-- Diagram sharing/collaborators UI support, per organized-ideas.md §8. The
-- diagrams/diagram_collaborators/diagram_snapshots tables and their RLS
-- already exist (init schema) — this migration adds the two small pieces
-- of backend those needed to actually be usable from a UI.

-- ----------------------------------------------------------------------
-- Username -> id lookup, for "share with @username". profiles_select
-- deliberately keeps a regular user from browsing other users' profiles
-- (organized-ideas.md §2/§6), but a username is meant to be a shareable
-- handle — that's the whole point of having one — so resolving it to an id
-- (and nothing else: no email, no role) is safe to expose broadly, unlike
-- the Admin-gated lookups elsewhere in this schema. Any authenticated user
-- can call this; there's no privilege check because none is needed.
-- ----------------------------------------------------------------------

create or replace function public.find_user_id_by_username(p_username text)
returns uuid
language sql
stable
security definer
set search_path = public
as $$
  select id from public.profiles where username = p_username;
$$;

-- ----------------------------------------------------------------------
-- Collaborator usernames for one diagram's sharing UI. Same problem as
-- above in reverse: diagram_collaborators only stores user ids, and
-- profiles_select_self_or_super_admin blocks a regular owner from reading
-- some *other* user's profile row directly to get their username. Gated
-- to "can you see this diagram at all" — the same condition as
-- diagrams_select's USING clause, reusing its own helper functions so the
-- two can't drift apart.
-- ----------------------------------------------------------------------

create or replace function public.diagram_collaborator_usernames(p_diagram_id uuid)
returns table(user_id uuid, username text)
language plpgsql
stable
security definer
set search_path = public
as $$
begin
  if not (
    public.is_super_admin()
    or public.diagram_owner_id(p_diagram_id) = auth.uid()
    or public.diagram_collaborator_permission(p_diagram_id, auth.uid()) is not null
  ) then
    raise exception 'insufficient_privilege' using errcode = '42501';
  end if;

  return query
    select dc.user_id, p.username
    from public.diagram_collaborators dc
    join public.profiles p on p.id = dc.user_id
    where dc.diagram_id = p_diagram_id;
end;
$$;

-- ----------------------------------------------------------------------
-- Rolling snapshot retention (organized-ideas.md §8: "keep a rolling
-- window of recent diagram snapshots... exact policy TBD" — settled on
-- count-based, 50 per diagram). Enforced at write time via a trigger
-- rather than a scheduled job: diagram_snapshots has no update/delete
-- policy for regular users at all (it's meant to be immutable from their
-- side), so pruning has to run as this SECURITY DEFINER function
-- regardless of whether it's trigger- or cron-driven — a trigger is
-- simpler than also standing up pg_cron for this app's scale.
-- ----------------------------------------------------------------------

create or replace function public.prune_diagram_snapshots()
returns trigger
language plpgsql
security definer
set search_path = public
as $$
begin
  delete from public.diagram_snapshots
  where diagram_id = new.diagram_id
    and id not in (
      select id from public.diagram_snapshots
      where diagram_id = new.diagram_id
      order by created_at desc
      limit 50
    );
  return new;
end;
$$;

create trigger trg_prune_diagram_snapshots
after insert on public.diagram_snapshots
for each row
execute function public.prune_diagram_snapshots();

-- ----------------------------------------------------------------------
-- Who saved each snapshot, for the version-history UI. Same shape as
-- diagram_collaborator_usernames above (gated to "can you see this
-- diagram", batched per diagram rather than per snapshot).
-- ----------------------------------------------------------------------

create or replace function public.diagram_snapshot_saved_by_usernames(p_diagram_id uuid)
returns table(user_id uuid, username text)
language plpgsql
stable
security definer
set search_path = public
as $$
begin
  if not (
    public.is_super_admin()
    or public.diagram_owner_id(p_diagram_id) = auth.uid()
    or public.diagram_collaborator_permission(p_diagram_id, auth.uid()) is not null
  ) then
    raise exception 'insufficient_privilege' using errcode = '42501';
  end if;

  return query
    select distinct p.id, p.username
    from public.diagram_snapshots s
    join public.profiles p on p.id = s.saved_by
    where s.diagram_id = p_diagram_id;
end;
$$;