-- Homepage banners are independent editorial content. A banner can either
-- reference a course (and always use its current cover) or use an uploaded
-- image stored in Bunny Storage.
create table home_banners (
  id uuid primary key default gen_random_uuid(),
  kind text not null check (kind in ('course', 'custom')),
  course_id uuid references courses(id) on delete cascade,
  image_url text,
  title text not null default '',
  description text not null default '',
  position integer not null check (position > 0),
  created_at timestamptz not null default now(),
  updated_at timestamptz not null default now(),
  constraint home_banners_source_check check (
    (kind = 'course' and course_id is not null and image_url is null) or
    (kind = 'custom' and course_id is null and image_url is not null)
  ),
  unique (position)
);

create trigger home_banners_set_updated_at before update on home_banners for each row execute function set_updated_at();