from typing import Type, TypeVar, Generic, Sequence, Optional, Callable, Awaitable
import math
from fastapi import Query
from pydantic import BaseModel
from tortoise.queryset import QuerySet
from tortoise.models import Model

T = TypeVar('T', bound=BaseModel)
M = TypeVar('M', bound=Model)

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"""
    page: int = Query(1, ge=1, description="Page number")
    size: int = Query(10, gt=0, le=200, description="Page size")
    order_by: Optional[str] = Query(None, max_length=32, description="Sort key")

async def pagination(
    pydantic_model: Type[T],
    query_set: QuerySet[M],
    params: Params,
    callback: Optional[Callable[[QuerySet[M]], Awaitable[QuerySet[M]]]] = None
) -> PaginationPydantic[T]:
    """分页响应"""
    page: int = params.page
    size: int = params.size
    order_by: Optional[str] = params.order_by
    total = await query_set.count()

    # 计算总页数
    total_pages = math.ceil(total / size) if total > 0 else 1

    if page > total_pages and total > 0:
        raise ValueError("页数输入有误")

    # 排序
    if order_by:
        order_by_fields = order_by.split(',')
        query_set = query_set.order_by(*order_by_fields)

    # 分页
    query_set = query_set.offset((page - 1) * size).limit(size)

    # 回调处理
    if callback:
        query_set = await callback(query_set)

    # 获取数据
    data = await pydantic_model.from_queryset(query_set)

    return PaginationPydantic[T](
        total=total,
        page=page,
        size=size,
        total_pages=total_pages,
        data=data
    )