smartbotic/lib/common/config_defaults.hpp

#pragma once

#include <nlohmann/json.hpp>

namespace smartbotic::common {

// Applies configSchema-declared defaults to a node config.
//
// Returns a copy of `config` with any property from
// `config_schema["properties"]` that declares a "default" filled in, but
// only when `config` does not already contain that key. A key that is
// present - even with a falsy value like false, 0, null, or "" - is a
// deliberate, stored value and is never overwritten.
//
// Scope limit (by design, not an oversight): only top-level properties are
// considered. Defaults nested inside object properties or array item
// schemas are NOT applied. Nodes are not currently written with nested
// config shapes that rely on defaults, so recursing was left out to keep
// this function's behaviour easy to reason about; revisit if that changes.
//
// Tolerant of a missing/null/non-object schema, or one with no
// "properties" - in all of those cases the config is returned unchanged
// rather than throwing.
//
// Write-time materialisation is permanent: once a workflow is saved with a
// default baked into its stored config, that key now counts as "present",
// so a later change to the schema's default will never reach that already-
// saved workflow - the read path correctly leaves a present key alone. This
// is an accepted consequence of applying defaults at write time, not a bug;
// it only affects workflows saved after write-time materialisation shipped,
// since a workflow saved before that never had the key baked in to begin
// with, and still picks up schema default changes at read time.
nlohmann::json applyConfigDefaults(const nlohmann::json& config,
                                    const nlohmann::json& config_schema);

} // namespace smartbotic::common