package corecfg

// deepMerge merges dict2 into dict1 in place and returns dict1, mirroring
// corecfg_manager.py's module-level deep_merge(): nested maps recurse,
// matching lists are concatenated, everything else is overwritten by dict2.
func deepMerge(dict1, dict2 map[string]interface{}) map[string]interface{} {
	for k, v := range dict2 {
		existing, exists := dict1[k]
		if exists {
			existingMap, existingIsMap := existing.(map[string]interface{})
			vMap, vIsMap := v.(map[string]interface{})
			if existingIsMap && vIsMap {
				dict1[k] = deepMerge(existingMap, vMap)
				continue
			}

			existingList, existingIsList := existing.([]interface{})
			vList, vIsList := v.([]interface{})
			if existingIsList && vIsList {
				dict1[k] = append(existingList, vList...)
				continue
			}
		}
		dict1[k] = v
	}
	return dict1
}