from sqlalchemy import func, select
from sqlalchemy.ext.asyncio import AsyncSession

from app.core.roles import ROLE_ADMIN
from app.core.security import hash_password
from app.models.user import User
from app.schemas.admin_user import AdminUserCreate, AdminUserUpdate

DEFAULT_PAGE_SIZE = 20
MAX_PAGE_SIZE = 100


class AdminUserError(Exception):
    def __init__(self, message: str) -> None:
        self.message = message
        super().__init__(message)


async def list_users(
    db: AsyncSession,
    *,
    page: int = 1,
    page_size: int = DEFAULT_PAGE_SIZE,
) -> tuple[list[User], int]:
    page_size = min(max(page_size, 1), MAX_PAGE_SIZE)
    page = max(page, 1)
    offset = (page - 1) * page_size

    total = await db.scalar(select(func.count()).select_from(User)) or 0
    result = await db.scalars(
        select(User).order_by(User.id.desc()).offset(offset).limit(page_size)
    )
    return list(result.all()), total


async def create_user(db: AsyncSession, body: AdminUserCreate) -> User:
    existing = await db.scalar(select(User).where(User.username == body.username))
    if existing is not None:
        raise AdminUserError("用户名已存在")

    if body.phone:
        phone_taken = await db.scalar(select(User).where(User.phone == body.phone))
        if phone_taken is not None:
            raise AdminUserError("手机号已被使用")

    user = User(
        username=body.username,
        password_hash=hash_password(body.password),
        phone=body.phone,
        role_id=body.role_id,
        vip_end_time=body.vip_end_time,
    )
    db.add(user)
    await db.flush()
    await db.refresh(user)
    return user


async def update_user(
    db: AsyncSession,
    user_id: int,
    body: AdminUserUpdate,
    *,
    actor_id: int,
) -> User:
    user = await db.get(User, user_id)
    if user is None:
        raise AdminUserError("用户不存在")

    if body.username is not None and body.username != user.username:
        taken = await db.scalar(select(User).where(User.username == body.username))
        if taken is not None:
            raise AdminUserError("用户名已存在")
        user.username = body.username

    if body.phone is not None:
        if body.phone != user.phone:
            taken = await db.scalar(select(User).where(User.phone == body.phone))
            if taken is not None:
                raise AdminUserError("手机号已被使用")
        user.phone = body.phone

    if body.role_id is not None:
        if user_id == actor_id and body.role_id != ROLE_ADMIN:
            raise AdminUserError("不能修改自己的管理员角色")
        user.role_id = body.role_id

    if body.password:
        user.password_hash = hash_password(body.password)

    if body.clear_vip_end_time:
        user.vip_end_time = None
    elif body.vip_end_time is not None:
        user.vip_end_time = body.vip_end_time

    await db.flush()
    await db.refresh(user)
    return user


async def delete_user(db: AsyncSession, user_id: int, *, actor_id: int) -> None:
    if user_id == actor_id:
        raise AdminUserError("不能删除当前登录账号")

    user = await db.get(User, user_id)
    if user is None:
        raise AdminUserError("用户不存在")

    await db.delete(user)