From cb684d50c1e8dcfed09ad820825cef70914f9c0b Mon Sep 17 00:00:00 2001
From: Takuro Sato <79583855+takuro-sato@users.noreply.github.com>
Date: Tue, 12 Dec 2023 11:37:01 +0000
Subject: [PATCH] Partially support TextEncoder Web API (#5863)

---
 js/ccf-app/src/textcodec.ts      | 61 ++++++++++++++++++++++++++++++++
 js/ccf-app/test/polyfill.test.ts | 34 ++++++++++++++++++
 2 files changed, 95 insertions(+)
 create mode 100644 js/ccf-app/src/textcodec.ts

diff --git a/js/ccf-app/src/textcodec.ts b/js/ccf-app/src/textcodec.ts
new file mode 100644
index 000000000000..b34d035fbc86
--- /dev/null
+++ b/js/ccf-app/src/textcodec.ts
@@ -0,0 +1,61 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the Apache 2.0 License.
+
+/**
+ * The `textcodec` module provides access to TextEncoder Web API class.
+ *
+ * Example:
+ * ```
+ * import * as ccftextcodec from '@microsoft/ccf-app/textcodec.js';
+ *
+ * const bytes = new ccftextcodec.TextEncoder().encode("foo")
+ * ```
+ *
+ * If you need TextEncoder Web API as a globally accessible class:
+ * ```
+ * import * as ccftextcodec from '@microsoft/ccf-app/textcodec.js';
+ *
+ * if (globalThis != undefined && (globalThis as any).TextEncoder == undefined) {
+ *   (globalThis as any).TextEncoder = ccftextcodec.TextEncoder;
+ * }
+ *
+ * ```
+ *
+ * @module
+ */
+
+import { ccf } from "./global.js";
+
+export type TextEncoderEncodeIntoResult = {
+  read?: number;
+  written?: number;
+};
+
+/**
+ * TextEncoder can be used to encode string to Uint8Array.
+ */
+export class TextEncoder {
+  /**
+   * Always returns "utf-8".
+   */
+  public readonly encoding: string = "utf-8";
+
+  /**
+   * Returns Uint8Array containing UTF-8 encoded text.
+   * @param input Input string to encode.
+   * @returns Encoded bytes.
+   */
+  encode(input: string): Uint8Array {
+    return new Uint8Array(ccf.strToBuf(input));
+  }
+
+  /**
+   * Not implemented.
+   * @param input
+   * @param output
+   * @throws Always throws an Error object.
+   */
+  encodeInto(input: string, output: Uint8Array): TextEncoderEncodeIntoResult {
+    throw new Error("Not implemented");
+  }
+}
diff --git a/js/ccf-app/test/polyfill.test.ts b/js/ccf-app/test/polyfill.test.ts
index 3f4c7274d59d..ef4ddf430325 100644
--- a/js/ccf-app/test/polyfill.test.ts
+++ b/js/ccf-app/test/polyfill.test.ts
@@ -8,6 +8,7 @@ import {
   RsaOaepAesKwpParams,
   RsaOaepParams,
 } from "../src/global.js";
+import * as textcodec from "../src/textcodec.js";
 import { generateSelfSignedCert, generateCertChain } from "./crypto.js";
 
 beforeEach(function () {
@@ -24,6 +25,39 @@ describe("polyfill", function () {
       assert.equal(ccf.bufToStr(ccf.strToBuf(s)), s);
     });
   });
+  describe("TextEncoder", function () {
+    it("returns utf-8 for encoding field", function () {
+      const encoder = new textcodec.TextEncoder();
+      assert.equal(encoder.encoding, "utf-8");
+      const s = encoder.encode("foo");
+    });
+    it("returns an empty array for default empty input", function () {
+      assert.deepEqual(
+        new textcodec.TextEncoder().encode(""),
+        new Uint8Array(),
+      );
+    });
+    it("encodes ascii strings correctly", function () {
+      const sample = "foo";
+      assert.deepEqual(
+        new textcodec.TextEncoder().encode(sample),
+        new Uint8Array([0x66, 0x6f, 0x6f]),
+      );
+    });
+    it("encodes UTF-8 strings correctly", function () {
+      // a (U+0061, 0x61 in UTF-8), pound sign (U+00A3, 0xC2 0xA3 in UTF-8)
+      const sample = "\u0061\u00A3";
+      assert.deepEqual(
+        new textcodec.TextEncoder().encode(sample),
+        new Uint8Array([0x61, 0xc2, 0xa3]),
+      );
+    });
+    it("throws when unsupported method is called", function () {
+      assert.throws(() =>
+        new textcodec.TextEncoder().encodeInto("test", new Uint8Array([])),
+      );
+    });
+  });
   describe("jsonCompatibleToBuf/bufToJsonCompatible", function () {
     it("converts JSON-compatible <--> ArrayBuffer", function () {
       const s = { foo: "bar" };