.formatToParts(instant)
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.find((part) => part.type === 'timeZoneName')?.value
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if (name === undefined) throw new Error(`no UTC offset for time zone "${zone}"`)
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if (name === 'GMT') return 'UTC+00:00'
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if (!/^GMT[+-]\d\d:\d\d$/.test(name)) throw new Error(`time zone "${zone}" has an unreadable offset "${name}"`)
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return `UTC${name.slice(3)}`
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}
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// Zones the server accepts that Intl.supportedValuesOf('timeZone') leaves
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// out: it lists only canonical zones, and UTC is not one of them.
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const unlistedZones = ['UTC', 'Etc/UTC', 'GMT', 'Etc/GMT']
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// timeZoneOptions lists every zone the browser supports, the unlisted UTC
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// zones, and kept (the saved and chosen zones, which may be aliases the
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// list leaves out), sorted by name.
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export function timeZoneOptions(kept: string[], instant: Date): TimeZoneOption[] {
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const zones = new Set([...Intl.supportedValuesOf('timeZone'), ...unlistedZones, ...kept])
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return [...zones].sort().map((zone) => ({ zone, offset: utcOffset(zone, instant) }))
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}
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// zoneLabel reads a zone as words: "America/Argentina/Buenos_Aires" is
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// "America / Argentina / Buenos Aires".
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export function zoneLabel(zone: string): string {
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return zone.replaceAll('_', ' ').replaceAll('/', ' / ')
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}
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// matchesZone is whether every word of the search text is in option's name
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// or offset, in any case.
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export function matchesZone(option: TimeZoneOption, search: string): boolean {
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const needle = search.trim().toLowerCase()
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if (needle === '') return true
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const haystack = `${option.zone} ${zoneLabel(option.zone)} ${option.offset}`.toLowerCase()
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return needle.split(/\s+/).every((word) => haystack.includes(word))
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}
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