import uuid
from datetime import datetime

from sqlalchemy import DateTime, ForeignKey, Index, String, Text, text
from sqlalchemy.dialects.postgresql import UUID
from sqlalchemy.orm import Mapped, mapped_column, relationship

from api.models.base import Base, new_uuid


BROADCAST = "broadcast"
MESSAGE_KINDS = ("message", "news", "standing")


class AgentMessage(Base):
    __tablename__ = "agent_messages"
    __table_args__ = (
        Index("ix_agent_messages_to_kind_archived", "to_agent", "kind", "archived_at"),
    )

    id: Mapped[uuid.UUID] = mapped_column(
        UUID(as_uuid=True), primary_key=True, default=new_uuid
    )
    from_agent: Mapped[str] = mapped_column(String(100), nullable=False)
    to_agent: Mapped[str] = mapped_column(String(100), nullable=False, index=True)
    subject: Mapped[str] = mapped_column(String(500), nullable=False)
    body: Mapped[str] = mapped_column(Text, nullable=False)
    thread_id: Mapped[uuid.UUID | None] = mapped_column(
        UUID(as_uuid=True),
        ForeignKey("agent_messages.id", ondelete="SET NULL"),
        nullable=True,
        index=True,
    )
    read_at: Mapped[datetime | None] = mapped_column(
        DateTime(timezone=True), nullable=True
    )
    archived_at: Mapped[datetime | None] = mapped_column(
        DateTime(timezone=True), nullable=True
    )
    # STATE-WP-0093: kind is only meaningful for broadcasts
    # (message | news | standing); direct messages stay "message".
    kind: Mapped[str] = mapped_column(
        String(20), nullable=False, default="message", server_default="message"
    )
    expires_at: Mapped[datetime | None] = mapped_column(
        DateTime(timezone=True), nullable=True
    )
    supersedes_id: Mapped[uuid.UUID | None] = mapped_column(
        UUID(as_uuid=True),
        ForeignKey("agent_messages.id", ondelete="SET NULL"),
        nullable=True,
    )
    created_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True),
        server_default=text("now()"),
        nullable=False,
    )

    thread_root: Mapped["AgentMessage | None"] = relationship(
        "AgentMessage",
        remote_side="AgentMessage.id",
        foreign_keys=[thread_id],
        lazy="select",
    )


class MessageReceipt(Base):
    """Per-reader state for broadcast messages (STATE-WP-0093).

    Written only for broadcasts; direct messages keep the global
    ``AgentMessage.read_at``.
    """

    __tablename__ = "message_receipts"

    message_id: Mapped[uuid.UUID] = mapped_column(
        UUID(as_uuid=True),
        ForeignKey("agent_messages.id", ondelete="CASCADE"),
        primary_key=True,
    )
    agent: Mapped[str] = mapped_column(String(100), primary_key=True, index=True)
    delivered_at: Mapped[datetime | None] = mapped_column(
        DateTime(timezone=True), nullable=True
    )
    read_at: Mapped[datetime | None] = mapped_column(
        DateTime(timezone=True), nullable=True
    )
    acknowledged_at: Mapped[datetime | None] = mapped_column(
        DateTime(timezone=True), nullable=True
    )