LibUnicode: Add IDNA::to_ascii

This implements the ToASCII operation of Unicode Technical Standard 46

Tests/LibUnicode/TestIDNA.cpp

@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2023, Simon Wanner <simon@skyrising.xyz>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibTest/TestCase.h>
+
+#include <LibUnicode/IDNA.h>
+
+namespace Unicode::IDNA {
+
+TEST_CASE(to_ascii)
+{
+#define TEST_TO_ASCII(input, expected, ...) EXPECT_EQ(TRY_OR_FAIL(to_ascii(Utf8View(input), ##__VA_ARGS__)), expected)
+
+    ToAsciiOptions const options_with_transitional_processing {
+        .transitional_processing = TransitionalProcessing::Yes
+    };
+#define TEST_TO_ASCII_T(input, expected) TEST_TO_ASCII(input, expected, options_with_transitional_processing)
+    TEST_TO_ASCII("www.аррӏе.com"sv, "www.xn--80ak6aa92e.com"sv);
+    TEST_TO_ASCII("ö.com"sv, "xn--nda.com"sv);
+    TEST_TO_ASCII("o\u0308.com"sv, "xn--nda.com"sv);
+
+    // Select cases from IdnaTestV2.txt
+    // FIXME: Download, parse and test all cases
+    TEST_TO_ASCII("Faß.de"sv, "xn--fa-hia.de"sv);
+    TEST_TO_ASCII_T("Faß.de"sv, "fass.de"sv);
+    TEST_TO_ASCII("¡"sv, "xn--7a"sv);
+    TEST_TO_ASCII("Bücher.de"sv, "xn--bcher-kva.de");
+    TEST_TO_ASCII("\u0646\u0627\u0645\u0647\u0627\u06CC"sv, "xn--mgba3gch31f"sv);
+    TEST_TO_ASCII("A.b.c。D。"sv, "a.b.c.d."sv);
+    TEST_TO_ASCII("βόλος"sv, "xn--nxasmm1c"sv);
+    TEST_TO_ASCII_T("βόλος"sv, "xn--nxasmq6b"sv);
+#undef TEST_TO_ASCII_T
+#undef TEST_TO_ASCII
+
+    EXPECT(to_ascii(Utf8View("xn--o-ccb.com"sv)).is_error());
+    EXPECT(to_ascii(Utf8View("wh--f.com"sv)).is_error());
+    EXPECT(to_ascii(Utf8View("xn--whf-cec.com"sv)).is_error());
+    EXPECT(to_ascii(Utf8View("-whf.com"sv)).is_error());
+    EXPECT(to_ascii(Utf8View("whf-.com"sv)).is_error());
+}
+
+}