✨(tools) extract domain from email address

This provides a standard way to extract the domain from an email
address. This is not used in the package but it could be used in several
projects.

CHANGELOG.md

@@ -8,4 +8,8 @@ and this project adheres to
 
 ## [Unreleased]
 
+### Added
+
+- ✨(tools) extract domain from email address #2
+
 [unreleased]: https://github.com/suitenumerique/django-lasuite/commits/main/

src/lasuite/tools/__init__.py

@@ -0,0 +1 @@
+"""Common tools for the LaSuite package or the projects."""

src/lasuite/tools/email.py

@@ -0,0 +1,19 @@
+"""Email related tools."""
+
+from email.errors import HeaderParseError
+from email.headerregistry import Address
+
+
+def get_domain_from_email(email: str | None) -> str | None:
+    """Extract domain from email."""
+    try:
+        address = Address(addr_spec=email)
+        if len(address.username) > 64 or len(address.domain) > 255:  # noqa: PLR2004
+            # Simple length validation using the RFC 5321 limits
+            return None
+        if not address.domain:
+            # If the domain is empty, return None
+            return None
+        return address.domain
+    except (ValueError, AttributeError, IndexError, HeaderParseError):
+        return None

tests/tools/__init__.py

@@ -0,0 +1 @@
+"""Tools tests."""

tests/tools/test_email.py

@@ -0,0 +1,55 @@
+"""Tests for email tools."""
+
+import pytest
+
+from lasuite.tools.email import get_domain_from_email
+
+
+@pytest.mark.parametrize(
+    ("email", "expected"),
+    [
+        ("user@example.com", "example.com"),
+        ("test.user@sub.domain.co.uk", "sub.domain.co.uk"),
+        ("name+tag@gmail.com", "gmail.com"),
+        ("user@localhost", "localhost"),
+        ("user@127.0.0.1", "127.0.0.1"),
+    ],
+)
+def test_get_domain_from_email_valid(email, expected):
+    """Test extracting domain from valid email addresses."""
+    assert get_domain_from_email(email) == expected
+
+
+@pytest.mark.parametrize(
+    "invalid_email",
+    [
+        None,
+        "",
+        "invalid-email",
+        "user@",
+        "@domain.com",
+        "user@domain@com",
+        "user@@domain.com",
+        "user domain.com",
+        "<script>alert('XSS')</script>@example.com",
+        "user@example.com\n",
+        "user@example.com;drop table users",
+    ],
+)
+def test_get_domain_from_email_invalid(invalid_email):
+    """Test handling of invalid email addresses."""
+    assert get_domain_from_email(invalid_email) is None
+
+
+def test_get_domain_from_email_length_limits():
+    """Test handling of extremely long email addresses."""
+    # Very long local part (should fail)
+    long_local = "a" * 65 + "@example.com"
+    assert get_domain_from_email(long_local) is None
+
+    # Very long domain (valid according to standards)
+    domain_parts = ".".join(["a" * 64] * 4)
+    long_domain = f"user@{domain_parts}"
+    # This might fail depending on email validation implementation
+    # The test expects None since such domains aren't typically valid in practice
+    assert get_domain_from_email(long_domain) is None