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');
+}