from fastapi import Depends, HTTPException, status
from fastapi.security import HTTPAuthorizationCredentials, HTTPBearer
from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from app.models.base import async_session
from app.models.user import User
from app.services.auth import decode_access_token, user_must_set_password
from app.services.credit.query_service import attach_credit_snapshot, get_available_credits
from app.services.system_config_cache import get_system_config_value

security = HTTPBearer(auto_error=False)


async def get_db():
    async with async_session() as session:
        try:
            yield session
            await session.commit()
        except Exception:
            await session.rollback()
            raise
        finally:
            await session.close()


async def get_current_user_allow_password_pending(
    credentials: HTTPAuthorizationCredentials | None = Depends(security),
    db: AsyncSession = Depends(get_db),
) -> User:
    if not credentials:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="未登录",
        )

    payload = decode_access_token(credentials.credentials)
    if not payload:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="登录已过期",
        )

    user_id = payload.get("sub")
    token_version = payload.get("ver", 0)
    device_type = payload.get("dev", "pc")

    # Skip captcha tokens
    if user_id and user_id.startswith("captcha:"):
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="无效的凭证",
        )

    result = await db.execute(select(User).where(User.id == user_id).limit(1))
    user = result.scalar_one_or_none()
    if not user or not user.is_active:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="账号不存在或已禁用",
        )

    # 单设备登录校验 — 根据全局开关 + 用户级覆盖决定是否启用
    override = getattr(user, "single_device_login_override", None)
    if override is True:
        enabled = True
    elif override is False:
        enabled = False
    else:
        # 跟随全局设置
        config_val = await get_system_config_value(db, "single_device_login_enabled")
        enabled = config_val is not None and config_val.lower() in ("true", "1", "yes")

    if enabled:
        # 按设备类型比对对应版本号
        if device_type == "mobile":
            current_version = user.mobile_token_version
        else:
            current_version = user.pc_token_version
        if token_version != current_version:
            raise HTTPException(
                status_code=status.HTTP_401_UNAUTHORIZED,
                detail="账号已在其他设备登录，请重新登录",
            )

    attach_credit_snapshot(user, await get_available_credits(db, user.id))
    return user


async def get_current_user(
    current_user: User = Depends(get_current_user_allow_password_pending),
) -> User:
    if user_must_set_password(current_user):
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail={
                "code": "PASSWORD_REQUIRED",
                "message": "请先设置登录密码",
            },
        )
    return current_user


async def get_optional_current_user(
    credentials: HTTPAuthorizationCredentials | None = Depends(security),
    db: AsyncSession = Depends(get_db),
) -> User | None:
    if not credentials:
        return None

    user_id = decode_access_token(credentials.credentials)
    if not user_id:
        return None

    if user_id.startswith("captcha:"):
        return None

    result = await db.execute(select(User).where(User.id == user_id).limit(1))
    user = result.scalar_one_or_none()
    if not user or not user.is_active:
        return None

    if user_must_set_password(user):
        return None

    attach_credit_snapshot(user, await get_available_credits(db, user.id))
    return user


async def get_admin_user(
    current_user: User = Depends(get_current_user_allow_password_pending),
) -> User:
    """验证后台用户权限。

    - user_type="admin" 的后台用户即可通过（含非管理员子账号）
    - 前端通过 allowed_menus 控制非管理员子账号的菜单可见性
    - 非后台用户: 403 拒绝
    """
    if current_user.user_type != "admin":
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="需要后台用户权限",
        )
    return current_user


async def get_backend_user(
    current_user: User = Depends(get_current_user_allow_password_pending),
) -> User:
    """与 get_admin_user 等价: 验证 user_type="admin" 的后台用户。"""
    if current_user.user_type != "admin":
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="需要后台用户权限",
        )
    return current_user