Add getFormat() method

src/Subtitles.php

@@ -166,6 +166,21 @@ public function content($format, $options = [])
         return $content;
     }
 
+    public static function getFormat($string)
+    {
+        $modified_string = Helpers::convertToUtf8($string);
+        $modified_string = Helpers::removeUtf8Bom($modified_string);
+        $modified_string = Helpers::normalizeNewLines($modified_string);
+
+        $input_converter = Helpers::getConverterByFileContent($modified_string, $string);
+
+        foreach (self::$formats as $format) {
+            if ($format['class'] === get_class($input_converter)) {
+                return $format;
+            }
+        }
+    }
+
     // for testing only
     public function getInternalFormat()
     {

tests/PublicInterfaceTest.php

@@ -4,6 +4,7 @@
 
 use Done\Subtitles\Code\Converters\VttConverter;
 use Done\Subtitles\Code\Helpers;
+use Done\Subtitles\Code\UserException;
 use PHPUnit\Framework\TestCase;
 use Done\Subtitles\Subtitles;
 use Helpers\AdditionalAssertionsTrait;
@@ -344,4 +345,19 @@ public function testTrim()
 
         $this->assertInternalFormatsEqual($expected_internal_format, $actual_internal_format);
     }
+
+    public function testGetsFormat()
+    {
+        $srt_path = './tests/files/srt.srt';
+        $format = Subtitles::getFormat(file_get_contents($srt_path));
+        $this->assertEquals('srt', $format['extension']);
+    }
+
+    public function testNotASubtitleFormatThrowsException()
+    {
+        $this->expectException(UserException::class);
+
+        $srt_path = './tests/files/slick.bin';
+        Subtitles::getFormat(file_get_contents($srt_path));
+    }
 }