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backend/app/services/auth_service.py

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+"""认证服务：注册、登录、登出、Session 校验。"""
+
+from app.core.errors import (
+    AuthRequiredError,
+    ConflictError,
+    InvalidCredentialsError,
+)
+from app.core.security import hash_password, verify_password
+from app.core.session import create_session, delete_session, get_session_user
+from app.models.user import User
+from app.repositories.plan_repo import PlanRepository
+from app.repositories.user_repo import UserRepository
+from sqlalchemy.orm import Session
+
+
+class AuthService:
+    def __init__(self, session: Session) -> None:
+        self._session = session
+        self._user_repo = UserRepository(session)
+        self._plan_repo = PlanRepository(session)
+
+    def register(self, username: str, email: str, password: str) -> tuple[User, str]:
+        """注册新用户。返回 (user, session_token)。
+
+        Raises:
+            ConflictError: 用户名或邮箱已存在
+        """
+        username_taken, email_taken = self._user_repo.exists_username_or_email(username, email)
+        if username_taken:
+            raise ConflictError("用户名已被占用。", code="USERNAME_TAKEN")
+        if email_taken:
+            raise ConflictError("邮箱已被注册。", code="EMAIL_TAKEN")
+
+        plan = self._plan_repo.get_or_create_free()
+        user = self._user_repo.create(
+            username=username,
+            email=email,
+            password_hash=hash_password(password),
+            plan_id=plan.id,
+        )
+        self._session.commit()
+
+        token = create_session(user.id)
+        return user, token
+
+    def login(self, username_or_email: str, password: str) -> tuple[User, str]:
+        """登录。返回 (user, session_token)。
+
+        Raises:
+            InvalidCredentialsError: 用户名/邮箱或密码错误
+        """
+        user = self._user_repo.get_by_username_or_email(username_or_email)
+        if user is None:
+            raise InvalidCredentialsError()
+        if not verify_password(password, user.password_hash):
+            raise InvalidCredentialsError()
+        if user.status != "active":
+            raise InvalidCredentialsError("账户已被禁用。")
+
+        token = create_session(user.id)
+        return user, token
+
+    def logout(self, session_token: str) -> None:
+        """登出：删除 session。"""
+        delete_session(session_token)
+
+    def get_current_user(self, session_token: str | None) -> User:
+        """根据 session token 获取当前用户。
+
+        Raises:
+            AuthRequiredError: 未登录或 session 已过期
+        """
+        if not session_token:
+            raise AuthRequiredError()
+        user_id = get_session_user(session_token)
+        if user_id is None:
+            raise AuthRequiredError("登录已过期，请重新登录。")
+        user = self._user_repo.get_by_id(user_id)
+        if user is None or user.status != "active":
+            raise AuthRequiredError()
+        return user
+
+    def change_password(self, user: User, new_password: str) -> None:
+        """修改密码。"""
+        self._user_repo.update_password(user, hash_password(new_password))
+        self._session.commit()