deduplicate json config file access

apps/backend/src/utils/json-file-store.ts

@@ -0,0 +1,36 @@
+import fs from 'node:fs'
+import path from 'node:path'
+
+type NormalizeJsonValue<T> = (value: unknown) => T
+
+export function readJsonFile<T>(
+  filePath: string,
+  fallback: T | (() => T),
+  normalize: NormalizeJsonValue<T>,
+): T {
+  if (!fs.existsSync(filePath)) {
+    return resolveFallback(fallback)
+  }
+
+  try {
+    const rawText = fs.readFileSync(filePath, 'utf8')
+    return normalize(JSON.parse(rawText))
+  } catch {
+    return resolveFallback(fallback)
+  }
+}
+
+export function writeJsonFile<T>(
+  filePath: string,
+  value: unknown,
+  normalize: NormalizeJsonValue<T>,
+): T {
+  const normalized = normalize(value)
+  fs.mkdirSync(path.dirname(filePath), { recursive: true })
+  fs.writeFileSync(filePath, `${JSON.stringify(normalized, null, 2)}\n`, 'utf8')
+  return normalized
+}
+
+function resolveFallback<T>(fallback: T | (() => T)): T {
+  return typeof fallback === 'function' ? (fallback as () => T)() : fallback
+}