Add streamline email filter

src/Filter/NormalizeToAlphanumericFilter.php

@@ -15,7 +15,7 @@
  */
 class NormalizeToAlphanumericFilter implements StringFilterInterface
 {
-    private StringFilterRunner $filterRunner;
+    private StringFilterInterface $filterRunner;
 
     public function __construct()
     {

src/Filter/NormalizeToAlphanumericLowercaseFilter.php

@@ -16,7 +16,7 @@
  */
 class NormalizeToAlphanumericLowercaseFilter implements StringFilterInterface
 {
-    private StringFilterRunner $filterRunner;
+    private StringFilterInterface $filterRunner;
 
     public function __construct()
     {

src/Filter/StreamlineEmailFilter.php

@@ -0,0 +1,32 @@
+<?php
+
+namespace Squirrel\Strings\Filter;
+
+use Squirrel\Strings\StringFilterInterface;
+
+/**
+ * Streamline email format, converting domain part to lowercase and keeping the username part case-sensitive
+ */
+class StreamlineEmailFilter implements StringFilterInterface
+{
+    public function filter(string $string): string
+    {
+        if (\strpos($string, '@') === false) {
+            return $string;
+        }
+
+        // Split up email in username and domain part
+        $emailParts = \explode('@', $string);
+
+        // The first part is always the username part
+        $username = \array_shift($emailParts);
+
+        // All the other parts are the domain part
+        $domain = \implode('@', $emailParts);
+
+        $lowercaseFilter = new LowercaseFilter();
+
+        // Only lowercase the domain part, username can be case sensitive
+        return $username . '@' . $lowercaseFilter->filter($domain);
+    }
+}

src/Filter/StreamlineInputNoNewlinesFilter.php

@@ -10,7 +10,7 @@
  */
 class StreamlineInputNoNewlinesFilter implements StringFilterInterface
 {
-    private StringFilterRunner $filterRunner;
+    private StringFilterInterface $filterRunner;
 
     public function __construct()
     {

src/Filter/StreamlineInputWithNewlinesFilter.php

@@ -7,7 +7,7 @@
 
 class StreamlineInputWithNewlinesFilter implements StringFilterInterface
 {
-    private StringFilterRunner $filterRunner;
+    private StringFilterInterface $filterRunner;
 
     public function __construct()
     {

tests/StringFilterTest.php

@@ -27,6 +27,7 @@
 use Squirrel\Strings\Filter\ReplaceUnicodeWhitespacesFilter;
 use Squirrel\Strings\Filter\ReplaceUnixStyleNewlinesWithParagraphsAndBreaksFilter;
 use Squirrel\Strings\Filter\SnakeCaseToCamelCaseFilter;
+use Squirrel\Strings\Filter\StreamlineEmailFilter;
 use Squirrel\Strings\Filter\StreamlineInputNoNewlinesFilter;
 use Squirrel\Strings\Filter\StreamlineInputWithNewlinesFilter;
 use Squirrel\Strings\Filter\TrimFilter;
@@ -374,4 +375,22 @@ public function testRemoveHTMLCharacters()
     {
         $this->assertEquals("  & haha strongmany/strong \xc2\xa0     grüss götter   \r\n\n\n\t  \n  \n  invalidl'etat\\ thing contained!!!™ ", (new RemoveHTMLTagCharacters())->filter($this->testString));
     }
+
+    public function testEmailStreamline()
+    {
+        $emails = [
+            'bademail' => 'bademail',
+            'BADEMAIL' => 'BADEMAIL',
+            '[email protected]' => '[email protected]',
+            '[email protected]' => '[email protected]',
+            '[email protected]' => '[email protected]',
+            '[email protected]' => '[email protected]',
+        ];
+
+        $emailFilter = new StreamlineEmailFilter();
+
+        foreach ($emails as $input => $expectedOutput) {
+            $this->assertSame($expectedOutput, $emailFilter->filter($input));
+        }
+    }
 }