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")