"""control0004_dunning_tracking

Adds three columns to `tenants` for tracking dunning (payment-failure
reminder) emails:
  - past_due_since  DATETIME NULL — when the tenant first entered past_due state
  - dunning_stage   TINYINT  DEFAULT 0 — 0=none, 1=day3, 2=day7, 3=day14
  - dunning_sent_at DATETIME NULL — timestamp of the last dunning email sent

All columns are guarded by INFORMATION_SCHEMA existence checks so this
migration is safe to re-run.

Revision ID: control0004_dunning_tracking
Revises: control0003_trial_reminder_sent
Create Date: 2026-06-29
"""

from alembic import op
import sqlalchemy as sa

revision = 'control0004_dunning_tracking'
down_revision = 'control0003_trial_reminder_sent'
branch_labels = None
depends_on = None


def _column_exists(table, column):
    result = op.get_bind().execute(sa.text(
        "SELECT COUNT(*) FROM information_schema.COLUMNS "
        "WHERE TABLE_SCHEMA = DATABASE() "
        "  AND TABLE_NAME   = :tbl "
        "  AND COLUMN_NAME  = :col"
    ), {'tbl': table, 'col': column})
    return result.scalar() > 0


def upgrade():
    if not _column_exists('tenants', 'past_due_since'):
        op.add_column('tenants', sa.Column('past_due_since',
                                           sa.DateTime(), nullable=True))

    if not _column_exists('tenants', 'dunning_stage'):
        op.add_column('tenants', sa.Column('dunning_stage',
                                           sa.SmallInteger(), nullable=False,
                                           server_default='0'))

    if not _column_exists('tenants', 'dunning_sent_at'):
        op.add_column('tenants', sa.Column('dunning_sent_at',
                                           sa.DateTime(), nullable=True))


def downgrade():
    for col in ('dunning_sent_at', 'dunning_stage', 'past_due_since'):
        if _column_exists('tenants', col):
            op.drop_column('tenants', col)