"""How often a source should reconcile itself.

Until now a sync ran only when an operator asked for one, which made an index
that keeps step with its folder or repository something a person had to
remember rather than something the platform did. ``sync_interval_seconds``
is what the scheduler reads.

Nullable, with no server default, on purpose. NULL means *only when asked* --
exactly what every existing source already does -- so this migration changes
the behaviour of precisely nothing until an operator sets an interval.
Periodically reading someone's filesystem or repository is a decision, not
something an upgrade should quietly begin doing.

The partial index covers the scheduler's only query: the sources that have an
interval at all. In a deployment where most sources are manual, that index
stays a fraction of the table.
"""

from __future__ import annotations

import sqlalchemy as sa
from alembic import op

revision = "0020_source_sync_schedule"
down_revision = "0019_job_listing_index"
branch_labels = None
depends_on = None


def upgrade() -> None:
    op.add_column(
        "sources",
        sa.Column("sync_interval_seconds", sa.Integer(), nullable=True),
        schema="content",
    )
    op.create_index(
        "ix_content_sources_due",
        "sources",
        ["last_sync_at"],
        schema="content",
        postgresql_where=sa.text("sync_interval_seconds IS NOT NULL"),
    )


def downgrade() -> None:
    op.drop_index("ix_content_sources_due", "sources", schema="content")
    op.drop_column("sources", "sync_interval_seconds", schema="content")