make generic handler

packages/server-shared/src/type-utilities/query-array-preprocessor.ts

@@ -1,5 +1,27 @@
 import { z } from 'zod';
 
+/**
+ * The core preprocessing logic for converting query parameters into arrays
+ */
+const queryArrayPreprocessFn = (val: unknown) => {
+  // Handle no value
+  if (!val) return undefined;
+
+  // Already an array, pass through
+  if (Array.isArray(val)) return val;
+
+  // Handle string input (single or comma-separated)
+  if (typeof val === 'string') {
+    return val
+      .split(',')
+      .map((item) => item.trim())
+      .filter(Boolean);
+  }
+
+  // Single value case (wrap in array)
+  return [val];
+};
+
 /**
  * Creates a preprocessor that converts query parameter strings into arrays.
  * Handles various input formats:
@@ -9,46 +31,12 @@ import { z } from 'zod';
  * - No value: undefined → undefined
  */
 export const createQueryArrayPreprocessor = <T>(schema: z.ZodArray<z.ZodType<T>>) => {
-  return z.preprocess((val) => {
+  return z.preprocess(queryArrayPreprocessFn, schema);
-    // Handle no value
-    if (!val) return undefined;
-
-    // Already an array, pass through
-    if (Array.isArray(val)) return val;
-
-    // Handle string input (single or comma-separated)
-    if (typeof val === 'string') {
-      return val
-        .split(',')
-        .map((item) => item.trim())
-        .filter(Boolean);
-    }
-
-    // Single value case (wrap in array)
-    return [val];
-  }, schema);
 };
 
 /**
  * Type-safe helper for creating optional query array preprocessors
  */
 export const createOptionalQueryArrayPreprocessor = <T>(itemSchema: z.ZodType<T>) => {
-  return z.preprocess((val) => {
+  return z.preprocess(queryArrayPreprocessFn, z.array(itemSchema).optional());
-    // Handle no value
-    if (!val) return undefined;
-
-    // Already an array, pass through
-    if (Array.isArray(val)) return val;
-
-    // Handle string input (single or comma-separated)
-    if (typeof val === 'string') {
-      return val
-        .split(',')
-        .map((item) => item.trim())
-        .filter(Boolean);
-    }
-
-    // Single value case (wrap in array)
-    return [val];
-  }, z.array(itemSchema).optional());
 };