initial commit

convex/lib/month.ts

@@ -0,0 +1,77 @@
+export type SalaryShiftSettings = {
+  enabled: boolean;
+  categoryNames: string[];
+  dayThreshold: number;
+};
+
+export function bookingMonth(bookingDate?: string): string | undefined {
+  if (!bookingDate) return undefined;
+  return bookingDate.slice(0, 7);
+}
+
+export function computeEffectiveMonth(
+  bookingDate: string | undefined,
+  assignedMonth: string | undefined,
+): string | undefined {
+  if (assignedMonth) return assignedMonth;
+  return bookingMonth(bookingDate);
+}
+
+export function addMonthsToMonthKey(monthKey: string, months: number): string {
+  const [yearStr, monthStr] = monthKey.split("-");
+  const date = new Date(Number(yearStr), Number(monthStr) - 1 + months, 1);
+  const y = date.getFullYear();
+  const m = String(date.getMonth() + 1).padStart(2, "0");
+  return `${y}-${m}`;
+}
+
+export function getDayFromDate(dateStr: string): number {
+  return Number(dateStr.slice(8, 10));
+}
+
+export function applySalaryShiftRule(
+  bookingDate: string | undefined,
+  amount: number,
+  categoryName: string | undefined,
+  salaryShift: SalaryShiftSettings,
+  existingAssignedMonth?: string,
+): string | undefined {
+  if (existingAssignedMonth) return existingAssignedMonth;
+  if (!salaryShift.enabled || !bookingDate || amount <= 0 || !categoryName) {
+    return undefined;
+  }
+  if (!salaryShift.categoryNames.includes(categoryName)) {
+    return undefined;
+  }
+  const day = getDayFromDate(bookingDate);
+  if (day < salaryShift.dayThreshold) {
+    return undefined;
+  }
+  const booking = bookingMonth(bookingDate);
+  if (!booking) return undefined;
+  return addMonthsToMonthKey(booking, 1);
+}
+
+export function resolveAssignedAndEffective(
+  bookingDate: string | undefined,
+  amount: number,
+  categoryName: string | undefined,
+  salaryShift: SalaryShiftSettings,
+  manualAssignedMonth?: string,
+): { assignedMonth?: string; effectiveMonth?: string } {
+  const assignedMonth =
+    manualAssignedMonth ??
+    applySalaryShiftRule(bookingDate, amount, categoryName, salaryShift);
+  const effectiveMonth = computeEffectiveMonth(bookingDate, assignedMonth);
+  return { assignedMonth, effectiveMonth };
+}
+
+export function monthKeyFromBasis(
+  tx: { bookingDate?: string; effectiveMonth?: string },
+  basis: "effective" | "booking",
+): string | undefined {
+  if (basis === "effective") {
+    return tx.effectiveMonth ?? bookingMonth(tx.bookingDate);
+  }
+  return bookingMonth(tx.bookingDate);
+}