feat(db): dialect helper is the one place SQL functions are spelled

server/src/db/dialect/sql-functions.ts

@@ -0,0 +1,35 @@
+import { raw, type RawQueryFragment } from '@mikro-orm/core';
+
+/**
+ * The only place a repository may spell a database function.
+ *
+ * Every helper takes an already-qualified column reference (`'t.created_at'`)
+ * and returns a fragment for the *current* dialect. The ORM exists so a
+ * Postgres driver can follow; when it does, this file gets a second
+ * implementation and no repository changes. Values are never interpolated —
+ * the day count in `dateAdd` is checked to be an integer before it is spelled.
+ */
+
+function column(ref: string): string {
+  if (!/^[a-z_][a-z0-9_]*(\.[a-z_][a-z0-9_]*)?$/i.test(ref)) {
+    throw new Error(`sql-functions: not a column reference: ${ref}`);
+  }
+  return ref;
+}
+
+/** The calendar date (`YYYY-MM-DD`) of a timestamp column. */
+export function dateOf(ref: string): RawQueryFragment {
+  return raw(`date(${column(ref)})`);
+}
+
+/** The timestamp column shifted by whole days, as a calendar date. */
+export function dateAdd(ref: string, days: number): RawQueryFragment {
+  if (!Number.isInteger(days)) throw new Error(`sql-functions: dateAdd needs an integer day count, got ${days}`);
+  const sign = days < 0 ? '-' : '+';
+  return raw(`date(${column(ref)}, '${sign}${Math.abs(days)} days')`);
+}
+
+/** The database clock, in the same text the column defaults produce. */
+export function currentTimestamp(): RawQueryFragment {
+  return raw('CURRENT_TIMESTAMP');
+}

server/tests/unit/db/dialect/sql-functions.test.ts

@@ -0,0 +1,44 @@
+import { afterAll, beforeAll, beforeEach, describe, expect, it } from 'vitest';
+import { createTestDb, resetTestDb } from '../../../helpers/test-db';
+import { createTestOrm, type TestOrm } from '../../../helpers/test-orm';
+import { createUser } from '../../../helpers/factories';
+import { Users } from '../../../../src/db/entities/Users.entity';
+import { currentTimestamp, dateAdd, dateOf } from '../../../../src/db/dialect/sql-functions';
+
+const testDb = createTestDb();
+let t: TestOrm;
+
+beforeAll(async () => { t = await createTestOrm(testDb); });
+beforeEach(() => { resetTestDb(testDb); t.clear(); });
+afterAll(async () => { await t.close(); testDb.close(); });
+
+describe('sql-functions (sqlite)', () => {
+  it('SQLF-001: dateOf yields the calendar date of a stored timestamp', async () => {
+    const { user } = createUser(testDb);
+    testDb.prepare("UPDATE users SET created_at = '2026-09-21 13:05:09' WHERE id = ?").run(user.id);
+    const row = await t.em.createQueryBuilder(Users, 'u')
+      .select([dateOf('u.created_at').as('d')])
+      .where({ id: user.id })
+      .execute('get', false);
+    expect(row).toEqual({ d: '2026-09-21' });
+  });
+
+  it('SQLF-002: dateAdd shifts by whole days', async () => {
+    const { user } = createUser(testDb);
+    testDb.prepare("UPDATE users SET created_at = '2026-09-21 13:05:09' WHERE id = ?").run(user.id);
+    const row = await t.em.createQueryBuilder(Users, 'u')
+      .select([dateAdd('u.created_at', 10).as('d')])
+      .where({ id: user.id })
+      .execute('get', false);
+    expect(row).toEqual({ d: '2026-10-01' });
+  });
+
+  it('SQLF-003: currentTimestamp is the DB clock in the wire format', async () => {
+    createUser(testDb);
+    const row = await t.em.createQueryBuilder(Users, 'u')
+      .select([currentTimestamp().as('now')])
+      .limit(1)
+      .execute('get', false);
+    expect(String((row as { now: string }).now)).toMatch(/^\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2}$/);
+  });
+});