-- migrate:up

-- The Linka Go accounts allowed to unlock the bikes for this reservation. They
-- are plain addresses, not app users: somebody who never logs in can still be
-- authorised, so this is not a link to `users`.
ALTER TABLE reservations ADD COLUMN linka_emails TEXT[] NOT NULL DEFAULT '{}';

-- A check constraint cannot hold a subquery, so this catches the empty string
-- rather than any blank one. The repository trims before writing, which turns a
-- whitespace-only address into the empty string caught here.
ALTER TABLE reservations ADD CONSTRAINT reservations_linka_emails_filled CHECK (
    array_position(linka_emails, NULL) IS NULL AND NOT ('' = ANY (linka_emails)));

-- migrate:down
ALTER TABLE reservations DROP CONSTRAINT reservations_linka_emails_filled;
ALTER TABLE reservations DROP COLUMN linka_emails;