from sqlalchemy import CheckConstraint, DateTime, ForeignKey, Index, Integer, String, Text, func
from sqlalchemy.orm import Mapped, mapped_column

from app.models.base import Base
from app.utils.id_gen import generate_id


class ChatGenerationTaskEvent(Base):
    """Append-only event log shared by ChatGenerationTask and GenerationRecord."""

    __tablename__ = "chat_generation_task_events"
    __table_args__ = (
        CheckConstraint(
            "(owner_type = 'chat_generation_task' AND task_id IS NOT NULL AND generation_record_id IS NULL) "
            "OR (owner_type = 'generation_record' AND task_id IS NULL AND generation_record_id IS NOT NULL)",
            name="ck_chat_generation_task_events_owner",
        ),
        Index("idx_chat_generation_task_events_task_created", "owner_type", "task_id", "created_at"),
        Index("idx_chat_generation_task_events_record_created", "owner_type", "generation_record_id", "created_at"),
        Index("idx_chat_generation_task_events_attempt_created", "owner_type", "generation_attempt_no", "created_at"),
    )

    id: Mapped[str] = mapped_column(String(32), primary_key=True, default=generate_id)
    owner_type: Mapped[str] = mapped_column(String(32), nullable=False, default="chat_generation_task", server_default="chat_generation_task", index=True)
    task_id: Mapped[str | None] = mapped_column(String(32), ForeignKey("chat_generation_tasks.id", ondelete="CASCADE"), nullable=True, index=True)
    generation_record_id: Mapped[str | None] = mapped_column(String(32), ForeignKey("generation_records.id", ondelete="CASCADE"), nullable=True, index=True)
    generation_attempt_no: Mapped[int] = mapped_column(Integer, nullable=False, default=1, server_default="1", index=True)
    generation_mode: Mapped[str | None] = mapped_column(String(32), nullable=True, index=True)
    event_type: Mapped[str] = mapped_column(String(64), index=True)
    from_status: Mapped[str | None] = mapped_column(String(32), nullable=True)
    to_status: Mapped[str | None] = mapped_column(String(32), nullable=True)
    from_stage: Mapped[str | None] = mapped_column(String(48), nullable=True)
    to_stage: Mapped[str | None] = mapped_column(String(48), nullable=True)
    message: Mapped[str | None] = mapped_column(Text, nullable=True)
    detail_json: Mapped[str | None] = mapped_column(Text, nullable=True)
    created_at = mapped_column(DateTime(timezone=True), server_default=func.now(), index=True)