-- Pinned messages: each conversation gets up to 5 anchored references to its
-- own messages. Any accepted member can pin/unpin. RLS mirrors conversation
-- membership; the cap is enforced by a BEFORE INSERT trigger because partial
-- unique indexes can't express "at most N rows per group".

create table if not exists public.pinned_messages (
  conversation_id uuid not null references public.conversations(id) on delete cascade,
  message_id      uuid not null references public.messages(id)       on delete cascade,
  pinned_by       uuid not null references auth.users(id)            on delete set null,
  pinned_at       timestamptz not null default now(),
  primary key (conversation_id, message_id)
);

create index if not exists pinned_messages_conv_idx
  on public.pinned_messages(conversation_id, pinned_at desc);

alter table public.pinned_messages enable row level security;

drop policy if exists pinned_messages_select_member on public.pinned_messages;
create policy pinned_messages_select_member
  on public.pinned_messages
  for select
  to authenticated
  using (public.is_conversation_member(conversation_id));

drop policy if exists pinned_messages_insert_member on public.pinned_messages;
create policy pinned_messages_insert_member
  on public.pinned_messages
  for insert
  to authenticated
  with check (
    public.is_conversation_member(conversation_id)
    and pinned_by = auth.uid()
  );

drop policy if exists pinned_messages_delete_member on public.pinned_messages;
create policy pinned_messages_delete_member
  on public.pinned_messages
  for delete
  to authenticated
  using (public.is_conversation_member(conversation_id));

-- Enforce the per-conversation cap. Trigger-based so cross-row counts work.
create or replace function public.pinned_messages_enforce_cap()
returns trigger
language plpgsql
as $$
begin
  if (select count(*) from public.pinned_messages where conversation_id = new.conversation_id) >= 5 then
    raise exception 'pinned_messages_cap_reached: at most 5 pins per conversation';
  end if;
  return new;
end;
$$;

drop trigger if exists pinned_messages_cap on public.pinned_messages;
create trigger pinned_messages_cap
  before insert on public.pinned_messages
  for each row execute function public.pinned_messages_enforce_cap();

alter publication supabase_realtime add table public.pinned_messages;