/**
* reminderDateParser.ts
* Helper utilities for parsing reminder dueDate strings safely across timezones.
*/
const DATE_ONLY_REGEX = /^\d{4}-\d{2}-\d{2}$/;
const DATE_ONLY_WITH_TZ_REGEX = /^(\d{4}-\d{2}-\d{2})(Z|[+-]\d{2}:?\d{2})$/i;
const DATE_TIME_NO_TZ_REGEX =
/^(\d{4}-\d{2}-\d{2})[ T](\d{2}):(\d{2})(?::(\d{2}))?(?:\.\d+)?$/;
const TIMEZONE_SUFFIX_REGEX = /(Z|[+-]\d{2}(?::?\d{2})?)$/i;
const toNumber = (value: string): number => Number.parseInt(value, 10);
const createLocalDate = (
year: number,
month: number,
day: number,
hour = 0,
minute = 0,
second = 0,
): Date | undefined => {
if ([year, month, day, hour, minute, second].some(Number.isNaN)) {
return undefined;
}
return new Date(year, month - 1, day, hour, minute, second, 0);
};
const normalizeTimezoneSegment = (segment: string): string => {
if (!segment) return segment;
if (segment === 'Z' || segment === 'z') return 'Z';
const clean = segment.replace(':', '').replace(' ', '');
if (clean.length === 3) {
return `${clean}:00`;
}
if (clean.length === 5) {
return `${clean.slice(0, 3)}:${clean.slice(3)}`;
}
return segment.includes(':')
? segment
: `${segment.slice(0, 3)}:${segment.slice(3)}`;
};
const normalizeIsoString = (value: string): string => {
let normalized = value.trim();
if (normalized.includes(' ') && normalized.indexOf(' ') === 10) {
normalized = `${normalized.slice(0, 10)}T${normalized.slice(11)}`;
}
normalized = normalized.replace(TIMEZONE_SUFFIX_REGEX, (match) =>
normalizeTimezoneSegment(match),
);
return normalized;
};
const parseWithNative = (value: string): Date | undefined => {
const normalized = normalizeIsoString(value);
const parsed = new Date(normalized);
return Number.isNaN(parsed.getTime()) ? undefined : parsed;
};
/**
* Parses reminder dueDate strings into Date objects without losing local timezone semantics.
*/
export const parseReminderDueDate = (
dueDate?: string | null,
): Date | undefined => {
if (!dueDate) return undefined;
const trimmed = dueDate.trim();
if (!trimmed) return undefined;
if (DATE_ONLY_REGEX.test(trimmed)) {
const [year, month, day] = trimmed.split('-').map(toNumber);
return createLocalDate(year, month, day);
}
const dateWithTzMatch = trimmed.match(DATE_ONLY_WITH_TZ_REGEX);
if (dateWithTzMatch) {
const [, datePart, tzSegment] = dateWithTzMatch;
return parseWithNative(
`${datePart}T00:00:00${normalizeTimezoneSegment(tzSegment)}`,
);
}
const localDateTimeMatch = trimmed.match(DATE_TIME_NO_TZ_REGEX);
if (localDateTimeMatch) {
const [, datePart, hourStr, minuteStr, secondStr] = localDateTimeMatch;
const [year, month, day] = datePart.split('-').map(toNumber);
const hour = toNumber(hourStr);
const minute = toNumber(minuteStr);
const second = secondStr ? toNumber(secondStr) : 0;
return createLocalDate(year, month, day, hour, minute, second);
}
if (TIMEZONE_SUFFIX_REGEX.test(trimmed)) {
return parseWithNative(trimmed);
}
return parseWithNative(trimmed);
};
