first commit

app/chats/models.py

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+from datetime import datetime
+from enum import Enum
+from typing import TYPE_CHECKING
+
+from sqlalchemy import DateTime, Enum as SAEnum, ForeignKey, String, UniqueConstraint, func
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from app.database.base import Base
+
+if TYPE_CHECKING:
+    from app.messages.models import Message
+    from app.users.models import User
+
+
+class ChatType(str, Enum):
+    PRIVATE = "private"
+    GROUP = "group"
+    CHANNEL = "channel"
+
+
+class ChatMemberRole(str, Enum):
+    OWNER = "owner"
+    ADMIN = "admin"
+    MEMBER = "member"
+
+
+class Chat(Base):
+    __tablename__ = "chats"
+
+    id: Mapped[int] = mapped_column(primary_key=True, index=True)
+    type: Mapped[ChatType] = mapped_column(SAEnum(ChatType), nullable=False, index=True)
+    title: Mapped[str | None] = mapped_column(String(255), nullable=True)
+    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), server_default=func.now(), nullable=False)
+
+    members: Mapped[list["ChatMember"]] = relationship(back_populates="chat", cascade="all, delete-orphan")
+    messages: Mapped[list["Message"]] = relationship(back_populates="chat", cascade="all, delete-orphan")
+
+
+class ChatMember(Base):
+    __tablename__ = "chat_members"
+    __table_args__ = (UniqueConstraint("chat_id", "user_id", name="uq_chat_members_chat_id_user_id"),)
+
+    id: Mapped[int] = mapped_column(primary_key=True, index=True)
+    chat_id: Mapped[int] = mapped_column(ForeignKey("chats.id", ondelete="CASCADE"), nullable=False, index=True)
+    user_id: Mapped[int] = mapped_column(ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True)
+    role: Mapped[ChatMemberRole] = mapped_column(SAEnum(ChatMemberRole), nullable=False, default=ChatMemberRole.MEMBER)
+    joined_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), server_default=func.now(), nullable=False)
+
+    chat: Mapped["Chat"] = relationship(back_populates="members")
+    user: Mapped["User"] = relationship(back_populates="memberships")