"""phase21 — template active flag

Adds `active` boolean column to `inspection_templates` so templates can be
deactivated without deletion.  Inactive templates are hidden from the
inspection-start form but remain accessible in the template management UI.

Safe to re-run — uses INFORMATION_SCHEMA column existence check.
"""

import sqlalchemy as sa
from alembic import op

revision      = 'phase21_template_active'
down_revision = 'phase20_inspector_assignments'
branch_labels = None
depends_on    = None


def _column_exists(bind, table, column):
    result = bind.execute(sa.text(
        "SELECT COUNT(*) FROM INFORMATION_SCHEMA.COLUMNS "
        "WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = :t AND COLUMN_NAME = :c"
    ), {"t": table, "c": column})
    return result.scalar() > 0


def upgrade():
    bind = op.get_bind()
    if not _column_exists(bind, 'inspection_templates', 'active'):
        op.add_column(
            'inspection_templates',
            sa.Column('active', sa.Boolean(), nullable=False, server_default=sa.true())
        )


def downgrade():
    bind = op.get_bind()
    if _column_exists(bind, 'inspection_templates', 'active'):
        op.drop_column('inspection_templates', 'active')