(wip|[skip ci]): Add initial implementation for TextString encoding and tests

- Implement `TextString` class with an `encode` method for CBOR text string encoding based on the length.
- Placeholder added for the `decode` method (not yet implemented).
- Create `TextStringTest` to validate encoding functionality with various test cases.
- Include a data provider for encoding tests, covering short and long strings.

Note: Decoding functionality is still pending implementation.

Author: shahmal1yev

src/CBOR/MajorTypes/TextString.php

@@ -0,0 +1,39 @@
+<?php declare(strict_types = 1);
+
+/**
+ * This file is part of the ATProto Core package.
+ *
+ * (c) Core Branch
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+namespace ATProto\Core\CBOR\MajorTypes;
+
+class TextString
+{
+    public static function encode(string $input): string
+    {
+        $length = strlen($input);
+
+        if ($length <= 23) {
+            $header = chr((0x03 << 5) | $length);
+        } elseif ($length <= 0xFF) {
+            $header = chr((0x03 << 5) | 24) . chr($length);
+        } elseif ($length <= 0xFFFF) {
+            $header = chr((0x03 << 5) | 25) . pack('n', $length);
+        } elseif ($length <= 0xFFFFFFFF) {
+            $header = chr((0x03 << 5) | 26) . pack('N', $length);
+        } else {
+            $header = chr((0x03 << 5) | 27) . pack('J', $length);
+        }
+
+        return $header . $input;
+    }
+
+    public static function decode(string $input): string
+    {
+        // TODO
+    }
+}

tests/Unit/CBOR/MajorTypes/TextStringTest.php

@@ -0,0 +1,57 @@
+<?php declare(strict_types = 1);
+
+/**
+ * This file is part of the ATProto Core package.
+ *
+ * (c) Core Branch
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+namespace Tests\Unit\CBOR\MajorTypes;
+
+use ATProto\Core\CBOR\MajorTypes\TextString;
+use PHPUnit\Framework\Attributes\DataProvider;
+use PHPUnit\Framework\TestCase;
+
+class TextStringTest extends TestCase
+{
+    #[DataProvider('provideCases')]
+    public function testItCanEncodeCorrectly(string $case, string $header): void
+    {
+        $actual = bin2hex(TextString::encode($case));
+        $expected = bin2hex($header . $case);
+
+        $this->assertSame($expected, $actual);
+    }
+
+    #[DataProvider('provideCases')]
+    public function testItCanDecodeCorrectly(string $case, string $header): void
+    {
+        $target = $header . $case;
+
+        $actual = TextString::decode($target);
+        $expected = $case;
+
+        $this->assertSame($expected, $actual);
+    }
+
+    public static function provideCases(): array
+    {
+        return [
+            ["f", "\x61"],
+            ["fo", "\x62"],
+            ["foo", "\x63"],
+            ["foob", "\x64"],
+            ["fooba", "\x65"],
+            ["foobar", "\x66"],
+            [
+                "This is a longer string. This is a longer string. This is a longer string. This is a longer string. 
+                This is a longer string. This is a longer string. This is a longer string. This is a longer string. 
+                This is a longer string. This is a longer string. This is a longer string. This is a longer string.",
+                "\x79\x01\x4D"
+            ]
+        ];
+    }
+}