feat: LimitOffsetPagination support (#6)

Add LimitOffsetPagination support

README.md

@@ -59,6 +59,7 @@ Other pagination classes that are available are:
 - `LinkHeaderCursorPagination`: This is similar to the normal [`CursorPagination`](cursor-pagination) class but using the `Link` header to return only the `next` and/or `prev` links. The `first` and `last` links are unavailable.
 - `LinkHeaderLinkResponseCursorPagination`: This is similar to
   `LinkHeaderCursorPagination`, but in addition to the `next` and/or `prev` URL's being in the `Link` header, the content of the response body is updated to include them as well. The body will be an object with the keys `next` (the next page's URL or None), `previous` (the previous page's URL or None), and `results` (the original content of the body).
+- `LinkHeaderLimitOffsetPagination`: [Uses the `LimitOffsetPagination` pagination class from DRF](https://www.django-rest-framework.org/api-guide/pagination/#limitoffsetpagination) to support `offset` and `limit` parameters instead of `page` to indicate offset into the queryset. 
 
 ## Configuration
 

drf_link_header_pagination/__init__.py

@@ -1,9 +1,10 @@
-from rest_framework.pagination import CursorPagination, PageNumberPagination
+from rest_framework.pagination import CursorPagination, PageNumberPagination, LimitOffsetPagination
 from rest_framework.response import Response
 from rest_framework.utils.urls import remove_query_param, replace_query_param
 
 __all__ = [
     "LinkHeaderPagination",
+    "LinkHeaderLimitOffsetPagination",
     "LinkHeaderCursorPagination",
     "LinkHeaderLinkResponseCursorPagination",
 ]
@@ -36,6 +37,35 @@ def get_paginated_response(self, data):
         return Response(data, headers=self.get_headers())
 
 
+class LinkHeaderLimitOffsetPagination(LinkHeaderMixin, LimitOffsetPagination):
+    """
+    Link header pagination with offset/limit links. Implements the regular
+    `LimitOffsetPagination` module with `Link: ` headers instead.
+    """
+    def get_first_link(self):
+        url = self.request.build_absolute_uri()
+        url = replace_query_param(url, self.limit_query_param, self.limit)
+
+        return remove_query_param(url, self.offset_query_param)
+
+    def get_last_link(self):
+        if not self.get_next_link():
+            return None
+
+        # We need to adjust for 0 offset, otherwise we'll get the last link
+        # to an empty page if count % limit == 0 (i.e. the "pages" line up
+        # exactly)
+        offset = max(0, self.count - ((self.count - 1) % self.limit) - 1)
+
+        url = self.request.build_absolute_uri()
+        url = replace_query_param(url, self.limit_query_param, self.limit)
+
+        return replace_query_param(url, self.offset_query_param, offset)
+
+    def get_paginated_response_schema(self, schema):
+        return schema
+
+
 class LinkHeaderPagination(LinkHeaderMixin, PageNumberPagination):
     """Inform the user of pagination links via response headers, similar to
     what's described in

tests/test_link_header_limit_offset_pagination.py

@@ -0,0 +1,107 @@
+import pytest
+from rest_framework import exceptions
+from rest_framework.pagination import PAGE_BREAK, PageLink
+from rest_framework.request import Request
+from rest_framework.test import APIRequestFactory
+
+import drf_link_header_pagination
+
+factory = APIRequestFactory()
+
+
+class TestLinkHeaderLimitOffsetPagination:
+    """
+    Unit tests for `pagination.LinkHeaderLimitOffsetPagination`.
+    """
+    def setup(self):
+        class ExamplePagination(drf_link_header_pagination.LinkHeaderLimitOffsetPagination):
+            default_limit = 4
+
+        self.pagination = ExamplePagination()
+        self.queryset = range(1, 101)
+
+    def paginate_queryset(self, request):
+        return list(self.pagination.paginate_queryset(self.queryset, request))
+
+    def get_paginated_response(self, queryset):
+        return self.pagination.get_paginated_response(queryset)
+
+    def get_html_context(self):
+        return self.pagination.get_html_context()
+
+    def test_no_offset(self):
+        request = Request(factory.get("/"))
+        queryset = self.paginate_queryset(request)
+        response = self.get_paginated_response(queryset)
+        context = self.get_html_context()
+
+        assert queryset == [1, 2, 3, 4]
+        assert response.data == [1, 2, 3, 4]
+        assert response["Link"] == (
+            '<http://testserver/?limit=4&offset=4>; rel="next", '
+            '<http://testserver/?limit=4>; rel="first", '
+            '<http://testserver/?limit=4&offset=96>; rel="last"'
+        )
+
+        assert context == {
+            "previous_url": None,
+            "next_url": "http://testserver/?limit=4&offset=4",
+            "page_links": [
+                PageLink("http://testserver/", 1, True, False),
+                PageLink("http://testserver/?offset=4", 2, False, False),
+                PageLink("http://testserver/?offset=8", 3, False, False),
+                PAGE_BREAK,
+                PageLink("http://testserver/?offset=96", 25, False, False),
+            ],
+        }
+        assert self.pagination.display_page_controls
+        assert isinstance(self.pagination.to_html(), type(""))
+
+    def test_second_page(self):
+        request = Request(factory.get("/", {"offset": 4}))
+        queryset = self.paginate_queryset(request)
+        response = self.get_paginated_response(queryset)
+        context = self.get_html_context()
+
+        assert queryset == [5, 6, 7, 8]
+        assert response.data == [5, 6, 7, 8]
+        assert response["Link"] == (
+            '<http://testserver/?limit=4>; rel="prev", '
+            '<http://testserver/?limit=4&offset=8>; rel="next", '
+            '<http://testserver/?limit=4>; rel="first", '
+            '<http://testserver/?limit=4&offset=96>; rel="last"'
+        )
+        assert context == {
+            "previous_url": "http://testserver/?limit=4",
+            "next_url": "http://testserver/?limit=4&offset=8",
+            "page_links": [
+                PageLink("http://testserver/", 1, False, False),
+                PageLink("http://testserver/?offset=4", 2, True, False),
+                PageLink("http://testserver/?offset=8", 3, False, False),
+                PAGE_BREAK,
+                PageLink("http://testserver/?offset=96", 25, False, False),
+            ],
+        }
+
+    def test_last_page(self):
+        request = Request(factory.get("/", {"offset": "96"}))
+        queryset = self.paginate_queryset(request)
+        response = self.get_paginated_response(queryset)
+        context = self.get_html_context()
+        assert queryset == [97, 98, 99, 100]
+        assert response.data == [97, 98, 99, 100]
+        assert response["Link"] == (
+            '<http://testserver/?limit=4&offset=92>; rel="prev", '
+            '<http://testserver/?limit=4>; rel="first"'
+        )
+        assert context == {
+            "previous_url": "http://testserver/?limit=4&offset=92",
+            "next_url": None,
+            "page_links": [
+                PageLink("http://testserver/", 1, False, False),
+                PAGE_BREAK,
+                PageLink("http://testserver/?offset=88", 23, False, False),
+                PageLink("http://testserver/?offset=92", 24, False, False),
+                PageLink("http://testserver/?offset=96", 25, True, False),
+            ],
+        }