feat(miniapp): improve billing settings controls

apps/miniapp/src/lib/timezones.ts

@@ -0,0 +1,93 @@
+const CURATED_TIMEZONES = [
+  'Asia/Tbilisi',
+  'Europe/Berlin',
+  'Europe/London',
+  'Europe/Paris',
+  'Europe/Warsaw',
+  'America/New_York',
+  'America/Chicago',
+  'America/Denver',
+  'America/Los_Angeles',
+  'Asia/Dubai',
+  'Asia/Bangkok',
+  'Asia/Tokyo',
+  'Australia/Sydney'
+] as const
+
+const CURATED_TIMEZONE_SET = new Set<string>(CURATED_TIMEZONES)
+
+type IntlWithSupportedValues = typeof Intl & {
+  supportedValuesOf?: (key: 'timeZone') => readonly string[]
+}
+
+function supportedTimezones(): readonly string[] {
+  const withSupportedValues = Intl as IntlWithSupportedValues
+
+  if (typeof withSupportedValues.supportedValuesOf === 'function') {
+    try {
+      const supported = withSupportedValues.supportedValuesOf('timeZone')
+      if (supported.length > 0) {
+        return supported
+      }
+    } catch {
+      // Ignore and fall back to the curated list below.
+    }
+  }
+
+  return CURATED_TIMEZONES
+}
+
+const TIMEZONES = [
+  ...CURATED_TIMEZONES,
+  ...supportedTimezones()
+    .filter((timezone) => !CURATED_TIMEZONE_SET.has(timezone))
+    .sort((left, right) => left.localeCompare(right))
+]
+
+export function canonicalizeTimezone(value: string): string | null {
+  const trimmed = value.trim()
+
+  if (trimmed.length === 0) {
+    return null
+  }
+
+  try {
+    return new Intl.DateTimeFormat('en-US', {
+      timeZone: trimmed
+    }).resolvedOptions().timeZone
+  } catch {
+    return null
+  }
+}
+
+export function isValidTimezone(value: string): boolean {
+  return canonicalizeTimezone(value) !== null
+}
+
+export function searchTimezones(query: string, limit = 10): readonly string[] {
+  const trimmed = query.trim()
+
+  if (trimmed.length === 0) {
+    return TIMEZONES.slice(0, limit)
+  }
+
+  const normalized = trimmed.toLowerCase()
+  const matches = TIMEZONES.filter((timezone) => timezone.toLowerCase().includes(normalized))
+
+  if (matches.length === 0) {
+    return TIMEZONES.slice(0, limit)
+  }
+
+  matches.sort((left, right) => {
+    const leftStartsWith = left.toLowerCase().startsWith(normalized)
+    const rightStartsWith = right.toLowerCase().startsWith(normalized)
+
+    if (leftStartsWith !== rightStartsWith) {
+      return leftStartsWith ? -1 : 1
+    }
+
+    return left.localeCompare(right)
+  })
+
+  return matches.slice(0, limit)
+}