feat(plans): adjust local draft schedule dates

frontend/src/__tests__/plan-draft-dates.test.ts

@@ -0,0 +1,37 @@
+import { draftDateDay, redistributeDraftDates, validateDraftDates } from '../lib/plan-draft-dates';
+
+beforeEach(() => jest.useFakeTimers({ now: new Date('2026-10-15T23:59:00Z') }));
+afterEach(() => jest.useRealTimers());
+
+test.each(['', '2026-02-30', '2027-02-29', '2026-13-01', '2026-1-01', '0000-01-01', '10000-01-01', 'Infinity'])('rejects invalid UTC date %s', date => {
+  expect(() => draftDateDay(date)).toThrow(/valid UTC/);
+});
+
+test('uses calendar days through leap years, year rollover and DST boundaries', () => {
+  for (const [first, last] of [['2028-02-28', '2028-02-29'], ['2026-12-31', '2027-01-01'], ['2026-10-24', '2026-10-25']]) {
+    expect(draftDateDay(last!) - draftDateDay(first!)).toBe(1);
+  }
+  expect(Number.isFinite(draftDateDay('0001-01-01'))).toBe(true);
+  expect(Number.isFinite(draftDateDay('9999-12-31'))).toBe(true);
+});
+
+test('checks fresh UTC today and strict step order at every operation', () => {
+  expect(() => validateDraftDates(['2026-10-16', '2026-10-17'])).not.toThrow();
+  for (const dates of [['2026-10-15'], ['2026-10-20', '2026-10-20'], ['2026-10-21', '2026-10-20']]) {
+    expect(() => validateDraftDates(dates)).toThrow();
+  }
+  jest.setSystemTime(new Date('2026-10-16T00:00:00Z'));
+  expect(() => validateDraftDates(['2026-10-16'])).toThrow(/future/);
+});
+
+test('redistributes the same count with rounded dates, including one and one hundred steps', () => {
+  const dates = ['2026-10-20', '2026-10-27', '2026-11-03'];
+  expect(redistributeDraftDates(dates, '2026-10-20', '2026-10-25')).toEqual(['2026-10-20', '2026-10-23', '2026-10-25']);
+  expect(dates[1]).toBe('2026-10-27');
+  expect(redistributeDraftDates([dates[0]!], '2026-10-21', '2026-10-21')).toEqual(['2026-10-21']);
+  const dense = redistributeDraftDates(Array.from({ length: 100 }, () => dates[0]!), '2026-10-20', '2027-01-27');
+  expect(new Set(dense).size).toBe(100);
+  expect(dense[99]).toBe('2027-01-27');
+  expect(() => redistributeDraftDates(dense, '2026-10-20', '2027-01-26')).toThrow(/one calendar day/);
+  expect(() => redistributeDraftDates(dates, '2026-10-21', '2026-10-20')).toThrow();
+});

frontend/src/__tests__/plan-schedule-preview.test.ts

@@ -29,7 +29,7 @@ test('shows truthful hypothetical dates, preserves parent values, and restores f
   expect((document.getElementById('preview-selected-date') as HTMLInputElement).value).toBe('2026-11-10');
   point.dispatchEvent(new KeyboardEvent('keydown', { key: 'ArrowLeft', bubbles: true }));
   expect(document.getElementById('preview-selected-step')?.textContent).toBe('Step 3');
-  expect(preview.querySelector('details')?.open).toBe(false);
+  expect(preview.querySelector<HTMLDetailsElement>('aside details')?.open).toBe(false);
   preview.dispatchEvent(new KeyboardEvent('keydown', { key: 'Escape', bubbles: true }));
   expect(document.getElementById('plan-schedule-preview')).toBeNull();
   expect(parent.inert).toBeFalsy();
@@ -61,3 +61,97 @@ test.each([
 test('uses UTC calendar dates across a year boundary for both real callers', () => {
   expect(suggestedPurchaseStartDate(3, new Date('2026-12-31T23:59:00Z'))).toBe('2027-01-05');
 });
+
+const field = (id: string): HTMLInputElement => document.getElementById(id) as HTMLInputElement;
+const changeDate = (id: string, value: string): void => {
+  const input = field(id);
+  input.focus(); input.value = value;
+  input.dispatchEvent(new Event('input', { bubbles: true }));
+  input.dispatchEvent(new Event('change', { bubbles: true }));
+};
+const point = (index: number): SVGGElement => document.querySelector(`[data-preview-step="${index}"]`)!;
+
+test('edits actual draft dates, guards collisions and preserves nodes, shares and parent values', () => {
+  openPlanSchedulePreview(draft, parent);
+  const input = field('preview-selected-date'), first = point(0);
+  expect(input.readOnly).toBe(false);
+  changeDate(input.id, '2026-10-21');
+  expect(first.getAttribute('aria-label')).toContain('2026-10-21, target 20%');
+  expect(point(0)).toBe(first);
+  first.dispatchEvent(new KeyboardEvent('keydown', { key: 'ArrowRight', altKey: true, bubbles: true }));
+  expect(input.value).toBe('2026-10-22');
+  expect(document.querySelectorAll('[data-preview-step]')).toHaveLength(4);
+  changeDate(input.id, '2026-10-27');
+  expect(first.getAttribute('aria-label')).toContain('2026-10-22');
+  expect(input.value).toBe('2026-10-27');
+  expect(field('preview-range-start').disabled).toBe(true);
+  point(2).dispatchEvent(new Event('click'));
+  expect(field(input.id)).toBe(input);
+  expect(document.activeElement).toBe(input);
+  expect(document.getElementById('preview-selected-step')?.textContent).toBe('Step 1');
+  expect(document.getElementById('preview-date-error')?.textContent).toMatch(/order/);
+  field('preview-reset-dates').click();
+  expect(input.value).toBe('2026-10-20');
+  expect(document.getElementById('preview-date-error')?.textContent).toBe('');
+  expect(parent.querySelector('input')?.value).toBe('unchanged');
+  expect(document.body.textContent).toContain('Save Plan does not apply these date edits');
+});
+
+test('retains partial paired inputs for correction and shows initial-to-draft differences', () => {
+  openPlanSchedulePreview(draft, parent);
+  const start = field('preview-range-start'), end = field('preview-range-end');
+  start.focus(); start.value = ''; start.dispatchEvent(new Event('input'));
+  point(0).dispatchEvent(new KeyboardEvent('keydown', { key: 'ArrowRight', bubbles: true }));
+  expect(start.value).toBe('');
+  expect(document.activeElement).toBe(start);
+  changeDate(start.id, '2026-11-20');
+  expect(start.value).toBe('2026-11-20');
+  expect(end.disabled).toBe(false);
+  expect(point(0).getAttribute('aria-label')).toContain('2026-10-20');
+  changeDate(end.id, '2026-12-10');
+  expect(document.activeElement).toBe(end);
+  expect(field(end.id)).toBe(end);
+  expect(point(2).getAttribute('aria-label')).toContain('2026-12-03');
+  expect(document.getElementById('preview-date-changes')?.textContent).toContain('2026-10-20 → 2026-11-20');
+  expect(field('preview-selected-date').disabled).toBe(false);
+});
+
+test('keeps single-step and legacy33 targets while exposing overlapping points through the Step selector', () => {
+  openPlanSchedulePreview({ ...draft, preset: 'immediate' }, parent);
+  expect(document.getElementById('preview-range-end')).toBeNull();
+  changeDate('preview-range-start', '2026-10-21');
+  expect(point(0).getAttribute('aria-label')).toContain('2026-10-21, target 80%');
+  openPlanSchedulePreview({ ...draft, preset: 'custom', stepPercent: '33' }, parent);
+  changeDate('preview-range-end', '2026-10-22');
+  expect(point(2).getAttribute('aria-label')).toContain('2026-10-22, target 79.2%');
+  openPlanSchedulePreview({ ...draft, coverage: '0' }, parent);
+  changeDate('preview-range-end', '2027-10-20');
+  const selector = document.getElementById('preview-step-select') as HTMLSelectElement;
+  for (const [index, date] of [[1, '2026-10-21'], [2, '2026-10-22']] as const) {
+    selector.value = String(index); selector.dispatchEvent(new Event('change'));
+    changeDate('preview-selected-date', date);
+  }
+  const left = (index: number): number => Number(point(index).querySelector('circle')!.getAttribute('cx'));
+  expect(left(1) - left(0)).toBeLessThan(3);
+  for (let index = 0; index < 4; index++) {
+    selector.value = String(index); selector.dispatchEvent(new Event('change'));
+    expect(point(index).getAttribute('aria-pressed')).toBe('true');
+    expect(field('preview-selected-date').value).toBe(['2026-10-20', '2026-10-21', '2026-10-22', '2027-10-20'][index]);
+  }
+});
+
+test('rechecks operation-time UTC midnight and refuses stale reset without replacing repaired dates', () => {
+  openPlanSchedulePreview(draft, parent);
+  jest.setSystemTime(new Date('2026-10-20T00:00:00Z'));
+  changeDate('preview-selected-date', '2026-10-21');
+  expect(point(0).getAttribute('aria-label')).toContain('2026-10-21');
+  changeDate('preview-range-end', '2026-11-11');
+  field('preview-reset-dates').click();
+  expect(point(0).getAttribute('aria-label')).toContain('2026-10-21');
+  expect(document.getElementById('preview-date-error')?.textContent).toMatch(/reopen/i);
+  point(2).dispatchEvent(new Event('click'));
+  jest.setSystemTime(new Date('2026-10-21T00:00:00Z'));
+  point(2).dispatchEvent(new KeyboardEvent('keydown', { key: 'ArrowRight', altKey: true, bubbles: true }));
+  expect(point(2).getAttribute('aria-label')).toContain('2026-11-04');
+  expect(document.getElementById('preview-date-error')?.textContent).toMatch(/future/);
+});

frontend/src/lib/plan-draft-dates.ts

@@ -0,0 +1,27 @@
+const DAY = 86_400_000;
+
+export function draftDateDay(date: string): number {
+  const time = Date.parse(`${date}T00:00:00Z`);
+  if (!/^\d{4}-\d{2}-\d{2}$/.test(date) || date.startsWith('0000') || !Number.isFinite(time)
+    || new Date(time).toISOString().slice(0, 10) !== date) throw new Error('Choose a valid UTC calendar date.');
+  return time / DAY;
+}
+
+export function validateDraftDates(dates: readonly string[]): void {
+  const today = Math.floor(Date.now() / DAY);
+  let previous = -Infinity;
+  for (const date of dates) {
+    const day = draftDateDay(date);
+    if (day <= today) throw new Error('Draft dates must remain in the future (UTC).');
+    if (day <= previous) throw new Error('Keep dates in step order, at least one calendar day apart.');
+    previous = day;
+  }
+}
+
+export function redistributeDraftDates(dates: readonly string[], start: string, end: string): string[] {
+  const first = draftDateDay(start), last = dates.length === 1 ? first : draftDateDay(end);
+  if (last - first < dates.length - 1) throw new Error('Allow at least one calendar day between every draft step.');
+  const result = dates.map((_, index) => new Date((first + (dates.length === 1 ? 0
+    : Math.round(index * (last - first) / (dates.length - 1)))) * DAY).toISOString().slice(0, 10));
+  return result;
+}