首个可运行的版本

backend/app/models/__init__.py

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+"""SQLAlchemy 模型包 - 导入所有模型供 Alembic 自动检测"""
+
+from app.models.user import User
+from app.models.conversation import Conversation
+from app.models.conversation_member import ConversationMember
+from app.models.message import Message
+from app.models.friend import Friend
+from app.models.friend_request import FriendRequest
+from app.models.system_config import SystemConfig
+
+__all__ = [
+    "User",
+    "Conversation",
+    "ConversationMember",
+    "Message",
+    "Friend",
+    "FriendRequest",
+    "SystemConfig",
+]

backend/app/models/conversation.py

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+"""会话模型（私聊 + 群聊）"""
+
+from datetime import datetime, timezone
+
+from sqlalchemy import String, DateTime, ForeignKey, Text
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from app.database import Base
+
+
+class Conversation(Base):
+    __tablename__ = "conversations"
+
+    id: Mapped[str] = mapped_column(String(36), primary_key=True)
+    type: Mapped[str] = mapped_column(String(20), nullable=False)  # private / group
+    name: Mapped[str | None] = mapped_column(String(100), nullable=True)  # 群聊名称
+    avatar_url: Mapped[str | None] = mapped_column(String(500), nullable=True)  # 群头像
+    description: Mapped[str | None] = mapped_column(String(500), nullable=True)  # 群描述
+    creator_id: Mapped[str | None] = mapped_column(String(36), ForeignKey("users.id", ondelete="SET NULL"), nullable=True)
+    last_message_at: Mapped[datetime | None] = mapped_column(DateTime, nullable=True)
+    last_message_preview: Mapped[str | None] = mapped_column(String(200), nullable=True)
+    created_at: Mapped[datetime] = mapped_column(DateTime, default=lambda: datetime.utcnow())
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime,
+        default=lambda: datetime.utcnow(),
+        onupdate=lambda: datetime.utcnow(),
+    )
+
+    # 关系
+    members = relationship("ConversationMember", back_populates="conversation", cascade="all, delete-orphan")
+    messages = relationship("Message", back_populates="conversation", cascade="all, delete-orphan")
+    creator = relationship("User", foreign_keys=[creator_id])

backend/app/models/conversation_member.py

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+"""会话成员模型"""
+
+from datetime import datetime, timezone
+
+from sqlalchemy import String, DateTime, ForeignKey, UniqueConstraint
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from app.database import Base
+
+
+class ConversationMember(Base):
+    __tablename__ = "conversation_members"
+    __table_args__ = (
+        UniqueConstraint("conversation_id", "user_id", name="uq_conv_user"),
+    )
+
+    id: Mapped[str] = mapped_column(String(36), primary_key=True)
+    conversation_id: Mapped[str] = mapped_column(
+        String(36), ForeignKey("conversations.id", ondelete="CASCADE"), nullable=False
+    )
+    user_id: Mapped[str] = mapped_column(
+        String(36), ForeignKey("users.id", ondelete="CASCADE"), nullable=False
+    )
+    role: Mapped[str] = mapped_column(String(20), default="member")  # owner / admin / member
+    nickname: Mapped[str | None] = mapped_column(String(50), nullable=True)  # 群内昵称
+    last_read_message_id: Mapped[str | None] = mapped_column(String(36), nullable=True)
+    joined_at: Mapped[datetime] = mapped_column(DateTime, default=lambda: datetime.utcnow())
+    left_at: Mapped[datetime | None] = mapped_column(DateTime, nullable=True)
+
+    # 关系
+    conversation = relationship("Conversation", back_populates="members")
+    user = relationship("User", back_populates="conversations")

backend/app/models/friend.py

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+"""好友关系模型"""
+
+from datetime import datetime, timezone
+
+from sqlalchemy import String, DateTime, ForeignKey, UniqueConstraint
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from app.database import Base
+
+
+class Friend(Base):
+    __tablename__ = "friends"
+    __table_args__ = (
+        UniqueConstraint("user_id", "friend_user_id", name="uq_friendship"),
+    )
+
+    id: Mapped[str] = mapped_column(String(36), primary_key=True)
+    user_id: Mapped[str] = mapped_column(
+        String(36), ForeignKey("users.id", ondelete="CASCADE"), nullable=False
+    )
+    friend_user_id: Mapped[str] = mapped_column(
+        String(36), ForeignKey("users.id", ondelete="CASCADE"), nullable=False
+    )
+    remark: Mapped[str | None] = mapped_column(String(50), nullable=True)  # 好友备注
+    created_at: Mapped[datetime] = mapped_column(DateTime, default=lambda: datetime.utcnow())
+
+    # 关系
+    user = relationship("User", foreign_keys=[user_id], back_populates="friends")
+    friend_user = relationship("User", foreign_keys=[friend_user_id], back_populates="friend_of")

backend/app/models/friend_request.py

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+"""好友请求模型"""
+
+from datetime import datetime, timezone
+
+from sqlalchemy import String, DateTime, ForeignKey
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from app.database import Base
+
+
+class FriendRequest(Base):
+    __tablename__ = "friend_requests"
+
+    id: Mapped[str] = mapped_column(String(36), primary_key=True)
+    from_user_id: Mapped[str] = mapped_column(
+        String(36), ForeignKey("users.id", ondelete="CASCADE"), nullable=False
+    )
+    to_user_id: Mapped[str] = mapped_column(
+        String(36), ForeignKey("users.id", ondelete="CASCADE"), nullable=False
+    )
+    message: Mapped[str | None] = mapped_column(String(200), nullable=True)  # 验证消息
+    status: Mapped[str] = mapped_column(String(20), default="pending")  # pending / accepted / rejected
+    created_at: Mapped[datetime] = mapped_column(DateTime, default=lambda: datetime.utcnow())
+    responded_at: Mapped[datetime | None] = mapped_column(DateTime, nullable=True)
+
+    # 关系
+    from_user = relationship("User", foreign_keys=[from_user_id], back_populates="sent_requests")
+    to_user = relationship("User", foreign_keys=[to_user_id], back_populates="received_requests")

backend/app/models/message.py

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+"""消息模型"""
+
+from datetime import datetime, timezone
+
+from sqlalchemy import String, Text, Boolean, DateTime, ForeignKey, Index
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from app.database import Base
+
+
+class Message(Base):
+    __tablename__ = "messages"
+    __table_args__ = (
+        Index("ix_messages_conv_created", "conversation_id", "created_at"),
+    )
+
+    id: Mapped[str] = mapped_column(String(36), primary_key=True)
+    conversation_id: Mapped[str] = mapped_column(
+        String(36), ForeignKey("conversations.id", ondelete="CASCADE"), nullable=False
+    )
+    sender_id: Mapped[str] = mapped_column(
+        String(36), ForeignKey("users.id", ondelete="CASCADE"), nullable=False
+    )
+    type: Mapped[str] = mapped_column(String(20), default="text")  # text / image / file / system
+    content: Mapped[str] = mapped_column(Text, nullable=False)
+    reply_to_id: Mapped[str | None] = mapped_column(
+        String(36), ForeignKey("messages.id", ondelete="SET NULL"), nullable=True
+    )
+    is_deleted: Mapped[bool] = mapped_column(Boolean, default=False)
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime, default=lambda: datetime.utcnow(), index=True
+    )
+
+    # 关系
+    conversation = relationship("Conversation", back_populates="messages")
+    sender = relationship("User", back_populates="sent_messages", foreign_keys=[sender_id])
+    reply_to = relationship("Message", remote_side="Message.id")

backend/app/models/system_config.py

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+"""系统配置模型"""
+
+from datetime import datetime, timezone
+
+from sqlalchemy import String, Text, DateTime, ForeignKey
+from sqlalchemy.orm import Mapped, mapped_column
+
+from app.database import Base
+
+
+class SystemConfig(Base):
+    __tablename__ = "system_configs"
+
+    id: Mapped[str] = mapped_column(String(36), primary_key=True)
+    key: Mapped[str] = mapped_column(String(100), unique=True, nullable=False, index=True)
+    value: Mapped[str] = mapped_column(Text, nullable=False)
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime,
+        default=lambda: datetime.utcnow(),
+        onupdate=lambda: datetime.utcnow(),
+    )
+    updated_by: Mapped[str | None] = mapped_column(
+        String(36), ForeignKey("users.id", ondelete="SET NULL"), nullable=True
+    )

backend/app/models/user.py

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+"""用户模型"""
+
+from datetime import datetime, timezone
+
+from sqlalchemy import String, Boolean, DateTime, Text
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from app.database import Base
+
+
+class User(Base):
+    __tablename__ = "users"
+
+    id: Mapped[str] = mapped_column(String(36), primary_key=True)
+    username: Mapped[str] = mapped_column(String(50), unique=True, nullable=False, index=True)
+    email: Mapped[str] = mapped_column(String(255), unique=True, nullable=False, index=True)
+    password_hash: Mapped[str] = mapped_column(String(255), nullable=False)
+    avatar_url: Mapped[str | None] = mapped_column(String(500), nullable=True)
+    bio: Mapped[str | None] = mapped_column(String(200), nullable=True)
+    status: Mapped[str] = mapped_column(String(20), default="offline")  # online/offline/away
+    is_admin: Mapped[bool] = mapped_column(Boolean, default=False)
+    is_banned: Mapped[bool] = mapped_column(Boolean, default=False)
+    banned_reason: Mapped[str | None] = mapped_column(String(500), nullable=True)
+    last_seen_at: Mapped[datetime | None] = mapped_column(DateTime, nullable=True)
+    created_at: Mapped[datetime] = mapped_column(DateTime, default=lambda: datetime.utcnow())
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime,
+        default=lambda: datetime.utcnow(),
+        onupdate=lambda: datetime.utcnow(),
+    )
+
+    # 关系
+    sent_messages = relationship("Message", back_populates="sender", foreign_keys="Message.sender_id")
+    conversations = relationship("ConversationMember", back_populates="user")
+    friends = relationship("Friend", foreign_keys="Friend.user_id", back_populates="user")
+    friend_of = relationship("Friend", foreign_keys="Friend.friend_user_id", back_populates="friend_user")
+    sent_requests = relationship("FriendRequest", foreign_keys="FriendRequest.from_user_id", back_populates="from_user")
+    received_requests = relationship("FriendRequest", foreign_keys="FriendRequest.to_user_id", back_populates="to_user")