Fix #97 -- Properly parse domain names in markdown links (#98)

The problem is described in #97.

I had to introduce a library -
[tldextract](https://github.com/john-kurkowski/tldextract/) to properly
parse all varieties of domain names.

---------

Co-authored-by: Johannes Maron <johannes@maron.family>

emark/message.py

@@ -116,7 +116,8 @@ def update_url_params(self, url, **params):
             return redirect_url
         site_url = self.get_site_url()
         # external links should not be tracked
-        top_level_domain = ".".join(site_url.split(".")[-2:])
+        top_level_domain = utils.extract_domain(site_url)
+
         if not redirect_url_parts.netloc.endswith(top_level_domain):
             return redirect_url
         tracking_url = reverse("emark:email-click", kwargs={"pk": self.uuid})

emark/utils.py

@@ -6,6 +6,10 @@
 
 __all__ = ["HTML2TextParser"]
 
+from urllib import parse
+
+import tldextract
+
 
 @dataclasses.dataclass
 class Node:
@@ -122,3 +126,25 @@ def __str__(self) -> str:
         # sanitize all wide vertical or horizontal spaces
         text = self.DOUBLE_NEWLINE.sub("\n\n", text.strip())
         return self.DOUBLE_SPACE.sub(" ", text)
+
+
+def extract_domain(url: str) -> str:
+    """Extracts the registered domain from a given URL.
+
+    If the domain is "localhost", it includes the port number in the returned string.
+
+    Args:
+        url (str): The URL from which to extract the domain.
+
+    Returns:
+        str: The registered domain or "localhost" with port if applicable.
+    """
+    extractor = tldextract.TLDExtract(suffix_list_urls=())
+    extracted = extractor(url)
+    if extracted.domain == "localhost":
+        registered_domain = "localhost"
+    else:
+        registered_domain = extracted.registered_domain
+    if port := parse.urlparse(url).port:
+        return f"{registered_domain}:{port}"
+    return registered_domain

pyproject.toml

@@ -36,7 +36,7 @@ classifiers = [
   "Framework :: Django :: 5.0",
 ]
 requires-python = ">=3.10"
-dependencies = ["django", "markdown", "premailer"]
+dependencies = ["django", "markdown", "premailer", "tldextract"]
 
 [project.optional-dependencies]
 test = [

tests/test_message.py

@@ -197,11 +197,13 @@ def test_open_in_browser__html(self, email_message):
             in email_message.html
         )
 
-    def test_get_site_domain__setting(self, email_message):
-        assert email_message.get_site_url() == "http://www.example.com"
+    @pytest.mark.parametrize("domain", ["www.example.com", "example.com"])
+    def test_get_site_url__setting(self, email_message, settings, domain):
+        settings.EMARK = {"DOMAIN": domain}
+        assert email_message.get_site_url() == f"http://{domain}"
 
     @pytest.mark.django_db
-    def test_test_get_site_domain__sites_framework(self, email_message, settings):
+    def test_get_site_url__sites_framework(self, email_message, settings):
         settings.EMARK = {"DOMAIN": None}
         settings.SITE_ID = 1
         assert email_message.get_site_url() == "http://example.com"
@@ -330,7 +332,27 @@ def test_update_url_params__tracking_uuid(self, email_message):
             "click?url=https%3A%2F%2Fwww.example.com%2F%3Futm_medium%3Dbaz%26utm_source%3Dfoo"
         )
 
-    def test_update_url_params__subdomain(self, email_message):
+    @pytest.mark.parametrize(
+        "domain",
+        ["www.example.com", "example.com", "test.example.com", "localhost:8000"],
+    )
+    def test_update_url_params__domains(self, settings, email_message, domain):
+        settings.EMARK["DOMAIN"] = domain
+        email_message.uuid = "12341234-1234-1234-1234-123412341234"
+        encoded_domain = domain.replace(":", "%3A")
+        expected_url = (
+            f"http://{domain}/emark/12341234-1234-1234-1234-123412341234/"
+            f"click?url=https%3A%2F%2F{encoded_domain}%2F%3Futm_medium%3Dbaz%26utm_source%3Dfoo"
+        )
+        assert (
+            email_message.update_url_params(
+                f"https://{domain}/?utm_source=foo", utm_medium="baz"
+            )
+            == expected_url
+        )
+
+    def test_update_url_params__subdomain(self, settings, email_message):
+        settings.EMARK["DOMAIN"] = "www.example.com"
         email_message.uuid = "12341234-1234-1234-1234-123412341234"
         assert (
             email_message.update_url_params(

tests/test_utils.py

@@ -110,3 +110,12 @@ def test_parse_html_email(self):
             "--------------------------------------------------\n"
             "some footer"
         )
+
+
+def test_extract_domain():
+    assert utils.extract_domain("https://example.com") == "example.com"
+    assert utils.extract_domain("https://www.example.com") == "example.com"
+    assert utils.extract_domain("https://www.example.co.uk") == "example.co.uk"
+    assert utils.extract_domain("https://www.example.com:1337") == "example.com:1337"
+    assert utils.extract_domain("https://localhost") == "localhost"
+    assert utils.extract_domain("https://localhost:8000") == "localhost:8000"