"""phase23 — support tickets

Creates two tables:
  support_tickets        — customer-submitted help requests
  support_ticket_replies — admin/staff replies to those tickets
"""

import sqlalchemy as sa
from alembic import op

revision      = 'phase23_support_tickets'
down_revision = 'phase22_comment_visibility'
branch_labels = None
depends_on    = None


def _table_exists(bind, table: str) -> bool:
    result = bind.execute(sa.text(
        "SELECT COUNT(*) FROM information_schema.tables "
        "WHERE table_schema = DATABASE() AND table_name = :t"
    ), {'t': table})
    return result.scalar() > 0


def upgrade():
    bind = op.get_bind()

    if not _table_exists(bind, 'support_tickets'):
        op.execute(sa.text("""
            CREATE TABLE support_tickets (
                id          INT          NOT NULL AUTO_INCREMENT PRIMARY KEY,
                customer_id INT          NULL,
                facility_id INT          NULL,
                subject     VARCHAR(200) NOT NULL,
                body        TEXT         NOT NULL,
                status      VARCHAR(20)  NOT NULL DEFAULT 'open',
                created_at  DATETIME     NOT NULL,
                CONSTRAINT fk_st_customer FOREIGN KEY (customer_id)
                    REFERENCES users(id) ON DELETE SET NULL,
                CONSTRAINT fk_st_facility FOREIGN KEY (facility_id)
                    REFERENCES facilities(id) ON DELETE SET NULL,
                INDEX ix_support_tickets_customer (customer_id),
                INDEX ix_support_tickets_status  (status),
                INDEX ix_support_tickets_created (created_at)
            ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
        """))

    if not _table_exists(bind, 'support_ticket_replies'):
        op.execute(sa.text("""
            CREATE TABLE support_ticket_replies (
                id         INT      NOT NULL AUTO_INCREMENT PRIMARY KEY,
                ticket_id  INT      NOT NULL,
                user_id    INT      NULL,
                body       TEXT     NOT NULL,
                created_at DATETIME NOT NULL,
                CONSTRAINT fk_str_ticket FOREIGN KEY (ticket_id)
                    REFERENCES support_tickets(id) ON DELETE CASCADE,
                CONSTRAINT fk_str_user FOREIGN KEY (user_id)
                    REFERENCES users(id) ON DELETE SET NULL,
                INDEX ix_support_replies_ticket (ticket_id)
            ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
        """))


def downgrade():
    bind = op.get_bind()
    if _table_exists(bind, 'support_ticket_replies'):
        op.execute(sa.text('DROP TABLE support_ticket_replies'))
    if _table_exists(bind, 'support_tickets'):
        op.execute(sa.text('DROP TABLE support_tickets'))