from __future__ import annotations

from datetime import UTC, datetime

from sqlalchemy import DateTime, Index, String, Text, text
from sqlalchemy.orm import Mapped, mapped_column

from deerflow.persistence.base import Base


class ScheduledTaskRunRow(Base):
    __tablename__ = "scheduled_task_runs"

    id: Mapped[str] = mapped_column(String(64), primary_key=True)
    task_id: Mapped[str] = mapped_column(String(64), index=True)
    thread_id: Mapped[str] = mapped_column(String(64), index=True)
    run_id: Mapped[str | None] = mapped_column(String(64), nullable=True)
    scheduled_for: Mapped[datetime] = mapped_column(DateTime(timezone=True))
    trigger: Mapped[str] = mapped_column(String(16))
    status: Mapped[str] = mapped_column(String(16), index=True)
    error: Mapped[str | None] = mapped_column(Text, nullable=True)
    started_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True), nullable=True)
    finished_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True), nullable=True)
    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=lambda: datetime.now(UTC))

    __table_args__ = (
        # At most one active (queued/running) run per task. This is the atomic
        # arbiter for the ``dispatch_task`` skip policy: the non-atomic
        # ``has_active_runs`` check-then-create is a fast path, but two
        # concurrent dispatches (double-click / client retry / manual trigger
        # racing the poller) can both pass it, so the DB must reject the second
        # active insert. Sibling of the ``runs`` table's ``uq_runs_thread_active``
        # (PR #4003); that one keys on ``thread_id`` and does not cover the
        # default ``fresh_thread_per_run`` context (every dispatch gets a new
        # thread), which is why the scheduled-task run row needs its own guard.
        #
        # Condition is status-only, not ``overlap_policy``: the policy is fixed
        # to "skip" in the MVP, so a status-only predicate enforces the current
        # invariant without denormalizing ``overlap_policy`` onto the run row
        # for an unimplemented non-skip policy. If a non-skip policy is added
        # this must become conditional (e.g. ``... AND overlap_policy = 'skip'``).
        #
        # Must live in ORM ``__table_args__`` (not just the migration) because
        # the empty-DB bootstrap path runs ``create_all`` + ``stamp head`` and
        # never executes the migration that also defines this index.
        Index(
            "uq_scheduled_task_run_active",
            "task_id",
            unique=True,
            sqlite_where=text("status IN ('queued', 'running')"),
            postgresql_where=text("status IN ('queued', 'running')"),
        ),
    )