refactor(core): Add base serializer for pagination params

Introduced `BaseLimitOffsetPaginationSerializer` to handle the validation of `limit` and `offset` query parameters.

Author: RandomProgramm3r

promo_code/core/pagination.py

@@ -1,6 +1,9 @@
+import rest_framework.exceptions
 import rest_framework.pagination
 import rest_framework.response
 
+import core.serializers
+
 
 class CustomLimitOffsetPagination(
     rest_framework.pagination.LimitOffsetPagination,
@@ -9,12 +12,13 @@ class CustomLimitOffsetPagination(
     max_limit = 100
 
     def get_limit(self, request):
-        raw_limit = request.query_params.get(self.limit_query_param)
-
-        if raw_limit is None:
-            return self.default_limit
+        serializer = core.serializers.BaseLimitOffsetPaginationSerializer(
+            data=request.query_params,
+        )
+        serializer.is_valid(raise_exception=True)
 
-        limit = int(raw_limit)
+        validated_data = serializer.validated_data
+        limit = validated_data.get('limit', self.default_limit)
 
         # Allow 0, otherwise cut by max_limit
         return 0 if limit == 0 else min(limit, self.max_limit)

promo_code/core/serializers.py

@@ -0,0 +1,31 @@
+import rest_framework.exceptions
+import rest_framework.serializers
+
+
+class BaseLimitOffsetPaginationSerializer(
+    rest_framework.serializers.Serializer,
+):
+    """
+    Base serializer for common filtering and sorting parameters.
+    Pagination parameters (limit, offset) are handled by the pagination class.
+    """
+
+    limit = rest_framework.serializers.IntegerField(
+        min_value=0,
+        required=False,
+    )
+    offset = rest_framework.serializers.IntegerField(
+        min_value=0,
+        required=False,
+    )
+
+    def validate(self, attrs):
+        errors = {}
+        for field in ('limit', 'offset'):
+            raw = self.initial_data.get(field, None)
+            if raw == '':
+                errors[field] = ['This field cannot be an empty string.']
+        if errors:
+            raise rest_framework.exceptions.ValidationError(errors)
+
+        return super().validate(attrs)