Adding CustomPaginator util.

b_dynamodb_common/utils/custom_paginator.py

@@ -0,0 +1,40 @@
+from operator import attrgetter
+from typing import List, Optional
+
+
+class CustomPaginator:
+    def __init__(self, objects: List[object], key: str) -> None:
+        self.__key = key
+        self.__objects = objects
+        self.__objects.sort(key=attrgetter(key), reverse=False)
+        self.__object_index_map = {_object.__getattribute__(key): index for index, _object in enumerate(self.__objects)}
+        self.__next_page_id = None
+
+    @property
+    def count(self) -> int:
+        return len(self.__objects)
+
+    @property
+    def next_page_id(self) -> Optional[str]:
+        return self.__next_page_id
+
+    def page(self, limit: Optional[int] = None, page_id: Optional[str] = None) -> List[object]:
+        if limit and (not isinstance(limit, int) or limit < 0):
+            raise ValueError('Limit must be a positive integer.')
+
+        limit = len(self.__objects) if limit is None else limit
+
+        page_start_idx = 0 if page_id is None else self.__object_index_map.get(page_id)
+
+        if page_start_idx is None:
+            return []
+
+        page_end_idx = page_start_idx + limit
+        page_end_idx = self.count if page_end_idx >= self.count else page_end_idx
+
+        if page_end_idx == self.count:
+            self.__next_page_id = None
+        else:
+            self.__next_page_id = self.__objects[page_end_idx].__getattribute__(self.__key)
+
+        return self.__objects[page_start_idx:page_end_idx]