refactor: centralize domain values and enforce numeric lint

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

@@ -1,3 +1,4 @@
+import { MILLISECONDS_PER_DAY } from '../../../common/time';
 import { BadRequestException } from '@nestjs/common';
 import {
   DateOnlyRange,
@@ -6,6 +7,12 @@ import {
   utcDate,
 } from '../investment-calendar';
 
+const DAILY_BUCKET_MAX_DAYS = 45;
+const WEEKLY_BUCKET_MAX_DAYS = 180;
+const DAYS_PER_WEEK = 7;
+const ISO_MONTH_LENGTH = 7;
+const ISO_YEAR_LENGTH = 4;
+
 export type IncomeBucketGranularity = 'day' | 'week' | 'month';
 
 export function planIncomePeriod(
@@ -36,9 +43,9 @@ export function planIncomePeriod(
     previous,
     yearAgo: yearAgoRange,
     granularity:
-      rangeDays(selected) <= 45
+      rangeDays(selected) <= DAILY_BUCKET_MAX_DAYS
         ? 'day'
-        : rangeDays(selected) <= 180
+        : rangeDays(selected) <= WEEKLY_BUCKET_MAX_DAYS
           ? 'week'
           : 'month',
   };
@@ -53,11 +60,19 @@ export function rangeBuckets(
   const buckets: DateOnlyRange[] = [];
   let cursor =
     granularity === 'week'
-      ? addDays(range.from, -((utcDate(range.from).getUTCDay() + 6) % 7))
-      : `${range.from.slice(0, 7)}-01`;
+      ? addDays(
+          range.from,
+          -(
+            (utcDate(range.from).getUTCDay() + DAYS_PER_WEEK - 1) %
+            DAYS_PER_WEEK
+          ),
+        )
+      : `${range.from.slice(0, ISO_MONTH_LENGTH)}-01`;
   while (cursor <= range.to) {
     const end =
-      granularity === 'week' ? addDays(cursor, 6) : endOfMonth(cursor);
+      granularity === 'week'
+        ? addDays(cursor, DAYS_PER_WEEK - 1)
+        : endOfMonth(cursor);
     buckets.push({
       from: cursor < range.from ? range.from : cursor,
       to: end > range.to ? range.to : end,
@@ -71,7 +86,7 @@ export function rangeDays(range: DateOnlyRange): number {
   return (
     Math.round(
       (utcDate(range.to).valueOf() - utcDate(range.from).valueOf()) /
-        86_400_000,
+        MILLISECONDS_PER_DAY,
     ) + 1
   );
 }
@@ -100,7 +115,7 @@ function dates(range: DateOnlyRange): string[] {
 }
 
 function firstOfMonth(value: string): string {
-  return `${value.slice(0, 7)}-01`;
+  return `${value.slice(0, ISO_MONTH_LENGTH)}-01`;
 }
 
 function endOfMonth(value: string): string {
@@ -126,7 +141,7 @@ function shiftDays(range: DateOnlyRange, days: number): DateOnlyRange {
 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')}-${String(day).padStart(2, '0')}`;
+    const result = `${String(year - 1).padStart(ISO_YEAR_LENGTH, '0')}-${String(month).padStart(2, '0')}-${String(day).padStart(2, '0')}`;
     return utcDate(result).toISOString().slice(0, 10) === result
       ? result
       : null;