Mattsson
885dd8a2e4
* feat: implement fiscal period date fields component and validation logic * feat: update fiscal period validation and naming logic
72 lines
2.6 KiB
TypeScript
72 lines
2.6 KiB
TypeScript
/**
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* Validates fiscal period duration per BFL 3 kap.
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* Maximum 18 months for any fiscal period (first year may be extended).
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* Normal ongoing periods are 12 months.
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*/
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/**
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* Parse a YYYY-MM-DD string into numeric parts without timezone issues.
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* Using new Date(dateStr) is unsafe because it creates UTC midnight,
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* but getDate()/getMonth()/getFullYear() return local-timezone values —
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* shifting the date by -1 day in Western timezones.
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*/
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export function parseDateParts(dateStr: string): { year: number; month: number; day: number } {
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const [year, month, day] = dateStr.split('-').map(Number)
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return { year, month, day }
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}
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/**
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* Calculate the number of months between two dates (inclusive of partial months).
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* Uses year/month arithmetic only — a mid-month start counts the start month fully,
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* which is conservative for the 18-month cap check.
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*/
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export function monthsBetween(start: string, end: string): number {
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const s = parseDateParts(start)
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const e = parseDateParts(end)
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return (e.year - s.year) * 12 + (e.month - s.month) + 1
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}
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export interface ValidatePeriodOptions {
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/** Allow any start day (not just 1st of month) for the first fiscal period per BFL 3 kap. */
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isFirstPeriod?: boolean
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}
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/**
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* Validate a fiscal period's duration and date constraints.
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* Returns null if valid, or an error message string if invalid.
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*/
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export function validatePeriodDuration(start: string, end: string, options?: ValidatePeriodOptions): string | null {
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const startParts = parseDateParts(start)
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const endParts = parseDateParts(end)
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// end must be after start (YYYY-MM-DD strings are lexicographically orderable)
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if (end <= start) {
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return 'Period end must be after period start'
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}
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// start must be 1st of month — unless this is the first fiscal period (BFL 3 kap.)
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if (startParts.day !== 1 && !options?.isFirstPeriod) {
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return 'Period start must be the 1st of a month'
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}
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// end must be last day of month
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// new Date(year, 1-indexed-month, 0) gives the last day of that month
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const lastDayOfEndMonth = new Date(endParts.year, endParts.month, 0).getDate()
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if (endParts.day !== lastDayOfEndMonth) {
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return 'Period end must be the last day of a month'
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}
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// Max 18 months per BFL 3 kap.
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const months = monthsBetween(start, end)
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if (months > 18) {
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return `Period duration ${months} months exceeds maximum 18 months (BFL 3 kap.)`
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}
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// First fiscal period must be at least 6 months per BFL 3 kap.
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if (options?.isFirstPeriod && months < 6) {
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return `First fiscal period must be at least 6 months (BFL 3 kap.)`
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}
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return null
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}
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