PoC for save validation on load via hooking the Reviver function and

static property validationData on classes

PoC/example implemented with HacknetNode:
  validates cores is a number in the range between 1 and HacknetNodeConstants.MaxCores
  validates level is a number in range between 1 and HacknetNodeConstants.MaxLevel
  validates ram is a number in range between 1 and HacknetNodeConstants.MaxRam
  validates onlineTimeSeconds in non negative number
  validates totalMoneyGenerated is a non negative number

src/utils/JSONReviver.ts

@@ -1,5 +1,7 @@
 /* Generic Reviver, toJSON, and fromJSON functions used for saving and loading objects */
 
+import { validateObject } from "./Validator";
+
 interface IReviverValue {
   ctor: string;
   data: any;
@@ -26,7 +28,11 @@ export function Reviver(key: string, value: IReviverValue | null): any {
     const ctor = Reviver.constructors[value.ctor];
 
     if (typeof ctor === "function" && typeof ctor.fromJSON === "function") {
-      return ctor.fromJSON(value);
+      const obj = ctor.fromJSON(value);
+      if (ctor.validationData !== undefined) {
+        validateObject(obj, ctor.validationData);
+      }
+      return obj;
     }
   }
   return value;

src/utils/Validator.ts

@@ -0,0 +1,31 @@
+export type ObjectValidator<T> = {
+  [key in keyof T]?: ParameterValidator<T, keyof T>;
+}
+
+interface ParameterValidator<T, U extends keyof T> {
+  default?: any;
+  min?: number;
+  max?: number;
+  func?: (obj: T, validator: ObjectValidator<T>, key: U) => void;
+}
+
+export function validateObject<T extends Record<string, unknown>, U extends keyof T>(obj: T, validator: ObjectValidator<T>): void {
+  for (const key of Object.keys(validator) as U[]) {
+    const paramValidator = validator[key];
+    if (paramValidator !== undefined)  {
+      if (paramValidator.func !== undefined) {
+        paramValidator.func(obj, validator, key);
+      } else {
+        if ((typeof obj[key]) !== (typeof paramValidator.default)) {
+          obj[key] = paramValidator.default
+        }
+        if (typeof obj[key] === 'number' && paramValidator.min !== undefined) {
+          if (obj[key] < paramValidator.min) obj[key] = paramValidator.min as T[U];
+        }
+        if (typeof obj[key] === 'number' && paramValidator.max !== undefined) {
+          if (obj[key] > paramValidator.max) obj[key] = paramValidator.max as T[U];
+        }
+      }
+    }
+  }
+}