"""Add diskhealthjson to endpointstates.

Per-drive health, kept separate from disksjson. That column answers "how full
is this drive"; this one answers "is this drive dying". Merging them would mean
a capacity collection failure and a health collection failure could not be told
apart, and the two come from different WMI sources with different failure modes.

JSON rather than scalar columns because a machine has a variable number of
drives and each carries its own verdict, and because the agent reports the same
drive from two sources - MSFT_PhysicalDisk for NVMe and Win32_DiskDrive for
ATA/SATA - which the server keeps side by side rather than collapsing.

MEDIUMTEXT for consistency with the other snapshot columns on this table.

Nullable with no backfill. A drive whose health has never been reported is not
a healthy drive, and defaulting to an empty list would read as "no disks have
problems" on every endpoint that predates this column.

Idempotent: the column-add checks the live schema first, so a re-run and a
db.create_all() site both stay clean on strict MySQL 8.
"""
from alembic import op

import sqlalchemy as sa


# revision identifiers, used by Alembic.
revision = 'endpoints0014diskhealth'
down_revision = 'endpoints0013inventorycolumns'
branch_labels = None
depends_on = None

TABLE_NAME = 'endpointstates'
COLUMN_NAME = 'diskhealthjson'


def _has_column(table_name, column_name):
    from sqlalchemy import inspect

    inspector = inspect(op.get_bind())
    if not inspector.has_table(table_name):
        return False
    return any(col['name'] == column_name
               for col in inspector.get_columns(table_name))


def upgrade():
    if not _has_column(TABLE_NAME, COLUMN_NAME):
        op.add_column(
            TABLE_NAME,
            sa.Column(COLUMN_NAME, sa.Text(length=16777215), nullable=True))


def downgrade():
    if _has_column(TABLE_NAME, COLUMN_NAME):
        op.drop_column(TABLE_NAME, COLUMN_NAME)