"""control0002 — add trial_reminder_sent_at to tenants

Adds a nullable DATETIME column that the trial-reminders cron endpoint writes
to after dispatching a warning email. Prevents duplicate sends within 22 hours.
"""

import sqlalchemy as sa
from alembic import op

revision = 'control0003_trial_reminder_sent'
down_revision = 'control0002_billing'
branch_labels = None
depends_on = None


def _col_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 _col_exists(bind, 'tenants', 'trial_reminder_sent_at'):
        op.execute(sa.text(
            "ALTER TABLE tenants "
            "ADD COLUMN trial_reminder_sent_at DATETIME NULL "
            "AFTER trial_ends_at"
        ))


def downgrade():
    bind = op.get_bind()
    if _col_exists(bind, 'tenants', 'trial_reminder_sent_at'):
        op.execute(sa.text(
            "ALTER TABLE tenants DROP COLUMN trial_reminder_sent_at"
        ))