refactor: organize backend by business responsibility

src/modules/investments/income/income-period.ts

@@ -0,0 +1,141 @@
+import { BadRequestException } from '@nestjs/common';
+import {
+  DateOnlyRange,
+  dateParts,
+  moscowDate,
+  utcDate,
+} from '../investment-calendar';
+
+export type IncomeBucketGranularity = 'day' | 'week' | 'month';
+
+export function planIncomePeriod(
+  from: string | undefined,
+  to: string | undefined,
+  openedDate?: Date,
+): {
+  selected: DateOnlyRange;
+  previous: DateOnlyRange;
+  yearAgo: DateOnlyRange | null;
+  granularity: IncomeBucketGranularity;
+} {
+  if (Boolean(from) !== Boolean(to)) throw invalidPeriod();
+  const today = moscowDate(new Date());
+  const selected =
+    from && to ? { from, to } : { from: firstOfMonth(today), to: today };
+  assertRange(selected, today);
+  const previous = isFullMonth(selected)
+    ? previousMonth(selected.from)
+    : shiftDays(selected, -rangeDays(selected));
+  const candidate = yearAgo(selected);
+  const yearAgoRange =
+    candidate && (!openedDate || candidate.from >= moscowDate(openedDate))
+      ? candidate
+      : null;
+  return {
+    selected,
+    previous,
+    yearAgo: yearAgoRange,
+    granularity:
+      rangeDays(selected) <= 45
+        ? 'day'
+        : rangeDays(selected) <= 180
+          ? 'week'
+          : 'month',
+  };
+}
+
+export function rangeBuckets(
+  range: DateOnlyRange,
+  granularity: IncomeBucketGranularity,
+): DateOnlyRange[] {
+  if (granularity === 'day')
+    return dates(range).map((date) => ({ from: date, to: date }));
+  const buckets: DateOnlyRange[] = [];
+  let cursor =
+    granularity === 'week'
+      ? addDays(range.from, -((utcDate(range.from).getUTCDay() + 6) % 7))
+      : `${range.from.slice(0, 7)}-01`;
+  while (cursor <= range.to) {
+    const end =
+      granularity === 'week' ? addDays(cursor, 6) : endOfMonth(cursor);
+    buckets.push({
+      from: cursor < range.from ? range.from : cursor,
+      to: end > range.to ? range.to : end,
+    });
+    cursor = addDays(end, 1);
+  }
+  return buckets;
+}
+
+export function rangeDays(range: DateOnlyRange): number {
+  return (
+    Math.round(
+      (utcDate(range.to).valueOf() - utcDate(range.from).valueOf()) /
+        86_400_000,
+    ) + 1
+  );
+}
+
+function assertRange(range: DateOnlyRange, today: string): void {
+  try {
+    dateParts(range.from);
+    dateParts(range.to);
+  } catch {
+    throw invalidPeriod();
+  }
+  if (range.from > range.to || range.to > today) throw invalidPeriod();
+}
+
+function addDays(value: string, days: number): string {
+  const date = utcDate(value);
+  date.setUTCDate(date.getUTCDate() + days);
+  return date.toISOString().slice(0, 10);
+}
+
+function dates(range: DateOnlyRange): string[] {
+  const result: string[] = [];
+  for (let date = range.from; date <= range.to; date = addDays(date, 1))
+    result.push(date);
+  return result;
+}
+
+function firstOfMonth(value: string): string {
+  return `${value.slice(0, 7)}-01`;
+}
+
+function endOfMonth(value: string): string {
+  const [year, month] = dateParts(firstOfMonth(value));
+  return new Date(Date.UTC(year, month, 0)).toISOString().slice(0, 10);
+}
+
+function isFullMonth(range: DateOnlyRange): boolean {
+  return (
+    range.from === firstOfMonth(range.from) && range.to === endOfMonth(range.to)
+  );
+}
+
+function previousMonth(from: string): DateOnlyRange {
+  const last = addDays(firstOfMonth(from), -1);
+  return { from: firstOfMonth(last), to: last };
+}
+
+function shiftDays(range: DateOnlyRange, days: number): DateOnlyRange {
+  return { from: addDays(range.from, days), to: addDays(range.to, days) };
+}
+
+function yearAgo(range: DateOnlyRange): DateOnlyRange | null {
+  const shift = (value: string) => {
+    const [year, month, day] = dateParts(value);
+    const result = `${String(year - 1).padStart(4, '0')}-${String(month).padStart(2, '0')}-${String(day).padStart(2, '0')}`;
+    return utcDate(result).toISOString().slice(0, 10) === result
+      ? result
+      : null;
+  };
+  const from = shift(range.from);
+  const to = shift(range.to);
+  return from && to ? { from, to } : null;
+}
+
+function invalidPeriod(): BadRequestException {
+  return new BadRequestException({ code: 'INVALID_INCOME_PERIOD' });
+}