from datetime import datetime
from typing import Optional

from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer
from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from app.core.database import get_db
from app.core.security import create_access_token, hash_password, verify_password, decode_access_token
from app.models.user import User, UserStatus
from app.schemas.user import UserCreate, UserLogin, Token

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="/api/auth/login")


class AuthService:
    """认证服务"""

    @staticmethod
    async def register_user(
        db: AsyncSession,
        user_data: UserCreate,
    ) -> User:
        """
        注册用户
        
        Args:
            db: 数据库会话
            user_data: 用户数据
            
        Returns:
            创建的用户对象
        """
        # 检查邮箱是否已存在
        result = await db.execute(select(User).where(User.email == user_data.email))
        if result.scalar_one_or_none():
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="邮箱已被注册"
            )
        
        # 创建用户
        hashed_password = hash_password(user_data.password)
        user = User(
            company_id=user_data.company_id,
            email=user_data.email,
            hashed_password=hashed_password,
            full_name=user_data.full_name,
            role=user_data.role,
        )
        
        db.add(user)
        await db.commit()
        await db.refresh(user)
        return user

    @staticmethod
    async def authenticate_user(
        db: AsyncSession,
        login_data: UserLogin,
    ) -> tuple[User, str]:
        """
        认证用户并生成 Token
        
        Args:
            db: 数据库会话
            login_data: 登录数据
            
        Returns:
            用户对象和访问令牌
            
        Raises:
            HTTPException: 认证失败
        """
        # 查找用户
        result = await db.execute(select(User).where(User.email == login_data.email))
        user = result.scalar_one_or_none()
        
        if not user:
            raise HTTPException(
                status_code=status.HTTP_401_UNAUTHORIZED,
                detail="邮箱或密码错误"
            )
        
        # 验证密码
        if not verify_password(login_data.password, user.hashed_password):
            raise HTTPException(
                status_code=status.HTTP_401_UNAUTHORIZED,
                detail="邮箱或密码错误"
            )
        
        # 检查用户状态
        if user.status != UserStatus.ACTIVE.value:
            raise HTTPException(
                status_code=status.HTTP_403_FORBIDDEN,
                detail=f"用户已被{user.status}"
            )
        
        # 更新最后登录时间
        user.last_login_at = datetime.utcnow()
        await db.commit()
        await db.refresh(user)
        
        # 生成 Token
        access_token = create_access_token(data={"sub": str(user.id), "email": user.email})
        
        return user, access_token

    @staticmethod
    async def get_current_user(
        token: str = Depends(oauth2_scheme),
        db: AsyncSession = Depends(get_db),
    ) -> User:
        """
        获取当前用户
        
        Args:
            token: JWT token
            db: 数据库会话
            
        Returns:
            当前用户对象
            
        Raises:
            HTTPException: Token 无效或用户不存在
        """
        credentials_exception = HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="无法验证凭据",
            headers={"WWW-Authenticate": "Bearer"},
        )
        
        payload = decode_access_token(token)
        if not payload:
            raise credentials_exception
        
        user_id: str = payload.get("sub")
        if not user_id:
            raise credentials_exception
        
        result = await db.execute(select(User).where(User.id == int(user_id)))
        user = result.scalar_one_or_none()
        
        if not user:
            raise credentials_exception
        
        if user.status != UserStatus.ACTIVE.value:
            raise HTTPException(
                status_code=status.HTTP_403_FORBIDDEN,
                detail="用户已被禁用"
            )
        
        return user


# 单例实例
auth_service = AuthService()