feat(income): add account income analytics API

src/tbank/income-period.spec.ts

@@ -0,0 +1,48 @@
+import { BadRequestException } from '@nestjs/common';
+import {
+  dateOnlyBounds,
+  planIncomePeriod,
+  rangeBuckets,
+} from './income-period';
+
+describe('income period planning', () => {
+  afterEach(() => jest.useRealTimers());
+
+  it('uses the Moscow current month and validates strict inclusive ranges', () => {
+    jest.useFakeTimers();
+    jest.setSystemTime(new Date('2026-01-31T22:30:00.000Z'));
+
+    expect(planIncomePeriod(undefined, undefined)).toMatchObject({
+      selected: { from: '2026-02-01', to: '2026-02-01' },
+    });
+    for (const [from, to] of [
+      ['2026-02-30', '2026-03-01'],
+      ['2026-03-02', '2026-03-01'],
+      ['2026-01-01', '2027-01-02'],
+      ['2026-01-01', '2026-04-01'],
+    ])
+      expect(() => planIncomePeriod(from, to)).toThrow(BadRequestException);
+  });
+
+  it('uses a full previous month, skips impossible year-ago dates, and keeps empty buckets', () => {
+    const fullMonth = planIncomePeriod('2026-03-01', '2026-03-31');
+    expect(fullMonth.previous).toEqual({
+      from: '2026-02-01',
+      to: '2026-02-28',
+    });
+    expect(planIncomePeriod('2024-02-29', '2024-02-29').yearAgo).toBeNull();
+    expect(
+      rangeBuckets({ from: '2026-01-01', to: '2026-02-15' }, 'week'),
+    ).toHaveLength(7);
+  });
+
+  it('does not send the unfinished Moscow day as a future instant', () => {
+    jest.useFakeTimers();
+    jest.setSystemTime(new Date('2026-08-27T21:44:18.510Z'));
+
+    expect(dateOnlyBounds({ from: '2026-08-01', to: '2026-08-28' })).toEqual({
+      from: new Date('2026-07-31T21:00:00.000Z'),
+      to: new Date('2026-08-27T21:44:18.510Z'),
+    });
+  });
+});