Create no-multiple-directrive (#6)

projects/ash-material-file-input/src/lib/directive/no-multiple.directive.spec.ts

@@ -0,0 +1,8 @@
+import { NoMultipleDirective } from './no-multiple.directive';
+
+describe('MultipleDirective', () => {
+  it('should create an instance', () => {
+    const directive = new NoMultipleDirective();
+    expect(directive).toBeTruthy();
+  });
+});

projects/ash-material-file-input/src/lib/directive/no-multiple.directive.ts

@@ -0,0 +1,24 @@
+import { Directive } from '@angular/core';
+import { NG_VALIDATORS, Validator, FormControl } from '@angular/forms';
+
+@Directive({
+  selector: 'ash-mat-file-input:not([multiple])',
+  providers: [{ provide: NG_VALIDATORS, useExisting: NoMultipleDirective, multi: true }],
+})
+export class NoMultipleDirective implements Validator {
+
+  constructor() {}
+
+  validate(control: FormControl) {
+    if (control.value?.length > 1) {
+      return {
+        multiple: {
+          maxFiles: 1,
+          currentFiles: control.value.length,
+        }
+      };
+    }
+    return null;
+  }
+
+}