-- ADR-0017: once an Organization starts configuring roles, every committed
-- state must contain exactly one active default. The deferred trigger permits
-- an atomic default switch while rejecting zero-default transitions.
CREATE FUNCTION cph_enforce_agent_role_default() RETURNS trigger
LANGUAGE plpgsql AS $$
DECLARE
  target_organization_id TEXT := COALESCE(NEW."organizationId", OLD."organizationId");
  active_default_count INTEGER;
BEGIN
  IF NOT EXISTS (SELECT 1 FROM "Organization" WHERE "id" = target_organization_id) THEN
    RETURN NULL;
  END IF;

  SELECT count(*) INTO active_default_count
  FROM "OrganizationAgentRole"
  WHERE "organizationId" = target_organization_id
    AND "isDefault" = true
    AND "disabledAt" IS NULL;

  IF active_default_count <> 1 THEN
    RAISE EXCEPTION 'Organization % must have exactly one active default Agent role; found %',
      target_organization_id, active_default_count;
  END IF;
  RETURN NULL;
END;
$$;

CREATE CONSTRAINT TRIGGER "OrganizationAgentRole_exactly_one_active_default"
AFTER INSERT OR UPDATE OR DELETE ON "OrganizationAgentRole"
DEFERRABLE INITIALLY DEFERRED
FOR EACH ROW EXECUTE FUNCTION cph_enforce_agent_role_default();