feat(max_count): add validator for maximum count of item

validators/iterable/max_count.ts

@@ -0,0 +1,23 @@
+// Copyright 2023-latest Tomoki Miyauchi. All rights reserved. MIT license.
+// This module is browser compatible.
+
+import { getSize } from "./utils.ts";
+import { interpolate, ScalarValidator } from "../../utils.ts";
+import error from "../error.json" assert { type: "json" };
+
+export class MaxCountValidator extends ScalarValidator<Iterable<unknown>> {
+  constructor(public size: number) {
+    super();
+    super.expect(({ input }) =>
+      interpolate(error.max_count, [size, getSize(input)])
+    );
+  }
+
+  override is(input: Iterable<unknown>): boolean {
+    return getSize(input) <= this.size;
+  }
+
+  toString(): string {
+    return `max item count of ${this.size}`;
+  }
+}