-- ============================================================================
-- 20260929000001_function_acl_hardening.sql
--
-- Function execution ACL hardening.
--
-- Background
--   Supabase's default privileges give every function that postgres creates in
--   schema public a *direct* EXECUTE grant to anon, authenticated and
--   service_role. `REVOKE ... FROM PUBLIC` therefore does not lock anon out.
--   Three early migrations only revoked PUBLIC (and sometimes authenticated):
--     * 20260409000003 increment_daily_usage -> anon could add any (negative)
--       amount to any user's daily_usage, wiping or exhausting quota.
--     * 20260413000004 admin_usage_by_feature / admin_top_users / admin_dau ->
--       SECURITY DEFINER bodies with no role predicate, callable by anon and
--       every signed-in user; admin_top_users leaks user ids and names.
--
-- Policy (single place; enforced by tests/function-acl.integration.sql)
--   * No SECURITY DEFINER function in schema public is executable by anon.
--   * SECURITY DEFINER trigger functions are executable by nobody but the
--     owner and service_role (triggers do not check EXECUTE when they fire).
--   * authenticated may execute a SECURITY DEFINER function only if it is on
--     the reviewed allowlist in tests/function-acl.integration.sql.
--   * Every SECURITY DEFINER function pins search_path.
--   New migrations keep writing their own
--     REVOKE ALL ON FUNCTION ... FROM PUBLIC, anon[, authenticated];
--     GRANT EXECUTE ON FUNCTION ... TO <the roles that need it>;
--   and add authenticated RPCs to the test allowlist. An omission is caught by
--   the local integration test (it is not run by CI yet).
--
-- Why default privileges are NOT changed here
--   A deny-by-default `ALTER DEFAULT PRIVILEGES` only works for anon if it is
--   the schema-less (global) form, because anon inherits the built-in PUBLIC
--   EXECUTE default. The global form also strips PUBLIC EXECUTE from pg_temp
--   helpers created by postgres, which breaks every integration test that
--   calls pg_temp.assert_true()/act_as() after SET ROLE authenticated, and it
--   would silently change the ACL of functions created by later migrations
--   that are being written against the current defaults. The schema-scoped
--   form alone is a no-op for anon. The sweep below plus the catalog test give
--   the same guarantee without those side effects.
-- ============================================================================

-- ----------------------------------------------------------------------------
-- 1. Sweep: apply the policy to every existing SECURITY DEFINER function in
--    schema public. authenticated/service_role access is preserved exactly
--    (except for trigger functions, which cannot be called directly anyway);
--    only anon/PUBLIC access is removed.
-- ----------------------------------------------------------------------------
DO $$
DECLARE
  fn record;
  target text;
  keep_authenticated boolean;
  keep_service_role boolean;
BEGIN
  FOR fn IN
    SELECT p.oid,
           n.nspname,
           p.proname,
           pg_get_function_identity_arguments(p.oid) AS identity_args,
           p.prorettype = 'trigger'::regtype AS is_trigger
      FROM pg_proc p
      JOIN pg_namespace n ON n.oid = p.pronamespace
     WHERE n.nspname = 'public'
       AND p.prosecdef
  LOOP
    target := format('%I.%I(%s)', fn.nspname, fn.proname, fn.identity_args);
    keep_authenticated := NOT fn.is_trigger
      AND has_function_privilege('authenticated', fn.oid, 'EXECUTE');
    keep_service_role := has_function_privilege('service_role', fn.oid, 'EXECUTE');

    EXECUTE format('REVOKE ALL ON ROUTINE %s FROM PUBLIC, anon', target);
    IF fn.is_trigger THEN
      EXECUTE format('REVOKE ALL ON ROUTINE %s FROM authenticated', target);
    END IF;

    -- Re-grant access that previously flowed only through PUBLIC.
    IF keep_authenticated THEN
      EXECUTE format('GRANT EXECUTE ON ROUTINE %s TO authenticated', target);
    END IF;
    IF keep_service_role THEN
      EXECUTE format('GRANT EXECUTE ON ROUTINE %s TO service_role', target);
    END IF;
  END LOOP;
END;
$$;

-- ----------------------------------------------------------------------------
-- 2. increment_daily_usage: service_role only, and the counter can no longer
--    go below zero. Negative amounts stay allowed for the service-role refund
--    path (functions/_shared/embedding-quota.ts releases reserved units with a
--    negative amount), but the stored total is clamped at 0.
-- ----------------------------------------------------------------------------
CREATE OR REPLACE FUNCTION public.increment_daily_usage(
  p_user_id uuid,
  p_feature text,
  p_amount integer DEFAULT 1
)
RETURNS integer
LANGUAGE plpgsql
SECURITY DEFINER
SET search_path = ''
AS $$
DECLARE
  v_new_count integer;
BEGIN
  IF p_user_id IS NULL OR p_feature IS NULL OR p_amount IS NULL THEN
    RAISE EXCEPTION 'increment_daily_usage: arguments must not be null'
      USING ERRCODE = '22004';
  END IF;

  INSERT INTO public.daily_usage (user_id, date, feature, count)
  VALUES (p_user_id, CURRENT_DATE, p_feature, greatest(p_amount, 0))
  ON CONFLICT (user_id, date, feature)
  DO UPDATE SET count = greatest(public.daily_usage.count + p_amount, 0)
  RETURNING count INTO v_new_count;

  RETURN v_new_count;
END;
$$;

REVOKE ALL ON FUNCTION public.increment_daily_usage(uuid, text, integer)
  FROM PUBLIC, anon, authenticated;
GRANT EXECUTE ON FUNCTION public.increment_daily_usage(uuid, text, integer)
  TO service_role;

-- ----------------------------------------------------------------------------
-- 3. daily_usage.count is a usage counter; negative totals are never valid.
--    Legitimate decrements (quota reservation release) already clamp with
--    greatest(count - 1, 0). Any negative row can only come from the abuse
--    above, so it is normalised to 0 before the constraint is validated.
-- ----------------------------------------------------------------------------
UPDATE public.daily_usage
   SET count = 0
 WHERE count < 0;

DO $$
BEGIN
  IF NOT EXISTS (
    SELECT 1
      FROM pg_constraint
     WHERE conrelid = 'public.daily_usage'::regclass
       AND conname = 'daily_usage_count_nonnegative'
  ) THEN
    ALTER TABLE public.daily_usage
      ADD CONSTRAINT daily_usage_count_nonnegative CHECK (count >= 0);
  END IF;
END;
$$;

-- ----------------------------------------------------------------------------
-- 4. Platform analytics RPCs: service_role only. Their bodies have no role
--    predicate and run as definer (RLS bypassed), so no end-user role may call
--    them. The admin console reads Supabase with the service-role key, like
--    the other admin_*_v1 RPCs.
-- ----------------------------------------------------------------------------
REVOKE ALL ON FUNCTION public.admin_usage_by_feature(date, date)
  FROM PUBLIC, anon, authenticated;
GRANT EXECUTE ON FUNCTION public.admin_usage_by_feature(date, date)
  TO service_role;

REVOKE ALL ON FUNCTION public.admin_top_users(date, date, integer)
  FROM PUBLIC, anon, authenticated;
GRANT EXECUTE ON FUNCTION public.admin_top_users(date, date, integer)
  TO service_role;

REVOKE ALL ON FUNCTION public.admin_dau(date, date)
  FROM PUBLIC, anon, authenticated;
GRANT EXECUTE ON FUNCTION public.admin_dau(date, date)
  TO service_role;

COMMENT ON FUNCTION public.increment_daily_usage(uuid, text, integer) IS
  'service_role only. Adds p_amount to today''s usage counter, clamped at 0.';
COMMENT ON FUNCTION public.admin_usage_by_feature(date, date) IS
  'service_role only. Platform analytics; no caller role predicate in body.';
COMMENT ON FUNCTION public.admin_top_users(date, date, integer) IS
  'service_role only. Returns user ids and names; no caller role predicate in body.';
COMMENT ON FUNCTION public.admin_dau(date, date) IS
  'service_role only. Platform analytics; no caller role predicate in body.';

-- ----------------------------------------------------------------------------
-- 5. Self-check: fail the migration if any public SECURITY DEFINER function is
--    still executable by anon.
-- ----------------------------------------------------------------------------
DO $$
DECLARE
  offenders text;
BEGIN
  SELECT string_agg(p.oid::regprocedure::text, ', ' ORDER BY p.oid::regprocedure::text)
    INTO offenders
    FROM pg_proc p
   WHERE p.pronamespace = 'public'::regnamespace
     AND p.prosecdef
     AND has_function_privilege('anon', p.oid, 'EXECUTE');

  IF offenders IS NOT NULL THEN
    RAISE EXCEPTION 'function_acl_hardening: anon can still execute SECURITY DEFINER functions: %',
      offenders;
  END IF;
END;
$$;