strawberry_django_paginated.py

from typing import Generic, TypeVar

import strawberry
from django.core.paginator import EmptyPage, Page, PageNotAnInteger, Paginator
from django.db.models.query import QuerySet

T = TypeVar("T")


MAX_PAGE_SIZE = 100


@strawberry.interface
class PageInput:
    page: int = 1
    page_size: int = 10

    def paginate(self, qs: QuerySet[T]) -> "Paginated[T]":
        return Paginated.paginate(qs, page=self.page, page_size=self.page_size)


@strawberry.interface
class PageInfo:
    page: int
    total_pages: int
    total_items: int
    has_next: bool
    has_prev: bool


@strawberry.type
class Paginated(Generic[T], PageInfo):
    page: int
    total_pages: int
    total_items: int
    has_next: bool
    has_prev: bool
    data: list[T]

    @classmethod
    def paginate(
        cls, qs: QuerySet[T], page: int = 1, page_size: int = 10
    ) -> "Paginated[T]":
        page = cls.get_page(qs, page_size, page)

        return cls(
            page=page.number,
            total_pages=page.paginator.num_pages,
            total_items=page.paginator.count,
            has_next=page.has_next(),
            has_prev=page.has_previous(),
            data=page.object_list,
        )

    @staticmethod
    def get_page(qs: QuerySet, page_size: int, page: int) -> Page:
        if page_size > MAX_PAGE_SIZE:
            page_size = MAX_PAGE_SIZE

        p = Paginator(qs, page_size)

        try:
            page_obj = p.page(page)
        except PageNotAnInteger:
            page_obj = p.page(1)
        except EmptyPage:
            page_obj = p.page(p.num_pages)

        return page_obj