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

from app.config import get_settings
from app.core.security import (
    create_access_token,
    hash_password,
    session_redis_key,
    verify_password,
)
from app.models.user import User
from app.schemas.auth import TokenResponse, UserPublic

settings = get_settings()


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


async def register_user(
    db: AsyncSession,
    *,
    username: str,
    password: str,
) -> TokenResponse:
    existing = await db.scalar(select(User).where(User.username == username))
    if existing is not None:
        raise AuthError("用户名已存在")

    user = User(username=username, password_hash=hash_password(password))
    db.add(user)
    await db.flush()
    await db.refresh(user)

    token = create_access_token(str(user.id))
    return TokenResponse(
        access_token=token,
        user=UserPublic.model_validate(user),
    )


async def login_user(
    db: AsyncSession,
    *,
    username: str,
    password: str,
) -> TokenResponse:
    user = await db.scalar(select(User).where(User.username == username))
    if user is None or not verify_password(password, user.password_hash):
        raise AuthError("用户名或密码错误")

    token = create_access_token(str(user.id))
    return TokenResponse(
        access_token=token,
        user=UserPublic.model_validate(user),
    )


async def store_session(redis_client, token: str, user_id: int) -> None:
    ttl = settings.access_token_expire_minutes * 60
    await redis_client.setex(session_redis_key(token), ttl, str(user_id))


async def revoke_session(redis_client, token: str) -> None:
    await redis_client.delete(session_redis_key(token))


async def session_user_id(redis_client, token: str) -> int | None:
    raw = await redis_client.get(session_redis_key(token))
    if raw is None:
        return None
    return int(raw)


async def get_user_by_id(db: AsyncSession, user_id: int) -> User | None:
    return await db.get(User, user_id)