create unique validator

npm/ng-packs/packages/core/src/lib/validators/unique-character.validator.ts

@@ -0,0 +1,20 @@
+import { AbstractControl, ValidationErrors, ValidatorFn } from '@angular/forms';
+import { isNullOrEmpty } from '../utils';
+
+export interface UniqueCharacterError {
+  uniqueCharacter: true;
+}
+
+export function validateUniqueCharacter(): ValidatorFn {
+  return (control: AbstractControl): UniqueCharacterError | null => {
+    if (isNullOrEmpty(control.value)) return null;
+
+    return isUnqiueCharacter(control.value) ? null : { uniqueCharacter: true };
+  };
+}
+
+function isUnqiueCharacter(value: string): boolean {
+  const set = new Set<string>(value.split(''));
+
+  return set.size == value.length;
+}