"""Disable sources on retired platforms, so the scheduler stops selecting them.

Milestone #406, phase 1 (switch pixiv off). Rule #171 records the scope decision.

## Why this is a migration and not a button

The live instance had one pixiv source still ENABLED when pixiv was retired
(read 2026-09-13, step 1) even though the operator believed it gone. Unregistering
a platform removes it from code; it does not touch the `source` rows that name it.
Left enabled, that row keeps being picked by the scheduler every interval, and
`download_backends` now refuses it with `unsupported_url` — forever, as a
climbing failure count on a source the operator has already given up.

A migration reaches the live instance on deploy without depending on anyone
finding the row and clicking it. The `run_download` guard is what makes a stale
enabled row SAFE; this is what makes it QUIET.

## Deliberately NOT done here

- **No rows are deleted.** Deleting a source sets its posts' `source_id` to NULL
  (FK `ON DELETE SET NULL`), and `uq_post_artist_external_id_null_source` can
  reject that if a source-less copy of one of those posts already exists. That
  needs checking against real data first, which is phase 2's job (step 6). A
  disable cannot collide with anything.
- **No posts or images are touched.** The art stays.
- **deviantart is included** because #3069 retired it and nothing disabled its
  rows either. The read found none, so for it this is a no-op — written anyway,
  so the statement names every retired platform rather than just the latest one.

## Hardcoded platform names

A migration is a record of one event, frozen in time, so it names the platforms
it acted on rather than importing today's registry — the registry will keep
changing and this revision must not.

Revision ID: 0097
Revises: 0096
Create Date: 2026-09-13

"""
from typing import Sequence, Union

from alembic import op

revision: str = "0097"
down_revision: Union[str, None] = "0096"
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    # Clears the failure state the same way `SourceService.update` does when a
    # source is disabled through the app (issue #1285), so a retired source
    # does not keep showing as failing after it stops being polled. A disable
    # done here and one done by clicking must leave identical rows.
    op.execute(
        "UPDATE source SET enabled = false, last_error = NULL, "
        "error_type = NULL, consecutive_failures = 0 "
        "WHERE enabled AND platform IN ('pixiv', 'deviantart')"
    )


def downgrade() -> None:
    # Irreversible by design: which of these rows were enabled before is not
    # recorded, and re-enabling every retired-platform source would resume
    # polling services the product no longer supports. Rule #22 owes no
    # migration story back to a dropped platform.
    pass