from typing import Generic, Optional, Sequence, TypeVar

import math
from fastapi import Query
from pydantic import BaseModel
from tortoise.queryset import QuerySet

T = TypeVar("T")


class PaginationPydantic(BaseModel, Generic[T]):
    """分页模型"""
    status_code: int = 200
    message: str = "Success"
    total: int
    page: int
    size: int
    total_pages: int
    data: Sequence[T]


class Params(BaseModel):
    """传参"""
    # 设置默认值为1，不能够小于1
    page: int = Query(1, ge=1, description="Page number")

    # 设置默认值为10，最大为100
    size: int = Query(10, gt=0, le=200, description="Page size")

    # 默认值None表示选传
    order_by: Optional[str] = Query(None, max_length=32, description="Sort key")


async def pagination(pydantic_model, query_set: QuerySet, params: Params, callback=None):
    """分页响应"""
    """
    pydantic_model: Pydantic model
    query_set: QuerySet
    params: Params
    callback: if you want to do something for query_set,it will be useful.
    """
    page: int = params.page
    size: int = params.size
    order_by: str = params.order_by
    total = await query_set.count()

    # 通过总数和每页数量计算出总页数
    total_pages = math.ceil(total / size)

    if page > total_pages and total:  # 排除查询集为空时报错，即total=0时
        raise ValueError("页数输入有误")

    # 排序后分页
    if order_by:
        order_by = order_by.split(',')
        query_set = query_set.order_by(*order_by)

    # 分页
    query_set = query_set.offset((page - 1) * size)  # 页数 * 页面大小=偏移量
    query_set = query_set.limit(size)

    if callback:
        """对查询集操作"""
        query_set = await callback(query_set)

    # query_set = await query_set
    data = await pydantic_model.from_queryset(query_set)
    return PaginationPydantic(**{
        "total": total,
        "page": page,
        "size": size,
        "total_pages": total_pages,
        "data": data,
    })