-- Follow-up to 20260808000002 (deferred from the final whole-branch review
-- before merge). Postgres migrations are append-only history, so this adds
-- new triggers and replaces the trigger function rather than editing the
-- already-applied 20260808000002 file.
--
-- Problem: sync_booked_slot() only ran `after insert`, and unconditionally
-- mirrored every new booking regardless of status. Three consequences:
--   1. If a confirmed booking was later cancelled (status update) or
--      deleted, its booked_slots mirror row was never removed, so the slot
--      stayed permanently blocked even though it was actually free again.
--   2. A booking inserted directly with status = 'cancelled' (the public
--      insert policy allows any status, not just the 'confirmed' default)
--      would still create a booked_slots row, incorrectly blocking a slot
--      nobody had actually confirmed.
--   3. Rescheduling a confirmed booking (changing date/time while it stays
--      'confirmed') didn't fire the trigger at all under an `of status`
--      qualifier, leaving the OLD slot permanently blocked and the NEW slot
--      showing as free even though it's now taken. Caught in review: a
--      status-qualified trigger silently misses any update that doesn't
--      touch the status column.
--
-- Fix: the trigger function now branches on TG_OP and the trigger fires on
-- every UPDATE (not just `of status`). On insert/update it only mirrors the
-- slot when the new row is 'confirmed' (fixing #2 above). On update where
-- the (date, time, status) triple actually changed and the OLD row was
-- confirmed, or on delete of a confirmed row, it removes the OLD slot's
-- mirror row, but only if no *other* confirmed booking still holds that
-- (date, time) -- the partial unique index added in 20260812000002
-- guarantees there can be at most one, but this guard keeps the function
-- correct even if that assumption ever changes.
create or replace function public.sync_booked_slot()
returns trigger
language plpgsql
security definer
set search_path = ''
as $$
begin
  if tg_op = 'DELETE' then
    if old.status = 'confirmed' then
      delete from public.booked_slots
      where date = old.date and time = old.time
        and not exists (
          select 1 from public.bookings b
          where b.date = old.date and b.time = old.time and b.status = 'confirmed'
        );
    end if;
    return old;
  end if;

  if tg_op = 'UPDATE' then
    -- Covers both a status change away from 'confirmed' (cancellation) and a
    -- reschedule of a still-confirmed booking to a different (date, time):
    -- either way, the OLD slot may no longer have any confirmed booking
    -- holding it and its mirror row needs to go.
    if old.status = 'confirmed'
       and (old.date, old.time, old.status) is distinct from (new.date, new.time, new.status) then
      delete from public.booked_slots
      where date = old.date and time = old.time
        and not exists (
          select 1 from public.bookings b
          where b.date = old.date and b.time = old.time and b.status = 'confirmed'
        );
    end if;
    if new.status = 'confirmed' then
      insert into public.booked_slots (date, time)
      values (new.date, new.time)
      on conflict do nothing;
    end if;
    return new;
  end if;

  -- INSERT
  if new.status = 'confirmed' then
    insert into public.booked_slots (date, time)
    values (new.date, new.time)
    on conflict do nothing;
  end if;
  return new;
end;
$$;

-- Unqualified `after update` (not `of status`): a reschedule that changes
-- date/time while status stays 'confirmed' must also resync the mirror --
-- the old slot needs freeing and the new slot needs blocking -- and an
-- `of status` trigger would never fire for that case.
create trigger booking_updated_sync_slot
  after update on public.bookings
  for each row
  execute function public.sync_booked_slot();

create trigger booking_deleted_sync_slot
  after delete on public.bookings
  for each row
  execute function public.sync_booked_slot();