"""conversations.last_curator_run_at — tracks scheduler progress per-conversation

Revision ID: 0048
Revises: 0047
Create Date: 2026-05-22

Phase 2 of the conversation+curator architecture (Fable #172). The
scheduler runs every 15 minutes and processes any journal conversation
with messages newer than its `last_curator_run_at` timestamp. NULL
means "never run; process all of today on first sweep."
"""
from alembic import op
import sqlalchemy as sa


revision = "0048"
down_revision = "0047"
branch_labels = None
depends_on = None


def upgrade() -> None:
    op.add_column(
        "conversations",
        sa.Column(
            "last_curator_run_at",
            sa.DateTime(timezone=True),
            nullable=True,
        ),
    )
    # Indexed because the scheduler's selection query is
    # WHERE conversation_type='journal' AND (last_curator_run_at IS NULL OR ...)
    # which benefits from a partial index narrowed to journal rows.
    op.create_index(
        "ix_conversations_journal_last_curator",
        "conversations",
        ["last_curator_run_at"],
        postgresql_where=sa.text("conversation_type = 'journal'"),
    )


def downgrade() -> None:
    op.drop_index(
        "ix_conversations_journal_last_curator",
        table_name="conversations",
    )
    op.drop_column("conversations", "last_curator_run_at")