1 files changed, 62 insertions, 0 deletions
diff --git a/webmentions_ssg/forms/validators.py b/webmentions_ssg/forms/validators.py
new file mode 100644
index 0000000..20d9ebf
--- /dev/null
+++ b/webmentions_ssg/forms/validators.py
@@ -0,0 +1,62 @@
+from urllib.parse import urlsplit
+
+from flask import current_app
+from wtforms import ValidationError
+
+
+class NotEqualTo:
+    """
+    Compares the values of two fields.
+
+    :param fieldname:
+        The name of the other field to compare to.
+    :param message:
+        Error message to raise in case of a validation error. Can be
+        interpolated with `%(other_label)s` and `%(other_name)s` to provide a
+        more helpful error.
+    """
+
+    def __init__(self, fieldname, message=None):
+        self.fieldname = fieldname
+        self.message = message
+
+    def __call__(self, form, field):
+        try:
+            other = form[self.fieldname]
+        except KeyError as exc:
+            raise ValidationError(
+                field.gettext("Invalid field name '%s'.") % self.fieldname
+            ) from exc
+
+        if field.data != other.data:
+            return
+
+        d = {
+            "other_label": hasattr(other, "label")
+            and other.label.text
+            or self.fieldname,
+            "other_name": self.fieldname,
+        }
+        message = self.message
+        if message is None:
+            message = field.gettext("Field must not be equal to %(other_name)s.")
+
+        raise ValidationError(message % d)
+
+
+class AllowedHostname:
+    def __init__(self, message=None):
+        self.message = message
+
+    def __call__(self, form, field):
+        if (
+            urlsplit(field.data).hostname
+            in current_app.config["WEBMENTIONS_SSG_ALLOWED_HOSTNAMES"]
+        ):
+            return
+
+        message = self.message
+        if self.message is None:
+            message = field.gettext("Invalid input.")
+
+        raise ValidationError(message)