refactor: extract business logic from routes into reusable service modules

server/src/services/settingsService.ts

@@ -0,0 +1,41 @@
+import { db } from '../db/database';
+
+export function getUserSettings(userId: number): Record<string, unknown> {
+  const rows = db.prepare('SELECT key, value FROM settings WHERE user_id = ?').all(userId) as { key: string; value: string }[];
+  const settings: Record<string, unknown> = {};
+  for (const row of rows) {
+    try {
+      settings[row.key] = JSON.parse(row.value);
+    } catch {
+      settings[row.key] = row.value;
+    }
+  }
+  return settings;
+}
+
+export function upsertSetting(userId: number, key: string, value: unknown) {
+  const serialized = typeof value === 'object' ? JSON.stringify(value) : String(value !== undefined ? value : '');
+  db.prepare(`
+    INSERT INTO settings (user_id, key, value) VALUES (?, ?, ?)
+    ON CONFLICT(user_id, key) DO UPDATE SET value = excluded.value
+  `).run(userId, key, serialized);
+}
+
+export function bulkUpsertSettings(userId: number, settings: Record<string, unknown>) {
+  const upsert = db.prepare(`
+    INSERT INTO settings (user_id, key, value) VALUES (?, ?, ?)
+    ON CONFLICT(user_id, key) DO UPDATE SET value = excluded.value
+  `);
+  db.exec('BEGIN');
+  try {
+    for (const [key, value] of Object.entries(settings)) {
+      const serialized = typeof value === 'object' ? JSON.stringify(value) : String(value !== undefined ? value : '');
+      upsert.run(userId, key, serialized);
+    }
+    db.exec('COMMIT');
+  } catch (err) {
+    db.exec('ROLLBACK');
+    throw err;
+  }
+  return Object.keys(settings).length;
+}